~;. . . .
*
ELSEV I ER
Agricultural
water management
Agricultural Water Management25 (1994) 203-219
Review Article
I r r i g a t i o n - a blessing or a curse
Jan v a n
Schilfgaarde
Natural Resources and Systems, Agricultural Research Service, U.S. Department of Agriculture, Bldg. 005,
Room 115, BARC-West, Beltsville, MD 20705, USA
Accepted 2 December 1993
Abstract
Irrigation is vital to the well being of the people in this world and plays a significant role in local,
national, and international economics. However, irrigation also has created problems, such as salinization of land and water resources, adverse socio-economic and cultural effects, and environmental
damage. Civilizations have risen and fallen with the growth and decline of their irrigation systems,
while others have maintained sustainable irrigation for thousands of years. In the last century or so,
many large and impressive irrigation projects have been installed as monuments to engineering
technology. Often, these systems have centralized (top-down) management, which is not in the best
interest of farmers and local people. Gradual development of existing local irrigation practices and
farmer (bottom-up) management, while less spectacular, may ultimately be more successful. Many
of the problems in irrigated agriculture can be mitigated or avoided by improved technology and
management, and by adequately addressing cultural, social, and environmental aspects.
Keywords: Irrigation development, socio-economiceffect, cultural effect; Sustainability, environmental impact,
history, management
1. Introduction
It is hardly a new observation that water is the staff of life. Goethe, in his Faust, quoted
Thales to say, in the 6th century B.C., that life arose out of water; about 300 years later,
Plato expressed deep concern over deforestation and erosion - the mismanagement of water.
Man has always known that water forms the basis of his existence.
Irrigation has formed the foundation of civilization in numerous regions for millennia.
Egyptians have depended on the Nile's flooding of the delta for 8000 years; this may well
be the longest period of continuous irrigation on a large scale. Mesopotamia, the land
between the Tigris and Euphrates, was the breadbasket for the Sumerian empire. At its
0378-3774/94/$07.00 © 1994Elsevier ScienceB.V. All rights reserved
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,I. van Schi!/~,,aarde / Aerie'u/rural Water Managemet~l 25 (1994) 203~ 21 ~
height, some 4000 years ago, this civilization managed a highly developed, centrally controlled irrigation system.
In that same time frame, irrigation apparently developed in present-day China and in the
Indus basin. In the Americas, there is historical evidence of irrigation dating back some
2000 years.
Not all of these systems survived. One hears that the Sumerian empire succumbed because
of a collapse of the irrigation system; possibly, the irrigation system collapsed because of a
deterioration in the social structure. Merrey (1987) cites Gibson as asserting that it was the
intervention of the State government that weakened and ultimately destroyed the agricultural
base of society in Mesopotamia. Centrally orchestrated interventions, aimed at increasing
production to meet rising expectations for food and revenues, were seen as leading to poor
management and consequent waterlogging, salinity, and siltation.
In any event, irrigation played an integral part in the development, the maintenance, as
well as the decline of numerous civilizations. Yes, all was not sweetness and light; declining
civilizations went hand-in-hand with declines in irrigation, just as rising cultures thrived
with irrigation.
2. The world
In more recent times, ancient practices of irrigation were given a major boost by European
colonialists who wished to further develop and use the resources they encountered, especially in Asia. The engineering works planned and constructed in the Punjab by the British,
in what is now Pakistan, were gigantic and presented a major engineering triumph. Begun
in the 1860s, there was developed a system of water storage and distribution that included
63 000 km of canals and distributaries and served 14 million ha.
Again after the second world war, we witnessed an outpouring of international technical
and financial assistance that led to a huge expansion of the area irrigated worldwide. Statistics
are not complete, and the numbers cited in the literature are often inconsistent. Even in the
U.S., with its obsession at inventorying everything, reliable estimates of the area irrigated
are hard to unearth. None the less, Tables 1 and 2 give an indication of the significance of
irrigation worldwide. Rangeley (1989), well-known consultant and past president of the
International Congress of Irrigation and Drainage, estimated that in the last half century the
gross area served by irrigation trebled from 95 M ha in 1940 to 280 M ha in 1989, reflecting
a compound growth rate of 2.7%. Hoffman et al. (1990) gave a somewhat lower estimate
of 226 M ha in 1984. They showed that in the distribution of irrigated land, five countries
dominate (Table 1), that over 60% of the irrigated land is in Asia, and more than 70% in
developing countries (Table 2). They also pointed out that the rapid rate of expansion of
the past half century has recently slowed from 2.7% to less than 1%.
