ENVIRONMENT REPORT OF VIETNAM, 2006
THE CURRENT STATE OF WATER ENVIRONMENT IN 3 RIVER BASINS OF CAU, NHUE - DAY AND DONG NAI
RIVER SYSTEM
Chapter I.
RIVER BASINS IN VIETNAM
1.1. OVERVIEW OF RIVER BASINS
IN VIETNAM
ation, environmental factors, value of
each basin etc...
Vietnam has a dense river network.
Rivers with a length of over 10 km total
about 2,372, comprising 13 large river
systems with a total area of 10,000 km2.
The 13 river basins, 10 of which are
trans-boundary systems, cover 80% of
the country's territory. Basins of the 9
largest river systems, which include Red,
Thai Binh, Bang Giang - Ky Cung, Ma,
Ca La, Thu Bon, Ba, Dong Nai and Cuu
Long, account for 90% of the total river
basins nationwide.
Table 1.1 provides information on the
9 major river systems and annual irrigating capacity according to their respective
area and population.
Each river basin has typical natural
resource characteristics as well as water
resources wich have a close linkage. In
practice, management approaches vary
from one basin to another, depending on
socio-economic conditions, land use situ-
Some large rivers in Vietnam such as
Cuu Long (Tien and Hau rivers), Red
River and Ca La River originate from
other countries. Some branches of
Mekong River start in Vietnam's territory. These include Se San and Srepok.
They flow through Lao and Cambodia
then come back to Mekong and outflow
through 9 estuaries (Cuu Long). Ky
Cung - Bang Giang is a large river which
originates from Chau Giang river in
China. Almost all of other small rivers
originate within the country.
Table 1.1. Some basic characteristics of 9 major river systems in Vietnam
Total volume of water flow
annual (bill m3)
Area of basin (km2)
No
River systems
External
part
1,980
Internal
part
11,280
Total
1
Bang Giang –
Ky Cung
13,260
2
Thai Binh
15,180
15,180
3
Hong
82,300
72,700
4
5
Ma
Ca - La
10,800
9,470
6
7
Thu Bon
Ba
8
9
Dong Nai
Mekong
10
Other rivers
Total
Overseas
In home
Capacity water flow
9.0
Thousand
m3/km2
798
m3/
person
9,070
1,550
5,160
Total
1.7
7.3
9.7
9.7
155,000
45.2
81.3
126.5
17,600
17,730
28,400
27,200
5.6
4.4
14.0
17.8
19.6
22.2
1,110
1,250
5,500
8,290
10,350
13,900
10,350
13,900
20.1
9.5
20.1
9.5
1,940
683
16,500
9,140
6,700
726,180
37,400
68,820
44,100
795,000
3.5
447.0
32.8
53.0
36.3
500.0
877
7,265
2,980
28,380
837,430
66,030
330,990
66,030
1,167,000
507.4
94.5
340
94.5
847.4
1,430
2,560
8,900
11,100
Source: National profile on water resources, the Department of Water Resources Management
Chapter 1: RIVER BASINS IN VIETNAM
3
ENVIRONMENT REPORT OF VIETNAM, 2006
THE CURRENT STATE OF WATER ENVIRONMENT IN 3 RIVER BASINS OF CAU, NHUE - DAY AND DONG NAI
RIVER SYSTEM
Vietnam is located in the tropical
monsoon area; the total annual rainfall is
about 1,940 mm. Three fourths of the
total land area is covered by mountains
therefore the rainfall is distributed
unevenly from one area to another and
varies with time. The long-term average
annual rainfall varies greatly, in some
areas the annual rainfall can reach 4,000
- 5,000 mm, especially up to 8,000 mm in
such as Bach Ma mountain, but in some
areas like Nha Ho and Binh Thuan the
annual rainfall reaches only 600 - 800
mm. The majority of the territory has a
long-term average annual rainfall from
1,400 to 2,400 mm. The variation of rainfall during the year affects the rainfall
regime and is the main cause of droughts
in the dry season and floods in the rainy
season.
