A Large International River: The
Danube. Summary of Hydrological
Conditions and Water Management
Problems in the Danube Basin
Hock, B. and Kovacs, G.
IIASA Working Paper
WP-87-011
January 1987
Hock, B. and Kovacs, G. (1987) A Large International River: The Danube. Summary of Hydrological Conditions and Water
Management Problems in the Danube Basin. IIASA Working Paper. IIASA, Laxenburg, Austria, WP-87-011 Copyright ©
1987 by the author(s). http://pure.iiasa.ac.at/3040/
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W O R K I N G PAPER
A LARGE INTERNATIONAL RIVER THE DANUBE
SUMMARY OF HYDROLOGICAL CONDITIONS AND
WATER MANAGEMENT PROBLEXS IN THE
DANUBE BASIN
B. Hock
G. Kovdcs
January 1987
WP-87-11
International Institute
for Applied Systems Analysis
NOT FOR QUOTATION
WITHOUT PERMISSION
OF THE AUTHOR
A LARGE INTERNATIONAL RIVER: THE DANUBE
SUMMAEW OF HYDROLOGICAL CONDITIONS AND
WATER MANAGEXENT PROBLEXS IN THE
DANUBE BASIN
B. Hock
G. Kovdcs
January 1987
WP-87-11
Working Papers are interim r e p o r t s on work of t h e International
Institute f o r Applied Systems Analysis a n d h a v e r e c e i v e d only limited review. Views o r opinions e x p r e s s e d h e r e i n d o not necess a r i l y r e p r e s e n t t h o s e of t h e Institute or of i t s National Member
Organizations.
INTERNATIONAL INSTITUTE FOR APPLIED SYSTEMS ANALYSIS
2361 Laxenburg, Austria
PREFACE
The demand of policy makers and managers to find environmentally
sound and sustainable economic development i s obvious. At t h e s a m e time,
various b r a n c h e s of sciences dealing with environmental issues have
become more and more specialized. The solution to problems
often of a
global c h a r a c t e r r e q u i r e s t h e interdisciplinary analysis of v e r s a t i l e systems consisting of natural, economic and social elements of t h e environment.
Within t h e long s e r i e s of water r e l a t e d topics of IIASA1s Environment
Programme, a new p r o j e c t Decision S u p p o r t S y s t e m s for Managing Large
I n t e r n a t i o n a l R i v e r s (Zm)w a s recently launched. The formulation of
environmentally sound management policy f o r land-use and water r e s o u r c e s
development r e q u i r e s t h e reliable prediction of t h e impacts of different
human interventions in o r d e r t o eliminate conflicts between different
i n t e r e s t groups, and t o p r e s e r v e t h e quality of life in both t h e biosphere
and society. S e v e r a l models f o r t h e assessment of various environmental
impacts a l r e a d y exist, b u t t h e l a r g e s c a l e of r i v e r basins and t h e amount of
d a t a t h e availability of which is even limited in some cases r e q u i r e t h e
development of aggregated systems of models t h a t c a n provide decision
makers with easily understandable information at various h i e r a r c h i c a l levels. Considering this requirement, t h e objective of t h e p r o j e c t i s t o cons t r u c t a computer-based interactive d a t a and information system to facilitate t h e effective participation of policy making authorities in determining
c u r r e n t conditions and expected changes in hydrological systems.
The outline of LIR emphasizes t h e importance of t h e p r e p a r a t i o n of
case studies. Their r o l e is not only t o check t h e applicability on t h e system
f o r solving actually occurring problems, but t h e analysis of t h e basins as
cases will assist in selecting t h e crucial questions t h a t should b e answered
by t h e Decision Support System. The Danube basin w a s chosen as t h e f i r s t
-
-
-
-
c a s e study t o b e investigated in t h e framework of LIR. The reason f o r this
choice i s partly t h a t IIASA is located in t h e basin, and, thus all information
easily accessible. The international c h a r a c t e r of t h e r i v e r ( t h e r e a r e 8
r i p a r i a n countries and 3 o t h e r s sharing a small p a r t of t h e catchment), t h e
rapidly developing problems of t h e utilization of water (canalization,
increasing transboundary pollution, seasonal water shortage), and t h e
e f f o r t s of t h e r i p a r i a n countries t o improve t h e conditions of water
r e s o u r c e s development within t h e basin (which i s clearly indicated by t h e
f a c t t h a t a joint declaration was signed) a r e also reasons supporting t h e
selection of t h e Danube as t h e f i r s t c a s e study.
Naturally, t h e hydrological conditions of t h e r i v e r system and t h e
water management problems occurring within t h e catchment a r e well known
f o r t h e e x p e r t s in water sciences working in t h e r i p a r i a n countries. For
e x p e r t s participating in t h e p r o j e c t and coming from o t h e r countries, o r ,
representing o t h e r scientific disciplines, i t i s necessary, however, t o summarize t h e most important information describing t h e water regime of t h e
r i v e r system and t h e obstacles hindering t h e development of water
r e s o u r c e s in t h e basin. This working p a p e r and t h e detailed list of r e f e r ences provide more information on water management in t h e Danube basin.
R.E. Munn
Environment Programme
A LARGE INTERNATIONAL RTVER- THE DANUBE
SUMAURY OF HYDROLOGICAL CONDITIONS AND
WATER MANAGEMENT PROBLEMS IN THE
DANUBE BASIN
B. Hock* and G. Kovdcs
INTRODUCTION
The Danube basin was selected as t h e f i r s t c a s e study t o b e analysed
within t h e framework of t h e IIASA p r o j e c t aiming at t h e development of a
decision support system ( h e r e a f t e r DSS) f o r managing l a r g e international
r i v e r s ( h e r e a f t e r LIR). It w a s felt necessary t o p r e p a r e a p a p e r which
would provide t h e e x p e r t s
- working in t h e p r o j e c t but not being familiar
with t h e water regime of t h e Danube
- with
the basic information on t h e
hydrological condition of the r i v e r system as w e l l a s on t h e historical
development and t h e p r e s e n t problems of water management within t h e
basin.
The compilation of t h e p a p e r w a s assisted by t h e excellent l i t e r a t u r e
dealing with t h e v e r s a t i l e problems of water r e s o u r c e s development in t h e
basin. The list of r e f e r e n c e s in this p a p e r provides guidance f o r r e a d e r s
who are interested in obtaining more detailed information on some
* s c i e n t i f i cAdviser, Research Centre f o r Water Resources Development (VITUKI),Budapest
p a r t i c u l a r topic in water management.
One publication t h a t deserves p a r t i c u l a r mention is t h e Danube Monogr a p h y (RZdD, 1986), t h e result of a joint p r o j e c t of t h e eight r i p a r i a n count r i e s where e x p e r t s collected lengthy d a t a s e r i e s characterizing t h e quantitative regime of t h e Danube and i t s main t r i b u t a r i e s . The d a t a were h a r monized by t h e Federal Hydrometeorological Institute in Belgrade and t h e
R e s e a r c h Institute f o r Water Management in Bratislava, who accepted
responsibility f o r coordination of national r e p o r t s .
Finally, t h e e n t i r e material, which contains not only t h e hydrological
data, b u t also t h e historical summary of water management activity in e a c h
country, w a s edited and published by t h e Bayerische Landesamt fiir
Wasserwirtschaft in Miinchen. Detailed information on quantitative conditions a n d water r e s o u r c e s development are available in t h i s publication.
Unfortunately, t h i s p r o j e c t w a s limited to traditional hydrology and t h e
water quality problems were not dealt with in t h i s framework. Therefore, i t
w a s necessary to give more detailed information on t h e conditions of water
quality in this working p a p e r , because in this field no such comprehensive
publication can be offered, where t h e qualitative d a t a are summarized in a
similar way.
Analyzing t h e problems hindering t h e utilization of water r e s o u r c e s in
t h e basin, i t w a s found t h a t t h e major obstacle at p r e s e n t and in t h e n e a r
f u t u r e i s water pollution due t o t h e r e l e a s e of waste waters not sufficiently
t r e a t e d from community systems and industries as w e l l as t h e non-point
s o u r c e pollution originating from intensified agriculture and urban areas.
Some qualitative p a r a m e t e r s indicate t h a t even t h e quality of bank filtered
water
- providing t h e l a r g e s t amount of water f o r community water supply -
i s endangered by t h e increasing deterioration of r i v e r waters. This w a s
also a motivation requiring more detailed information on quality conditions.
A l s o t h e r e w a s a t h i r d a s p e c t giving r e a s o n s f o r studying t h e water
quality
problems of
t h e Danube.
The implementation of
a regional
UNDP/WHO p r o j e c t will commence in 1987 aiming a t t h e determination and
improvement of water quality conditions in t h e Danube basin within t h e
framework of which t h e r i p a r i a n countries will make joint e f f o r t s t o solve
t h i s serious problem of water management.
There a r e s e v e r a l common
elements in t h e two p r o j e c t s (i.e. UNDP/WHO p r o j e c t on t h e Danube water
quality and t h e IIASA LIR Danube case study). Therefore, i t w a s decided
t h a t t h e i r implementation should b e closely coordinated.
Hence, while
preparing this p a p e r i t w a s considered t h a t t h i s should also s e r v e as a
background document f o r t h e UNDP/WHO project.
There a r e two annexes t o this r e p o r t . The f i r s t i s t h e Declaration by
t h e r i p a r i a n countries signed in December 1985; and t h e second is a summary
evaluation
of
the
environmental
impact
assessment
of
the
Gabcikovo-Nagymaros b a r r a g e system.
In t h e Declaration, r e p r e s e n t a t i v e s of t h e eight r i p a r i a n countries
expressed t h e i r willingness t o solve t h e problems of water management in a
coordinated manner, as i t w a s recognized t h a t t h e obstacles hindering t h e
reasonable utilization of water r e s o u r c e s can b e removed only by joint
e f f o r t s in a n international r i v e r basin. Decision w a s also r e a c h e d concerning t h e institutional framework r e q u i r e d t o implement t h e programmes
defined in t h e Declaration in t h e fields of water quality control, flood protection and general water management. The DSS of LIR and t h e results of
t h e Danube case study are offered t o t h e relevant authorities of t h e eight
countries as usable tools t o achieve t h e objectives p u t forward in t h e
Declaration.
The modification of environmental conditions in t h e r i v e r and in t h e
surrounding region due t o t h e construction of b a r r a g e s w a s r a i s e d in some
r i p a r i a n countries as a s e r i o u s environmental concern. The s a m e happened
in Hungary in connection with t h e Gabcikovo-Nagymaros b a r r a g e system
now under construction. A detailed environmental impact assessment was,
t h e r e f o r e , p r e p a r e d t o survey t h e side-effects of t h e system, t o determine
t h e measures needed f o r t h e prevention of undesirable impacts and f o r t h e
utilization of positive changes. A brief evaluation of t h i s study i s given in
Annex 11.
1. INTERNATIONAL IMPORTANCE OF THE DANUBE BASIN
The Danube is a characteristically international r i v e r , passing through
eight
countries (FRG, Austria,
Czechoslovakia,
Hungary, Yugoslavia,
Romania, Bulgaria and t h e USSR), and draining v e r y small areas of a
f u r t h e r f o u r non-riparian countries: Italy, Switzerland, Poland, Albania.
Due t o t h e relatively low contribution t o t h e t o t a l area of t h e basin, t h e
economic conditions of t h e latter countries and t h e impacts of t h e i r economy on t h e water regime will not b e discussed in t h i s p a p e r . In addition, t h e
Danube connects also t h e two different socio-economic groups of West and
East European countries.
The size of t h e catchment belonging t o t h e t e r r i t o r y of various count r i e s and t h e number of population living t h e r e (Figure 1 , Table 1 ) demons t r a t e t h e importance of t h e r i v e r in t h e economic life of t h e s e countries.
The r a t i o of catchment a r e a t o t h e t o t a l country a r e a and catchment population t o total country population a r e fairly significant (see Table 1 ) with
t h e exception of t h e Soviet Union (WHO, 1976). The multi-purpose utilization of t h e Danube River is of vital importance f o r approximately 7 1 million
inhabitants living in t h e basin (Ldszldffy, 1967).
With eight r i p a r i a n countries sharing t h e waters of t h e Danube, t h e
environmentally sound utilization of water r e s o u r c e s and t h e development of
suitable land u s e policy within t h e catchment are strongly r e q u i r e d t o maintain t h e p r o p e r quantity and quality along t h e whole r i v e r . The achievements of t h e s e goals pose many interesting international considerations and
unique opportunities f o r cooperation.
Having recognized this necessity, in 1985 t h e eight Danube r i p a r i a n
countries issued in Bucharest a common declaration about t h e cooperation
t o b e realized on t h e field of water r e s o u r c e s management. In this declaration, t h e Governments expressed t h e i r readiness t o c o o p e r a t e in o r d e r t o
conserve and rationally utilize t h e water r e s o u r c e s of t h e Danube River.
The cooperation t o b e c a r r i e d out in t h e framework of t h r e e working
groups, will include all t h e eight Danube countries. The protocol entitled
"Joint measures t o b e taken in t h e c o u r s e of cooperation of t h e Danube
countries aiming a t t h e solution of t h e water management problems of t h e
Danube River with special r e g a r d t o i t s protection from pollutions", drawn
Table 1
C h a r a c t e r i s t i c d a t a of t h e Danube
(WHO, 1976; RZdD, 1986)
1
2
Country
Country's
territory
thousand
h2
3
4
5
Area of country Counin Danube catch- t r y ' s
ment
populati o n
million
people
thousand
% of country
asi in*
6
7
8
People of
country in
Danube
catchment
% of
Danube
bank
length
in
country
mill. % of
people
in
Danube
c a t chment
country
populati o n
83.9
80.7
96.3
7
7
100
12
Czechoslovakia
127.9
73.0
57.1
14
7
50
3
Yugoslavia
255.8
183.2
71.6
19
13
68
17
Rumania
237 5
232.2
97.8
19
19
100
24
Bulgaria
110.9
48.2
43.4
8
4
50
7
22402.2
44.3
Austria
USSR
Other
countries
(I,CH,PL,fi)
h he
Om 2
226
1
0.4
3.0
d a t a a r e e s t i m a t e d , s i n c e n a t i o n a l s t a t i s t i c s do n o t
c o n t a i n such breakdown
2
a t t h e time t h e Declaration was signed, already contained a c o n c r e t e plan of
actions f o r achieving t h e above-mentioned goals.
P a r a g r a p h 7 of t h e Declaration states t h a t
". . . in
o r d e r t o success-
fully c a r r y out t h e foreseen measures, t h e governments of t h e Danube count r i e s will t a k e advantage of t h e possible cooperation with t h e United
Nations Organisation, with i t s specialized agencies as w e l l as with o t h e r
i n t e r e s t e d international organisations" (see Annex I).
In t h i s connection, t h e P r o j e c t Proposal of t h e UNDP/WHO European
Regional Bureau p r e p a r e d in 1986 d e s e r v e s special attention, identifying
t h e following goals f o r water quality protection of t h e Danube River:
-
t o safeguard human health by protecting drinking and irrigation water
s o u r c e s against pollution;
-
t o develop a common regional s t r a t e g y towards t h e effective control of
pollution of a l a r g e international r i v e r intersecting regions belonging
t o different socio-economic systems;
-
t o strengthen existing national water quality management practices;
-
to promote t h e t r a n s f e r and exchange of technology in water quality
control activities.
So f a r , 5 Danube countries have announced t h e i r readiness to p a r t i c i p a t e in
t h e program (WHO, 1986).
Similar close cooperation c a n b e established between IIASA and t h e
Danubian countries in t h e implementation of t h e p r o j e c t LIR and, especially
of t h e case study dealing with t h e Danube basin. Most of t h e countries have
a l r e a d y expressed t h e i r i n t e r e s t and also t h e i r willingness to p a r t i c i p a t e in
t h e development of t h e decision s u p p o r t system. F u r t h e r s t e p s are needed
t o create formal connection between t h e
LIR p r o j e c t and t h e panel
representing t h e signatory countries of t h e Declaration.
Finally, considering the close interrelationship between a n d ,t h e supplementary c h a r a c t e r of t h e two p r o j e c t s (i.e. IIASA/LIR and UNDP/WHO), i t
i s advisable to join t h e efforts of t h e two organisations in t h e implementation.
2. WATER RESOURCES OF THE DANUBE BASIN
2.1 Geographical Conditions
The r i v e r Danube is t h e 21st longest r i v e r in t h e world and t h e second
longest in Europe, being almost 3000 km long from i t s s o u r c e at a height of
1078 m in t h e Black Forests (FRG) t o i t s delta on t h e Black Sea (USSR). I t s
basin of 817 000 km2 r e p r e s e n t s 8%of t h e area of Europe. The c r e e k s Breg
and Brigach, with t h e i r springs in t h e Black Forest, get a new name
(Danube), downstream of t h e i r confluence at Donaueschingen. Between this
point and t h e delta t h e elevation difference i s 678 m and t h e length of t h e
r i v e r i s 2857 km (Benedek-Ldszlb,
1980). The bottom slope conditions of
t h e r i v e r Danube are shown in Figure 2 (Ldszldffy, 1967).
In t h e stream system of a huge r i v e r like t h e Danube, t h e r e are also
numerous important tributaries.
About 120 r i v e r s flow into t h e Danube
itself, from which t h e g r e a t e s t ones also have important t r i b u t a r i e s (of 2nd
o r d e r ) . A survey of t h e most important tributaries of 1st o r d e r is given in
Table 2.
According t o its geological s t r u c t u r e and geographic layout t h e
Danube basin can b e divided into t h r e e regions, namely t h e upper, middle,
and lower Danube basin.
a ) The u p p e r Danube b a s i n c o v e r s t h e t e r r i t o r y from t h e s o u r c e
streams in t h e Black Forest Mountain down t o the Devin Gate eastward from
Vienna. I t includes in t h e north t h e t e r r i t o r i e s of t h e Swabian and Falconian mountains, p a r t s of t h e Bavarian Forest and Bohemian Forest down t o
t h e Austrian Muhl- and Waldviertel, and t h e Bohemian-Moravian Uplands.
Southward from t h e Danube extends t h e Swabian-Bavarian-Austrian
foothill belt, comprising major p a r t s of t h e Alps up t o t h e watershed divide
in t h e crystalline Central Alps.
b) The m i d d l e Danube b a s i n c r e a t e s a magnificent and unique geographic unit. I t spreads from t h e Devin Gate, dividing t h e last promontories
of t h e Alps (Leitha Mountains) from t h e Little Carpathians downstream of t h e
confluence of t h e March/Morava and Danube, t o t h e mighty fault section
between t h e Southern Carpathians and t h e Balkan Mountains n e a r t h e Iron
Gate Gorge. The middle Danube section is t h e largest one. It is confined by
Donowschingen
t 18
Ulm
Kelheim
Regensbuq
o
Kre ms
Vim0
Brob slovo
Gobtikovo
No moros
s"%peS+
Adony
P
Fajq
Hohocs
Novi Sod
Belpmde
Orsovo
Turnu Sever in
Gruio
Cernovodo
Broilo
Figure 2.
-4
I
4.-1
Bottom slope conditions of t h e Danube (Liepolt, 1967)
Table 2
The major t r i b u t a r i e s of t h e Danube (RZdD, 1986)
Mouth a t
Danube Ian
nl e r
Inn
Tr aun
Enns
Ybbs
v&
Hron
Ipel
Si6
D r au/Dr 6va
Tisza/Tisa
Sava
Temes
Velika Morava
Timok
Jiu
Iskar
01t
Jantra
Vedea
Arges
Ialomit a
Siret
Prut
Length
h
Catchment
A722
right
right
left
left
left
right
right
right
right
right
left
left
Lech
81t m ' i h l
Naab
Regen
Isar
K-P
Mar c h h o r ava
Mosonyi Duna
(Lajta,R&ba,etc.)
Side
1 794
right
left
left
left
right
right
left
right
left
right
right
left
right
left
right
left
left
left
left
left
. l 8 061
t h e Carpathians in t h e north, by t h e Karnische Alps and Karawanken,
Julische Alps in t h e east and southeast, and by t h e Dinaric Mountains in t h e
west and south. This closed c i r c l e of mountains embraces t h e South Slovakian and East Slovakian Lowland, t h e Hungarian Lowland and t h e Transylvanian Uplands.
c ) The Lower Danube basin i s composed of t h e Romanian-Bulgarian
Lowland, t h e S i r e t and P r u t r i v e r basins, and t h e surrounding upland plat e a u s and mountains. I t is confined by t h e Carpathians in t h e west and t h e
n o r t h , by t h e Bessarabian upland plateau in t h e east, and by t h e Dobrogea
and t h e Balkan Mountains in t h e south. A t t h e P r u t mouth t h e Dobrogea promontories p r o j e c t into t h e Bessarabian upland plateau.
The Danube a c c e p t s waters from high mountains and t h e i r foothills,
from highlands, plains, lowlands, and depressions. T h e r e f o r e , its c h a r a c t e r
v a r i e s from a high-mountainous stream t o a lowland r i v e r .
The distribution of t h e Danube among i t s r i p a r i a n countries is as follows:
In t h e Federal Republic of G e r m a n y , from t h e confluence of t h e s o u r c e
streams Brigach and Breg down t o t h e Austrian b o r d e r , t h e Danube flows a
distance of 580 km. A r e a c h about 180 km long i s constrained by narrow
valleys in which t h e Danube c u t s i t s way through mountain ridges.
On a
s t r e t c h about 400 km long, t h e Danube passes through wide valleys.
The A u s t r i a n Danube i s about 350 km long, including 21 km as f r o n t i e r
r e a c h with t h e FRG and about 8 km with Czechoslovakia. About 150 km in
total consists of sections passing through narrow valleys in which t h e
Danube c u t s its way through mountain ranges. Over about 200 km t h e
Danube flows through t h e flatlands and four g r e a t basins. The descent of
t h e Danube in Austria is about 150 m.
The Czechoslovak portion of t h e Danube on t h e left (northern) r i v e r
bank r e a c h e s from t h e mouth of t h e Mach/Morava River about 172 km down-
stream t o t h e mouth of t h e Ipel'/Ipoly. The section on t h e r i g h t (southern)
r i v e r bank i s only 22.5 km long, t h e remainder being a n 8 km f r o n t i e r with
Austria, and a 142 km b o r d e r with Hungary.
The H u n g a r i a n Danube r e a c h i s 417 km long, within a n 142 km t h e
b o r d e r with Czechoslovakia.
I t starts on t h e mighty alluvial fan of t h e
stream at t h e u p p e r margin of t h e Pannonian Basin reaching a s f a r as t h e
c e n t r e of t h a t Basin.
The Y u g o s l a v i a n r e a c h of t h e Danube, which i s about 587 km long lies
mainly (358 km) in t h e Pannonian Basin. Along this f i r s t r e a c h , t h e slope of
t h e r i v e r i s only 0.05-0.04 p e r mill. Upstream from t h e fault g o r g e section
at t h e Iron Gate, close to t h e mouth of t h e Nera River, i t creates a common
b o r d e r with Romania and remains a f r o n t i e r r i v e r down to t h e Timok mouth,
about a 229 km long s t r e t c h .
In t h e downstream direction, t h e Danube i s a f r o n t i e r r i v e r between
Romania and Bulgaria on a 472 km long reach.