Frederick (1992), in a recent issue of Resources, used another statistic to illustrate growth.
From 1950 to 1985, the number of reservoirs with storage capacity exceeding 100 M m 3
had increased 3-fold, while storage increased 9-fold worldwide. He, like Hoffman et al.,
pointed to a recent decline, and expected future slowing, of further development.
Many of the irrigation enterprises, especially in Asia and northern Africa, share a number
of characteristics:
205
J. van Schilfgaarde /Agricultural Water Management 25 (1994) 203-219
Table 1
Countries with major irrigated areas in 1986"
Millions of
hectares
irrigated
India
China
Russia
United States
Pakistan
55
47
21
19
16
Indonesia
Iran
Mexico
Spain
Turkey
Thailand
Egypt
Japan
Italy
Romania
7.3
5.8
5.3
3.3
3.3
3.2
3.2
3.0
3.0
3.0
Percent of
country's cultivated
land irrigated
33
48
9
10
77
34
39
21
16
12
16
100
63
25
28
*Adapted from Hoffman et al., 1990.
Table 2
Worldwide distribution of irrigated areas in 1984"
Millions of
hectares
Percent of
world total
Percent of
cultivated area
Asia
North America
Russia
Europe
Africa
South America
Central America
Australia and Oceania
137
25
21
16
10
8
7
2
62
9
9
7
5
4
3
1
30
8
8
11
6
6
18
4
Developing countries
Industrial countries
160
66
71
29
20
9
World
226
100
15
*Adapted from Hoffman et al., 1990.
• T h e y reflect a high level o f p r o f e s s i o n a l i s m in terms o f design and construction o f the
water i m p o u n d m e n t and c o n v e y a n c e facilities. In fact, one cannot but h a v e the greatest
admiration for the e n g i n e e r i n g skills displayed.
• T h e y are d e s i g n e d and operated in a top-down, centralized manner, and they generally
deliver water on a fixed rotational schedule. Put differently, the systems are designed and
206
J van Schi!fgaarde /A~4ricuitural Water Management 25 ~1994) 203-2 ] 9
operated by engineers for the convenience of engineers, with limited attention Io the
needs, skills and wishes of the presumed beneficiaries of the water, the farmers.
• As often as not, the operating rules are designed to maximize yields of crops that are
suited for export, in order to provide desired revenue for, earlier, the colonial mast,',".;.
and now, the Government planners.
• They tend to lack adequate drainage facilities, leading to potential- or realized- salinafion
and waterlogging.
• At times, they introduce inappropriate technology, such as the selection of pumps for
local tubewell operation from suppliers who are unable to provide service and parts, or
the use of water control structures that are prone to vandalism and theft.
None of these observations is new or original. In fact, one encounters them time and again
in the literature. Like all generalizations, they have their limitations and one can readily find
exceptions or variations. Just the same, listing them helps to focus our thinking. The
following specific cases illustrate some of these points.
3. Pakistan
In describing the status of irrigation in Pakistan, Rangeley (1987) pointed out how the
Warabandi system of fixed turn rotations with constant delivery rates was designed to
operate with regime flow to minimize sedimentation and scouring. The system represents a
proud engineering monument that works well hydraulically, requiring a minimum of control
structures and maintenance; in the early days, it worked reasonably well from the irrigator's
point of view as well, when holdings were targeted to be 10 ha and aggregated, for purposes
of water delivery and rotation, to 100 or 130 ha. However, from the beginning, the farmer's
opportunity to optimize crop water management was severely restricted; as population
pressures increased and holdings decreased in size, the time of set became unmanageably
short, making effective irrigation difficult, if not impossible. Thus, a system designed "top
down", for convenience of the central system managers and for hydraulic efficiency of the
delivery system, changed from one that placed severe but acceptable limits on the farmer's
ability to manage his crop and his water, to one that no longer functioned well.