The rain season occurs from April to
October, particularly from July to
December in central coastal area. The
rainfall in the rainy season accounts for
75 - 85% of the total annual rainfall. The
dry season starts from July to August
with low rainfall which accounts for 15 25% of the total annual rainfall. In some
areas there is either no rain for 3-4
months
or
very
little
rainfall.
Accordingly, there are two seasons in
river water flow that corresponds to the
dry and rainy seasons. There is one
month difference in the starting and ending times of rainy and flood seasons on
large river systems. The start and end
time of the flood season is also different
from area to area and tends to be later
from north to south.
The majority of river water is from
rainfall. The long-term average annual
rainfall in Vietnam is about 640 billion
m3. In many years, the average annual
4
Box 1.1. Values of river basin
Multi-functional characteristics of river
basins:
- Providing valuable resources for production
and domestic use: water, land, forest, minerals and aquatic products,
- Protecting human lives and eco-systems,
- Serving as a medium for receiving, transferring and cleaning waste,
- A source of many natural materials with high
economic value,
Values of water resources in river basins:
Direct values:
- Providing water for domestic and industrial
uses,
- Irrigation
- Hydro power
- Aquaculture and fishery
- Preventing salt intrusion
- Agricultural development
Indirect values:
- Water transport
- Sand exploitation
- Receiving and self-cleaning of waste
- Aesthetic landscape
- Water entertainment and sport
Conservation values:
- Involved in the natural water cycle
- Maintaining fresh water eco-systems
- Conserving aquatic biodiversity
- Conserving wetlands of high value.
water flow of all rivers in Vietnam reaches 830 - 840 billion m3; of which the
water flow generated from outside the
country is 520 - 525 billion m3, accounting for 63% of the total water flow. The
total annual water flow of Mekong river
system accounts for 59% of the country's
total annual water flow, followed by
Hong river system accounting for 14.9%
Chapter 1: RIVER BASINS IN VIETNAM
ENVIRONMENT REPORT OF VIETNAM, 2006
THE CURRENT STATE OF WATER ENVIRONMENT IN 3 RIVER BASINS OF CAU, NHUE - DAY AND DONG NAI
RIVER SYSTEM
Table 1.2. Vietnam's water resource is
unsustainable
Global climate change has led to the depletion
of water resources. Recent researches have
forecasted that the total surface water will be
96%, 91% and 86% of the current volume by
2025, 2070 and 2100, respectively.
The present average per capita water volume
is about 3,840m3 per year, taking into account
only the water generated inside Vietnam .
With the current population growth rate, the
figure would be 2,830m3 per person per year
by 2025. According to the International Water
Resource Association, a country with an average water volume per capita below 4000m3
per person per year is considered as a country in water shortage.
Water resource are distributed unevenly
across the country. About 60% of the total
water flow of the whole country is distributed
in Cuu Long river delta where 20% of the
country's population live, the remaining 40%
of water flow is thus shared among the
remaining 80% of the population as well as
having to meet 90% of production, commercial
and other services activities
The total water generated in 3 - 5 months of
the flood season contributes 70 - 80% of the
total annual water flow. In the dry season
which lasts 7 - 9 months, the water flow provided is only 20 - 30%.
Source: National Strategy on Water resources
external water sources are excepted then
Vietnam would be faced with a water
shortage by 2025. Those calculations
show the importance of international
agreements on water resources to
Vietnam as it is located in the lower sections of large river systems.
Water supply capacity also varies
from area to area in the country. Within
Dong Nai river basin (the area which
contributes 40% to the total GDP), the
current water supply capacity reaches
2,350 m3 per person per year and might
decrease to 1,600 m3 per person per
year by 2025 if the population continues to grow as at present. This is an
alarming figure. The problem is even
worse in Cau and Nhue-Day river
basins where water supply capacity is
only 656 and 2,830 m3 per person per
year, respectively.