The Danube flows through a 1075 km long r e a c h of R o m a n i a n t e r r i t o r y , s t a r t i n g in t h e area of t h e middle Danube above t h e mountainous r e a c h
of t h e Iron Gate down to t h e e s t u a r y , so t h a t Romania h a s t h e l a r g e s t portion of t h e Danube course. From t h i s total length 229 km i s t h e b o r d e r with
Yugoslavia between t h e N e r a and Timok r i v e r s . A f u r t h e r 472 km long section i s t h e b o r d e r with Bulgaria. Downstream from t h e P r u t mouth t h e r i v e r
follows t h e b o r d e r with t h e Soviet Union on about 80 km down to t h e bend of
t h e Kilia branch and f u r t h e r to t h e Black Sea estuary (RZdD, 1986).
The Danube Delta, covering a n area of 5640 km2, i s t h e second l a r g e s t
one in Europe. Eighty p e r c e n t of i t belongs to t h e Soviet U n i o n and 20% t o
Romania (Liepolt, 1973).
2.2 Climate
Due to t h e elongated s h a p e of t h e Danube Basin in a west-east direction
and d i v e r s e relief f e a t u r e s , t h e climatic conditions are also r a t h e r variable. In t h e western regions of t h e u p p e r Danube, t h e r e i s a n Atlantic influence, while e a s t e r n t e r r i t o r i e s are more continental in climate. In t h e
u p p e r and middle Danube basin, especially in t h e Drau/Drdva and Sava
basins t h e climate i s also influenced by t h e Mediterranean Sea.
The basic c h a r a c t e r of climate, determined by t h e spacious layout of
t h e Danube, i s differentiated and modified by t h e mighty mountainous sys-
t e m s into natural regions.
The dependence of climatic elements on altitude is a f u r t h e r contribution t o t h e diversified climate, since t h e basin r e a c h e s from high mountain
r a n g e s covered with glaciers, o v e r h a r s h mid-mountains and upland platforms, t o hot (in summer) lowlands.
The climatic elements most important f o r water r e s o u r c e s management
are precipitation and snow cover. In t h e following, a detailed description of
t h e s e two elements will b e given. Note t h a t t h e basic l i t e r a t u r e (RZdD,
1986) contains more detailed information about t h e o t h e r climatic elements
(radiation, a i r t e m p e r a t u r e , evaporation, wind).
2.2.1 Precipitation
The amount of a v e r a g e annual precipitation fluctuates within t h e r a n g e
from 3000 mm in high mountains t o 400 mm in t h e delta region.
Already t h e u p p e r Danube b a s i n shows a n astonishingly variable
c h a r a c t e r . In t h e high alpine regions t h e values of 2000 mm are sometimes
surpassed, t h e mountain marginal belts being extraordinarily r i c h in precipitation. The increment of mean annual precipitation values amounts t o
about 50 mm p e r 100 m r i s e in height in t h e n o r t h e r n alpine promontories
and in t h e Alps. A f u r t h e r influence of mountains, o c c u r s o n t h e windward
slopes where precipitation i n c r e a s e s due t o o r o g r a p h i c lifting. Thus t h e
isohytes almost parallel t h e height contours of t h e mountains. In t h e northe r n alpine foothills t h e amount of precipitation d e c r e a s e s in this way from
about 1500 mm p e r y e a r on t h e p e r i p h e r y of t h e mountains t o 700 mm p e r
y e a r in t h e Danube valley. About 1500 mm p e r y e a r of precipitation fall
also in t h e Danube s o u r c e a r e a , in t h e Black Forest and in t h e higher
regions of t h e Bavarian and Bohemian Forests.
Other t e r r i t o r i e s show a v e r a g e precipitation values between 600 and
1000 mm, t h e valleys and basins (for instance t h e Naab valley, t h e Vienna
Basin) being relatively d r y with about 700 mm of precipitation. Relatively
d r y also are t h e intermontane valleys. The u p p e r Inn r i v e r valley, extending in t h e west-east direction
(Lower Engadin) is considered as a
c h a r a c t e r i s t i c interalpine d r y valley with only 600-700 mm of precipitation. Generally, t h e mean annual precipitation (annual s e r i e s 1931-1960) in
t h e German p a r t of t h e Danube catchment area amounts t o 950 mm p e r y e a r .
In t h e m i d d l e Danube b a s i n t h e highest values of mean annual precipitation o c c u r on t h e o u t s k i r t s of mountains surrounding t h e lowlands. The
highest precipitation values 2000 mm to 3000 mm show t h e effect of t h e
southward oriented mountain chains of t h e Julische Alps and t h e Dinaric
system, which are exposed t o t h e humid-warm a i r masses coming from t h e
Mediterranean Sea. In t h e Carpathians t h e mean precipitation values a r e
between 1000 and 2000 mm. In t h e rain-shadow of t h e mountains of t h e east
Bohemian-Moravian
Uplands, as w e l l as in t h e Carpathian Foothills, t h e
a v e r a g e precipitation amounts t o 600-1000 mm. In t h e southern p a r t of t h e
c e n t r a l Danube Lowland t h e annual precipitation d r o p s t o 600-800 mm, in
t h e Hungarian Lowland t o 560 mm, and in t h e region of t h e middle Tisza/Tisa
River t o 500 mm. The dryness of t h e climate increases in t h e middle Danube
Lowland in t h e n o r t h e r n and e a s t e r n directions.
In t h e plains of t h e Lower Danube t h e amount of precipitation r e a c h e s
also only 500-600 mm, while t h e lowest precipitation values are r e c o r d e d at
t h e Danube e s t u a r y with less than 400 mm. In some y e a r s t h e r e is no p r e cipitation at all o v e r t h e e n t i r e summer period. Due t o low precipitation
and high summer temperatures, t h e region of t h e Danube e s t u a r y may be
considered as a t e r r i t o r y with steppe climate (RZdD, 1986).
2.2.2 Snuw cover
The number of days with snow c o v e r as well as t h e duration and thickness of t h e snow c o v e r i n c r e a s e with t h e altitude. In alpine valleys only 58
days p e r y e a r are c h a r a c t e r i z e d with precipitation falling in t h e form of
snow (average o v e r t h e period 1931-1970), while on t h e Zugspitze (3000 m)
191dayswere recorded.
The s h o r t e s t duration of snow cover (9-12 days) i s a t t h e Black S e a
coast. The snow c o v e r lasts for only 20-30 days in t h e plains of t h e middle
Danube basin, 40-60 days in t h e u p p e r Danube basin, t h e mean proportion
of snow in t h e total annual precipitation being 10-15 p e r cent. In t h e alpine
foothills and in high regions of mid-mountains t h e snow c o v e r lasts more
than 100 days. In those regions about 20-30 p e r cent of t h e annual precipitation fall in t h e form of snow. A t a n the altitude of 1500 m t h e snow c o v e r
stays from f o u r months (Central Alps) t o 6 months (peripheral mountains).
A t a n altitude of 2000 m more than 6-8 months; and at 2500 m more than
8-10 months. The snow line is at a n altitude of 2900 m on humid windward
sides, and 3200 m in t h e Central Alps.
The snow cover stays f o r a longer period in t h e Carpathians than in t h e
Alps. A t altitudes above 2000 m t h e snow c o v e r lasts 300 days in t h e Tatras,
Bucegi, Fagaras and Retezat Mountains, and on t h e peak Lomnickf S t i t even
324 days.
In t h e highest mountain regions about 80-90% of t h e annual precipitation fall in t h e form of snow.
The snow cover thickness i s generally slight in plains and lowlands.
Snow, falling frequently already in October, lasts usually only 1-3 days.
Continuous snow c o v e r i s usually formed in December and January, reaching
t h e maximum of 15-20 cm in February, and melting away in March.
In
e x t r a o r d i n a r y cold winters, r i c h in snow, as f o r instance t h e period
1941-1942 in t h e u p p e r Danube basin, o r 1953-1954 in t h e lower Danube
basin, 40-60 cm snow thickness w e r e r e c o r d e d in t h e lowlands. Such snow
conditions are exceptions and are frequently followed by r a p i d warming,
causing partial o r complete snow melting.
In t h e medium altitudes of 1500-2000 m a snow cover starts to develop
already in October-November.
In February t h e a v e r a g e snow c o v e r thick-
ness may r e a c h 150-250 cm. The snow melt period lasts from March to May.
A t altitudes above 2000 m t h e snow c o v e r maximum is attained in Februa r y , t h e snow cover thickness reaching in some places 500 cm o r more.
The reliability and a c c u r a c y of d a t a on snow cover thickness d e c r e a s e
with increasing altitude above sea level.
Snow c o v e r thickness v a r i e s
locally due t o snow-drifts. A t high altitudes of t h e Carpathians and Alps
50-70 days with snow storms are recorded, while in the plains only 1-3 days
with snow s t o r m s o c c u r (RZdD, 1986).
2.3 Hydrological Regime of the Danube Basin
In t h e Danube .Basin, systematic hydrological observations in t h e
r i p a r i a n countries are available f o r between 1 0 0 and 150 y e a r s .
A t about t h e end of t h e last century t h e network f o r water level observations developed rapidly in t h e Danube Basin. By t h e beginning of o u r cent u r y , already s e v e r a l hundreds of gauging stations had been installed mostly
on t h e main r i v e r s . The development of r e g u l a r observation of t h e smaller
-
t h i r d rank
-
t r i b u t a r i e s h a s taken place, however, only a f t e r Second
World War. In 1950 t h e r e w e r e more than 1000 and today t h e r e a r e considerably more than 2000 gauging stations in t h e Danube Basin (RZdD, 1986).
2.3.1 Mean discharge conditions
The a v e r a g e runoff conditions of t h e Danube Basin are c h a r a c t e r i z e d
on t h e basis of d a t a s e r i e s of 48 gauging stations, from which 24 are on t h e
Danube itself and 24 on i t s most important t r i b u t a r i e s . Of course, when
selecting t h e s e gauging stations, n e i t h e r all requirements regarding
representativity and d a t a quality n o r length of r e c o r d , i.e., t h e full observation period 1931/70, could b e m e t .
Table 3 is a survey of t h e gauging stations selected and Figure 3 i s a
layout showing t h e s i t e s of t h e gauges.
The values MQ, MHQ and MLQ* computed from t h e d a t a s e r i e s of these
48 gauging stations, t h e r a t i o of t h e latter two values t o MQ as well as t h e
corresponding specific runoff values M q , M L q are listed in Table 4.
Figure 4 is t h e hydrological longitudinal profile of t h e Danube River.
The Upper Danube i s definitively c h a r a c t e r i z e d by t h e high runoff supplies from t h e Alps. Already t h e t r i b u t a r i e s Iller, Lech and I s a r bring considerable inflows but t h e g r e a t e s t and definitive change i s due t o t h e Inn
River. Although t h e catchment a r e a of t h e Inn, 26,130 km2, i s only 52% of
t h a t of t h e Danube till t h e mouth of t h e Inn, t h e mean annual discharge of
t h e Inn, 743 m3/s, s u r p a s s e s by 8%t h a t of t h e Danube itself. In t h e domain
of t h e mean flood discharges M H Q , this difference i s even h i g h e r (609.) and
only in t h e domain of mean low discharges MLQ is t h e value of t h e Danube
o or explanation o f t h e symbols M Q , M H Q , MLQ, M q , M H q , MLQ s e e f o o t n o t e t o Table 4 .
Table 3
List of selected aauges in the Danube Basin (RZdD, 1986)
Nr.
Gauge
River
Irm
3
4
Catchment
ar ea2
A. km
1
2
5
Observed
discharge data
from the ~eriod
6
Danube
Danube
Danube
Danube
Danube
2
2
2
2
2
458.3
376.1
256.9
225.3
135.2
20 001
35 399
47 496
76 597
79 490
1931-1970
1931-1970
1931-1970
1931-1970
1931-1970
Stein--ems
7 Wien-Iiussdorf
8 Bratislava
10 ~ u n a a l d s
Danube
Danube
Danube
Danube
2 002.7
1934.1
1 868.8
1 751.8
96 045
101700
131 338
171 720
1931-1970
1931-1970
19 31-1970
1948-1970
11
12
13
14
15
Naggmaros
MoGcs
Bezdan
Bogojevo
~anEevo
Danube
Danube
Danube
Danube
Danube
1
1
1
1
1
183
209
210
251
525
534
064
250
593
009
1931-1970
1931-1970
1931-1970
1931-1970
1931-1970
16
17
18
19
20
V. ~radiite
@:ova
Novo Selo
Lom
Svistov
Danube
Danube
Danube
Danube
Danube
1 059.8
955.0
833.6
743.3
554.3
570 375
576232
584900
588 860
650 340
1931-1970
1931-1970
1937-1970
1941-1970
1931-1970
Danube
Danube
Danube
554.0
495.6
658 400
669 900
1931-1970
1931-1970
375.5
689 700
1941-1970
Danube
Danube
252.3
72.0
709 100
807 000
1931-1970
1931-1970
1 rzlgolstadt
2 Regensburg
3 Hofkirchen
4 Passau-Ilzstadt
5 Linz
6
21 Zimnicea
22 Ruse
23
Silistra
24 Vadu Oii-Hirsova
25 Ceatal Izmail
694.6
446.8
425.5
367.4
153.3
Pas sau-Ingl ing
Salzburg
S t egr
Moravsky Jan
Sala
Inn
3.1
Salzach
64.4
EXI~S
30.88
March/Morava 67.6
Vah
3309
26
4
5
24
10
B r ehy
Hron
102 05
I p e l ' /Ipolg 42.9
Drau/Dr&va 481.2
Mu/Mura
114.4
3 82l
4 838
1 0 415
8 340
Csenger
Pel sBz a01ca
Mako
S r ,Mitrovica
L joblost
Sornes/Szamos 46.6
~ l a n & / S a6j 50.1
Idures/Maros 23.7
Sava
136.0
Q. Morava
39.9
15
6
30
87
37
Orahovica
Stoenesti
Storozinec
Lungoci
C ernovci
Iskar
01t
Siret
Siret
Prut
Ipelsky Sokolec
X?eubrUcke
Landacha
084
427
915
129
620
Donji Miholjac
Qilok
Tiszabecs
Szeged
Senta
27 05
71 -2
448 0
74.0
772 -0
283
440
149
996
320
8 370
22 683
672
36 036
6 890
Table 4_
Characteristic discharge values for the observation periodx) (RZdD. 1986)
Ingolstadt/Danube
308
Regensburg/Danub e
435
645
Hofkirchen/Danube
Passau-Ilzstadt/Danub e 1430
Linz/Danube
1509
S tein-Krems/Danube
1864
Wien-Nussdorf/Danube 1943
Bratislava/Danube
2020
~unaalm6s/~anube
2314
symbols adopted are the following:
catchment area
multiannual mean discharge
: MQ/A -multiannual specific mean discharge
mean of annual peak discharges
= MHQ/A
multiannual specific flood discharge
mean of annual lowest discharges
= MLQ/h multiannual specific low discharge
-
-
-
-
-
Nagyrnaros/Danube
Mohdc s/Danub e
Be z dan/Danub e
Bogo j evo/Danube
Pancevo/Danube
2379
2389
2479
306 0
5490
Vadu Oii-Hir sova/
6216
, Danube
Ceatal Izmail/Danube 6550
Moravsky Jan/MsrchMorava
Sal a/V&
110
152
32. Ipelsky Sokolec/Ipel
21
33. Neubr Ucke/Drau/Drdv,a
266
208
910
36. Don ji Mihol jac/
Dr au/Dr 6va
5 54
1341
/IPO~Y
1 e9
98.3
9.90
3.42
0.09
0. 37
23 5
2.42
0.42
4.34
25.5
43 *O
87 *4
0.38
9.44
LOO
Fimure 4.
4
I'
H v d r o l o n i c a l l o n n i t u d i n a l u r o f i l e of t h e D a n u b e (RZdD, 1986)
16% h i g h e r t h a n t h a t of t h e Inn. Considering t h e d i f f e r e n t specific runoff
values, t h o s e of t h e Inn Basin are significantly h i g h e r in all t h r e e domains.
Danube b e f o r e Inn
6.46
13.6
Inn
9.85
28.5
Danube a f t e r Inn
7.46
19.0
39.2
114
53.8
The high specific runoff values of t h e Danube a f t e r t h e mouth of t h e
River Inn are somewhat f u r t h e r increased by t h e Austrian alpine t r i b u t a r i e s Traun, ~ b n and
s Ybbs (Mq and MLq), o r , at l e a s t k e p t constant till t h e
mouth of t h e March/Morava River ( M H q ) .
The mean annual d i s c h a r g e
i n c r e a s e s from 1430 m3/s at t h e mouth of t h e Inn t o a b o u t 1950 m3/s at t h e
gauging station of Wien-Nussdorf with a catchment area of 102,000km2.
Until t h e mouth of t h e Drau/Drdva River, t h e catchment area redoubles t o a b o u t 210 000 km2 while t h e mean d i s c h a r g e i n c r e a s e s only by 530
m3/s r e a c h i n g t h e value of 2,480 m3/s above t h e mouth of t h e Drau/Drdva
River.
Except t h e West Carpathians (V&I
14.3 l/s.km2 and Hron 13.1
l/s.km2), t h i s g r e a t intermediate catchment a r e a is v e r y low in precipitation
and runoff (March/Morava 4.5 l/s.km2, Ipelt/Ipoly 4.3 l/s.km2).
In t h e Hun-
g a r i a n Lowland t h e specific runoff values fall even below 3 l/s.km2.
Correspondingly, t h e specific runoff values computed f o r t h e whole (accumulated) catchment a l s o d e c r e a s e (MLq from 7.9 t o 4.6 l/s.km2, Mq from
19.1 t o 11.8 l/s.km2).
The l a r g e s t d e c r e a s e i s t h a t of t h e mean specific
flood runoff MHq (from 53 t o 23.4 l/s.km2) due t o t h e lowering of t h e peak
d i s c h a r g e s along t h i s long r i v e r r e a c h by t h e l a r g e r e t e n t i o n capacity of
t h e considerable a r e a s inundated on t h e flood plain.
Within t h e following 270 km long Danube r e a c h in Yugoslavia, t h e t h r e e
g r e a t e s t t r i b u t a r i e s join t h e Danube. They i n c r e a s e t h e accumulated catchment area of t h e Danube by 150% (from 210,000 km2 at Bezdan t o 525,000
km2 at Pancevo) and t h e mean discharge by 120%from 2480 m3/s t o 5490
m3/s. These t r i b u t a r i e s are: t h e Drau (Drava) r i v e r (A
= 40,000 km2, MQ =
= 157, 000 km2, MQ = 766 m3/s), and t h e
Sava r i v e r (A =95, 700 km2, MQ = 1610 m3/s). The increase rates of t h e
554 m3/s), t h e Tisza (Tisa) r i v e r (A
mean low discharge (from 976 t o 2,240 m3/s) and of t h e mean flood discharge
(from 4,290 m3/s t o 10,070 m3/s) a r e more or less t h e same. The relatively
high runoff rates of t h e Drau/Drava (Mq =15 l/s.km2) and t h e Sava River
(Mq = 18 l/s.km2) originate from t h e rainy catchments of t h e Southern Alps
and t h e Dinaric Mountains. On t h e o t h e r hand, t h e Tisza/Tisa r i v e r , collecting t h e major p a r t of t h e waters of t h e Hungarian Lowland, achieves at its
mouth only a mean specific discharge of 5.4 l/s.km2 in s p i t e of its many t r i butaries from t h e Carpathians.
Contrary to t h e absolute values mentioned, t h e changes of specific runoff rates r e l a t e d t o t h e accumulated catchment area of t h e Danube are not
significant along this 270 m long r e a c h :
Wq
from
4.6
to
4.3
l/s.km2
Mq
from
11.8
to
10.4
l/s.km2 and
MHq
from
23.4
to
19.2
l/s.km2
Along t h e about 1,000 km long r e a c h between t h e Iron Gate and t h e
mouth of t h e Danube in t h e Black S e a , t h e catchment a r e a i n c r e a s e s by
almost 300,000 km2 up t o 817,000 km2 while t h e increase of t h e mean annual
discharge i s only about 1000 m3/s (from 5,490 t o 6,550 m3/s). The niean
specific runoff from this area is, in s p i t e of inflows from t h e Carpathians
(Olt 7.1 l/s.km2) and t h e Balkan Mountains (Iskar 7.1 l/s.km2), r a t h e r low:
3.7 l/s.km2, i.e.
even lower than t h e specific runoff from t h e relatively
poorly contributing a r e a between t h e mouths of t h e March (Morava) and t h e
Sava r i v e r s with its 4.9 l/s.km2.
Although t h e d e c r e a s e of t h e mean specific runoffs r e l a t e d t o t h e
whole (accumulated) Danube Basin seems to b e insignificant (Mq from 10.4 t o
8 . 1 l/s.km2, MLq from 4 . 3 t o 3.6 l/s.km2 and MHq from 19.2 to 13.2 l/s.km2),
t h e r e a l e x t e n t of t h e changes will b e c l e a r when considering t h e r e l a t i v e
indices of d e c r e a s e , which are: f o r Mq 22%, f o r MLq 15%and f o r MHQ 31%.
The disproportionately strong d e c r e a s e of t h e mean specific flood runoff
also shows t h e impact of t h e long r i v e r bed r e a c h e s and t h e relatively l a r g e
inundation areas.
The i n c r e a s e of t h e discharge along a r i v e r c a n also b e visualized by
duration curves. They a r e shown, f o r selected gauging stations of t h e
Danube, in Figure 5.
The seasonal changes of t h e multiannual means of t h e monthly discharges
c a n b e applied, in connection with t h e climatic f a c t o r s of t h e runoff event,
f o r t h e description and characterization of t h e hydrological regime. The
variation of t h e monthly mean discharges along t h e Danube are shown in
Figure 6.
The monthly discharges of various probabilities are shown f o r one selected
station in Figure 7 (UjvAri, 1967; RZdD, 1986).
2.3.2 Flood conditions
Flood events can o c c u r in t h e whole Danube Basin both due t o storms o r
to snowmelt and rain. In t h e second case, t h e runoff is increased also when
t h e soil i s frozen or water-saturated.
The floods caused only by snowmelt
a r e hardly dangerous in t h e Upper Danube Basin. However, t h e importance
of floods is quite high f o r t h e f l a t catchments along t h e Middle and Lower
Danube.
In t h e alpine region, summer cold a i r intrusions are of p a r t i c u l a r
importance since they t r i g g e r low-pressure activities in t h e Mediterranean
region. In t h e warm s e c t o r of low-pressure a r e a s moving from t h e Gulf of
Genoa in n o r t h e r n or north-eastern directions o v e r t h e Alps, t h e v e r y hot
and vapor-saturated a i r of t h e Mediterranean region i s c a r r i e d in t h e
n o r t h e r n direction. When t h e migration velocities are slow, t h e precipitations c a n last s e v e r a l days and cause considerable floods, beginning in t h e
southern alpine region (catchments of t h e Drau (Drbva) and ,of t h e Upper
Figure 5.
Discharge duration curves of selected gauges on the Danube
(RZdD, 1986)
Figure 6.