Furthermore, the flat terrain in the Punjab and the lack of provisions for drainage led to
rising water tables and salination. During the Kennedy administration in the U.S., major
studies were initiated to address the decreasing effectiveness of Pakistan irrigation. It was
estimated that, during the 50s and 60s, 20 to 40 000 ha per year were going out of production
due to waterlogging and salinity (White House, 1964). This and later developments led to
the introduction of tubewells to simultaneously lower water tables and enable conjunctive
use of ground and surface waters. In the short run, this approach was technically sound; in
the long run, it still could not resolve the salt balance problem. However, its success also
depended on mutual cooperation between farmers and system operators, and a balancing of
the needs of the distribution system and those of the crops.
If tubewell operation is scheduled to coincide with minimal electric demand, rather than
to match crop water needs, one cannot expect it to exert significant impact on water-use
efficiency or cropping intensity, even if the drainage problem may be reduced. The literature
J. van Schilfgaarde /Agricultural Water Management 25 (1994) 203-219
207
indeed suggests that the success of tubewells in improving the overall operation and effectiveness has been disappointing. In fact, to the extent they are used, centrally managed
tubewells seem to have been replaced by farmer-operated ones, a symptom of a problem
addressed later in this article.
The use of Persian wheels was prevalent before the British period, and they were used
generally to facilitate a mixture, at the village level, of seasonal flood irrigation, pump
irrigation, rainfed cropping, and grazing. With the introduction of the canal system and the
associated centralization of the water management, the Persian wheels tended to be abandoned until they were reintroduced, in the form of tubewells, after lack of drainage caused
the waterlogging problem.
It is, of course, unfair to imply and untrue that irrigation development usually is focused
on export earnings without regard to farmer welfare. Certainly the donor agencies assisting
Pakistan have put emphasis in their planning on local food sufficiency. Just the same, the
trickle-down theory has had major impact on irrigation management. The thought behind
the' 'export crop" concept seems to be based on the idea that overall economic effectiveness
will lead to an improvement in general welfare. Use of the economic internal rate of return
for assessing the viability of a project formalizes that concept. Unfortunately, such a theory
fails to take adequate account of the distribution of benefits, as well as of the ability of the
farmer to adapt to the management necessary for the new, potentially improved regime.
The farmer tends to be more interested in feeding his family than in providing products for
sale. In a word, the view from the top may be very different from the view from the bottom.
4. Sudan
The Gezira Scheme in Sudan had its beginning with the construction of the Sennar Dam
on the Blue Nile in 1925. It became Africa's largest irrigation project, with 890 000 ha
irrigated, and one of its most successful - until the 1970s, when something went wrong
(Farbrother, 1989).
In contrast to the Punjab, the irrigation-delivery system here was designed with elaborate
controls to permit modulation of water delivery based on crop need. The possibility of
frequent change in indents, or water orders, was advantageous from the cultivator's viewpoint but led to substantial canal siltation and high maintenance requirements. Notwithstanding, the system was highly successful in terms of crop production. The system was designed
for long-staple cotton production, virtually a monoculture system, with allowance of small
areas for sorghum and fodder crops to pacify the farmer. Cotton, of course, was preferred
because of the expected high export earnings it would produce. Over time, farmers' ingenuity
and informal acquiescence led to a more relaxed rotation and, after the completion of the
Roseares Dam in 1966, the cropping rules were formally relaxed. Thus, a diversified menu
of cotton mixed with peanuts, wheat, sorghum, and vegetables emerged. The demand
delivery this system provided, together with the farmer's freedom - official or on-the-sly to select his own crop rotation and implement his own irrigation management schedules, in
effect changed the Gezira from a top-down to a bottom-up operation.