Some areas in Vietnam are already
experiencing water shortage due to population growth. In following parts of the
Report, water shortage and water quality depletion will be discussed in more
detail.
and Dong Nai - 4.3%. The river systems
of Ma, Ca La, Thu Bon have a total water
flow of about 20 billion m3, other systems
such as Bang Giang - Ky Cung, Thai
Binh and Ba total about 9 billion m3. The
total river flow of Vietnam accounts for
about 2% of total water flow of all rivers
in the world.
At national level, Vietnam is endowed
with abundant water resources, however
if the Mekong river water is not taken
into account, Vietnam would be faced
with a water shortage by 2050. If all
Chapter 1: RIVER BASINS IN VIETNAM
Red River
Source: John Hook
5
ENVIRONMENT REPORT OF VIETNAM, 2006
THE CURRENT STATE OF WATER ENVIRONMENT IN 3 RIVER BASINS OF CAU, NHUE - DAY AND DONG NAI
RIVER SYSTEM
Figure 1.1. Map of large river basins in Vietnam
6
Source: VEPA
Chapter 1: RIVER BASINS IN VIETNAM
ENVIRONMENT REPORT OF VIETNAM, 2006
THE CURRENT STATE OF WATER ENVIRONMENT IN 3 RIVER BASINS OF CAU, NHUE - DAY AND DONG NAI
RIVER SYSTEM
1.2. CHARACTERISTICS OF 3 RIVER BASINS OF CAU,
NHUE-DAY AND DONG NAI RIVER SYSTEM
1.2.1. Cau river basin
Natural area: 6,030 km2 (accounting for
2% of the total country area)
Annual water flow: about 4,5 billion m3,
Main rivers in the basin: Cho Chu,
Nghinh Tuong, Du, Cong, Ca Lo, Ngu
Huyen Khe.
Density: varying from 0.7 - 1.2 km/km2.
Provinces located in Cau river basin:
Bac Can, Thai Nguyen, Vinh Phuc, Bac
Ninh, Bac Giang, Hai Duong and Hanoi.
Population: 6,859,000 (2005).
Population density: 427 persons per
km2 (two times higher than the average
density of the country).
Industrial entities: 800
Craft villages: 200
Medical establishments: 1,200 with
15,400 beds.
Figure 1.2. Map of provinces related to Cau river basin
Source: VEPA
Chapter 1: RIVER BASINS IN VIETNAM
7
ENVIRONMENT REPORT OF VIETNAM, 2006
THE CURRENT STATE OF WATER ENVIRONMENT IN 3 RIVER BASINS OF CAU, NHUE - DAY AND DONG NAI
RIVER SYSTEM
Natural characteristics
Cau is a large river in Thai Binh river
system, which originates from Phia Deng
(1,527m altitude) on the south east of
Pia-Bi-Oc range in Bac Kan, Cao Bang.
Cau river is 288 km long. The river flows
through Bac Kan, Thai Nguyen, Bac
Giang, Bac Ninh provinces and finally
merges with Thai Binh river at Pha Lai.
Cau river basin covers almost all of Bac
Kan and Thai Nguyen provinces and a
part of Bac Ninh, Bac Giang, Vinh Phuc
and Hai Duong provinces, and two districts of Hanoi (Dong Anh, Soc Son).
In general, Cau basin terrain slopes in
a NW-SE direction and is divided into 3
regions: Mountain, Highland and Plain.
Cau river basin has a diverse river
and stream system which are distributed
along the main river. Almost all of main
rivers in the basin are on the right bank
of the river basin such as: Cho Chu, Du,
Cong, Ca Lo,... There are 68 rivers and
streams with the length of over 10 km
each in the whole basin.
The total water flow of Cau river
basin is of 4.5 billion m3 per year of
which Ca Lo and Cong rivers contribute
0.9 m3 per year. The flood season starts
from June and lasts to October, the low
water season often last from seven to
eight months with a water flow of 18 25% of the total water flow, the lowest
water season falls in January, February
and March with water flow of 5,6 - 7,8%
of the total water flow.
Natural resources and environmental characteristics
Cau river basin
resources including
minerals, etc. There
mines in the basin
8
is rich in natural
forests, water and
are several mineral
such as iron, zinc,
coal, gold, tin, etc... The average forest
cover in the whole basin is about 45%.