Inter-annual distribution of monthly mean discharges along t h e
Danube (RZdD, 1986)
LOO -
4
I
Figure 7.
n
4
2
II I V V VlvlVIIlX X X I X I I
Inter-annual distribution of monthly mean discharges of various probabilities at t h e gauge Danube/Mohdcs, 1930/70 (RZdD,
1986)
Sava rivers), through t h e Bohemian Forest and t h e north-eastern domains of
t h e Carpathians, up t o t h e basin of t h e Oder (Odra) r i v e r . On t h e n o r t h e r n
edge of t h e Alps, this weather situation is often connected with enhanced
precipitation coming from West o r Northwest. Above them, a humid, w a r m
a i r from t h e South streams causing additional abundant orographic precipitation. The g r e a t floods of 1940, 1954, 1965 and 1966 were caused by this
type of weather situations. Additionally, a snowmelt in t h e mountains may be
superimposed covering g r e a t height differences from t h e v e r y low up t o t h e
v e r y high regions. This happened during t h e floods of 1940 and 1965.
Summer storms c a n lead t o g r e a t o r even v e r y g r e a t floods almost in
t h e whole Danube Basin. In t h e southern regions under Mediterranean influe n c e t h e r e is a f u r t h e r storm period in late autumn (mostly November)
which also c a n cause g r e a t floods (Drau/Drdva, Sava and t h e t r i b u t a r i e s
from t h e Balkan Mountains).
The g r e a t e s t floods known on t h e Danube upstream from t h e mouth of
t h e Inn were due t o snowmelt with r a i n onto a more o r less frozen soil s u r f a c e (March 1945, F e b r u a r y 1862, December/January 1881/1882). During
t h e common observation period 1931/70, floods of March 1947 and March
1956 along t h e u p p e r Danube r e a c h gave only a slight idea of what n a t u r e
could do in t h a t a r e a . Along t h e c o u r s e of t h e Danube, both floods mentioned r e a c h e d really considerable dimensions. This type of flood
melt combined with spring precipitation
-
-
snow
o c c u r s on t h e middle and lower
Danube, particularly downstream from t h e Tisza (Tisa) mouth, relatively
often with g r e a t discharges.
The seasons o r months, respectively, in which t h e probability f o r flood
surpassing (e.g. s e e
events is t h e highest, c a n be r e a d from t h e c u r v e of 1%
Figure 7). This does not exclude, of course, t h e possibility of g r e a t floods
c a n o c c u r during o t h e r periods as well. A s examples of t h i s situation, t h e
floods on t h e r i v e r Inn of February 1862 (4,500 m3/s), September 1899
(6,600 m3/s) and September 1920 (5,310 m3/s) can be mentioned.
In e a r l i e r times, along s e v e r a l Danube r e a c h e s t h e r e were also floods
due t o i c e jams. They caused g r e a t damages and were t h e r e f o r e v e r y much
f e a r e d . The danger of such floods decreased considerably due t o r i v e r
training. The floods are practically eliminated along t h e Upper Danube, due
t o t h e closed b a r r a g e chain from Ulm t o Vienna. A s a r e s u l t of t h e operation of t h e b a r r a g e s , no i c e d r i f t t a k e s place any more along this s t r e t c h .
R a r e cases can be mentioned as exceptions when a v e r y s h a r p cold wave
o c c u r s during a flood.
The propagation of floods along the Danube may follow v e r y different
forms. For example, a mighty flood on t h e Upper Danube, such a s t h a t of
1954, can flatten out as i t moves toward t h e Lower Danube 'in such a way
t h a t i t will b e absorbed t h e r e by t h e recession hydrograph of a small,
belated spring flood (Figure 8). On t h e o t h e r hand, i t might a l s o happen
t h a t s m a l l incipient flood waves on t h e u p p e r r e a c h develop t o g r e a t floods
on t h e Middle and Lower Danube. I t also can clearly b e recognized t h a t t h e
wave peaks c a n considerably flatten along t h e long t r a n s p o r t r e a c h e s and
t h e relatively g r e a t flood plains of t h e Middle and Lower Danube whenever
t h e intermediate areas d o not contribute t o a f u r t h e r sharpening of t h e
flood event (RZdD, 1986).
2.3.3 Low-water conditions
The seasons o r months, respectively, in which low discharges (streamflow droughts) often o c c u r , are v e r y w e l l recognizable from t h e form of t h e
99% exceedance c u r v e (e.g. Figure 7). Since t h e duration of low discharges
generally i s longer, t h e i r impact on t h e mean discharge of t h e corresponding month is also s t r o n g e r than t h a t of a s t e e p flood wave with a s m a l l water
volume. Thus, t h e graphical representations are more reliable as f a r as
t h e o c c u r r e n c e of streamflow droughts i s concerned than in r e s p e c t t o t h e
o c c u r r e n c e of floods. Low discharges can v e r y often b e observed along t h e
whole Danube in autumn and winter. Due to t h e variability of t h e f e a t u r e s of
t h e various catchments, t h e minimum values o c c u r in one place mostly in
autumn, and in winter in o t h e r catchments.
The absolute minimum values almost coincide in time from t h e s o u r c e to
t h e mouth of t h e Danube, since t h e events resulting in low discharges
depend on a synoptic weather situation of long duration.
Such a case happened in t h e autumn of 1947 when extremely low
discharges were observed along t h e e n t i r e Danube. During t h e period from
30 August t o 2 November t h e r e w a s almost no precipitation (its value being
in t h e surroundings of Vienna only 13%of t h e multiannual a v e r a g e value of
t h a t period), leading to an extreme drought and v e r y low discharges in all
streams of t h e Danube Basin.
lngolstadt
Regensburg
Hofkirchen
tim
Pantevo
V. ~radigte
Orsovo
Nwo Selo
Lorn
Svistov
Ruse
Si listra
Vodu Oii
MAY
Figure 8.
I JUNE 1
\\
JULY IAUGUST. ISEPT.
I
Flood hydrographs at different gauging stations on t h e Danube
in 1954 (RZdD, 1986)
In January 1954, a more extreme low discharge o c c u r r e d along t h e
whole Danube, even lower than in 1947. A longer d r y period in t h e autumn
of 1953 had been followed by a cold winter s o t h a t t h e whole precipitation
was accumulated in t h e snow cover. In such a way t h e y e a r 1954 brought f o r
a long r e a c h of t h e Upper Danube two v e r y r a r e extremes:
t h e low
discharges in January and t h e mighty flood in July.
In t h e y e a r s 1933, 1934, 1948 and 1964 f u r t h e r very clear-cut streamflow drought periods were observed along t h e whole Danube.
The low
discharges along t h e Danube f o r all t h e periods mentioned are graphically
r e p r e s e n t e d in Figure 9. The inhomogeneities, recognizable in t h e figure
might b e due t o t h e problems of discharge measurements, which c a n b e cons i d e r a b l e not only in t h e r a n g e of high discharges but in t h a t of low ones as
well.
The low discharges of a n area (base flow) depend mostly on t h e amount
of water s t o r e d e i t h e r on t h e s u r f a c e (in lakes) o r in t h e aquifers. Along
t h e Upper Danube, t h e r e are two contrasting extremes: t h e foothill b e l t of
t h e Alps, r i c h in lakes and extended gravel fields on t h e southern side,
while in t h e n o r t h , t h e Bavarian and Bohemian Forests are made of basement
r o c k s , which have poor s t o r a g e capacity.
For general characterization of t h e low discharge conditions of a r i v e r
o r a catchment area, one could use, besides t h e a v e r a g e low discharge
period, also t h e r a t i o MLQ:MQ (see Table 4, RZdD, 1986).
2.3.4 Water balance of the Danube basin
The water balances t o b e compiled f o r t h e whole Danube basin as well
as f o r i t s balance a r e a s (subcatchments and national a r e a s ) is confined t o
t h e most simple variant of t h e water balance:
only t h e long-term mean
values of t h e t h r e e basic balance elements:
-
-
precipitation (P)
evaporation (E)
runoff (R)
will b e investigated. In t h i s case, i t is not necessary t o s e p a r a t e t h e components of precipitation (rain and snow), a e r i a l evaporation (soil evaporation, f r e e water s u r f a c e evaporation and transpiration of plants), and runoff (surface runoff, intermediate flow, groundwater runoff).
Since t h e
water consumption of water u s e r s i s considerable only in t h e case of irrigation and t h e a r e a of i r r i g a t e d fields is relatively low in t h e basin, t h e
d i f f e r e n c e between water intake a n d r e t u r n flow i s also negligible in t h e
long t e r m a n d l a r g e s c a l e water balance. T h e r e i s a f u r t h e r simplification
a c c e p t a b l e when long-term mean values are considered in t h e balance equation: t h e c h a n g e s of t h e w a t e r volume s t o r e d in t h e soil a n d on t h e t e r r a i n
c a n a l s o b e neglected (Domokos-Sass, 1986).
The balance elements mentioned a b o v e h a v e b e e n investigated f o r t h e 47
sub-catchments of t h e Danube basin.
The w a t e r balance elements of t h e most important sub-catchments of
t h e Danube basin are listed in Table 5, grouped according t o t h e physicogeographical c h a r a c t e r of t h e sub-catchments:
high mountains, mid-
mountains a n d hilly regions.
The sub-catchments of t h e high mountainous region, all of them in t h e
Alps (with t h e exception of t h e Vdh catchment) p r o v i d e a v e r a g e t e r r i t o r i a l
p r e c i p i t a t i o n values between 900 a n d 1500 mm. The runoff coefficient is
between 0.44 a n d 0.68.
While Table 5 yields information about t h e w a t e r b a l a n c e and runoff
coefficient conditions of t h e t r i b u t a r i e s , Table 6 contains s t a t i s t i c s on
w a t e r balance elements a n d runoff coefficients f o r t h e accumulated c a t c h ments of 5 d i f f e r e n t Danube sections.
The contribution of e a c h Danube c o u n t r y t o t h e total d i s c h a r g e leaving
t h e c o u n t r y ' s downstream b o r d e r c a n b e calculated from t h e d a t a of t h e
water balance:
1. F e d e r a l Republic of Germany
90.5%
2. Austria
62.2%
3. Yugoslavia
34.8%
4. Czechoslovakia
32.5%
5. Romania
17.4%
6. Soviet Union
9.5%
7. Bulgaria
7.4%
8. Hungary
5.0%
Water balances f o r s e l e c t e d r e g i o n s of t h e Danube Basin
(RZdD, 1986)
----
-
--
-
Subcat chment
r .
River
-
- -
Areal mean value of
Precipi&aporatation
tion
E
P
b2
mm/a
mm/a
H i g h m o u n t a i n s
Catchment
ezea
Runoff
R
mm/a
Runoff
coef f icient
& = -
R
P
2 Lech
6 Iser
8 livl
1 0 Ezlns
1 4 V&
4 398
8 369
26 976
5 940
9 714
1 349
1 174
1 315
1 483
536
536
436
483
534
769
614
868
1 016
415
0- 57
0.52
0.66
0.68
0.46
24 Drau/Drdva
28 Sava
41 810
94 778
1 091
998
575
634
435
514
0 44
0.47
9 06
Mid-mountains and h i l l y l a n d
645
633
702
415
251
767
640
738
694
809
49 0
483
592
549
514
288
141
130
157
290
0.37
0.22
0.18
0.23
0.36
I p e l '/Ipoly
4 594
sib
1 5 129
Tisza/Tisa 158 182
V. Morava
38 233
Jiu
1 0 731
-661
663
744
746
831
531
572
560
540
576
139
177
216
278
0.21
0.12
0.24
0.29
0. 33
7 811
24810
3 380
11 814
1 0 305
7 25
873
599
800
738
455
592
512
577
556
230
234
66
190
146
0.32
0.27
0.11
0.24
0.20
45 420
28 945
757
606
550
470
1.57
96
0.21
0.16
4
12
13
16
Naab
lldarch
~aab/Rdba
Nitra
18 Hron
20
22
26
30
32
34
36
38
40
42
Isk~r
Olt
Lorn
Arges
Ialomita
44 S i r e t
46 Prut
5
27
14
5
5
81
Table 6
Runoff balances of selected Danube s e c t i o n s (RZdD, 1986)
Name of
boundary
s e c ti o n
Ca,tchment
sea
hn2
Areal mean value of
pr e c i p i t a runoff
tion
P
R
mm/a
mm/a
Danube t o
Lech
1 5 654
Danube upstream of
92 154
Danube LIPstream of
Tisza/Tisa
423 182
834
301
Danube upstream of
Sava
529 156
878
337
Danube mouth
817 000
816
264
Runoff
coefficient
*=
-PR
The difference between 100% and t h e above percentage values is p a r t
of t h e t r a n s i t water volume which generally increases from t h e source down
t o t h e mouth of a r i v e r .
2.3.5 Water temperature and ice conditions
The annual a v e r a g e water temperature of Danube v a r i e s between 9 and
12°C. The minimum temperature is 0°C along t h e whole r i v e r , whereas t h e
maximum i s 21"-28°C. Midsummer r a n g e s of t h e t h r e e r e a c h e s are 16-17°C.
18-22°C and 22-23.5"C.respectively (WHO,1982).
Standing ice c o v e r occurs usually in January. The period of permanent
ice c o v e r is 5-8 days in t h e u p p e r Danube, 22-23 days downstream of the
confluence with t h e Drau/Drdva r i v e r and 28-30 days in t h e delta region
(Liepolt, 1973).
I t should b e noted t h a t e a r l i e r i c e statistics may be misleading, due t o
w a r m water discharged into the r i v e r (sewage and industrial waste water,
cooling water of power plants), t h e effect of r i v e r b a r r a g e s and t h e activity
of i c e - b r e a k e r vessels (cfr. P a r a 2.3.2).
3. ECONOMIC CONDITIONS OF THE DANUBE BASIN
A s h o r t review i s given h e r e for each Danubian country, summarizing
t h e most important economic activities and land use forms within t h e catchment.
Federal R e p u b l i c of G e r m a n y . In t h e southern p a r t of Bavaria t h e r e
are natural gas, oil and brown coal r e s o u r c e s .
In t h e vicinity of t h e
Czechoslovakian b o r d e r pirite, lead, zinc, tin and brown coal r e s o u r c e s c a n
b e found. The a g r i c u l t u r e i s characterized by ploughland cultures and
livestock breeding. In addition, meadow and grassland c u l t u r e are a l s o well
developed. In t h e southern p a r t t h e r e are l a r g e forests.
A u s t r i a . Here brown and black coal, various metals, natural oil and
gas r e s o u r c e s are available. Crop lands are mostly confined to t h e basin of
Vienna and to t h e southeast zone of t h e country, n e a r t h e Hungarian
b o r d e r . More than half of t h e country's a r e a i s covered by f o r e s t s , while
non-fertile a r e a s extend in t h e highest regions of t h e Alps with permanent
snow and i c e cover.
C z e c h o s l o v a k i a . In this p a r t of t h e Danube basin, along t h e lower
r e a c h of t h e March/Morava r i v e r , t h e r e are natural oil and gas r e s o u r c e s ,
while in t h e basins of the. Hron and Vdh r i v e r s various metal o r e s , smaller
natural gas and brown coal r e s o u r c e s are found.
Ploughland c u l t u r e s
c h a r a c t e r i z e t h e valley of Morava r i v e r and t h e southern p a r t of Slovakia.
The middle and u p p e r p a r t s of Slovakia a r e mostly covered by f o r e s t s with
p a s t u r e s and meadow cultures in t h e valleys.
Hungary i s characteristically agricultural country with a fairly well
developed industry.
The main agricultural products are: wheat, maize,
s u g a r beet, potato, g r a p e s f o r wine, f r u i t s , fodder, vegetables. Livestock
breeding is a l s o developed. Mining and mineral r e s o u r c e s involve: bauxite,
brown coal, natural g a s and oil, lignite, uranium, bentonite, gravel, pirite.
Y u g o s l a v i a i s r i c h in mineral resources. Coal and ore r e s o u r c e s a r e
abundant (copper and bauxite being t h e most important), while oil and gas
r e s o u r c e s a r e s c a t t e r e d . Cropland culture dominates in t h e n o r t h , and
grassland and p a s t u r e in t h e south. Forests c o v e r t h e land at h i g h e r elevations.
Romania is also r i c h in mineral r e s o u r c e s . H e r e r i c h natural gas and
oil r e s o u r c e s are well known. There are considerable black coal r e s o u r c e s
too. Non-ferrous metals can b e found a t s e v e r a l locations. The majority of
t h e country's t e r r i t o r y is cropland. The mountainous regions of t h e Carpathians and the Transylvanian Middle Ranges are covered with f o r e s t s and
-
extensive pastures.
B u l g a r i a . This p a r t of t h e Danube basin consists of mainly agricul-
t u r a l land. In t h e vicinity of Sofia brown coal, and along the north-west
b o r d e r black coal r e s o u r c e s c a n b e found. Forests c o v e r t h e ridges of t h e
Balkan Mountains along t h e basin.
USSR. Most of t h i s p a r t of t h e Danube basin belongs to t h e catchment
of t h e P r u t r i v e r , and is mainly agricultural land. There is no significant
mineral r e s o u r c e (Rado, 1985).
Along t h e banks of t h e Danube, t h e r e a r e 1 0 major c i t i e s with a population exceeding 100,000:
Regensburg (125,000), Linz (260.000). Vienna
(1,650,OOO), Bratislava (250,000), Budapest (2,000,000), Novisad (170,000),
Beograd (1,100, OOO), Braila (120,000), Galati (150,000), Ruse (176,000).
Other major cities (over 100,000 inhabitants) in t h e Danube basin a r e Munich, Augsburg, Innsbruck, Salzburg, Graz, Miskolc, Debrecen, Szeged, PBcs,
Gyor, Nyiregyhdza, SzBkesfehBrvAr, Kecskemdt, Zagreb, Osijek, Subotica,
Bucaresti, Brasov, Cluj-Napoca, Timisuara, Jasi, Craiova, Oradea, Arad,
Sibiu, Bacau, Pitesti, Tirgu-Mures, Baie Mare, Satu Mare, Sofija, Pleven
(Radd, 1985).
The waterway provided by t h e Danube enhances t h e development of
industries: t h e gradual improvement of this waterway allows t h e transportation of more and more cargo.
In t h e Danube basin tourism r e p r e s e n t s also a significant economic factor.
Among the water uses fishery plays an important role with a total c a t c h
of 4,400 tons/year (Table 8). A f u r t h e r 45,000 ton/year are taken from
ponds in t h e floodplains and t h e delta (Liepolt, 1973).
The GNPs p e r c a p i t a in t h e countries of t h e Danube basin are summarized in Table 7 (Radd, 1985).
4. UTILIZATION OF WATER RESOURCES IN THE DANUBE BASIN
The development of water management in the countries of t h e Danube
basin depends on t h e i r geographical location and on t h e d e g r e e of economic
development. In the u p p e r p a r t of t h e basin t h e morphological and climatic
conditions limit t h e development of irrigation.
In t h i s region t h e basic
forms of water uses are t h e industrial and drinking water supply, and
hydroelectricity generation. The o t h e r important type of hydraulic s t r u c t u r e s i s t h e canalization of t h e r i v e r by constructing b a r r a g e s .
These
s t r u c t u r e s facilitate t h e utilization of t h e continuously renewing energy
content of the r i v e r , improve navigation and reduce t h e r i s k of floods. The
canalization w a s also extended to t h e upper r e a c h e s of t h e tributaries.
Along t h e middle and lower r e a c h e s of t h e Danube, flood protection,
r i v e r regulation, agricultural, industrial and communal water supply are
t h e dominating water uses.
Along the lower Danube a n i n c r e a s e in t h e
demand f o r supplementary irrigation i s expected (WHO, 1982).
The water demand d a t a within t h e basin estimated f o r t h e y e a r 1980 and
predicted f o r 2000 are summarized in Table 9 (OMm, 1975; Kovdcs et al.
1983). I t i s interesting to note t h a t t h e prediction assumed a n annual
i n c r e a s e of 4-6% in water demand. Considering t h e world-wide economic
recession which strongly affected t h i s region, t h e estimated i n c r e a s e might
b e exaggerated. By evaluating t h e p r e s e n t conditions i t c a n b e supposed
Table 7
GNP per capita in the countries of the Danube Basin
(~ad6,1985)
Country
FRG
Austria
Czechoslovakia
Hungary
Yugoslavia
Rumania
Bulgaria
USSR
t h a t t h e demand p r e d i c t e d f o r 2000 will b e achieved only during t h e f i r s t
q u a r t e r of t h e n e x t c e n t u r y . The slowing down of t h e i n c r e a s e in demand
especially c h a r a c t e r i z e s t h e development of irrigation.
The l a r g e s t amount of w a t e r a b s t r a c t e d from t h e Danube a n d i t s tribut a r i e s is used f o r cooling p u r p o s e s in industry, a n d in thermal a n d n u c l e a r
power plants. I t was e a r l i e r estimated t h a t up to 20 n u c l e a r r e a c t o r s are
likely t o be c o n s t r u c t e d within t h e basin (IAEA, 1975). However, only
are now operating.
7
Table 8
Annual average f i s h catch i n the Danube River
(Liepolt, 1973)
country
t/~ear
FRG
Austria
Czechoslovakia
HW=Y
Yugo slavia
Rumania
Bulgsria
USSR
Total
4400
5. HYDROTECHNICS
5.1 Preliminary Remarks
The development of hydraulic s t r u c t u r e s and water r e s o u r c e s management along t h e Danube and in i t s basin i s closely i n t e r r e l a t e d with t h e
development of population, economy, c u l t u r e and technology in this region.
Constructions have always served t h e fulfillment of actual requirements and
have utilized t h e available technical and economic tools.
The f i r s t hydraulic s t r u c t u r e s in t h e basin originate from t h e time of
t h e Roman Empire. The middle ages w a s a period of stagnation, in accordance with t h e low demands. The basis of t h e p r e s e n t water management w a s
laid down in t h e second half of t h e 18th century, when t h e increase in both
Table
2
Water consumption of t h e c o u n t r i e s i n t h e Danube Basin
(OWE, 1975; Kovdcs e t al. 1983)
communal
and
Irriga- pishe-
lotal
Communal
and
Industrial
Irrigati o n
Fisheries
Total
Industrial
ries
FRG
170
-
Czechoslovakia
220
1970
12
2202
591
3740
12
4343
Hung-Y
411
4710
265
5 386
729
9297
282
10308
Yugoslavia
224
1220
95
1539
381
4056
95
4532
Rumania
595
12760
623
13978
984
26934
698
28616
Bulgaria
148
5680
-
5828
201
8608
-
8809
82
1029
18
1129
85
1738
20
1843
1970
27606
1013
30589
3481
55055
1107
59643
USSR
Tot a1
population and economy considerably a c c e l e r a t e d in t h e basin. Since then,
t h e requirements f o r t h e r i v e r s and water r e s o u r c e s rapidly increased.
The m o s t important demands were: r i v e r s should b e navigable by l a r g e r
ships independently from the discharge conditions; in t h e frequently inundated r i v e r valleys the developing settlements and a g r i c u l t u r e should be
b e t t e r protected; continuous and s a f e supply of water of suitable quality i s
r e q u i r e d f o r communities, industry and irrigation; t h e e n e r g y content of
r i v e r s should b e utilized f o r t h e economy and since r i v e r s a r e recipients of
wastes produced in t h e hydrological cycle in t h e society, t h e i r selfpurification capacity should be maintained. In o r d e r to achieve t h e goals
outlined,
large
number
of
hydrotechnical
constructions
and
water
r e s o u r c e s systems have already been realized. Consequently, r i v e r beds,
suspended sediment and bedload t r a n s p o r t , t h e water quality and even t h e
flow discharges have been considerably changed along s e v e r a l stretches.