The resulting efficient operation of the system, responsive to farmer demands, and the
quality of the on-farm management, led to remarkable and ever increasing production up
2()8
,1 ~an Schil]gaarde /Agrtcultural Water Management 25 (1994) 203-21~
to 1975. However, by 1980, cotton production had been reduced to 50% of its peak. At
least in part, the decline was due to political intervention that tbrced the water-delivery
system to revert from a version of "on-demand" back to a rotational delivery on a 14-day
schedule. Admittedly, it was also aggravated by a rise in fuel prices and increased incidents
of plant pests.
The issue here is again top-down decisions and management, compared to a system
responsive to the cultivator's needs. Up to 1975, farmers were able to order water and apply
it substantially in accordance with crop needs. The system of water distribution worked out
locally by farmers with their neighbors worked well. When the experts took over and
superposed their wisdom, efficiency soon fell. According to Farbrother (1989), evaluation
by the World Bank has not been particularly helpful because its recommendations, too,
stressed inappropriate centralized decision-making, ignoring the on-the-land experience of
many years.
Elsewhere in Sudan, the New Halfa Scheme, on the Atbara River in eastern Sudan, was
developed to provide an opportunity to resettle the Nubians displaced when the Aswan High
Dam was built in Egypt. Salem-Murdock (1987) has described, in some detail, how this
scheme has distorted the existing social infrastructure, led to an accumulation of wealth
among a few and poverty for many, caused serious environmental degradation, and ultimately reduced land productivity with a substantial decrease in area irrigated since the mid70s. She argued that the World Bank efforts at rehabilitation laudably and appropriately
stressed a shift from export crops to a mix of locally accepted crops and livestock but that
the method proposed to accomplish this change - depending on confined livestock rather
than herding - was likely to lead to failure. In other words, insufficient attention to local
mores and indigenous social structure, specifically insufficient recognition of the need to
integrate use of dryland grazing, irrigated crop production, and fodder provision during the
dry season, may make long-term improvement difficult. As an aside, it is interesting to note
that she hypothesises that centralization of wealth in a few individuals is directly related to
environmental degradation.
5. Sub-Sahelia
Moving farther south, a quite different situation is encountered in the sub-Sahelian region.
Both Moris and T h o m ( 1 9 9 0 ) and Kortenhorst et al. (1989) raise a question of definition.
In Egypt, there is little doubt about what is meant by irrigation; with only trivial precipitation
in 1 or 2 months of the year, crop production depends totally on the application of irrigation
water. In sub-Saharan Africa, the distinction is not so clear, because there one deals with a
graduation from full dependence on "imported" water to making better use of seasonal
flood or rain waters. The one extreme seems to be typical of donor-sponsored "schemes",
while the latter is better described a s ' 'traditional" systems. The distinction goes far beyond
semantics and is crucial in identifying and resolving policy issues for water development
in Africa.
Both sets of authors report that there is a large potential for further irrigation development
in Africa. For example, they cite FAO estimates that the potential irrigated area in subSaharan Africa is 33 641 000 ha, of which only 15% was developed in 1982. Table 3
J. van Schilfgaarde /Agricultural Water Management 25 (1994) 203-219
209
illustrates some of these potentials. A good case can be made for the further development
of irrigation on a large scale. Aside from the obvious need for increased production to feed
and support an expanding population, the presence of good dam sites, of fertile soils and of
underutilized water supplies all would seem to point to an ideal situation for development.
Thus, the question is not whether further irrigation development is warranted or even
mandatory; it is what form such development should take in Central Africa.
Paraphrasing Moris and Thorn, investment in large irrigation schemes may be inappropriate if, among other things, it will result in massive displacement of people, exacerbate
social tensions, or intrude on a fragile environment; or if the infrastructure is weak, marketing
and transportation facilities are lacking, long-term donor commitment is absent, or past
failures go unexplained.
In too many recent projects, several of these conditions existed. Indeed, the record of
sponsored projects is not good. Formal reports often show respectable internal rates of
return, but careful scrutiny does not necessarily support these conclusions. The claims often
are based on excessively high estimates of crop yields - typically double true yields - and
reflect the situation upon project completion, rather than at maturity. Kortenhorst et al.
(1989) cited two examples of declining farm income to illustrate the problem. Pre-project
net farm income at Lac Alaotra in Madagascar was $ 511; at project completion it was
$1149, but 4 years later only $ 636. For the Gambia Agricultural Development Project, the
corresponding figures were $ 653, $ 668 and $ 269.