The elements of the natural landscape in
the basin have changed considerably.
There is no more natural forest along
rivers and streams. The forest contribution has therefore also significantly
depleted, being incapable of retaining
moisture for the dry season and of preventing flooding in the rainy season. As
a results land has been degraded, with
severe flooding in the rainy season and
long lasting droughts in the dry season.
In the basin, there are some protected
areas such as Tam Dao National Park,
Kim Hy Natural Conservation Area and
other cultural and environmental conservation areas with high eco-system values. Fauna and flora in the basin are also
very abundant with several precious
plant and animal species.
Deforestation, accompanied by socioeconomic development activities such as
industry, mining, craft villages and agriculture have created high pressure on
the natural environment of the basin.
Socio-economic characteristics
The basin covers about 47% of the total
natural area of 6 provinces with about 6.9
million people (2005) of which 5.9 million
live in rural areas, 1 million in urban
areas. The population density is about
427 persons per km2, double the average
population density of the whole country.
The population density is lowest in
mountainous and midland areas, where
15% of total population of the basin live
in an area accounting for 63% of the total
basin area. The population density is
higher in urban and central areas.
The economy of these provinces
depends mostly on agriculture, forestry
Chapter 1: RIVER BASINS IN VIETNAM
ENVIRONMENT REPORT OF VIETNAM, 2006
THE CURRENT STATE OF WATER ENVIRONMENT IN 3 RIVER BASINS OF CAU, NHUE - DAY AND DONG NAI
RIVER SYSTEM
and industry while fishery contributes
minimally. In the last 5 years, the GDP of
these provinces has increased significantly, almost doubling.
The industrial growth rate in the area
is higher than the country's average.
Agricultural, forestry, and fishery products account for 26% and is showing a
decreasing trend. A high growth rate in
industry, construction and services is
recorded in Thai Nguyen, Bac Ninh and
Vinh Phuc provinces.
Mining and ore screening industries
concentrate in the 2 upstream provinces
of Bac Kan and Thai Nguyen. There are
about 200 craft villages located in Bac
Ninh and Bac Giang provinces. Waste
water from villages specializing in iron
and steel production, copper and lead
casting, paper production, weaving and
dying is discharged directly into rivers
and streams. Typical examples are Phong
Khe and Duong O paper recycling villages, Dai Bai copper casting village and
Da Hoi metal refinery village... The
waste water from industrial and mining
areas, craft villages and from urban areas
Figure 1.3. GDP of provinces in Cau river basin
Source: Statistical Year Book 2005
is discharged directly into rivers without
any treatment.
Sand and gravel exploitation with an
increasing volume along Cau river bank
has caused turbidity of the water, bank
erosion and changes in water currents,...
In agriculture, chemicals and insecticides are excessively used, especially in
Thai Nguyen and Bac Ninh provinces.
NO2 and NOx content in the ground is
especially high in intensive rice, vegetable cultivated areas in Bac Ninh
province and in Me Linh district of Vinh
Phuc province and in downstream areas
of the basin.
Cau River
Chapter 1: RIVER BASINS IN VIETNAM
Source: Documentary photo
9
ENVIRONMENT REPORT OF VIETNAM, 2006
THE CURRENT STATE OF WATER ENVIRONMENT IN 3 RIVER BASINS OF CAU, NHUE - DAY AND DONG NAI
RIVER SYSTEM
1.2.2. Nhue - Day river basin
Natural characteristics
Nhue-Day river basin is located in the
south-west of the Northern Plain, on the
right bank of Hong River. Although Day
river is a branch of Hong river it has its
own basin with tributary rivers including Tich, Thanh Ha, Hoang Long, Vac,
Nhue, Chau, Sat and Dao rivers. It is
also connected with Ninh Co river and
Quan Lieu channel. The basin stretches
from mountainous areas belonging to
Ha Tay and Hoa Binh provinces to the
coast in Nam Dinh and Ninh Binh
provinces with a total natural area of
7,665 km2. The basin is long in shape
with fan blades which include Ha Tay,
Ha Nam, Ninh Binh, Nam Dinh and a
part of Ha Noi and Hoa Binh provinces.