The l a r g e hydraulic s t r u c t u r e s and systems
recently planned
- have
-
those a l r e a d y realized and
l a r g e radii of influence and, t h e r e f o r e , they are
not independent of e a c h o t h e r , but t h e i r impacts
b are
interwoven. When
g r e a t e r projects are planned and realized, i t i s necessary t h a t t h e neighbouring countries inform e a c h o t h e r , t a k e into account mutual i n t e r e s t s ,
harmonize t h e i r measures and even realize some p r o j e c t s jointly.
A common task i s to utilize t h e available water r e s o u r c e s of t h e Danube
and t h e basin a r e a in a possibly optimal way and to p r o t e c t t h e environment
as w e l l as t o fight jointly against t h e dangers of floods and droughts. This
task itself h a s a l r e a d y contributed considerably to c r e a t e a new consciousness of interdependence and cooperation of t h e Danube countries and t o
develop i t f u r t h e r in t h e f u t u r e (RZdD, 1986).
5.2 River Training
A t f i r s t w e review t h e most important r i v e r training activities realized
on t h e Danube by the r i p a r i a n countries.
Federal Republic of Germany
The approximately 85 km long Danube r e a c h from Sigmaringen to t h e mouth
of t h e Iller at Ulm, was f i r s t regulated in the y e a r s 1850-89. Downstream
from Ulm till t h e g o r g e a t Weltenburg t h e e n t i r e s t r e t c h w a s regulated
s t a r t i n g from the y e a r 1806 and implemented mainly in t h e period 1829-85.
The meandering c o u r s e was shortened by 21% constructing s e v e r a l cut-offs
and a stabilized r i v e r bed w a s provided f o r t h e a v e r a g e flow in this way. On
a n o t h e r German section of t h e Danube, the r i v e r training w a s confined to
t h e cut-offs, of t h r e e l a r g e r i v e r loops between Regensburg and Vilshofen.
Between 1931 and 1970, the regulation of the l o w - w a t e r bed w a s p e r formed from 2.376 km (Regensburg) to 2.250 km (Vilshofen) in o r d e r to
improve navigation conditions. However, i t turned out t h a t i t w a s not feasible to maintain t h e d e p t h required f o r navigation permanently due t o progressive deepening of t h e bed and canalization of t h e s t r e t c h became necessary.
Austria
In 1773, Empress Maria Theresia founded t h e f i r s t national authority f o r
planning and implementing r i v e r training.
The "Imperial Directory f o r
Navigation" existed till 1885. This authority, like o t h e r subsequent organisations, focused i t s activity on t h e improvement of navigation conditions on
dangerous rocky sections of t h e stream, and on t h e construction of hauling
t r a c k s . In 1778-91 t h e m o s t dangerous stream section, t h e "Greiner Strudel" was trained by r o c k blasting and construction of r i v e r banks. In 1829
works on t h e "Aschacher Kachlet" had been performed and from 1850 to
1866 t h e navigation conditions in "Brandstatter Kachlet" were improved by
r o c k blasting of t h e "Hausstein-Felsen"
n e a r Grein. The completion of
training works of t h e substantial p a r t of t h e Strudengau continued till 1905.
In 1850 t h e f i r s t l a r g e regulation works were s t a r t e d in the area where
t h e original bed was divided into s e v e r a l b r a n c h e s by deposited sediments.
S h a r p bends were removed by means of guide s t r u c t u r e s and cut-offs. Adjac e n t t r i b u t a r i e s were closed and a channel width f o r mean water of 320-410
m w a s gradually provided with uniform bank fortification. A s e a r l y a s 1920
t h e majority of regulation works f o r mean and low water stages (aiming at
navigation improvement) were completed in t h e respective sections.
Czechoslovakia
The r e a c h between t h e March (Morava) mouth and Gonyii (i.e. about half of
t h e whole r e a c h ) lies on a gigantic alluvial fan. Due t o continuous sedimentation i t i s extraordinarily difficult t o perform and maintain successful
regulation h e r e . By means of a mean-water regulation, c a r r i e d out from
1886 t o 1896, a stable main channel was provided among numerous r i v e r
branches.
A t t h e same time c u r v a t u r e s were smoothed, cut-offs con-
s t r u c t e d , and side b r a n c h e s closed below t h e level of mean water. The stabilization of t h e waterway f o r navigation by means of t h i s regulation w a s
l e s s successful on t h i s crucial Danube r e a c h than elsewhere. The low-water
regulation necessary f o r t h i s purpose was, t h e r e f o r e , continued since 1900
by means of groynes. However, i t i s still difficult t o maintain even by p e r manent dredging a 2 m d e e p and 80 and 120 m wide waterway at low water
stages.
Hungary
River training s t a r t e d in 1870, a f t e r a detailed geodetic survey of t h e
e n t i r e Danube r e a c h , which c r e a t e d a r e l i a b l e d a t a base f o r t h i s activity.
Substantial s u p p o r t f o r this activity was given by numerous i c e floods, since
t h e r i v e r channel originally divided into s e v e r a l branches creating narrow
meanders, which were not able t o t r a n s p o r t ice masses coming from
upstream sections of t h e Danube. I c e clogging caused a n i n c r e a s e in water
level upstream, ice jams inundating l a r g e a r e a s on t h e plain, and a f t e r suddenly breaking through t h e i c e jams, heavy floods o c c u r r e d along t h e lower
s t r e t c h e s causing serious damages. Therefore, t h e f i r s t task was the cons t r u c t i o n of a uniform main r i v e r channel with continuous t r a c k between
Devin and VBnek (1880-1791 km). The engineering works included: cut-off
of branches, straightening of bends, cutting across loops and revetment of
banks.
After t h e catastrophic flood of 1838, when 15%of t h e houses of Buda
and 50% of P e s t were destroyed, t h e regulation of this s t r e t c h w a s also
implemented.
The S o r o k s d r side branch was c u t off, t h e main Budafok
branch dredged, protecting walls and bank revetments built.
By the beginning of World War I t h e major p a r t of mean-water regulation works had been finished o v e r t h e e n t i r e Hungarian Danube. Thus, a
substantial improvement of t h e convergence of flood discharge and ice had
been attained. The original length of t h e Danube w a s shortened by constructing 30 cut-offs from472 t o 417 km.
The significance of rapidly developing water t r a n s p o r t considerably
increased t h e importance of r i v e r training.
Engineering works were
already s t a r t e d in t h e 19th century to remove shoals and t o construct
groynes and guidance embankments f o r low-water regulation, thus creating
a waterway with sufficient capacity having t h e depth of 2.5 m and minimum
width of 150 m.
Yugoslavia
Riverbed training in t h e Pannonian Lowland s t a r t e d in 1895 downstream
from Paks in Hungary, and were identical t o those described above concerning t h e Hungarian Danube section, namely, closing of side branches,
straightening of meanders, cut-offs, r i v e r bank revetment regulation f o r
low water by means of groynes and guidance embankments. Three l a r g e
cut-offs upstream of t h e Drau (Drdva) inflow should also b e mentioned. By
t h e beginning of World War I t h e section down t o t h e mouth of t h e Tisza
(Tisa) w a s completed. A waterway having a depth of 1.8 m and a width of 100
m was thus provided. In t h e period between t h e two world wars, training
works continued t o b e c a r r i e d o u t downstream from t h e mouth of t h e Tisza
(Tisa) .
From t h e time of t h e construction of Traian's road by the Romans on
t h e r i g h t r i v e r bank until t h e beginning of t h e 19th century, no attempts
were made t o improve the extraordinary difficult navigation conditions
along t h e c a t a r a c t section of t h e Iron Gate (Djerdap/Portile d e Fier). From
1834 t o 1837 t h e well-known Szdch6nyi r o a d had been carved in t h e r o c k s
on t h e left r i v e r bank t o provide help f o r navigation at low water stages.
Already in those days s e v e r a l cliffs and r o c k s were removed by blasting.
Thus, a small waterway within t h e cataracts Kozla-Dojke was c r e a t e d . After
various projects had been p r e p a r e d and international agreement attained,
extensive training works were implemented between 1890 and 1898 t o
improve navigation through c a t a r a c t s . They included construction of five
canals 60 m wide e a c h , with minimum depth of 2 m, t h e i r total length being
13 km, leading through t h e c a t a r a c t s .
To c a r r y out t h e improvement of this waterway t h e removal of 650,000
m3 of r o c k s w a s required, which would b e a difficult task even with modern
technology. Due t o strong streamflow, reaching 5 m/sec in t h e 73 m wide
and 3 m d e e p canal within t h e Iron Gate during high water, only limited navigation w a s possible with special barges. A haulage r o a d was, t h e r e f o r e , cons t r u c t e d during World War I, and locomotives took o v e r t h e haulage. In
s p i t e of all e f f o r t s , navigation through t h e whole c a t a r a c t section remained
r a t h e r burdensome, requiring t h e help of pilots and sometimes being completely unfeasible.
The final solution of a l l navigation problems w a s
achieved by t h e construction of t h e b a r r a g e Djerdap (Portile d e Fier I),
impounding t h e whole c a t a r a c t section.
Romania
The regulation of t h e I r o n Gates c a t a r a c t section, where t h e Danube bord-
ers Yugoslavia, h a s a l r e a d y been described above. To e n a b l e l a r g e maritime ships t o r e a c h Danubian ports, the Sulina b r a n c h in t h e Danube delta
w a s straightened by 10 cut-offs reducing t h e length from 85 km to ca. 62 km
in t h e period between 1857 and 1902. Thus, a waterway having a depth of
7.3 m and a width of 80 m was provided un to t h e p o r t Tulcea. This waterway
w a s extended to Braila, about 170 km upstream of t h e estuary. The maintenance of navigation on t h i s waterway r e q u i r e s continuous dredging of sediment.
5.3 Navigation
One of t h e goals of r i v e r training described so f a r h a s always been t h e
safeguarding of navigation.
The Danube, especially i t s middle and lower r e a c h , had become of
foremost importance since the e a r l i e s t times as a natural waterway. Since
ancient times t r a n s p o r t of heavy c a r g o e s w a s substantially e a s i e r by water
than overland, only t h e dimensions of vessels h a s changed (Kresser, 1984).
International cooperation of Danube countries concerning navigation i s
based on s e v e r a l agreements concluded since 1856. During t h e Danube
Conference held in 1948 in Beograd, t h e "Danube Commission" w a s founded
with h e a d q u a r t e r s in Budapest. Within t h e scope of activity of this commission all common problems concerning navigation, and hydraulic s t r u c t u r e s
serving navigation have been dealt with. Thus recommendations concerning
t h e dimensions t o b e guaranteed on t h e waterway (navigable depth, width,
c u r v a t u r e , slope, size of lock gates, discharge capacity, etc.) f o r t h e whole
navigation r o u t e from Regensburg t o t h e Black Sea have been worked out.
The considerable i n c r e a s e of water t r a n s p o r t on t h e Danube since t h e foundation of t h e Danube Commission testifies t h e successful cooperation among
Danubian countries within t h i s organisation.
In addition to t h e Danube, some t r i b u t a r i e s are also naturally navigable, o r were adapted by t h e respective countries f o r navigation:
- t h e Drau/Drdva
- t h e Tisza/Tisa
up to Cadarice (105 km),
up t o Dombrdd (about 600 km) as well as i t s t r i b u t a r y
Bodrog up t o t h e Hungarian-Czechoslovak b o r d e r ,
- t h e Sava up t o Sisak (583 km) f o r smaller ships,
- t h e P r u t on a s h o r t section of i t s lower course.
The Backa Canal (Yugoslavia), connecting t h e Danube with t h e Tiszaflisa i s
also navigable (RZdD, 1986).
The basic d a t a of goods t r a n s p o r t e d on European waterways are summarized in Table 10. I t i s seen from t h e t a b l e t h a t t h e contribution of t h e
Danube water system to t h i s navigation i s fairly modest (4-5%). This proportion will, however, b e rapidly changed when t h e Danube-Main-Rhine
Canal (see Section 5.4) interconnecting t h e two systems i s finalized (Kovdcs
et al., 1983).
The huge amount of goods to b e t r a n s p o r t e d economically r e q u i r e s a
naval fleet of increased tonnage capacity; a n increased depth i s t h e r e f o r e
needed f o r navigation.
Here i t must b e mentioned that t h e Hungarian
Danube r e a c h , especially t h e common Czechoslovak-Hungarian
stretch,
does not m e e t t h e recommended dimensions of t h e Danube Commission and
t h e required depth cannot b e achieved by applying t h e traditional r i v e r
Table 10
Goods transported on important European waterways,
as of 1970 ( O m , 1973)
Region
West European
waterways
network
Danube
and its
tributaries
Trans orted goods
10 t/year
E
Country
Belgium
Czechoslovakia
France
The Netherlands
Poland
GDR
FRG
Schwitzerland
FRG
Austria
Czechoslovakia
H W ~ Y
Yugoslavia
Rumania
Bulgaria
USSR
European part of USSR
without Daaube
training (Benedek et al., 1980). This is clearly indicated by Figure 10,
which r e p r e s e n t s t h e r a t i o of t h e costs spent f o r t h e maintenance of t h e
waterway along t h e various s t r e t c h e s taking t h e average cost as 100%.
Even with such efforts only 2.0-2.2
m navigation depth c a n b e ensured
along t h e critical r e a c h , c o n t r a r y t o t h e minimum depths of 2.5 m and 3.5 m
p r e s c r i b e d by t h e Danube Commission before and a f t e r t h e opening up of
t h e Danube-Main-Rhine
Canal system, respectively. In t h e vicinity of t h e
fords temporary navigation restrictions have t o b e o r d e r e d from time t o
time (OMFB, 1973).
Figure 10. Costs of r i v e r training works assuring navigtion along t h e
Danube (OMFB, 1973)
I t should a l s o be noted t h a t among t h e most significant developments which
could affect t h e regime of t h e r i v e r t h e r e are t h e proposals to improve
navigation by constructing inter-river canals to connect different international r i v e r systems with each o t h e r , or with t h e s e a , namely:
-
Rhine-Main-Danube
canal, providing a continuous waterway from
t h e North S e a t o t h e Black S e a ,
- Danube-Odera-Elbe
canal, providing links between t h e Baltic and
the Black Seas,
-
Danube-Morava-Vardar-Axios
Aegean Sea (WHO, 1983).
canal, providing a link with t h e
5.4 Flood Control
Jn t h e following, a s h o r t review will b e given, f o r e a c h Danube country,
about t h e flood control situation along t h e Danube.
FederaL RepubLic of G e r m a n y
Flood protecting levees built in 1849-1897 from 2,540 km (Dillingen) t o
2,510 km (Donauworth) hindering henceforth t h e floods t o overflow t h e
banks and inundate the t e r r i t o r y covering t h e a r e a of about 115 km2. Flood
protecting levees from 2,460 km Ongolstadt) to 2,427km (Eining) were built
in 1913-24 and fortified in 1965-75. They p r o t e c t an a r e a of 80 km2. Flood
protection levees from 2,376 km (Regensburg) to 2,256 km (Hofkirchen)
were constructed in 1930-56, protecting a n area of about 120 km2, but giving only p a r t i a l protection f o r t h e t e r r i t o r y between Regensburg and
Straubingen. On t h e basis of experiences gained during t h e floods in 1954
and 1965 these levees and t h e inland drainage have to b e improved.
Numerous completed dams and impounding r e s e r v o i r s took o v e r a p a r t
of t h e flood protection by lowering flood peaks.
Improved flood protections of Kehlheim and Regensburg are planned
f o r t h e future.
The protection measures envisaged f o r Passau should
proceed also in the f u t u r e through rebuilding of old houses and changing
t h e utilization of t h e i r ground-floor.
Austria
Subsequent t o flood d i s a s t e r s in 1830 and 1864 t h e f i r s t more extensive
measures were performed in 1869-1875 f o r t h e protection of Vienna against
floods. The c o r e of engineering works w a s a 26 km long r i v e r training work
for which two l a r g e cut-offs had been established. For t h e f i r s t time in Cen-
tral Europe they were implemented o v e r t h e whole length and dredging the
complete width, while in the p a s t i t was usual t o r e l y on t h e r i v e r itself t o
perform this work o v e r a long period. The amount of e a r t h moved in this
operation was, t h e r e f o r e , a s high a s 16.5 mil.m3.
Other measures were also included, such as closing s t r u c t u r e s f o r t h e
Danube Canal, various flood control embankments and levees.
Since
1898-99 a 180 m wide waterway in t h e regulated section w a s provided by
means of groynes, securing navigation at low water stages.
From 1882 t o 1920 about 200 km of flood control levees were cons t r u c t e d from Vienna down t o t h e March (Morava) r i v e r , in t h e Tullnerfeld
and in Linz area.
Following t h e s e v e r e floods in 1954 flood protection in t h e town of Linz
w a s increased considering t h e flood with 500-year r e t u r n period as design
value. The system was f u r t h e r improved parallel to t h e construction of t h e
b a r r a g e a t Abwinden-Asten.
The p r e s e n t flood control system in t h e Vienna area is being improved
t o handle a discharge of 14,000 m3.s1, which corresponds t o t h e peak
discharge of a n e x t r a o r d i n a r y high flood. F o r t h i s purpose a r e l e a s e canal
will b e constructed, s e p a r a t e d from t h e Danube canal by a 17 km long and
200 m wide island. In t h e downstream direction t h e levee system i s dimensioned f o r a discharge of about 13,200 m3.s1, since in t h e case of more serious floods i t i s necessary to t a k e also into consideration, with r e s p e c t t o
t h e lower lying downstream countries, t h e retention of t h e March (Moravian) Field.
Czechoslovakia
Flood control embankments had been built already in t h e second half of t h e
19th century. Except f o r two s h o r t s t r e t c h e s where t h e banks are relatively higher a complete system of levees w a s built f o r t h e e n t i r e n o r t h e r n
Danube bank and s o u t h e r n Little Danube bank.
Disastrous floods, most
recently in 1965, stimulated h e r e , as well as on t h e opposite bank, fortification and raising of levees and improvement of drainage within t h e protected
area.
Hungary
A q u a r t e r of t h e Hungarian t e r r i t o r y , about 23,000 km2, i s a potential inundation area from which 23% lies directly in t h e Danube valley. Therefore,
flood mitigation and protection i s of major importance in t h i s country. As
e a r l y as in t h e 16th century protection levees were constructed t h e r e . A
systematic construction of flood protection dykes s t a r t e d in t h e f i r s t half of
t h e 19th century. Since 1840 t h e r e h a s been legislation t o regulate t h e
implementation of hydraulic s t r u c t u r e s , r i v e r training, construction and
maintenance of flood control s t r u c t u r e s , and t h e necessary drainage of
excess water. According t o this regulation Water Associations were established unifying a l l i n t e r e s t e d persons and organisations in a given region
and a p a r t of t h e investments was covered by t h e members.
A decisive
motive to complete t h e levee system w a s t h e o c c u r r e n c e of s e v e r e floods in
1881 and 1888. By the end of t h e 19th century t h e protection system w a s
practically completed.
The straightening of t h e Danube between dykes caused a f u r t h e r
i n c r e a s e of flood stages, s o t h a t many previous levees were too l o w a f t e r
t h e completion of t h e whole system. In t h e f i r s t half of t h e 20th century t h e
levees were raised and fortified, so t h a t a safe protection against floods of
60-year r e t u r n period w a s provided.
A t t h e beginning of t h e p r e s e n t s t a g e of flood control development t h e
legal basis has been modified. Proceeding from t h e circumstance t h a t t h e
safety of t h e main protection line h a s not only local, but also national significance, t h e state took o v e r t h e responsibility from t h e associations f o r
important flood-control dykes. From t h e total main flood control line in
Hungary, having a length of 4,183 km, 1,350 km lies along t h e Danube. I t is
supplemented by t h e secondary lines of 260 km length and by the special
protection of Budapest, t h e length of which is 1 8 km.
The significance of flood control in Hungary is evident from t h e following data: Within t h e potential inundation area live a q u a r t e r of t h e total
population; about 30%of t h e railway network, and 20%of highways lie t h e r e .
Yugoslavia
L a r g e inundation areas requiring flood protection s p r e a d only along t h e
middle Danube r e a c h in t h e Pannonian Basin. Systematic construction of
flood control levees also s t a r t e d in t h e 19th century. By World War I a continuous protection system had been constructed linked t o t h e Hungarian
levees, reaching on t h e l e f t bank down to t h e mouth of t h e Tisza (Tisa), and
on the r i g h t bank t o t h e mouth of t h e Drau (Dravd). F u r t h e r downstream,
t h e levee system on t h e left r i v e r bank w a s still deficient at t h a t time, while
on t h e right bank flood control dykes were constructed only at P e t r o v a r a din and Zemun.
In t h e p e r i o d between t h e two world wars t h e system of l e v e e s w a s
expanded ( f o r instance, at Pancevo on t h e l e f t bank a n d at Smederovo and
Godominsko P o l j e on t h e r i g h t bank).
After World War I1 some new sections were built t o complete t h e flood
protection. A p a r t of old dykes was r a i s e d , fortified, a n d r e s t o r e d a c c o r d ing t o e x p e r i e n c e s gained during t h e c a t a s t r o p h i c flood in 1965 and based
o n advanced soil mechanics.
A t p r e s e n t t h e r e i s a continuous system of dykes o n t h e l e f t bank from
t h e Hungarian b o r d e r down t o t h e mountainous r e a c h of t h e I r o n Gate. Due
t o local conditions o n t h e r i g h t r i v e r bank, i t was sufficient t o c o n s t r u c t
l e v e e s at only a few sections: from t h e Hungarian b o r d e r down to t h e mouth
of t h e Drau (Drava), at P e t r o v a r a d i n and Zemun, as w e l l as at Smederevo.
The l a t t e r was a l s o r e q u i r e d b e c a u s e of t h e construction of t h e Djerdap I
(Portile d e Fier) barrage.
The crest of flood c o n t r o l dams i s usually 1.5-1.7
m a b o v e t h e water
s t a g e of a food of 100-year r e t u r n period.
Bulgaria
Over t h e y e a r s from 1930 t o 1950, a b o u t 300 km of flood c o n t r o l dams were
c o n s t r u c t e d t o p r o t e c t a n area of a b o u t 72,600 ha. The height of t h e l e v e e s
was dimensioned a c c o r d i n g to t h e e x t r e m e flood in 1897.
Romania
The construction of flood control levees f o r p r o t e c t i o n of a g r i c u l t u r a l land
w a s initiated i n t h e 19th century. The p r o t e c t e d area was i n c r e a s e d from
ca. 50,000 h a in 1940 to ca. 100,000 h a in 1960 a n d h a s b e e n f u r t h e r
i n c r e a s e d up to t h e p r e s e n t t o ca. 400,000 ha. The t o t a l length of flood cont r o l l e v e e s is 1,000 km (RZdD, 1986).
5.5 Barrages
The idea t o c o n s t r u c t a navigable waterway connecting t h e Main a n d
t h e Danube a n d thus t h e North Sea with t h e Black S e a , d a t e d back t o a n c i e n t
times. A s e a r l y as 793, Charlemagne t r i e d to create a connection between
t h e two r i v e r systems, c l o s e t o t h e town Treuchtlingen (FRG), where t h e dist a n c e between two t r i b u t a r i e s of t h e two systems i s only 2 km a n d t h e differe n c e i n altitude i s only a b o u t 1 0 m.