Without going into further detail, the literature strongly suggests that the performance of
many African irrigation projects has been severely disappointing. In most cases, these
disappointments - whether one wants to call them failures or not - are related to the failure
to give due consideration to local conditions, both physical and social, and to the desire of
donors and their contractors to have a quick impact, and to collect substantial fees, in a
limited period of time.
Compared to Asia, it appears that irrigation development in Africa is more costly. Kortenhorst et al. (1989) cited an FAO report that estimated the cost for irrigation development
in South Asia at $1600 per ha and up, and in Africa from $ 9500 per ha, raising a priori
questions of economic viability.
Analysis is often based on internal rates of return, or economic viability seen from
Table 3
Potentially irrigable areas in sub-Saharan Africa
Country
Irrigation
potential
(M ha)
Total
developed
(K ha)
Percent
developed
Angola
Mozambique
Tanzania
Zalre
Zambia
6.7
2.4
2.3
4.0
3.5
10
70
140
20
16
0
3
6
1
0
Source: FAO (1986), from Kortenhorst et al., 1989.
210
J. v,m Schi[[gaarde ~Agricultural Water Management 25 ! 1994) 203-. 21 !;
society's viewpoint. What may be missing is a financial analysis, or an evaluation whether
the farmer will be able to find adequate and timely resources to manage his share, in terms
of cash flow, labor, and other inputs necessary for a successful operation.
Most important, successful development must be compatible with other components of
the farming, or more broadly, the local economic system. Thus, projects designed by
outsiders far removed from the scene without adequate reference to existing circumstances
have a low probability of success. Even superficially trivial issues can become vital, such
as the use of"stealable" components; if gates, valves, and other components can be removed
and sold, they may not last long, unless the local community has "bought in" to the project.
Finally, one must consider risk avoidance. It is common wisdom that irrigation, by
reducing the uncertainty of water supply, reduces risks. In fact, irrigation projects that
replace low yielding food crops with potentially high-valued export crops, but require
increased financial resources as well as continued, integrated system maintenance, marketing structures and stable prices, may actually increase risk to subsistence farmers, or be
perceived to increase such risk (Kortenhorst et al., 1989).
Do these observations lead to the conclusion that irrigation development in Africa is
inappropriate? Far from it. The need for further development is clear, not debatable, and
urgent. The proper conclusion is that, in planning and implementing further development,
appropriate technologies be identified by starting with the farmer and his or her circumstances. Returning to the earlier comment on the definition of irrigation, it may well be that
enhancing "traditional" irrigation is preferable over investment in large-scale "schemes".
To quote Moris and Thom again, ' ~... spontaneously evolved technologies feed more people
than do the introduced systems ..." (p. 3) even if apparently crude.
Further irrigation development, urgently needed, is more likely to succeed if it is planned
from the farmers' point of view, if the farmer is given a clear and explicit stake in the
outcome from the beginning, if it builds on traditional farming practices and if it is compatible with social and cultural customs. O/ten, it must start with refinements and subtle
modification of traditional systems that evolved historically and made good use of those
resources that man encountered and could manage with a minimum of technology. Such
development is not glamorous, makes it difficult to commit large capital investments in a
short time, requires long-term commitments, and demands greater intellectual ingenuity as
well as social sensitivity than the relatively easier approach of harnassing the water with
large structures. Such gradual development, however, has a much greater chance of success.
6. Egypt
In the water distribution system in Egypt's Nile delta, the water courses typically deliver
water 30 to to 60 cm below ground level, Upon inquiry, Egyptian Ministry officials explained
that this system was superior: it required the farmer to expend substantial effort to lift the
water and hence would make him more conscious of the need for efficiency. When Colorado
State University scientists, working on an AID-sponsored contract, initiated a demonstration
of gravity delivery to a set of irrigators, these farmers eagerly showed how to take advantage
of the better opportunity to manage their water, but official skepticism prevailed.