Natural area: 7,665 km2 (accounting for 2%
of the total country area)
Annual water flow: about 28,8 billion m3,
Main rivers in the basin: Nhue, Thanh Ha,
Tich, Hoang Long, Chau Giang, Dao, Ninh Co
and To Lich (a main branch of Nhue river
receiving water from Lu, Kim Nguu and Set
Rivers.
Density: varying from 0.7 - 1.2 km/km2.
Provinces located in Nhue-Day river basin:
Ha Noi, Ha Tay, Ha Nam, Hoa Binh, Ninh Binh
and Nam Dinh.
Population: 10,186,000 (2005).
Population density: 874 persons per km2 (3.5
times higher than the average density of the
country).
Industrial entities: 4,000
Craft villages: 458
Medical establishments: 1,400 with 26,000
beds.
Figure 1.4. Map of relevant provinces in Nhue-Day river basin
Source: VEPA
10
Chapter 1: RIVER BASINS IN VIETNAM
ENVIRONMENT REPORT OF VIETNAM, 2006
THE CURRENT STATE OF WATER ENVIRONMENT IN 3 RIVER BASINS OF CAU, NHUE - DAY AND DONG NAI
RIVER SYSTEM
Day River is 237 km long flowing
through Ha Tay, Ha Nam, Nam Dinh
and Ninh Binh provinces, finally outflowing to the sea at Day estuary. Day
River is a tributary of Red River. Since
1937, after the construction of Day dam,
Hong river water has not flown into
Day river very often therefore Day has
become a draining river and serves to
diverge floods in the flood season.
Nhue River is 74 km long and receives
water from Hong River through Lien Mac
trench. Nhue River also serves as a drainage
system for Ha Noi city and Ha Dong town.
It meets Day River at Phu Ly town. Nhue
river basin has an area of 1,070 km2.
Some main rivers receive water from
Red River through canals. These include
Day, Nhue, Chau Giang and Dao rivers.
Besides, there are some other drainage
rivers flowing though cities, towns, residential areas, industrial areas, services
areas and craft villages such as Tich,
Hoang Long and Thanh Ha rivers.
Red River provides about 85-90% of
the total water flow for Nhue-Day river
basin. The total annual water flow of
Day river basin is about 28.8 billion m3 of
which 25.7 billion m3, equivalent to
89.5% of the water flow is from Dao
River (Nam Dinh province); 1.35 billion
m3, accounting for 4.7%, comes from Tich
and Day Rivers in Ba Tha.
About 70% - 80% of the annual total
water flow of the basin results from the
flood season, from June to October.
During the dry season, from November
to May of the following year, the water
flow is mainly from Hong River. Nhue
River receives water from Hong River
though Lien Mac canal; Dao River
receives water from Hong River and outflows to Day River.
Chapter 1: RIVER BASINS IN VIETNAM
The current water regime of Day
River is influenced, not only by climatic factors (primarily rainfall) but also
by the current water regime of Hong
River and the tidal regime in the Gulf
of Tonkin. The water current of Nhue
River depends completely on the operational regime of controlling canals
such as Lien Mac (Hong River) and
Thanh Liet (To Lich River) and other
canals on the main stream such as Ha
Dong, Dong Quan, Nhat Tuu and
Luong Co-Diep Son.
Nhue-Day river basin is also influenced by the daily tidal regime in the
Gulf of Tonkin. The tide affects the
capacity of these rivers in regard to
waste water drainage, flood dispersion
and irrigation.
Natural resources and environmental characteristics
Thanks to a diverse terrain with mountains, hills and plains, the basin has different eco-systems such as hills, limestone
mountains, fresh water and wetlands.
Though the major part of the basin has
been exploited for many years, the biology of the basin remains diverse and
abundant since part of the basin is set
aside as special use forest area, including
Cuc Phuong and Ba Vi national parks,
Huong Son and Hoa Lu protected areas
and Van Long and Xuan Thuy wetland
conservation areas.