From 1836 t o 1845 t h e 'Zudwig-Donau-Main Kanal" of 1 7 7 km long was
built from Kehlheim to Bamberg with 100 navigation locks. Unfortunately,
t h i s canal soon lost i t s significance since the 120-ton vessels hauled by
h o r s e s could not stand t h e competition from t h e railway, which in those days
w a s installed. In 1945, t h i s canal was still in operation and only in 1949 w a s
i t finally abandoned.
Since 1959 t h e new Main-Donau-Kana1 has been under construction, i t s
dimensions being: 5 5 m water level width, 31 m bottom width, 4.0-4.25
m
water depth, 1 2 m wide and 190 m long navigation locks adequate f o r a p a i r
of 1,500 ton and 90 m long Type Europe I1 barges. The 204 km long canal
between Regensburg and Bamberg is divided into 18 sectors from which 1 0 3
km with 1 0 s e c t o r s i s canal with standing water, and 1 0 1 km is impounded
s t r e t c h of r i v e r s .
In connection with t h e new Main-Danube waterway, t h e completion of
which is envisaged f o r t h e f i r s t half of t h e decade 1990-2000, 15.0 m3.s-I of
water should b e conveyed from t h e Danube t o t h e Main r i v e r basin. Howe v e r , water withdrawal should t a k e place only when t h e Danube discharge i s
above t h e a v e r a g e low discharge MLQ.
In 1984 a 64 km long Danube-Black S e a canal between Cernavoda and
Constants (Romania) was completed, at f i r s t only f o r internal operation.
The mean width i s 90 m, depth 7.5 m, both ends are provided with 310 m long
and 25 m wide twin navigation locks. The navigation r o u t e was shortened by
370 km. This canal, t h e construction of which r e q u i r e d t h e removal of 300
million m3 of e a r t h (more than in the case of t h e Suez Canal: 275 million m3)
a l s o provides water f o r irrigation of 700.000 h a of a r a b l e land in Dobrogea.
In t h e following, a s h o r t review about b a r r a g e s on the Danube is given
f o r each Danube country.
FederaL Republic of G e r m a n y
The Kachlet b a r r a g e (2,230 km) at Vilshofen, built in 1924-27 was t h e f i r s t
member of t h e canalization system of t h e Danube. I t improved navigation in
t h e r o c k y s t r e t c h of t h e "Hilgardsberger Kachlet".
I t was followed by t h e
b a r r a g e at Jochenstein, constructed in cooperation with t h e Federal Republic of Germany and Austria on the common b o r d e r in 1952-55.
During t h e
period 1952-84 a continuous chain of 1 5 b a r r a g e s w a s built from Ulm t o
Ingolstadt. In t h e majority of these schemes a p a r t of t h e f o r m e r inundation
a r e a i s overflowed during flood events, t o prevent t h e unfavourable
i n c r e a s e of flood discharges in t h e downstream section. The releases t a k e
place, in a regulated way through spillways and movable weirs. The alluvial
f o r e s t s are often inundated, though t h e agricultural land i s submerged only
during disastrous floods.
Three b a r r a g e s , Regensburg (2,381 km), Bad Abbach (2,401 km) and
Geisling (2,354 km) were built with t h e purpose of extending t h e waterway
on t h e Danube up t o Kelheim and to interconnect it with t h e Main-Danube
canal.
A t p r e s e n t one b a r r a g e is under construction a t Straubing (2,324 km),
whose purpose is t o improve navigation conditions. Some o t h e r s are also
planned (one t o extend t h e waterway until t h e Kachlet b a r r a g e and two more
downstream from Ingolstadt to prevent t h e rapid scouring and deepening in
this reach.
Austria
The systematic development of t h e Danube cascades began with t h e construction of t h e b a r r a g e a t Jochenstein, on t h e German-Austrian b o r d e r ,
completed in 1954. Up t o t h e p r e s e n t about 250 km of t h e 350 km long Aust r i a n Danube section i s canalized and t h e r e a r e plans t o f u r t h e r develop
t h i s cascade system.
Barrages in flatlands of t h e Danube basin are supplemented by dyke
systems t o provide protection f o r the densely populated inundation a r e a
against floods. However, l a r g e r retention a r e a s remain p r e s e r v e d , similarly as in t h e German Danube section, also after the constrliction of b a r rages. In all five, completed water schemes situated in t h e plain high-water
overflows were built into t h e p a r a l l e l l a t e r a l levees, thus making possible
t h e overflow of water above a c e r t a i n flood-discharge onto t h e f o r m e r inundation plain. In this way a t higher floods a significant portion of t h e flood
retention is maintained. In addition, the former inundation conditions in t h e
alluvial plains and f o r e s t s a r e preserved.
Czechoslovakia
Since 1978 t h e hydropower plant Gabcikovo has been construction jointly
with Hungary. With i t s l a r g e derivation canal i t d i f f e r s from all o t h e r completed and planned water schemes on t h e Danube. The combined navigation
and hydropower canal should d i v e r t a discharge of 5,200 m3.s"
from t h e
Danube at Dunakiliti, which r e t u r n s t o t h e main r i v e r bed only after a
length of about 30 km. I t is planned to construct in cooperation with Hung a r y downstream from Gabcikovo a n o t h e r water scheme at Nagymaros. Only
a f t e r completion of t h i s b a r r a g e will i t b e possible t o create a complex
water utilization scheme f o r peak hydropower production. The two barr a g e s will a l s o provide a final solution of flood control on t h e Danube r e a c h
concerned.
Hungary
The canalization p r o j e c t at Gabcikovo-Nagymaros, to b e constructed jointly
with Czechoslovakia, h a s a l r e a d y been described above. More details can be
found in Annex 11.
Yugoslavia
For solving t h e s e r i o u s problems concerning navigation on t h e Danube and
f o r utilizing of t h e hydraulic power potential, Yugoslavia and Romania cons t r u c t e d jointly in t h e period 1964-72 a t 942.94 km a dam of 32 m height,
t h e "Hydroenergy and Navigation System Djerdap (Portile d e Fier I)". The
backwater extends at low water s t a g e as far as 270 km to t h e mouth of t h e
Tisza (Tisa). In case of flood, t h e head i s reduced t o 6.5 m, so t h a t at high
floods t h e backwater ends a distance of about 120 km at Veliko Gradiste.
In. 1984 t h e b a r r a g e Gruia (Portile d e Fier 11) at 863 km w a s put in
operation. I t s backwater zone i s linked with t h e scheme Djerdap (Portile d e
Fier I), thus serving a s compensation r e s e r v o i r during t h e peak operation
of t h e hydropower plant. This p r o j e c t w a s implemented also as a common
Yugoslav-Romanian scheme.
Romania
Both r i v e r power p r o j e c t s at t h e Iron Gate I and I1 have a l r e a d y been dealt
with in connection with t h e development in Yugoslavia (RZdD, 1986).
5.6 Hydropuwer
In o r d e r t o c h a r a c t e r i z e t h e problems of b a r r a g e s from t h e viewpoint
of energetics, in Figure 11, the longitudinal section of energy-potential
(discharge multiplied with slope) of t h e Danube is shown.
The diagram
clearly indicates t h a t t h e highest specific power r e s o u r c e s are concent r a t e d in t w o r e a c h e s : between Passau and Gonyu, a n d downstream from
Belgrade, in t h e Iron Gate region.
The f i r s t r e a c h (between Passau and Gonyii) i s especially significant
due t o its high slope of 150 m along about 435 km length of t h e r i v e r . A t t h e
second r e a c h (downstream of Belgrade) t h e high energy potential i s due t o
t h e g r e a t discharges of t h e r i v e r .
A sudden break in t h e slope of t h e r i v e r bed at Gonyu can b e s e e n in
Figure 11. This r e s u l t s in problems of sediment accumulation at t h e breakpoint. Accordingly, t h e annual bed load t r a n s p o r t at Bratislava i s about
650,000 m3 while i t i s only 13,000 m3 above Budapest. This i s t h e reason f o r
the
well-known
"bottle
neck"
in
the
navigation
along
the
critical
Czechoslovakian-Hungarian r e a c h (Benedek , 1986).
The plans f o r t h e complex utilization of t h e Danube's water r e s o u r c e s
involve 49 r i v e r b a r r a g e s of which so f a r 31 have been constructed. The
sections and capacities of t h e s e hydropower plants are listed in Table 11.
The locations of t h e s e hydropower stations according t o countries i s shown
in Table 12. The tables show t h a t t h e p r e s e n t utilization of t h e total capacity (61%) will b e gradually increased to more than 90% by t h e t u r n of t h e
century (DoKW, 1985; OVH, 1985). Figure 1 2 gives some information on t h e
extensive hydropower utilization of t h e Austrian Danube section (DoKW,
1985).
win
ABWINEN- ASTEN
0 planned
in operation
river km from
Black Sea -2200
-2150-
2100-2050
4 2 0 0 0 -1950-1900
SUM
2574 '
copacity
(in 1000 kW 1
r with 112 portion of JOCHENSTEIN
Figure 12. Austrian hydropower stations (DoKW, 1985)
Table 11
Existing and planned hydropower s.tations in the
Danube Basin
.
Serial
No
-
(OVH. 1985; DoKW. 1985)
River barrage
or hydro-power stations
Capacity
-
Power output
Gwh
20 hydro-power stat ions
between ULm and Kelheim
Bad-Abbach
Regensburg
Geisling
Straubing
Deggendorf
Aicha
V i l shof en
Kachlet
Jochenstein
Aschach
31
Ot tensheim-Wilhering
179
1143
32
Abwinden-Ba ten
168
1028
33.
Wallsee-Mitterkirchen
210
1320
34.
Ybb s-Per senbeug
200
1282
35.
Melk
187
1180
Table 11
(cont. )
Serial
no.
River barrage or hydro-power st a t i o n s
Capacity
UW
Power output
Gwh
Rtihr sdorf
Alt enwijrth
Greif e n s t e i n
Wien
Hainburg
Gabcikovo
Naggmaros
Adong
Fa j s z
Novi Sad
Iron Gate 1
Iron Gate 2
Turnu Marmureie
C ernavo da
Total
7959
43565
Table 12
Ca~acityand power-output of the hydropower stations
on the Danube. mouped according to countries
(DoKW, 1985)
.
Serial
No
Country
10-28.
29
MW
MW
(1985) (2000)
(1985) (2000)
283
364
1735
2216
FRGAustria
130
130
850
850
2008
2509
12071
14766
-
846
-
Austria
41-42.
Czechoslovakia-Hungary
-
Yugoslavia
-
46-47. Yugoslavia-Rumania
2450
2450
--
45.
GWh
FRG
30-40.
43-44.
GWh
Hungary
o
48,
Bulgaria-Rumania
-
760
49.
Rumania
o
400
12400
-
3608
o
12400
3800
3000
Total
4871
7459
27056
40640
Total ($1
61.2
9307
62.1
93.3
WATER QUALITY
6.1 Preliminary Remarks
Abstracted water becomes polluted during use: t h i s i s a n inevitable
processs. Historically society has relied on dilution and natural purification taking place when t h e waste water i s r e t u r n e d t o t h e Danube. However,
with increased abstraction, t h e r e i s a corresponding diminution in t h e
volumes of clean water remaining t o dilute and promote t h e self-purification
of t h e r e t u r n e d waste water. The situation is worsened when the waste
water i s contaminated with many materials r e s i s t a n t t o n a t u r a l degradation,
which p e r s i s t and are accumulated in t h e channel. Unfortunately, such
potentially harmful materials a r e becoming more common constituents of
waste waters from many domestic, industrial and agricultural sources.
The problem becomes more complicated considering t h a t with today's
complex r a n g e of chemicals and many by-products
produced in t h e i r
manufacturing and use, routine analytical measure may b e of limited value
unless t h e analyst i s provided with some guidance on what to seek.
To solve t h e problem, r i p a r i a n countries have e n t e r e d into bilateral
and multilateral arrangements, some of them long standing, on s h a r e d water
r e s o u r c e s , but such agreements tend to b e limited both in number and
scope, usually concentrating on navigation, e n e r g y production, flood cont r o l o r sharing water quantity, r a t h e r than directed to controlling water
quality. Some multilateral and bilateral agreements having impact on t h e
Danube are shown in Table 13 (WHO, 1982).
6.2 Water Quality Sampling Network and D a t a E v a l u a t i o n
Unfortunately, one cannot speak of a harmonized water quality s a m pling network along t h e Danube. For example, t h e frequency of sampling in
t h e FRG, in Austria and in Hungary a r e quite different. The sampling network r e l a t e d t o t h e Hungarian s t r e t c h of t h e Danube i s shown in Table 1 4
(OVH, 1984). In t h e FRG, samples are taken from t h e Danube e v e r y second
week, while in Austria monthly (Danecker et al. 1981).
Table 1 3
Some m u l t i l a t e r a l and b i l a t e r a l aareements having impact
on the Danube
Year
(WHO.
Countries
1982)
Topic of agreement
(Austria),Bulgaria,
Czechoslovakia,Hungary ,Rumania, Ukr a i n e , USSR,Yugoslaria
Danube Convention on navigat i o n of R, Danube
Hungary, USSR
Convention t o prevent floods
and r e g u l a t e R, Tisza
Rumania, USSR
Convention t o prevent floods
and r e g u l a t e R, Prut
Austria,Yugoslavia
Austr ia,Yugo s l a v i a
Convention concerning water
m a n a g e m e n t questions r e l a t i n g t o
R. Drava
Convention concerning water
m a n w e n t questions r e l a t i n g
R,
Rumania,Yugoslavia
Hungary,Yugoslavia
Mura
Agreement concerning control
of f r o n t i e r waters
Agreement concerning water
management
Austria, Hungary
Albania,Yugoslavia
Treaty conc erniag water
m a n a g e m e n t in f r o n t i e r region
Agreement concerning water
m a n a g e m e n t in f r o n t i e r region
Hungary,Yugoslavia
Agreement concerning f i s h ing in f r o n t i e r waters
Rumania, USSR
Agreement extending R.Prut
convention (1952) t o Tisza..
Suceava and ~ i r e,t and
other f r o n t i e r waters
.
Czechoslovakia,
Poland
-
-
-
Bgreement concerning use of
f r o n t i e r water resources
.
Table 13
(cont )
-
Year
Countries
1958
Bulgaria, Yugoslavia
-
Topic of agreement
Agreement concerning water
manageme11t
1959
Rumania, USSR
Agreement extending R .But
convention (1952) to Danube
Agreement relating to navigation and power generation
Iron Gates
1967
Austria, Czechoslovakia
Treaty relating to management of frontier waters
1969
Hungary, Rumania
Convention relating to control of frontier waters
1971
F.R. Germany,
Czechoslovakia
Local (non-government) commission dealing with pollution and management of
frontier waters
Regular collection of water quality d a t a o n t h e Hungarian r e a c h of t h e
Danube h a s b e e n going o n f o r a b o u t 20 y e a r s . From 1968, monthly, f o r t nightly, o r weekly samples have b e e n t a k e n from r e g u l a r points (VITUKI,
1978). Samples in g e n e r a l are t a k e n from t h e main c u r r e n t , but owing t o t h e
anomalies which had a l r e a d y a r i s e n in t h e sixties, in some points t h e measurements are c a r r i e d o u t at d i f f e r e n t points on a cross-section. (For examp l e , l e f t bank, main c u r r e n t , r i g h t bank). At t h e r e g u l a r sampling points,
t h e measurement of t h e g e n e r a l physical. inorganic and o r g a n i c chemical
p a r a m e t e r s i s predominant (Benedek et al., 1978.)
From t h e o t h e r Danube c o u n t r i e s we have n o information a b o u t t h e i r
sampling systems.
The evaluation of w a t e r quality d a t a i s c a r r i e d o u t using d i f f e r e n t
methods in t h e r i p a r i a n countries. In t h e FRG a n d in Austria t h e biological
a s p e c t s of w a t e r quality are emphasized, while in t h e CMEA c o u n t r i e s t h e
chemical ones. Not only t h e evaluation b u t a l s o t h e classification systems
Table
14
Water q u a l i t y samplimz network on the Hungarian Danube
reach (OVH. 1984a)
Place o f sampling
Kom&om, upstream from River V&I
AJdsneszm6ly, downstream from
River V&
Szob, downstream from River
Ipoly/Ipel'
Surf ace water intake of
Budape st
North of Budapest
South of Budape st
Section,
Rkm
Bequency
of y esampling
arly
are different in t h e r i p a r i a n countries. A s a consequence, comparison of
t h e individual national r i v e r sections is almost impossible (WHO, 1982).
So i t i s not worthwhile displaying and comparing water quality maps
produced by different r i p a r i a n countries (Danecker et al., 1981, OVH,
1984b, Massing, 1980).
6.3 Chemical Evaluation of Water Quality
A s a r e s u l t of t h e high levels of oxygen concentration occurring along
t h e r i v e r , coupled with t h e generally high dilution available t o effluents
discharged into it, t h e Danube exhibits a n excellent self-purification capacity and much evidence is available t o demonstrate i t s power of r e c o v e r y
downstream of polluting discharges, at least in r e s p e c t of degradable
materials.
However, even with such pollutants, problems c a n o c c u r in
winter, when ice c o v e r and low temperatures r e d u c e t h e rates of oxidation
and different kind of organic and inorganic materials may subsequently
a f f e c t t h e taste and odour of potable water supplies derived from t h e r i v e r
(Liepolt, 1979).
The p r e s e n c e of high concentrations of ammonia has also been identified a s a possible f a c t o r endangering t h e use of some r e a c h e s of t h e Danube
a s s o u r c e s of potable water supply (Benedek et al., 1980, VITUKI, 1985).
The maximum ammonium-ion concentrations o c c u r in winter when t h e water
t e m p e r a t u r e is low and t h e nitrification processses are suppressed, while
striking n i t r a t e concentrations are typical in e a r l y spring owing t o t h e high
s u r f a c e runoff from cultivated a r e a s (see Figure 13) (Laszlo-Homonnay,
1985).
Extreme values of some classical chemical components of t h e Danube are
summarized in Table 15, based on samplings and analyses c a r r i e d out
between 1956 and 1964 in t h e 8 r i p a r i a n countries (Liepolt, 1967).
Regarding such a conventional parameter as BOD5' t h e water quality of
t h e Danube is fairly good (see Table 16) (Benedek-Laszlo, 1980). H e r e i t
must b e mentioned t h a t t h e water quality of t h e Danube is presently much
b e t t e r than t h e water quality of t h e Rhine (KfW, 1977). but downstream of
l a r g e r waste water discharges locally both t h e micropollutants and t h e
decomposable organic content greatly increase in t h e sediment (WHO, 1982).
I
Figure 13.
0
U
I V V
-
v l v O v a 1 x x
XIXI
month
'Monthly a v e r a g e values of NH; and NO< upstream and downstream from Budapest based on sampling between 1979-84
(VITUKI, 1985)
Table 1 5
Extreme values of some conventional chemical components
on t h e Danube River. 1956-1964 ( L i e ~ o l t ,1962)
Component
Dimens ion
m
m
iu
m
value
Maxjmum
value
pH
Conductivity
Total hardness
Carbonat hardness
Calcium, ca2+
e2+
Magnesium,
Iron, Fe 3+
Snlphata, SO:-
ammonium,
mi
N i t r i t , NO;
n i t r g t , NO;
O r t opho sphat
, PO:-
COD (=O4)
Dissolved owgen
m g e n - s a t u r a t ion
* This
value i s not r e a l i s t i c . It m a y have been measured
close t o a sewage o u t l e t
Table 16
p r o f i l e of the Danube upstream o f t h e Iron Gate
-BOD
5
in t h e e a r l y s e v e n t i e s (Benedek-Ldszlo', 1980)
River km
BOD,
References
Bayerisches Landesamt, 1972
n
n
11
n
I1
It
11
I1
Von der Emde, Fleckseder, 1977
n
VITUKI, 1975
It
It
I1
Milor adov, 1977
n
n
n
A s c a n b e concluded from t h e r e g u l a r monitoring and survey of t h e
Hungarian Danube section, water quality i s mainly determined by t h e pollution caused by t h e upstream countries. Regarding t h e conventional paramet e r s , water quality of t h e Hungarian s t r e t c h i s fairly good ( t h e e n t i r e r e a c h
is in t h e second class (OVH, 1984a)), but some troubles a r e caused by certain pollutants of industrial origin, such a s heavy metals and oil derivatives
(Benedek-Laszlo, 1980).
One of t h e biggest pollution s o u r c e s of t h e Danube i s Budapest with t w o
million inhabitants, with a r a t h e r developed industry and with v e r y modest
sewage and waste water treatment. In spite of this, due to t h e high dilution
(60-100
times dilution at low flow) and t o t h e excellent self-purification
capacity of t h e r i v e r , t h e r e i s no enormous difference in t h e water quality
of t h e Danube upstream and downstream of Budapest (Table 17) (VITUKI,
1985).
The r a t i o of accumulated heavy metals in t h e bottom deposit in t h e Hungarian Danube and i t s t r i b u t a r i e s i s as high as 2 t o 20 times t h e background
values (see Table 1 8 ) (Literathy-Laszlo, 1980, Somlyody-Hock, 1985).
Some t r i b u t a r i e s of t h e Danube system c a n p r e s e n t problems, particularly when they contain effluent residual derived f r o m neighbouring count r i e s o v e r which t h e water u s e r has no control. One such r i v e r i s a second a r y t r i b u t a r y of t h e Danube, t h e Slana (Sajo), where a high d e g r e e of reuse by successive water u s e r s t a k e s place. I t s quality i s f a r from satisfact o r y a s a r e s u l t of lignine sulphonic acid in the r i v e r water entering Hungary, in addition to containing high concentrations of heavy metals (WHO,
1977a).
A s has been mentioned in connection with t h e navigation problems
(Chapter 5.2), t h e Danube Commission is confined to hydrological surveys
and waterway regulation. The only water quality task i s t h e supervision and
prevention of water pollution caused by navigational vessels (BenedekLaszlo, 1980).
Table 17
Characteristic water quality data of the Danube upstream and
downstream from Budapest, 1980-1984 (VITUKI, 1985)
DimanComponent
:+
upstream
cgsY*
0
downstream
from Budapest
--
upstream
downstream
from Budape st
-
Temperature
OC
Total dissolved
solids
mgn
Dissolved oxygen
mg/l
Total hardness
mg/l
Oil
mg/l
%/I
Phenols
Detergents
(anionactive)
"a %
Pantle-Buck index
- 11.
- 111.
m
a
%
-
Class
+
Class
average values
* values of
95 % duration
Table 18
Bottom d e p o s i t p o l l u t i o n along t h e H u w a r i a n Danube
reach
(Litertithy-Lbszl6 1986; Somly6dy-Hock, 1985)
-
Heavy metal
compnnent
Background
v a l u e s , &kg
(Taylor ,1976)
Lead
12.9
Mer c u r 7
0.02
Cadmium
0.7
- 98
- 8.4
- 16.8
- 32.9
- 0.12
- 1.2
Manganese
3.8
- 1156
Zinc
43
Chromium
3.9
Copper
9.2
Measured sediment
malkg
minimum
maximum
16
4 200
3
186
1
74
4
140
0.03
2.0
1.0
6.0
20
1 200
6.4 Biological and Bacteriological Evaluation of Water Quality
With r e s p e c t to hydrobiology i t c a n b e said t h a t t h e only informal
international a c t i v i t y f o r t h e Danube i s being conducted b y t h e SIL-IAD
(International Society f o r Limnology, International Working Community of
t h e Danube Countries) International R e s e a r c h Committee. I t s p r i m a r y t a s k
i s to c o o r d i n a t e t h e hydrobiological r e s e a r c h activities on t h e Danube
accomplished in t h e r i p a r i a n countries.
o u t by t h e Committee itself.