J. van Schilfgaarde /Agricultural Water Management 25 (1994) 203-219
211
7. The United States
Water development in the U.S. was a major component of the developmental ethos that
stimulated early settlers to move west from the eastern seaboard (van Schilfgaarde, 1987).
Inspired by the Jeffersonian concept of private land ownership, many hopefuls moved out
to seek their fortune in the vast and often uncharted lands of a seemingly endless continent.
First, there was the drive to "conquer the swamp" and, somewhat later, there came the
development of irrigation farther west.
Lest we forget, irrigation in the Americas preceded the present era by many centuries.
The Papago long managed to harness storm runoff in the Sonoran desert of the southwestern
U.S. and to spread it in order to raise a crop of beans. Before the Papago, the Hohokam the "lost" people - built elaborate water distribution systems along the Gila in Arizona;
between the 4th and 10th centuries, they irrigated substantial tracts of land; one canal alone
commanded 3200 ha (Worster, 1985).
Early modem attempts at irrigation developments in Utah, Colorado, and elsewhere, met
with mixed success. Often, the high capital requirements of development stood in the way,
or even led to failure. One such example was the Newlands Project near Reno, Nevada.
Francis Newlands, later Congressman Newlands and then Senator Newlands, started this
private development, but purportedly lost over $1 million before it failed.
The situation illustrated by the Reno experience provided the impetus for the Reclamation
Act of 1902. This act brought about a fundamental change in the irrigation scene, from no
Federal involvement, to a policy of Federal loans to support development, to, ultimately, a
program of Federal financing, design, construction, and operation. The oft-quoted objective
of the Reclamation Act was to provide the opportunity for homesteading in order to develop
family farms, not to exceed 160 acres (65 ha), on public land. Other, less lofty, objectives
may also have played an important role, such as the opportunity to relieve eastern cities of
unwanted people, and the opening of markets for railroads and industrialists. Without doubt,
the Reclamation Act has had a profound and lasting impact on the development of the
western U.S.
The developments during this reclamation era were indeed impressive and, in some
instances, spectacular. Some of the structures that were built were marvels of engineering;
and the area irrigated expanded rapidly from the 1.4 M ha under irrigation in the 1890s. By
1940, it had grown to 8 M ha, and by 1990 to 24 M ha. Not all of this development can be
credited to the Bureau of Reclamation; in fact, the Bureau controls less than 25% of the
area irrigated in the West. In all, however, irrigation contributes substantially to agricultural
production. In 1982, 32% of the value of crops produced was from crops grown on the 13%
of the area that was irrigated (Frederick and Sedjo, 1991 ). That ratio is essentially the same
as is found worldwide (Arar, 1987). As has been pointed out frequently, this vast expanse
of irrigated land has tended to stabilize the production of food and fiber and has permitted
a significant shift in the American diet, with a variety of fruits and vegetables available
year-round. This is truly an important benefit, even if most of the irrigated land is devoted
to low-value staple crops.
A recent estimate of the extent of irrigation in the U.S. is taken from the Irrigation Journal
(Table 4). This tabulation shows a slight decrease in total area irrigated in recent years; it
212
J. van Schi!/~,,aarde / Agrlcultural Water Management 2.5 (1994) 203 219
Table 4
Ten-year history of area irrigated in the U.SA
Year
Total area
irrigated
( I000 ha)
% Sprinkler
')~ Gravily
1991
1990
1989
1988
1987
1986
1985
1984
1983
1982
23,779
24,026
23,364
23,553
24,003
24,028
24,272
24,974
24,823
25,009
43
42
42
41
40
39
37
36
35
35
57
58
58
59
60
61
63
64
65
65
From Shank, 1992.
also shows a shift away from gravity for sprinkler irrigation. Not explicit from this table,
but clear from the survey data on which it is based, the shift is towards more water (and
labor) efficient systems.
Notwithstanding some pain and disappointments, occasional severe conflict and outright
failure, the era driven by the developmental ethos led to an extraordinary expansion of
irrigation, together with water supply development for municipalities and industry, and an
explosion in regional population. Especially in the period following World-War II, expansion was rapid.
8. An environmental ethic
However, of late this drive toward more irrigation seems to have run out of steam.