With a diverse topography and the
majority of the land area being plains,
Nhue-Day river basin has advantages for
economic development. However, there
are typical difficulties concerning river
dykes. There are several rivers flowing
across the basin and the dykes are often
11
ENVIRONMENT REPORT OF VIETNAM, 2006
THE CURRENT STATE OF WATER ENVIRONMENT IN 3 RIVER BASINS OF CAU, NHUE - DAY AND DONG NAI
RIVER SYSTEM
threatened by floods. Many dyke sections are lower than the standard height
by 0.2 - 1.2 meter. Lower areas and
swamps, particularly the flood diverging
areas of Day River, are often inundated
in the rainy season. Whenever flooding
occurs at level III, the area is always
inundated under 1 - 4 meter depth. Local
people are often faced with difficulties in
their domestic and production activities
during the rainy season.
Nhue-Day river basin has many tributaries flowing through cities, towns, residential areas, industrial zones, services
areas and craft villages etc… These are
important water sources serving agricultural and industrial production as well as
domestic needs.
Socio-economic characteristics
The population of the 6 provinces
belonging to Nhue-Day river basin is
10.2 million people (2005) with an average density of 847 persons per km2,
which is 3.5 times higher than the country's average. Ha Noi, Ha Tay and Nam
Dinh have a higher density compared to
other provinces. During the period of
1996 - 2002, the population living in the
basin had increased by 1.27% on average, particularly in the urban areas.
An urban network has developed in
the river basin with Hanoi capital, Nam
Dinh city (second-class city) and many
other towns and industrial zones. The
urban population of these provinces and
cities had increased significantly in the
period of 1996 - 2003 with an average
rate of 5% per year (particularly, 5.58%
for Hanoi). The urbanization process in
the region is happening rapidly while
the infrastructure is incompatibly developed.
12
Figure 1.5. Population density and population distribution per provinces in Nhue-Day river basin
Source: Statistical Year Book 2005
At the present, Nhue - Day river basin
is under great pressure of socio-economic development activities, especially of
industrial zones, exploiting and processing areas and residential areas, etc. The
establishment and operation of industrial zones, craft villages, small factories,
army economic entities, mining and processing, and agricultural activities in the
flood draining corridor, etc. have caused
significant changes to the environment in
general and the water environment of
the basin in particular.
The economy of the related provinces
in the basin depends on industry, agriculture and small industries. Agriculture
and small industry contribute considerably to the GDP (21% of the total GDP of
the basin). About 60-70% of the population lives on agriculture. In recent years,
the economy of these provinces has
developed strongly.
In the basin there are 458 craft villages, specializing in different areas such
as weaving, dying, food processing, iron
and metal processing, handicraft and
fine arts, woodwork etc... Ha Tay
province has 219 craft villages.
Chapter 1: RIVER BASINS IN VIETNAM
ENVIRONMENT REPORT OF VIETNAM, 2006
THE CURRENT STATE OF WATER ENVIRONMENT IN 3 RIVER BASINS OF CAU, NHUE - DAY AND DONG NAI
RIVER SYSTEM
1.2.3. Dong Nai river basin system
Natural characteristics
Natural area: 37,400 km (accounting for 11%
of the total country area)
2
Annual water flow: about 36.6 billion m3,
Main rivers in the basin: Dong Nai, Be, Sai
Gon, Thi Vai,
Density: varying from 0.3 - 0.8 km/km2,
Provinces located in Dong Nai river basin:
Dac Nong, Lam Dong, Binh Phuoc, Dong Nai,
Binh Thuan, Ninh Thuan, Tay Ninh, Binh
Duong, HCM city, Ba Ria - Vung Tau, Long An
Population: 16,431,000 (2005),
Population density: 269 persons per km2
(2.811 person/km2 in HCM city) 11 times higher
than the average density of the country),
Industrial entities: more than 9,000
Craft villages: 491
Medical establishments: 1,633 with 35,000
beds.