However, investigations c a r r i e d
The Committee issued a monograph on t h e
Danube crossing eight countries, an accomplishment of which w a s supported
by t h e e x p e r t s of e v e r y r i p a r i a n country (Liepolt, 1967). Unfortunately,
since t h e publication of this excellent work a lot of changes of water quality
have taken place on t h e Danube catchment.
In t h e framework of t h e researci activities of SIL-IAD, in Austria t h e
socio-ecological effects of the impoundments are being studied (Oeko.,
1984), which extends beyond t h e routine activity of SIL-IAD.
In Czechoslo-
vakia bacteriological and zooplankton r e s e a r c h i s emphasized (Rotschein,
1976, 1981; Daubner, 1972). In Hungary the fish fauna, t h e primary production and oxygen balance a s p e c t s have mainly been studied (Bartalis, 1984;
Berczik, 1976; Bothdr, 1973; Dvihally 1971; Nemeth, 1971, Toth, 1982). In
Yugoslavia saprobiological and fish-faunistical investigations, while in Bulg a r i a zooplankton and zoobenthos studies a r e c a r r i e d out.
Soviet -and
Romanian e x p e r t s are involved in r e s e a r c h of t h e phyto- and zooplankton
and r e e d s of the Danube delta and fish-faunistical investigations (Curcin,
1985; Levina-Serge jev. 1985, Zankov et al., 1984).
The activity of SIL-IAD c o v e r s t h e following 3 fields:
- description of t h e main c h a r a c t e r i s t i c s of t h e r i v e r ,
- continuous survey of t h e changes in t h e s e c h a r a c t e r i s t i c s ,
- investigation on t h e impacts of human activities (Liepolt, 1979).
Along most r e a c h e s of t h e Danube t h e water quality of biological g r a d e I1
(0-meso-saprobic); can b e measured, but downstream of major polluting
discharges, quality d r o p s t o g r a d e I11 (a-meso-saprobic).
This indicates
t h a t c u r r e n t pollution control measures a r e inadequate, which could lead t o
f u t u r e r e s t r i c t i o n s on water uses and t o higher treatment costs (WHO,
1976).
The suspended solids content fluctuates in t h e r a n g e of 30-100 mg/l on
t h e a v e r a g e , but in the cases of extreme floods, 1500 mg/l, which i s t h e
highest value t o have o c c u r r e d . Suspended plankton consists mainly of diatoms, and t h e brown assimilative pigments thereof give t h e brown and by no
means "blue" colour of t h e Danube water. The bottom sediment includes
gravel, gravelly sand and sandy loam; the biomass of t h e bottom fauna is
only 5-6 kg/m2 (Benedek e t al.. 1978).
From t h e bacteriological point of view i t has been found t h a t bacteriophages and enteroviruses show high survival rates in t h e Danube and
may even r e s i s t t h e water treatment processses c u r r e n t l y given t o some
potable supplies (WHO, 1977a). Bacterial counts in t h e r i v e r can exceed t h e
recommended limits f o r irrigation o r aquatic r e c r e a t i o n (Benedek e t al.
1980).
As i s well known, downstream of major waste water discharge points
(Bratislava, Budapest) t h e hygienic situation is r a t h e r severe. Table 1 9
shows a typical bacteriological picture of t h e Danube, at t h e water intake
of Mohscs and, in t h e water distribution system of P d c s f o r which t h e water
is provided by t h i s intake (Geldreich, 1984). The virological investigations
by public health organisation need f u r t h e r development.
6.5 Sewage and Waste Water Disposal
6.5.1 Present situation
The list of t h e m a j o r towns situated along t h e banks of t h e Danube or
--
located in t h e catchment is included in Section 3. The common c h a r a c t e r i s t i c of t h e s e cities is t h a t they
- with a few exceptions - do not have sewage
and waste water treatment plants, o r , if they do, t h e treatment efficiency i s
not adequate. Due t o t h i s fact, t h e Danube and its t r i b u t a r i e s r e c e i v e significant organic and inorganic loads.
In addition, t h e Danube r e c e i v e s non-treated or partially t r e a t e d
effluents f r o m a wide r a n g e of industries including pulp and p a p e r mills,
iron and steel mills, petroleum refineries, chemical plants, cement works,
coal and o t h e r mineral processsing, breweries, s u g a r r e f i n e r i e s and canneries. The p a p e r , petroleum, iron and steel industries have been identified as those m o s t urgently in need of industrial pollution control measures
(WHO, 1977b).
Industrial pollution of the Danube may b e potentially more serious in
t h e upper r e a c h , as more industrial plants are sited t h e r e and lower
volumes of flow are available f o r diluting t h e resulting effluents (Liepolt,
1979).
Table 1 9
B a c t e r i o l o ~ i c a lwater huality from t h e Danube-water
d i s t r i b u t i o n network of P6cs
i n t a k e a t Mohdcs t o t h e
(Geldreich, 1984)
C o l i f orm
Fecal
Fecal
Clos tr i d i a
total
C o l i f orm
Strep.
( p e r 1 0 0 ml) ( p e r 100ml) (per 100ml) (per 40
Type of water
SPC (37Oc
per ml
m~/l
- -
mube-water a t Mohdcs 5 200-72 ,400 200-4.600
. a r i f i e d water of
Moh AC s
;ored mixed water
a t PBce
lter reaching t h e
a c t i v e carbon
.
160-1200
-
40-2100
(100-500
-
-
-
-
lrif i e d drinking
water
;ored d r i n k i n g water
xx
-
xx
rter i n t h e network
xx
-
xx
Data from t h e p e r i o d October 1983 t o March
P r a c t i c a l l y n o t demonstrable
64-240
1984
-
3800-98,000
210-960
95-850
0.17-1.32
0.2 -0.96
0.04-1.10
3-43
t 0 . l -0.42
4-9
C 0.1
Some information of t h e major pollution s o u r c e s in the r i p a r i a n count r i e s determining t h e c h a r a c t e r and nature of t h e pollution load i s given in
Table 20 (Benedek, 1986).
There i s no adequate warning and emergency system between t h e
r i p a r i a n countries; accidents which r e s u l t in water pollution a r e of particul a r concern. In just one y e a r t h e r e were almost 20 accidents in t h e Danube
catchment resulting from oil pipeline failures alone (WHO, 1977a).
In t h e p a s t , the most serious accidental spills o c c u r r e d in Vienna, Bratislava and Vdc (40 km north of Budapest) (WHO, 1982). In 1976, a t t h e
Nussdorf water works n e a r Vienna alcylphenols in t h e water caused a
longer quarantine of t h i s plant (Frischherz-Bolzer,
1984) and in 1980 at
Vdc o r g a n i c solvents resulted in t h e same situation. Significant hazard w a s
caused to t h e Bratislava water works by t h e leakage of oil r e s o u r c e s at a
nearby oil r e f i n e r y (WHO, 1982). In all these c a s e s t h e rehabilitation of t h e
contaminated wells e i t h e r lasted f o r a n extended period o r t h e w e l l s had t o
b e abandoned.
The forecasting of such events and the organisation of t h e i r control i s
a
very
important
task
for
all
Danube
countries
(WHO,
1984;
Benedek-Hammerton, 1985; Katona, 1984).
Thermal pollution s o f a r h a s not caused any detectable damage,
although t h e r i v e r i s being used as a s o u r c e of cooling water f o r industry
and f o r power generation (Liepolt, 1979). Similarly, a t t h e c u r r e n t level
(see p a g e 41) of development of nuclear power stations along t h e r i v e r , t h e
safety precautions should provide adequate protection from radioactive
discharges (IAEA, 1979).
6.5.2 Future developments
The amount of pollution derived from domestic sewage will i n c r e a s e as
a r e s u l t of t h e necessary improvements of water supply and sanitation.
More connections t o a piped water s e r v i c e and, particularly, m o r e connection t o sewer systems c a n intensify t h e load discharged t o t h e water c o u r s e ,
even if some treatment i s given. This i s particularly t r u e in r e s p e c t t o
nutrients, which intensify t h e growth of algae and fungi, affecting t h e oxygen balance of t h e Danube in this manner.
Table 20
&;lor
p o l l u t i o n sources along t h e e n t i r e Danube
(Benedek, 1986)
River
b
citiesX
with waste
without o r with
partial
treatment
waste treatment
-.
T r i b u t a r i e s with
major i n d u s t r i a l
~ o l l u t i o n( P ~ P
and paper, chemical, etc.)
Regensburg FRG
Passau r e g i o n
FRG
Linz A
Ems A
Mar ch/Mor ava
A/CS
B r a t i s l a v a Cz
Gy6r region H
Budapest H
Novi Sad Yu
Sava YU
Beograd
(Belgrade) Yu
Morava YU
Jiu R
Olt R
J a n t r a BG
Arges RO
* with
population equivalent of 500.000 o r more
Increased water use will result, inevitably, in increased volumes of
industrial effluents being discharged into t h e r i v e r system. With g r e a t e r
sophistication of industrial manufacture, i t a p p e a r s probable t h a t t h e quantities of bio-resistant chemicals requiring disposal will also increase. This
potential pollution will come not only from d i r e c t discharges of liquid
effluents but a l s o from t h e need to dispose of sludges and o t h e r solid wastes
derived from industry and settlements (WHO, 1982).
Construction of sewage and industrial effluent treatment plants will not
completely overcome t h e pollution problems, as i t h a s been established t h a t
a considerable p a r t of t h e pollution load originates from non-point sources,
mainly from u r b a n and agricultural runoff (Benedek et al., 1980), although
additional hazards are presented by inadequate control o v e r indirect pollution of groundwater (and subsequently of t h e Danube) from dumping of waste
materials (Ainsworth, 1981).
The development of more nuclear power generating capacity within t h e
Danube catchment will call f o r increased quantities of cooling water,
increasing t h e r i s k of local thermal pollution (WHO, 1982).
6.6 Bank-Well Filtration f o r Water S u p p l y
6.6.1 B a s i c p r o b l e m s o f bank-well f i l t r a t i o n
The most important utilization of t h e Danube water i s t h e drinking
water intake through bank-well filtration f o r potable and o t h e r supply purposes.
The water quality of t h e bank-filtered w e l l s is endangered by t h r e e
effects caused by t h e increase in pollution load of t h e Danube:
-
simultaneously with t h e deterioration of " r a w water" t h e purification
capacity of t h e f i l t e r l a y e r also decreases.
-
a n o t h e r mechanism i s accumulation of micropollutants in bottom sediment as precipitation,
-
anaerobic conditions in t h e filtration l a y e r Benedek-Laszlo, 1980).
The n i t r a t e content of t h e groundwater along t h e Danube is mostly due t o
t h e agriculture. In o r d e r t o reduce it, t h e r e is a p r o j e c t underway in Hung a r y , supported by UNDP in cooperation with FA0 (UNDP-FAO, 1982-86).
Use of water i s often hampered by micropollutants mostly bound t o t h e
suspended sediment; silting causes t h e accumulation of ppllutants in t h e bottom sediment. This phenomenon deserves more detailed attention f r o m t h e
point of view of water uses because when settled, i t menaces bank-filtered
water quality, while in suspended form i t menaces d i r e c t drinking water- and
irrigation water-intakes. To this group of micropollutants belong t h e diff e r e n t f o r m s of heavy metals, e.g., mercury, cadmium and organic compounds of higher molecular weight and of less p o l a r c h a r a c t e r , such as
polyaromatic hydrocarbons, s e v e r a l mineral oil fractions and oil derivatives (Benedek-Laszlo, 1980).
If t h e oxygen content in t h e water i s not sufficiently high o r t h e bottom
deposit i s over-polluted with inorganic material, z e r o oxygen might o c c u r in
t h e benthos, o r in the filtration l a y e r (anaerobic conditions).
In water abstraction regions where anaerobic filtration processses
dominate in t h e aquifer, t h e following c h a r a c t e r i s t i c water quality changes
o c c u r during bank-well filtration: The dissolved oxygen, r e d o x potential
and pH decrease, n i t r a t e i s reduced to n i t r i t e and ammonia, iron and manganese are redissolved.
The pollutant removal efficiency of t h e bank-well filtration p r o c e s s is
sufficient for t h e majority of components a t t h e p r e s e n t pollution level of
t h e Danube. Downstream of Budapest a t a typical horizontal well, t h e removal efficiencies can b e s e e n in Figure 14. Considerable redissolution of iron
and manganese is typical in t h e anaerobic filtration layer. Flow from t h e
background zone towards t h e wells is responsible for t h e high values of
potassium, sulphate, chloride, calcium, hardness, conductivity, magnesium,
sodium (Laszlo-Homonnay, 1985).
A s a consequence of t h e t h r e e effects mentioned above, t h e conventional
technology (disinfection via chlorination f o r health protection) i s not satisf a c t o r y f o r potable water and t h e introduction of post-withdrawal treatment
is necessary a t some water works along the Danube (Benedek-Bulkai, 1981;
WHO, 1984).
Patio of mem
conctntmtioru
in we1 water
and D c n u k water
+
Figure
14.
Water
quality
changes
due
to
bankwell
filtration
(Laszlo-Homonnay, 1985)
6.6.2 Bank-well filtration at different Danube countries
Federal Republic of G e r m a n y
Along the Danube t h e r e i s no bank-well filtration system in operation.
Austria
Bank-well filtration of r i v e r water h a s been practised f o r more than 40
y e a r s t o supply Vienna. The water work at Nussdorf can m e e t about 15%of
Vienna's water demand with a maximum output of 100,000 m3/day.
chlorination i t i s pumped
After
into r e s e r v o i r s and t o t h e supply system
(Frischherz-Bolzer, 1984).
The city of Linz also obtains i t s drinking water from bank-well filtered
Danube water. Austria obtains only 1%
of i t s potable water supply from
bank-well filtration (WHO, 1981).
The use of bank-well filtrated water in Austria poses t h e following
problems:
-
There are sometimes taste and odour problems originating from unknown waste water effluents upstream of Vienna.
-
There is no effective alarm system f o r r i v e r water contamination
(F'rischherz-Bolzer,
1984).
Czechoslovakia
Bank f i l t e r e d water constitutes a n important proportion of drinking water
supplies. The city of Bratislava is dependent on bank f i l t e r e d water from
t h e Danube with t h e capacity of 160,000m3/day. The water works of Bratislava have been damaged by petroleum derivatives coming from t h e "background" (Lehoczky, 1978). In addition t o natural r e c h a r g e by t h e Danube,
t h e Zitny Ostrov aquifer i s expected t o provide t h e key f u t u r e s o u r c e of
drinking water f o r Southern Slovakia (UNDP-WHO, 1977).
Hungary
There i s a quite different situation in Hungary, where about 22% of t h e
population r e l i e s directly on t h e Danube f o r i t s drinking water and about
one-half of t h e industrial water i s obtained from t h e r i v e r (Benedek, 1977).
Europe's l a r g e s t bank-well abstraction scheme supplies drinking water
t o Budapest. The Municipal Water Works obtain approximately 310 million
m3/year drinking water from bank-wells located along t h e Danube upstream
and downstream of Budapest in a length of 90 km. Bank-well filtration plus
additional disinfection by chlorination h a s resulted in high-grade drinking
water quality f o r decades (Laszlo-Homonnay, 1985).
Fortunately, t h e water gained from bank-filtered wells i s of a fairly
good quality because in t h e slightly polluted f i l t e r l a y e r s t h e a e r o b i c conditions promote t h e physical, chemical and biochemical processses providing
decomposition of oil, phenols and detergents, nitrification processses and
adsorption of heavy metals (Benedek-Laszlo, 1980).
I t may b e mentioned h e r e t h a t t h e bank filtered water r e s o u r c e s
located along t h e Hungarian Danube s t r e t c h are o v e r 5.5 million m3/day,
and about 2 million m3/day are located along o t h e r t r i b u t a r i e s (WHO, 1983).
Yugoslavia
Both Belgrade and Z a g r e b r e l y heavily on bank-well f i l t e r e d water f o r pota b l e supply, t h e f o r m e r obtaining 95% of i t s t o t a l needs via t h i s system.
Z a g r e b obtains potable water of excellent quality from t h e relatively unpolluted waters of t h e S a v a r i v e r . Novisad a l s o obtains i t s w a t e r via a n extens i v e r a d i a l bank-well filtration system o p e r a t i n g along t h e banks of t h e
Danube. In t h e p r o v i n c e of Voivodina, w h e r e more t h a n 1 0 %of Yugoslavia's
population live, 15%of a l l water requirements are satisfied by bank-well filt r a t i o n supplies.
Romania
An increasing number of drinking water supplies depend o n water obtained
via bank-wells located along t h e b a n k s of t h e Danube. Bank-well f i l t r a t i o n
is important in supplying both Craiova and Galati with drinking water. At
a n o t h e r location on t h e banks of t h e Jiul r i v e r , a bank-well f i l t r a t i o n capac i t y of 60,000 m3/day i s in operation.
BuLgaria
No information i s available.
LESR
T h e r e i s no bank-well filtration system in o p e r a t i o n along t h e Danube (WHO,
1984).
I t i s t o b e noted t h a t along t h e Danube t h e situation of bank-well f i l t r a tion, f o r t h e time being, i s much b e t t e r t h a n along t h e Rhine in t h e FRG,
where t h e most common t r e a t m e n t applied i s oxygenation a n d a c t i v a t e d carbon f i l t r a t i o n to remove o r g a n i c micropollution (WHO, 1984).
In a l l probability a similar situation will develop along t h e Danube in
t h e distant f u t u r e . As a consequence, t h e investment and o p e r a t i n g c o s t s
will b e much h i g h e r than now.
6.6.3 D i r e c t surface intake
The quality of t h e water i s s a t i s f a c t o r y almost o v e r t h e e n t i r e length of
t h e Danube and suitable even f o r drinking water supply by d i r e c t s u r f a c e
intake, a f t e r a simple treatment, filtration and chlorination as i t i s applied
in Budapest (about 20%of t h e e n t i r e water demand i s met d i r e c t l y from t h e
river).
A s a consequence of t h e rapid industrialization of t h e r i p a r i a n
countries, however, t h e hazard of persistent micropollutants i s growing and
presumably t h e simple water treatment technology will not be satisfactory
in t h e n e a r f u t u r e (Benedek-Laszlo, 1980).
6.7 Effects of River Training and B a r r a g e s
6.7-1G e n e r a l r e m a r k s
The multipurpose utilization of t h e Danube water i s of vital importance
f o r t h e approximately 71 million inhabitants in t h e r i v e r basin.
The
economic development in t h e r i p a r i a n countries, and t h e i n c r e a s e of navigation a c c e l e r a t e d by t h e Rhine-Main-Danube canal interconnecting t h e two
important transcontinental waterways ranging from t h e Atlantic Ocean to
t h e Black S e a will likely cause water quality problems affecting considerably t h e r i p a r i a n countries from t h e point of view of public health
(Benedek-Laszlo, 1980).
I t i s worth mentioning t h a t a l a r g e stream like t h e Danube may c r e a t e a
lot of water pollution control problems even without t h e b a r r a g e s a l r e a d y in
operation and under construction (Benedek et al., 1980).
Construction of r i v e r b a r r a g e s and o t h e r regulatory s t r u c t u r e s (i.e.
groins) a f t e r t h e installation of bank-wells may significantly a l t e r t h e
hydraulic conditions in a r i v e r and may have a n effect upon t h e groundwa-
ter level, too. Reduced velocity in t h e r i v e r bed may lead to increased
deposits of t h e smaller-grained, silt-like material, and may cause a reduction in dissolved oxygen content of t h e r i v e r water, leading to subsequent
water quality changes, (solubility of iron and manganese, reduction of sulphates and nitrates, problems of t a s t e and odour, etc., in t h e impounded
water, WHO, 1984).
The high concentrations of nutrients discharged into t h e Danube as
constituents of sewage and o t h e r effluents i n c r e a s e eutrophication, s o t h a t
much of the brown colour of t h e r i v e r is associated with assimilated brown
pigments from diatoms growing on those nutrients. The effects of biological
growth and decay on the quality of impounded water can influence t h e use o r
t h e treatment requirements of t h e water (WHO, 1982).
Bio-resistant materials, persisting in t h e water, c a n b e accumulated by
aquatic organisms o r absorbed on t h e suspended solids in t h e water course;
they also c a n be deposited and accumulated in t h e sediments. Alterations in
t h e flow regime of t h e r i v e r , by constructing r i v e r b a r r a g e s o r groins, may
thus provide a long-term r e s e r v o i r of pollutants, capable of subsequently
being mobilized by bio-chemical o r physical processses and s o providing
f u r t h e r hazards t o water quality.
Deposition of sediments, possibly contaminated with toxic metals and
organic chemicals, will b e increased by r e i t e r a t e d improvements of r i v e r
regulation systems intended to improve navigation and facilitate hydroelect r i c power generation (WHO, 1982).
An increase of navigation expected a s a r e s u l t of improved r i v e r regulations, can a l s o lead t o a n increase in t h e likelihood of accidents resulting
in increased pollution of t h e r i v e r water (WHO, 1984).
The inter-river canals particularly when considered in combination
with t h e proposed impoundment r e s e r v o i r s , have a potential to change t h e
ecosystem of t h e Danube. I t is probable t h a t t h e improved communication
and t r a n s p o r t facilities provided by such links will encourage still more
urban and industrial development in the r i v e r basin as wider markets for
industrial and agricultural products become available. The r i s k of pollution
of t h e Danube will i n c r e a s e with t h e t r a n s f e r of water between t h e different
r i v e r systems, while t h e e x t r a t r a f f i c and development s o generated will
i n c r e a s e t h e r i s k of accidents (WHO, 1982).
6.7.2 Experiences by different Danube countries
Federal Republic of Germany
Reports on publications dealing with this topic are not available.
Austria
Whenever a new b a r r a g e h a s been built in t h e Austrian Danube section t h e
water of t h e wells, along new impoundments has begun t o d e t e r i o r a t e with
increasing iron and manganese contents causing t a s t e and odour problems
due
to
dissolved
oxygen
(Frischherz-Bolzer, 1984).
depletion
and
anaerobic
conditions
An example of b a r r a g e construction in t h e Austrian s t r e t c h of t h e
Danube s e r v e s t o demonstrate some of t h e changes which c a n b e expected
and the problems t h a t c a n result. A t t h e water intake s i t e of Godworth,
sited upstream of t h e power station of Ottensheim-Wilheving,
t h e water
level in the Danube has subsequently been raised by a n a v e r a g e of 9 m
above t h e original level due to canalization. This has resulted in reduced
flow velocities and a n increase in deposit of organic matter in t h e r i v e r
bed, causing blanketing and subsequent reduced capacity of t h e bank-well
filtration plant.
A t t h e water works of Ybbs and at t h e water supply facilities at
Goldwarth supplying t h e town of Linz, t h e reduced oxygen levels in t h e r i v e r
water, resulting from a n increase in organic matter in t h e r i v e r sediments,
have necessitated t h e introduction of post-extraction treatment t o produce
a drinking water of acceptable quality (WHO, 1984).
In Austria a complex investigation about t h e ecological, technical and
sociological impacts of one of t h e b a r r a g e s (Altenworth, downstream of
Krems) h a s been s t a r t e d (Oeko., 1984).
Czechoslovakia and Hungary
Gabcikovo-Nagymaros
b a r r a g e system i s being planned and constructed
(see Annex 11). According to a f o r e c a s t , suspended solids content which
d e c r e a s e s by 30%o v e r a r i v e r s t r e t c h of about 70 km downstream of Bratislava at p r e s e n t , will d e c r e a s e by 55X a f t e r t h e construction of t h e barr a g e (Benedek et al., 1978; Rotschein, 1976). The r e g u l a r dredging of this
sediment should be included as p a r t of t h e normal maintenance service.
Additionally, t h e decomposing organic and pathogene microorganism
content originating from untreated municipal wastes, will obviously result in
anaerobic decomposition and consequently a n oxygen loss in t h e bottom sediment, t h e r e b y creating b e t t e r conditions f o r t h e growth of zoobenthos.
The m a s s thereof will be even g r e a t e r than 100 g/m2 o v e r t h e backwater
r e a c h of t h e b a r r a g e s . No significant change can b e expected, however, in
floating zoo- and phytoplankton, and probably t h e diatoms will dominate in
t h e f u t u r e , too (Rotschein, 1976).
I t i s worthwhile t o mention a n investigation c a r r i e d out by t h e Hungarian Research Centre f o r Water Resources Development (VITUKI). I t s aim
w a s t o f o r e c a s t t h e effect of t h e b a r r a g e s t o t h e trophic conditions, to t h e
change in primary production and planktonic communities. The r e s e a r c h
h a s been c a r r i e d out in existing r i v e r b r a n c h e s of low flow velocity and of
increased transparency. While t h e main Danube i s mesotrophic, some of t h e
b r a n c h e s studied are in eutrophic condition. The number of algae and t h e
biomass are s e v e r a l times higher in t h e low flow branches. A s a consequence, t h e meso-trophic
level of
t h e Danube will be higher when
impounded. This means t h a t t h e extended nutrient input and all t h e waste
water discharged should b e controlled by a n increased treatment program
(VITUKI, 1985).
YugosLavia and R o m a n i a
The Yugoslavian experiences r e l a t e d t o t h e I r o n Gate b a r r a g e (Djerdap)
c a n b e summarized as follows:
-
Since t h e construction of the b a r r a g e t h e turbidity in t h e lacustrine
p a r t of t h e r e s e r v o i r h a s decreased and t h e r e h a s been intensive sedimentation of suspended organic and inorganic particles;
-
The temperature gradient down to 20 m (the maximum height of
impounded head water is 33.5 m) w a s low in August ranging between
0.2"C and O.SdegreesC, s o t h a t stratification did not o c c u r ;
-
The oxygen deficiency was higher in t h e lacustrine p a r t than in t h e
fluent one, less being absorbed from t h e atmosphere and more being
r e q u i r e d for t h e decomposition of organic matter;
-
The KMn04 consumption showed a temporary increase in t h e lacustrine
p a r t suggesting t h a t t h e r e was a temporary increase of t h e content of
soluble organic matter;
-
The phosphate and ammonia content as well as the concentration of
total solubles were also higher, f r o m time to time, in t h e lacustrine
p a r t of t h e r e s e r v o i r than in t h e fluent p a r t ;
-
There was a g r e a t e r KMn04 demand and a higher concentration of phosphate and total dissolved s a l t s at 20 m depth than in shallower water.
-
The vertical distributions of t h e phosphates, ammonia, d r y residuals,
sulphates and t h e KMnO,, demand showed t h a t t h e r e was a temporary
chemical stratification although i t w a s not strongly marked.
-
The concentrations of calcium, biocarbonate, carbonate hardness and
alkalinity w a s not significantly different in t h e two p a r t s of the reserv o i r (Jankd, 1978; Petrovid, 1975; Petrovid, 1978).
R e p o r t s dealing with t h e effects of impoundment on t h e operation of Water
Works in Belgrade are not available.
Bulgaria and USSR
T h e r e i s no hydropower system in operation.
Finally, t w o r e a c h e s of t h e Danube- -have to b e mentioned where poste x t r a c t i o n treatment i s necessary although they are not affected by any
barrage:
-
At t h e Lobau water treatment plant (near Vienna), t h e bank-well filt e r e d water h a s t o b e t r e a t e d f o r iron and manganese removal because
of the l o w dissolved oxygen level in t h e filtration l a y e r .
-
Similar situation i s p r e s e n t at a plant of t h e Budapest Municipal Water
Works, located south of Budapest where ozoneaxidation i s used f o r
i r o n and manganese removal of bank-well filtered water (WHO, 1984).
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Levina, O., Sergejev, A. (1985). The succession of t h e zoobenthosbiocenosis
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Miloradov. M. (1977). Some r e s u l t s of r e s e a r c h on water quality, dispersion
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ANNEX I
(Draft translation from Hungarian)
DECLARATION ON
THE COOPERATION OF THE DANUBE COUNTRIES
ON WATER MANAGEMENT AND ESPECIALLY WATER
POLLUTION CONTROL ISSUES OF THE RIVER DANUBE
A c c e p t e d in B u c h a r e s t
13 December. 1985
A t the Bucharest Conference dealing with t h e issues of water management of t h e Danube, r e p r e s e n t a t i v e s of t h e governments of t h e Danube
countries
-
being aware of t h e high importance of t h e rational management
and pollution control of t h e Danube water f o r t h e welfare and t h e
health of the peoples of t h e Danube countries a s w e l l as f o r t h e
economical and' social development t h e r e o f ,
-
being convinced t h a t besides t h e coordination of national e f f o r t s
and necessary measures among t h e neighbouring Danube count r i e s , t h e efficiency of actions against t h e pollution of t h e Danube
water could essentially b e increased by means of a multilateral
cooperation of all Danube countries,
-
taking into account t h e importance of t h e educational work to b e
performed in wide c i r c l e s of t h e youth in t h e i n t e r e s t of protecting, preserving and especially improving t h e quality of t h e Danube
water,
-
guided by generally accepted principles and r u l e s of international
law, including t h e Constitution of United Nations, in accordance
with t h e i n t e r e s t s and t h e sovereignty of all Danube s t a t e s ,
-
striving f o r the consideration of t h e content of t h e Closing Document of t h e Conference f o r European Security and Cooperation a s
well as of t h e theses of t h e Closing Document accepted on t h e
Madrid meeting of t h e r e p r e s e n t a t i v e s of t h e European countries,
in o r d e r t o promote regional cooperations aiming a t pollution cont r o l and utilization of water r e s o u r c e s ,
d e c l a r e t h e following:
1.
The preservation and rational utilization of water r e s o u r c e s , t h e
prevention, termination and control of t h e i r pollution constitute a n
organic p a r t of the national water management and environment protection policies of t h e Governments of t h e Danube countries.
Taking into consideration t h e f a c t t h a t t h e water of t h e Danube is being
utilized f o r various purposes, among o t h e r s f o r water supply of t h e
population, t h e Governments of t h e Danube countries
of t h e p r e s e n t and f u t u r e generations as well
-
- in t h e i n t e r e s t
are ready to t a k e
measures, according t o t h e prescriptions of t h e legal r u l e s valid in t h e
different countries and within t h e frame of t h e techno-economic possibilities, t o safeguard t h e water of t h e Danube from pollution, with special r e g a r d t o dangerous and radioactive substances and t o a gradual
d e c r e a s e of t h e d e g r e e of pollution, taking into account also t h e ecological requirements connected with t h e water of t h e Danube.
The
Governments also effectuate on t h e i r respective t e r r i t o r i e s a systematic monitoring of t h e waste waters released into t h e Danube and
authorize t h e introduction of these waters only in accordance with t h e
legal r u l e s valid in t h e different countries; they also control t h e
accomplishment of t h e conditions of introduction and at t h e same time
observe the changes in water quality.
2.
The complex measures, worked out f o r long ranges by t h e p r o p e r
e f f o r t s of t h e Governments of t h e Danube countries, and especially t h e
execution of t h e s e measures, c a n be completed and confirmed, in a way
corresponding t o t h e goals defined above, by means of bi- and multila-
teral international cooperation.
F o r t h i s purpose, t h e Governments of t h e Danube c o u n t r i e s s t r i v e f o r t h e
following:
2.1 In t h e framework of t h e i r bi- and multilateral cooperations they c a r r y
o u t systematical observations o n t h e w a t e r quality of t h e Danube, on
t h e basis of programmes and methods enabling t h e collection of comp a r a b l e d a t a . To t h a t end, t h e y work o u t a p p r o p r i a t e programmes and
methods not l a t e r t h a n within one o r two y e a r s following t h e signing of
t h i s Declaration.
,
The w a t e r quality observations will b e performed in t h e crosss-sections
where t h e Danube s t e p s from t h e national t e r r i t o r y of o n e Danube
c o u n t r y t o t h a t of a n o t h e r ; when t h e Danube constitutes t h e state
b o r d e r , in t h e beginning a n d final crosss-section of t h e common f r o n t i e r r e a c h , o r in o t h e r sections determined in t h e f r a m e of b i l a t e r a l
relations.
If i t is n e c e s s a r y , t h e Danube countries i n t e r e s t e d can
determine, in t h e f r a m e o f . t h e i r b i l a t e r a l relations, o t h e r c r o s s s sections as well, s u c h as t h o s e up- and downstream of t h e major t r i b u -
taries of t h e Danube, up and downstream of major towns a n d impounding
r e s e r v o i r s , and f u r t h e r in t h e main b r a n c h e s of t h e Danube d e l t a at
t h e Black S e a t h o s e r e p r e s e n t a t i v e crosss-sections, downstream of
which n o anthropogenic impact c a n modify t h e water quality any more.
In 6 months time, a f t e r having fixed t h e methodology, w a t e r quality
observations a n d analyses will b e s t a r t e d , according to t h a t methodology. In two y e a r s a f t e r t h e s t a r t of t h e observations t h e water quality
c h a r a c t e r i s t i c s of t h e Danube, as o b s e r v e d during t h e given period,
will b e determined by d a t a processing according t o t h e methodology
fixed.
2.2. The Governments inform e a c h o t h e r about t h e i r o r g a n s competent f o r
monitoring of t h e pollution of t h e water of t h e Danube a n d establish t h e
methods and t h e programme of w a t e r quality observations; t h e y also
designate t h e i r o r g a n s to which t h e results and evaluations r e g a r d i n g
t h e w a t e r quality of t h e Danube as well as all u r g e n t informations connected with accidental pollutions and measures aiming at t h e i r removal,
mutually have t o b e r e p o r t e d .
2.3 The Governments will study t h e possibility of automatization of t h e
observation of t h e Danube's water quality a n d of t h e installation of
automatized monitoring systems in t h e cross-sections mentioned above.
2.4 The Governments will inform e a c h o t h e r , through t h e i r abovementioned competent o r g a n s , whenever n e c e s s a r y b u t at l e a s t e v e r y
two y e a r s , about t h e r e s u l t s of analyses a n d evaluations performed in
t h e o b s e r v a t i o n crosss-sections.
They inform e a c h o t h e r o n t h e i r
measures aiming at t h e p r o t e c t i o n of t h e Danube w a t e r from pollution
as well as a b o u t t h e agreements taking e f f e c t between Danube count r i e s t o t h i s p u r p o s e , including t h e r e s u l t s achieved by means of t h e i r
realization; t h e y a l s o inform e a c h o t h e r about t h e t e c h n i c a l solution of
sewage t r e a t m e n t , a b o u t w a t e r analyses, investigations of water
r e s o u r c e s and t h e i n t e r n a l s t a t e norms f o r w a t e r quality protection.
2.5 The Governments promote, whenever n e c e s s a r y , but at least e v e r y two
y e a r s , t h e organisation of t h e meeting of t h e r e p r e s e n t a t i v e s of t h e
competent o r g a n s of t h e Danube c o u n t r i e s aiming at comparing t h e
results of t h e analysis and evaluation of t h e Danube's w a t e r quality as
well as at t h e solution of o t h e r problems a r i s i n g in t h e c o u r s e of t h e
cooperation t o b e r e a l i z e d o n t h e basis of t h i s Declaration.
2.6 The Governments inform e a c h o t h e r about t h e i r competent o r g a n s
working out t h e b a l a n c e s of water r e s o u r c e s and needs, a n d about t h e
r e s u l t s of t h e s e works whenever r e g a r d i n g a f r o n t i e r r e a c h of t h e
Danube. Within a y e a r , a f t e r signing this Declaration, a harmonized
method f o r comparing t h e w a t e r balances of t h e Danube c o u n t r i e s will
b e developed in o r d e r to obtain comparable r e s u l t s in t h e b o r d e r sections.
On t h i s b a s i s , they will s t r i v e f o r compiling t h e summarized
water balance of t h e Danube.
3.
In t h e i n t e r e s t of realizing t h e goals of t h i s Declaration, t h e Governments of t h e Danube c o u n t r i e s will gradually s t r i v e t o a r r a n g e , by
means of bi- and multilateral agreements, t h e c o n c r e t e issues of t h e
water quality c o n t r o l of t h e Danube which are of basic i n t e r e s t f o r t h e
respective states.
4.
In o r d e r t o fight against floods on t h e Danube and against t h e
dangerous i c e phenomenon causing floods, the Governments of t h e
Danube countries will inform each o t h e r , through t h e i r competent
organs, about t h e development and passing of floods as well as about
t h e i c e phenomena f o r e c a s t f o r the crosss-sections selected by agreements.
5.
The Governments of the Danube countries continue
means of creating legal r u l e s
- with
- among
o t h e r s by
striving f o r taking measures f o r
protecting. preserving and improving t h e environment and f o r t h e
enforcement of increased responsibility. particularly in t h e field of
protecting waters from pollution.
6.
In o r d e r t o r e a l i z e the measures f o r e s e e n by this Declaration, t h e competent o r g a n s of t h e Danube countries
these measures
-
-
t o be appointed f o r taking
will coordinate t h e i r measures in alternation with
each o t h e r , beginning with t h e competent o r g a n of t h e state taking t h e
initiative and continuing according t o t h e o r d e r of succession a g r e e d
upon at t h e f i r s t meeting.
7.
In o r d e r to successfully c a r r y out t h e measures laid down by this
Declaration, t h e Governments of t h e Danube countries will t a k e advantage of t h e possibilities of cooperation with the United Nations Organisation, with i t s specialized organs as well as with o t h e r international
organisations interested.
The original copies of this Declaration will be guarded by t h e Government of
Romanian Socialist Republic.
The Government of each Danube country will r e c e i v e from t h e Government
of Romanian Socialist Republic t h e a t t e s t e d duplicate of t h i s Declaration.
Each Danube state will make public and s p r e a d t h e t e x t of t h i s Declaration
and e n s u r e its widespread knowledge.
The Government of t h e Romanian Socialist Republic i s invited to hand o v e r
t h e text of t h i s Declaration t o t h e S e c r e t a r y General of t h e United Nations
Organization, in o r d e r t o pass it, as a n official working document of t h e
United
Nations
Organisation,
to all members of
that
Organisation,
f u r t h e r m o r e t o hand i t o v e r t o t h e S e c r e t a r y General of t h e World Meteorological Organisation, t o t h e Managing Director of t h e United Nations Educational, Scientific and Cultural Organisation, t o the Director of t h e World
Health Organisation, to t h e Managing S e c r e t a r y of t h e United Nations
Organisation's Economic Commission f o r Europe, t o the Director General of
t h e International Atomic Energy Agency, to the President of t h e Danube
Commission and t o t h e Director of t h e United Nations Organisation's P r o gramme f o r Environmental Protection.
The r e p r e s e n t a t i v e of t h e Danube countries have signed t h e Declaration
aware of t h e high importance of t h i s document.
Accepted in Bucharest, on t h e 13th of December, 1985, in Bulgarian, Czech,
Hungarian, German, Russian, Romanian and Serbo-Croatian languages.
ANNEX I1
ENVIRONMENTAL IMPACT ASSESSMENT OF THE
GABCIKOVO-NAGYMAROS BARRAGE SYSTEM
In September 1977, a n agreement was signed between t h e Governments
of Czechoslovakia and Hungary on t h e implementation of a joint p r o j e c t aiming at b e t t e r utilization of t h e s t r e t c h of t h e Danube between Budapest and
Bratislava, where t h e r i v e r i s the common b o r d e r between t h e two countries
along a length of about 140 km. The project includes two subsystems.
-
The u p p e r one h a s a b a r r a g e a t Dunakiliti closing the main a r m of t h e
Danube and diverting t h e discharge into a derivation canal having a
length of 30 km. On t h e canal t h e r e i s a hydropower plant and a navigtion lock a t Gabcikovo. The tailwater canal r e t u r n s t o the main a r m a t
Palkovicovo.
-
The lower subsystem is a r i v e r b a r r a g e constructed in t h e bed a t
Nagymaros. i t i s composed of t h r e e main parts: t h e weirs closing t h e
bed, t h e hydropower plant and t h e navigation lock.
The construction of t h e system s t a r t e d in 1978. Since then t h e derivation
canal was almost completed. The construction of t h e s t r u c t u r e s a t Gabcikovo is also in a w e l l developed phase. At Dunakiliti the foundation of t h e
b a r r a g e was finalized. According t o the timetable in 1990 t h e power plant
on the derivation canal will b e in operation. A t Nagymaros only preliminary
work was done until now. I t i s planned t o s t a r t t h e construction in 1987 and
finish in t h e e a r l y 90s s o t h a t t h e whole system should b e completed before
1994.
In t h e meantime some environmental concerns were r a i s e d in connection with the modification of t h e r i v e r regime. The Hungarian National
Water Authority, which i s responsible f o r planning and designing t h e system,
have a n environmental impact assessment p r e p a r e d . i n cooperation with t h e
National Environment Authority. For this study, t h e r e s u l t s of numerous
e a r l i e r investigations were utilized together with t h e recommendations of
s e v e r a l special committees set up by the Hungarian Academy of Sciences f o r
t h e analysis of t h e environmental and agricultural impacts of t h e b a r r a g e
system. The purpose of this p a p e r is t o give a s h o r t evaluation of this
environmental impact assessment.
DENELOPMENT O F WATER MANAGEMENT IN THE DANUBE VALLJ3Y
Water management in l a r g e r i v e r valleys aims at t h e utilization of
natural r e s o u r c e s (water, energy, bed load) and o t h e r economic advantages
(transport, recipient of wastes, recreation) offered by t h e r i v e r .
Four
main phases can b e distinguished in i t s development:
f l o o d - p l a i n m a n a g e m e n t , when man adapts his activity to t h e natural
conditions determined by t h e random c h a r a c t e r of t h e water regime
and utilizes t h e advantages provided by t h e p r e s e n c e of water considering t h e limitations determined by these conditions;
p r i m a r y control of' w a t e r regime ( r i v e r training, flood control and
water control o v e r t h e catchment), when l a r g e r a r e a s become a r a b l e ,
navigation i s improved and settelements c a n move n e a r t h e r i v e r establishing c l o s e r contact with water by decreasing t h e damages which
might b e caused by random hydrological events;
r i v e r c a n a l i z a t i o n , t h e main purpose of which i s t h e stabilization of
the water level, t h e d e c r e a s e of its fluctuation and t h e utilization of
t h e energy in t h e r i v e r by constructing b a r r a g e s and maintaining
s t r e t c h e s with low slope between them;
complete (quantitative and qualitative) c o n t r o l of' r u n o f l , which c a n be
achieved by regulating t h e discharge according to t h e demands using
t h e retention capacity of l a r g e r e s e r v o i r s and by efficacious treatment of wastes r e l e a s e d into t h e r i v e r .
Naturally t h e r e are no s h a r p limits between t h e s e phases. They are overlapping e a c h o t h e r and may b e interwoven in s p a c e and time. The subsequent p h a s e s c a n b e well recognized, however, as t h e main c h a r a c t e r of
water r e s o u r c e s development in a n y r i v e r valley.
In t h e Danube valley, t h e r i v e r w a s always a decisive f a c t o r influencing
t h e socio-economic
development of t h e r i p a r i a n countries.
Until t h e
eighteenth c e n t u r y , t h i s relationship w a s absolutely extensive, t h e societies
t r i e d to utilize t h e advantages provided by t h e r i v e r (navigation, f i s h e r y ) ,
b u t t h e development w a s limited by random e v e n t s c h a r a c e r i z i n g t h e water
regime (particularly by s e v e r e floods). The transition to t h e second p h a s e
of water management (i.e. primary c o n t r o l by constructing flood p r o t e c t i n g
s t r u c t u r e s and r i v e r training) took p l a c e gradually depending on t h e level
of economic development at v a r i o u s s t r e t c h e s of t h e Danube, and i t w a s
completed p r a c t i c a l l y in t h e whole basin a t t h e beginning of t h i s c e n t u r y .
The need f o r canalization also followed t h e economic development, and i t
became almost a g e n e r a l requirement f o r t h e fifties. Most of t h e b a r r a g e s
--
along t h e Upper Daube were completed between 1925 and 1985. In t h e basin
of t h e Middle Danube t h e construction s t a r t e d in t h e f o r t i e s , and t h e work is
still going on. Along t h e Lower Danube t h e canalization r e a c h e d only t h e
planning phase until now.
THE PURPOSE OF GABCMOVO-NAGYIUROS BARRAGE SYSTEM
The need f o r canalization along t h e s t r e t c h of t h e Danube upstream
Budapest w a s r a i s e d at f i r s t by navigation. Member c o u n t r i e s of t h e Danube
Commission h a v e assumed a n obligation t o e n s u r e t h e undisturbed t r a f f i c of
s h i p s having submergence of 2.5m between t h e i r b o r d e r s and a c c e p t e d a
recommendation to i n c r e a s e t h i s depth to 3.5 m if possible. Between Bratislava a n d Gyor this goal cannot b e achieved by usually applied r i v e r
training. The navigable depth is only about 2.0 m in t h e l a r g e s t p a r t of t h e
y e a r and even l e s s in low-water periods, although considerable amount of
money i s s p e n t f o r dredging and r i v e r training s t r u c t u r e s . The importance
of t h i s East-West European waterway will b e even i n c r e a s e d a f t e r completing t h e Rhine-Danube
canal, a f a c t t h a t u r g e s t h e improvement of
navigation conditions along this s t r e t c h .
I t is obvious t h a t t h e flood r i s k should be decreased a s the value of t h e
protected a r e a increases. Not only the enormous damages caused in both
Czechoslovakia and Hungary by t h e l a r g e floods in 1954 and 1965, but t h e
high costs of flood protecting activity had needed in o t h e r y e a r s when t h e
floods were not s o extremely high but similarly dangerous indicates t h e
need to improve t h e protecting systems. The multipurpose s t r u c t u r e s of
canalization can also meet this requirement.
There are still areas where random hydrological events may cause considerable damages in agriculture. Such areas are t h e higher flood plains
not y e t endiked, and innundated by high floods, low lands without efficient
control of s u r f a c e runoff o r where t h e groundwater level i s influenced by
t h e water level of t h e Danube which may c r e a t e urifavourable conditions in
extreme cases.
The necessary water control can be solved in a more
economical way in t h e s e cases when it is combined with t h e construction of
s t r u c t u r e s serving t h e purpose of canalization.