Dong Nai river basin area is about
37,400 km2 (accounting for 84.8% of total
the basin area). The basin covers almost
all territorial areas of Lam Dong, Binh
Phuoc, Binh Duong, Tay Ninh, Dong
Nai, HCM city and a part of Dak Nong,
Long An, Ba Ria - Vung Tau, Binh
Thuan, Ninh Thuan provinces (11
provinces and cities in total).
Dong Nai river basin is shaped as
tree branches, of which Dong Nai is the
main stream flowing in NE-SW direction. The main rivers flowing into Dong
Nai are La Nga River (on the left bank
of Dong Nai River) and Be, Sai Gon and
Vam Co (on the right bank of Dong Nai
River).
Dong Nai River has a length of 470
km with a basin area of 14,800 km back
Figure 1.6. Map of relevant provinces in Dong Nai river basin system
Source: VEPA
Chapter 1: RIVER BASINS IN VIETNAM
13
ENVIRONMENT REPORT OF VIETNAM, 2006
THE CURRENT STATE OF WATER ENVIRONMENT IN 3 RIVER BASINS OF CAU, NHUE - DAY AND DONG NAI
RIVER SYSTEM
to Tri An falls. Sai Gon River is 256 km
long with a basin area of 4,710 km2. Be
River is 344 km long with a basin area of
7,170 km2. La Nga River is 290 km long
with a basin area of 4,100 km2. The basin
has 266 rivers and streams with a length
of over 10 km each.
The river system flows to the sea at
two main estuaries of Ganh Rai and Soai
Rap. In the downstream area, tides cause
salt intrusion to the fresh water. This is
recorded in Sai Gon River, at Dau Tieng
dam which is 148 km distance from the
river mouth and also at Tri An dam.
The total water flow of the river basin
is about 36.3 billion m3; of which 32 billion m3 originate from in-country parts of
the basin (accounting for 89% of the total
water flow of the basin); the annual
water flow of Be river is about 8 billion
m3, Sai Gon River - 3 billion m3, Vam Co
and La Nga Rivers - 5 billion m3 each.
Dong Nai river basin has a tropical
monsoon climate with two seasons rainy and dry. The rainy season starts in
May and ends in October with a rainfall
accounting for 85% of the total annual
rainfall.
The basin has several dams and lakes
such as Tri An hydropower plant, Dau
Tieng reservoir and other hydropower
plants including Don Duong, Dai Ninh
in Dong Nai River; Thac Mo, Srok
Fuming, Can Don in Be River; Ham
Thuan and Da Mi in La Nga River.
After the construction of Tri An
hydropower plant and Dau Tieng reservoir, the water flow increased by 4 - 5
times in the dry season (Feb., Mar.,
Apr.) and decreased by 50% in the flood
season.
14
Natural resources and environmental characteristics
Dong Nai river basin system is rich in
mineral resources including gold, iron,
tin, zinc,... which have now attracted lots
of attention and are being exploited.
The upstream forest system plays a
very important role in the Dong Nai
river basin. The current total forest cover
of Dong Nai river basin system is about
950,000 ha accounting for 18.66% of the
total natural land area of the 9 south
eastern provinces, of which 280,000 ha
are special use forests. The upstream
forests play an important role as they
help to maintain water sources for Dong
Nai River in the dry season and prevent
flash-flooding in the rainy season. In
addition, the forests are also important
in protecting valuable species and conserving biodiversity of tropical ecosystems. However, the forests are being progressively destroyed and becoming
unable to play their protecting role.
Quantitatively, 89% of the flora mass is
not able to conserve water since the
decay layer is very thin. This also affects
the capacity of the forest in balancing the
water resource in the dry season.
There are several natural protected
areas with high economic and ecological
values in the Basin. Can Gio Wetland
Biosphere Conservation Area, which is
73,360 ha is an example. (It is recognized
by UNESCO as the first World's biosphere area of Vietnam).Another biosphere conservation area is Cat Tien
National Park with an area of 73,878 ha.