E x p e r t s working in energy industry have different opinions of t h e reasonable r a t e of thermal, nuclear and hydro stations within t h e development
of power production, t h e capacity of which should always c o v e r t h e everincreasing demand of society. The judgement of environmentalists on t h e
impacts of such stations differs similarly. In spite of divergences in opinions i t c a n b e s t a t e d that one of t h e main goal of canalization i s the utilization of Danube's energy. I t i s a waste t o leave t h e discharge of Danube,
which i s continuously renewed energy r e s o u r c e not requiring t h e use of any
r a w material, t o r u n down in its bed without doing t h e work what i t can do
f o r o u r society. The investments r e q u i r e d to construct a hydro power station is higher than t h a t needed in the c a s e of a thermal o r nuclear plant,
but t h e difference i s reimbursed in a few y e a r s by the almost negligible
operation cost. The economic analysis has shown, for instance, t h a t t h e
cost of a thermal o r nuclear power plant having t h e same capacity in energy
production as t h e Gabcikovo-Nagymaros system can c o v e r not only t h e
p r i c e of t h e hydropower stations, but about 63% of t h e total investment of
t h e whole canalization if t h e costs of investment, operation and maintenance
is converted into capital f o r a period of twenty y e a r s . Since t h e lifespan of
hydraulic s t r u c t u r e s i s considerably longer than 20 y e a r s , t h e comparison
is more favourable f o r hydropower generation. Although t h e living conditions of aquatic ecosystems are modified by the control of both water level
and velocity, a i r pollution or radiation hazard from o t h e r power s o u r c e s
may cause much more serious damages in t h e environment. Another advant a g e of hydro power i s i t s flexibility, namely, t h e production can b e
changed rapidly according t o t h e i n c r e a s e o r d e c r e a s e of consumption.
This is a v e r y important a s p e c t especially in energy systems with high portion of nuclear plants, t h e regulation of which i s not desirable.
THE TASK OF PLANNING AND DESIGN
In Hungary an office having t h e same s t r u c t u r e and responsibilities
like a ministry (National Water Authority) coordinates a l l activities r e l a t e d
t o water r e s o u r c e s development. Hence, t h e planning and design of t h e barr a g e system w a s also t h e responsibility of NWA.
Details r e l a t e d t o t h e
activities of o t h e r economic b r a n c h e s were coordinated with t h e relevant
ministries and authorities (e.g. t h e required capacity of t h e hydropower
plants with t h e Ministry of Industry being responsible f o r e n e r g y industry,
t h e navigation conditions with t h e Ministry of Transport and t h e evaluation
of environmental impacts with t h e National Environment Authority). The
Hungarian Academy of Sciences also gave assistance by providing t h e
planners with scientific recommendations p r e p a r e d by various commissions
of t h e Academy. The r e s e a r c h , design, and management of constructions
were and are continuously implemented mostly by institutes belonging t o
NWA (Research Centre f o r Water Resources Development, Design Bureau
f o r Hydraulic S t r u c t u r e s , Investment Bureau f o r Water Management), but
o t h e r institutes were a l s o involved t o solve special problems requiring
interdisciplinary approaches.
Considering all t h e aspects listed and comparing t h e goals t o t h e
development conditions along t h e s t r e t c h of t h e Danube upstream Budapest
i t w a s obvious t h a t t h e demands can b e m e t economically only by constructing a multipurpose water r e s o u r c e s system, i.e. by t h e canalization of the
r i v e r . Apart from t h e i n t e r e s t of t h e main u s e r s (i.e. navigation, water
management, power generation) some f u r t h e r a s p e c t s should have also been
taken into account like t h e increasing demand f o r r e c r e a t i o n , t h e utilization
of the gravel dredged from t h e r i v e r bed f o r building industry (which
already caused about 60-70 c m lowering of the water level in low flow
periods at t h e most sensitive s t r e t c h ) and last but not l e a s t t h e preservation of t h e quality of life and environment in t h e Danube valley. The task in
t h e planning period w a s to compare a l a r g e number of possible variants and
s e l e c t t h e one which satisfy all these demands in t h e b e s t combination
ensuring at t h e same time reasonably positive cost-benefit balance.
I t i s obvious t h a t t h e r e are unavoidable damages caused by constructing b a r r a g e s which should be considered as a n additional cost of t h e project (e.g. t h e value of t h e land occupied by t h e s t r u c t u r e s o r innundated).
Most of t h e harmful impacts foreseen can, however, b e prevented by constructing and operating sufficient supplementary s t r u c t u r e s . Naturally all
expenses should be allocated as a n integer p a r t of t h e total investment. An
example of such preventive measures i s t h e r e c h a r g e of groundwater where
t h e lowering of t h e water t a b l e is expected due to t h e change in t h e water
regime of t h e r i v e r . There are also positive secondary effects t h e utilization of which should also b e planned (e.g. t h e stabilized water level and t h e
l a r g e water s u r f a c e upstream t h e b a r r a g e s provide a n excellent opportunity f o r r e c r e a t i o n and water sports). In general i t c a n be stated t h a t t h e
new natural and social environment c r e a t e d by t h e construction of t h e b a r r a g e system i s not worse than t h e e a r l i e r conditions, if sufficient measures
are taken t o prevent t h e harmful changes and to utilize t h e advantages
offered by t h e new conditions. Apart from selecting t h e best v a r i a n t of t h e
system a n o t h e r important task w a s t h e r e f o r e t o p r e d i c t i t s secondary
e f f e c t s in t h e natural and social environment as well as t o design s t r u c t u r a l
and operational measures needed t o prevent
- or at least t o minimize - t h e
undesired impacts, and t o make use of t h e positive ones.
The planning r e q u i r e d a long s e r i e s of international negotiations not
only because t h e s t r e t c h of t h e Danube t o b e utilized i s t h e common b o r d e r
between Czechoslovakia and Hungary, b u t also because t h e agreement of t h e
member s t a t e s of t h e Danube Commission is necessary according to t h e Belg r a d e Convention f o r every l a r g e s c a l e modification of t h e navigation
conditions along t h e Danube.
Another important a s p e c t of international
harmonization w a s t h e determination of t h e sections of b a r r a g e s . Some sections h a d t o b e r e g a r d e d as fixed points (e.g. a b a r r a g e had t o be cons t r u c t e d downstream t h e I r o n Gate t o improve t h e navigation conditions
along t h e g o r g e s located here). The l a r g e c i t i e s located at relatively low
levels (Vienna, Bratislava, Budapest, Novi S a d , Belgrade) limited t h e r i s e of
water levels along t h e i r banks. I t w a s also n e c e s s a r y t o e n s u r e t h e continuous navigable water way and t h e possible highest utilization of e n e r g y by
limited overlapping of backwater s t r e t c h e s .
HISTORY OF PREPARATORY PLANNING
The planning period of t h e Gabcikovo-Nagymaros
b a r r a g e system
s t a r t e d in 1951 and ended in 1977 when t h e intergovernmental agreement
w a s signed by Czechoslovakia and Hungary f o r t h e multipurpose utilization
of t h e common s t r e t c h of t h e Danube. Although t h e t a s k of planning w a s
v e r y v e r s a t i l e as it was summarized above, t h e r e were quite o t h e r r e a s o n s
r e q u i r i n g such long p r e p a r a t i o n .
A t t h e beginning t h e cost-benefits r a t i o of t h e hydropower plants
seemed t o b e favourable compared t o c o a l thermo-plants, b u t in t h e fifties
t h e oil took o v e r gradually t h e p l a c e of coal and t h e hydroplants were not
a b l e e i t h e r t o compete with t h e oil p r i c e being v e r y low in t h a t time. Such
economic a s p e c t s prolonged again and again t h e decisions concerning t h e
construction of t h e b a r r a g e s .
Delay w a s also caused by t h e f a c t t h a t financially favourable conditions
were needed simultaneously in both participating countries t o a c c e p t t h e
responsibility of investing l a r g e c a p i t a l into a system which t a k e s p a r t only
partially i n d i r e c t production and s e r v e s partially t h e improvement of t h e
i n f r a s t r u c t u r e . Other a s p e c t s of internal policy (e.g. t h e proportional
development of t h e various regions in t h e countries) might r e d u c e in some
time t h e willingness of t h e i n t e r e s t e d p a r t i e s t o start t h e construction of
t h e l a r g e b a r r a g e system.
After t h e f i r s t oil c r i s i s when t h e economic p r o s p e r i t y w a s still
increasing, i t was r e a s o n a b l e t o decide t h e implementation of t h e canalization f o r t h e utilization of t h e continuously renewing e n e r g y of t h e Danube.
The agreement w a s signed and t h e construction s t a r t e d immediately in 1978.
The long-lasting planning period caused by t h e fluctuating i n t e r e s t of
t h e participating p a r t i e s r e q u i r e d quite considerable financial and mental
e f f o r t s but i t had also s e v e r a l advantageous consequences. In t h e plans
reworked again and again t h e r e s u l t s of t h e r a p i d technical development
w a s always considered raising gradually t h e efficiency in t h i s way. The policy m a k e r s did not want to tell e i t h e r definite y e s or no, b u t t h e i r intention
was only to delay t h e final decision. They asked, t h e r e f o r e , t h e investigation of new v a r i a n t s or t h e analysis of some expected impacts. Although
t h e s e studies were n o t synthetized in a n environmental impact assessment
t h i s t e r m w a s not y e t used and even known in t h e fifties and s i x t i e s
-
- they
contained most of t h e important information needed f o r t h e evaluation of
environmental changes.
The detailed s u r v e y of t h e n a t u r a l and socio-economic conditions, t h e
evaluation of s e v e r a l p r a c t i c a b l e options of t h e system and t h e studies analysing t h e most s e r i o u s impacts made it possible to s e l e c t t h e most r e a l i s t i c
version of t h e hydraulic s t r u c t u r e s immediately a f t e r a g r e e n light w a s
given f o r t h e construction. The same materials were used f o r t h e p r e p a r a tion of a n environmental impact assessment when same environmental objections were r a i s e d against t h e p r o j e c t . The availability of a l a r g e number of
feasibility studies facilitated t h e p r e p a r a t i o n of t h e assessment in a relatively s h o r t time.
ENVIRONMENTAL CONCERNS RELATED TO THE PROJECT
A s t h e anxiety f o r t h e preservation of environmental values gradually
increased all o v e r t h e world, t h e preparation of detailed impact analyses
became a general requirement in connection with all l a r g e s t r u c t u r e s . A t
t h e beginning of t h e eighties more and more environmental objections w e r e
also r a i s e d against t h e b a r r a g e system. I t w a s t h e r e f o r e necessary to summarize t h e studies p r e p a r e d e a r l i e r , to c a r r y out supplementary r e s e a r c h
and to answer t h e questions in t h e form of a comprehensive assessment of
t h e expected environmental changes. The objective of this assessment was
not only t o survey t h e impacts but also to propose measures needed f o r
avoiding undesired processes and t o determine t h e positive changes t h e
utilization of which may i n c r e a s e t h e efficiency of t h e system. The detailed
description of all debated problems i s not possible in a s h o r t a r t i c l e , but
some of t h e most important points and r e s u l t s are listed below.
Along t h e 30 km long derivation canal t h e water level will b e lowered
considerably in t h e r i v e r , which would also cause t h e depression of t h e
groundwater table, if no protective measures w e r e applied. Two options
were investigated: (i) t o supplement t h e water provided e a r l i e r by capillarity f o r t h e plants in t h e form of irrigation, or (ii) t o construct a combined drainage and r e c h a r g e system which c a n control t h e water table
according to t h e requirement of agriculture. The second alternative w a s
applied in t h e final design because i t offers not only t h e prevention of dama g e s but also t h e improvement of t h e agricultural conditions.
Field and
l a b o r a t o r y experiments, simulation models and s e v e r a l similar systems
already in operation, e.g. along t h e canalized s t r e t c h e s of t h e Rhine and
t h e Rhone, prove t h e relatively high reliability of t h e effectiveness of
groundwater control.
Some discharge should b e released through t h e natural r i v e r bed even
in low water periods when almost t h e total amount of water is conveyed t o
t h e power station in t h e derivation canal. The opinions concerning t h e size
of this discharge were, however, v e r y different: t h e i n t e r e s t of power generation was to minimize t h e r e l e a s e , while the l a r g e r t h e discharge t h e
smaller t h e change in the aquatic ecosystem.
The requirements f o r t h e
minimum allowable discharge varied from 50 t o 500 m3 s-l, where the
minimum n a t u r a l d i s c h a r g e i s a b o u t 700 m3 s-' and t h e multiannual a v e r a g e
value i s 2.000-2,200
m3 s-l. Unfortunately, t h e s c i e n c e of hydrobiology i s
not developed enough t o b e a b l e to quantify biological p r o c e s s e s . I t w a s not
possible. t h e r e f o r e , t o p r e d i c t t h e quality of a q u a t i c life depending o n t h e
size of t h e d i s c h a r g e r e l e a s e d in t h e n a t u r a l bed. I t was decided t h a t t h e
final value should b e determined o n t h e b a s i s of o p e r a t i o n a l experiments
between 5 0 a n d 200 m3s-l, b u t some r i v e r t r a i n i n g should b e implemented
maintaining a unified bed e v e n in t h e case of such small discharges.
The n e x t problem was t h e maintenance of t h e self-purification c a p a c i t y
of t h e r i v e r . The velocity d e c r e a s e s considerably upstream t h e b a r r a g e s , a
f a c t t h a t modifies both t h e oxygen balance a n d t h e s t r u c t u r e of t h e aquatic
ecosystem.
The simulation of t h e chemical p r o c e s s e s indicated t h a t t h e
e x p e c t e d lowering of oxygen content i s negligible b e c a u s e t h e t w o opposite
a c t i o n s ( t h e d e c r e a s e of velocity and t h e i n c r e a s e of s u r f a c e a r e a ) a r e
almost compensating o n e a n o t h e r . The e f f e c t of a e r a t i o n at t h e sections of
b a r r a g e s may even s u r p a s s t h e lowering of dissolved oxygen along t h e
b a c k w a t e r s t r e t c h e s . The r e s e a r c h aiming at t h e determination of t h e relationship between t h e biotop a n d t h e hydraulic c h a r a c t e r of r i v e r s i s only a
p r e s e n t l y developing topic in hydrobiology. T h e r e f o r e , i t was not possible
t o give quantified predictions concerning t h e e x p e c t e d biological impacts of
canalization.
Considering t h e r e s u l t s of t h e chemical models a n d t h e e x p e r i e n c e s
gained at a l r e a d y canalized r i v e r s t r e t c h e s (according t o which t h e
improvement of water quality i s more p r o b a b l e t h a n i t s d e t e r i o r a t i o n ) i t was
s t a t e d t h a t harmful changes are not expected. The field e x p e r i e n c e s proving t h e validity of t h i s sttement include t h e detailed evaluation of t h e long
s e r i e s of quality d a t a collected along t h e canalized s t r e t c h e s of t h e r i v e r
Tisza, and t h e information o n t h e impacts of b a r r a g e s being in o p e r a t i o n
s i n c e d e c a d e s along t h e U p p e r Danube. The analysis emphasized t h e need of
t h e more efficient t r e a t m e n t of sewages r e l e a s e d from settelements a n d
industrial plants into t h e backwater s t r e t c h e s . Since o n e of t h e m o s t s e r i ous o b s t a c l e s of t h e utilization of Danube's water r e s o u r c e s i s t h e rapidly
growing pollution of t h e r i v e r , i t i s a positive f e a t u r e of t h e b a r r a g e sys-
t e m , t h a t i t s construction u r g e s t h e improvement of sewage t r e a t m e n t in t h e
basin.
The most important s o u r c e of water supply in the region is t h e bankfiltered water. Wells tapping t h e alluvial gravel filling up t h e flood plain
provide t h e water, which is directly r e c h a r g e d from the r i v e r . The gravel
l a y e r s a c t a s natural filters and, t h e r e f o r e , t h e water is suitable f o r d i r e c t
consumption without any pretreatment.
Canalization may endanger t h e
quantity and quality of bank-filtered water along t h e backwater s t r e t c h e s
by t h e deposition of fine silt o v e r the gravel layer, which increases t h e
resistance against t h e percolation and may c r e a t e anaerob conditions in t h e
groundwater resulting in the increase of iron and manganate content. Downstream t h e b a r r a g e s the lowering of the water level may also d e c r e a s e t h e
yield of wells, if considerable dredging is implemented t o increase t h e head
utilized at the power station.
In t h e case of t h e Gabcikovo-Nagymaros system downstream dredging
was planned below t h e section of Nagymaros. In the meantime, however,
considerable amount of gravel was exploited h e r e f o r building industry
causing the sinking of low water levels with 50-70 cm, which is more than
t h e value envisaged in t h e plan. The remaining task i s only to improve t h e
tracing of t h e bed which a s p e c t was not considered during exploitation.
This activity r a t h e r improves than deteriorates t h e conditions. Undesirable effects can be caused, however, if the bed i s f u r t h e r deepened due t o
t h e d r a g f o r c e of water being poor in suspended sediment a f t e r crossing the
barrage.
The prediction of the modification of bed morphology would
r e q u i r e b e t t e r knowledge of bedload movement than t h e one existing a t
p r e s e n t especially under t h e very complicated conditions prevailing at t h e
s t r e t c h in question (influence of stabilized banks, strong contractions,
rocky thresholds, etc.). F u r t h e r r e s e a r c h i s needed and t h e relatively slow
development of processes allows the implementation of protective measures
on t h e basis of t h e evaluation of changes monitored during t h e operational
period.
Several examples indicate that t h e most reasonable way t o p r o t e c t t h e
water supply plants exploiting bank-filtered water against t h e impacts of
silting along backwater s t r e t c h e s is t h e r e g u l a r dredging of t h e fine
material from the s u r f a c e of the gravel. The most detailed experiences
concerning t h e impacts of impoundment on t h e operation of bank filtered
water supply schemes were gained a t t h e w e l l field providing water f o r Linz.
Although t h e water level was raised considerably in t h e r i v e r , t h e yield of
wells decreased due to t h e deposit of a silt l a y e r over, t h e aquifer. The
change in water quality indicated also t h e development of anacrobic conditions below t h i s clogging layer. Several experiments were c a r r i e d out t o
improve the production of w e l l s but results were achieved only by dredging
t h e clogged l a y e r . A slight d e c r e a s e of t h e yield from t h e wells a t Belgrade
w a s also observed due t o t h e backwater effect of t h e b a r r a g e constructed
a t t h e Iron Gate. Although t h e detailed survey w a s not a b l e to make c l e a r
distinction between t h e impact of t h e b a r r a g e and t h e normal ageing of
wells, i t was proposed as a conclusion of r e s e a r c h t h a t dredging should b e
c a r r i e d out a l s o h e r e f o r t h e improvement of t h e well fields. Considering
t h e s e experiences t h e r e g u l a r dredging of t h e bed in f r o n t of the plants
exploiting bank f i l t e r e d water was included in t h e operational plan of t h e
b a r r a g e system as a p a r t of t h e normal maintenance service. The detailed
design of t h i s activity r e q u i r e s f i r s t of a l l t h e continuous monitoring of t h e
changes in bed morphology. F u r t h e r r e s e a r c h of bed load and sediment
movement in n a t u r a l beds may also assist t h e managers with t h e determination of t h e efficient policy of protecting t h e quantity and quality of bankfiltered water resources.
SOME GENERAL CONCLUSIONS OF THE IMPACT ASSESSMENT
The most important conclusion of t h e environment impact assessment of
t h e Gabcikovo-Nagymaros b a r r a g e system w a s t h e statement t h a t t h e r e i s
no such serious harmful impact foreseen, which may give any grounds t o
modify basically t h e accepted plan o r t o stop t h e construction s t a r t e d
already. In some cases t h e objections raised against t h e system provided
good ideas t o improve both t h e design and t h e plai of operation. The application of groundwater control, t h e development and maintenance of a unified small water bed where the derivation canal lowers t h e discharge of t h e
r i v e r , o r . t h e need of r e g u l a r dredging as a p a r t of t h e maintenance s e r v i c e
c a n b e mentioned a s examples. In several o t h e r c a s e s t h e anxiety was not
justified.
I t i s obvious t h a t t h e natural p r o c e s s e s a r e influenced by numerous
random events.
Therefore, to r e a c h a safety of 100% in any prediction
would be a n unrealistic t a r g e t . I t i s necessary, however, to indicate t h e
r a n g e of uncertainty and t h e task of design i s t o construct flexible systems,
t h e operation of which c a n b e adaptable to t h e actual conditions developing
in t h e environment. To achieve this goal t h e continuous observation of
environmental changes is needed. The monitoring system is, t h e r e f o r e , a n
indispensable p a r t of any l a r g e hydraulic s t r u c t u r e and water management
system.
The uncertainty caused by t h e randomness of influencing f a c t o r s is
f u r t h e r increased by t h e limited knowledge of t h e development of natural
processes. To i n c r e a s e the reliability of impact assessments t h e scientific
r e s e a r c h should b e continued f o r t h e b e t t e r understanding of t h e hydrological cycle and i t s interactions with t h e environment.
According t o t h e
p r e s e n t c a s e , t h e weakest e y e within t h e chain of t h e various b r a n c h e s of
sciences i s hydrobiology. H e r e o u r knowledge i s limited t o t h e description
of different aquatic ecosystems but not sufficient f o r t h e quantification of
expected changes. Similarly, f u r t h e r r e s e a r c h i s needed in t h e field of
r i v e r morphology and sediment t r a n s p o r t .
I t is also worthwhile t o mention t h a t t h e raising of environmental obstac l e s against t h e b a r r a g e system w a s intensified simultaneously with t h e
worldwide economic depression in t h e e a r l y eighties. Most of the various
i n t e r e s t groups in competition with t h e system t o get a l a r g e r s h a r e from
t h e v e r y limited funds f o r investments hide t h e i r d i r e c t goals behind t h e
shield of environment. The groups of t h e different lobbies (e.g. coal, oil,
nuclear, hydropower within energy industries) were f u r t h e r enlarged by
people having individual reasons t o oppose t h e implementation of t h e b a r r a g e s (e.g. whose p r o p e r t y w a s expropriated). I t w a s v e r y difficult t o make
distinction between t h e r e a l environmental concerns and t h e obstacles
r a i s e d only to impede t h e implementation of t h e system. Although i t w a s evident t h a t this second group could not be convinced, t h e i r questions had t o
be equally answered even in cases when t h e objections had no physical,
scientific background at all.
The final conclusion is t h a t t h e p r e p a r a t i o n of a comprehensive
environmental impact study is a v e r y useful and indispensable p a r t of t h e
planning and design of l a r g e hydraulic s t r u c t u r e s . It assists t h e designer t o
think o v e r t h e concept of the plan again and t o improve gradually some elements of t h e system considering t h e far-reaching interactions. The policy
makers being responsible t o make decisions concerning t h e economic
development of a country r e q u i r e also t h e evaluation of a l l primary and
secondary e f f e c t s because t h e b e t t e r utilization of t h e advantages offered
by t h e system and t h e minimization of undesirable impacts may improve t h e
efficiency of t h e investment. The protection af environmental values in gene r a l and t h e sound utilization of water r e s o u r c e s especially cannot b e
solved without t h e considerable participation of t h e g e n e r a l public. The
impact assessment also s e r v e s t h e i r reliable information.