Besides, there are other forests in the
catchment area which are not only very
valuable in terms of landscape and ecological values but also important for balancing and protecting water sources in
the basin.
Chapter 1: RIVER BASINS IN VIETNAM
ENVIRONMENT REPORT OF VIETNAM, 2006
THE CURRENT STATE OF WATER ENVIRONMENT IN 3 RIVER BASINS OF CAU, NHUE - DAY AND DONG NAI
RIVER SYSTEM
The delta of Dong Nai river system is
known as a breeding area of aquatic
species. Aquatic products contribute significantly to the local economy.
Socio-characteristics
Population of the 11 provinces in the
basin in 2005 is about 16.4 million people
in total (accounting for 19.7% of the
country's total population) of which 8.3
million are rural population and the
remaining is urban. The population distribution is different from area to area
and from urban to rural areas.
The average population density in the
basin is 296 persons per km2, particularly in HCM city the density is 2,811 persons per km2.
In the basin, urbanization is progressing rapidly. The average population
Figure 1.7. Population of provinces in Dong Nai
river basin
Source: Statistical Year Book, 2005
growth rate in the whole basin is 5.5%,
the rate is especially high in Binh Duong
province with 15.6%. HCM city, Dong
Nai, Binh Duong, Ba Ria - Vung Tau
provinces are considered as having high
urbanization rates.
Although having a high urbanization
rate, infrastructure in the basin such as
transport system, hospital, water supply
etc… has not yet developed sufficiently.
Dong Nai river basin is the most
dynamic economic development region
in the whole country. Tay Ninh, Long
An, Binh Duong, Dong Nai, Ba Ria Vung Tau provinces and HCM city are
located in the southern focal economic
region which contributes up to 40% of
total revenue to the state budget. This is
one of the economic development
regions with a high and sustainable
growth rate and is considered as an economic momentum for the economic
growth of the whole country.
Presently, there are about 60 industrial areas and export processing zones
located in the basin, mostly in the 6
provinces and cities of the southern focal
economic region and located in the
downstream to lower sections of rivers.
Other provinces have established their
own industrial zones, the operational
rate of which however is still very low.
An Ha - Thay Cai Canal, Ho Chi Minh city
Source: Documentary photo
Chapter 1: RIVER BASINS IN VIETNAM
15
ENVIRONMENT REPORT OF VIETNAM, 2006
THE CURRENT STATE OF WATER ENVIRONMENT IN 3 RIVER BASINS OF CAU, NHUE - DAY AND DONG NAI
RIVER SYSTEM
Figure 1.8. Industrial production growth of provinces in Dong Nai river basin system
Source: Statistical Year Book 2005
The industrial share in the basin
accounts for 58% of the total industrial
share in the country's GDP.
The total agricultural land is 1.45 million ha (accounting for 24.3% of the total
basin area). South eastern region and
south Tay Nguyen is characterized by
perennial industrial trees such as rubber,
coffee, tea, cashew, pepper and sugar
cane etc… and others like corn, cassava,
pea nut, bean, etc.
Thanks to favorable natural conditions, animal husbandry is undergoing
rapid development. The number of cattle
was 2.7 million in 2001 and increased to
4.4 million in 2005.
The area has a high potential in aquaculture and fishery with several high
value species such as clawed shrimp,
white bass, Chia Voi fish etc… The total
aquaculture area in the basin is about
71,800 ha with a yield of about 449,000
tons per year.
Water transport: According to statistical data, there are 37 small and big ports
in the southern focal economic region,
which serve 1,000-30,000 DWT of shipping coming in and out of the country
(Source: National Report on Inland
source of Marine Pollution, 2004).
Sai Gon River
16
Source: Documentary photo
Chapter 1: RIVER BASINS IN VIETNAM
ENVIRONMENT REPORT OF VIETNAM, 2006
THE CURRENT STATE OF WATER ENVIRONMENT IN 3 RIVER BASINS OF CAU, NHUE - DAY AND DONG NAI
RIVER SYSTEM
Chapter 1: RIVER BASINS IN VIETNAM
17