Somewhat arbitrarily, 1962 is taken as the year that the developmental ethos encountered
an opposing force in an environmental ethic. That was the year in which Rachel Carson
published her "Silent Spring"; and that book illustrates an awakening among the American
public that all was not well, that unbridled development brought along not only insults to
the environment, but also to the structure of society and to the basic premise on which this
country was founded.
As in many similar situations, neither the time of initiation nor the delineation of this
environmental ethic is precise. As used here, it includes elements of economic reality, of
concern with fouling the natural environment, of recognition of cultural diversity, of competition for resources, of re-examining issues of equity, and of a reawakening of a respect
for land and land stewardship. Several of these elements will be considered separately, in
anecdotal rather than formal form, to illustrate the concerns. These disparate ideas will then
be related into a sense for the future of irrigation.
J. van Schilfgaarde /Agricultural Water Management 25 (1994) 203-219
213
9. Irrigation constraints
Starting with the mundane and harsh reality of resource exhaustion, the Texas High Plains
will be considered first. As described in detail by Musick et al. (1990), irrigation by means
of ground water pumping in the 41 counties included in the Texas High Plains started during
the drought years of the 1930s; the area irrigated continued to expand until it peaked in
1974 at 2.25 M ha; it then dropped to 1.6 M ha in 1989. Annual groundwater use dropped
in that same period from 10.0X 109 m 3 to 5.6X 10 9 m 3. This 30% drop in area irrigated
over a 15-year period had several causes, but key among them was the gradual depletion of
the groundwater reservoir with the associated increase in cost of pumping. A series of heroic
if ill-advised attempts were made to develop a water importation scheme with water from
the Mississippi, but so far reason has prevailed. There has been a shift to higher value crops
and to more efficient irrigation systems. These include pivot sprinklers, LEPA (low energy
precision application) systems, surge irrigation, limited irrigation furrow systems and a
variety of other techniques. Over time, one may expect a dynamic equilibrium between
groundwater recharge and pumping for irrigation, attained by a further partial return to
dryland farming, and continuing increases in more deliberate use of that water still pumped
for irrigation.
An entirely different set of forces has come into play in relation to water quality. As one
example, consider the Colorado River. One of the most highly developed major rivers in
the U.S. and possibly the world, the Colorado has the special distinction that by court decree
its discharge; as allocated among the 7-basin States and Mexico, has been substantially
augmented beyond that which Mother Nature has provided. With an average annual flow
of about 17 X 109 m 3, the courts have allocated over 20 X 109 m 3. Especially if we stipulate
the supremacy of nature over the laws of man, it becomes clear that the Colorado River is
heavily used. One consequence is a gradual increase in salinity from the headwaters to the
mouth, with concomitant adverse effects on water users. Until the early 1970s, the extensive
controversies, negotiations, and litigation concerning allocation of the waters of the Colorado dealt almost exclusively with the quantity of water, and not its quality. In the 1970s,
the emphasis shifted to salinity (cf. Colorado River Basin Salinity Control Act of 1974). It
was estimated at that time that 37% of the salinity in the river could be attributed to irrigation,
but the major damage from this salinity, however calculated, was suffered in municipal use.
Looking at it in another way, salinity had been recognized for well over a century as a
crucial problem associated with irrigation, but the concern had generally been with the
effect of soil (or water) salinity on the crop; now the focus shifted from the damage by salt
to irrigated crops, to the off-site damage from irrigation to downstream water users.
One significant consequence of the Colorado River debate was the emergence of the
recognition that irrigation efficiency, or rather inefficiency, was an important factor in water
quality. Without belaboring exact definitions, efficiency in irrigation historically tended to
be seen in terms of labor and investment costs, or economic efficiency, rather than in terms
of water use per unit of production. Water was seen as a nearly free good, and even more
to the point, downstream values were not a consideration for the irrigation farmer.
The trigger that brought about action to control salinity on the Colorado was a dispute
with Mexico on the quantity as well as the quality of the river's water that was permitted to
cross the international border. The price extracted by the western States for cooperation
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with the Federal Government was a Federal subsidy to reduce the salinity in the river's
water used north of the border. Several options were considered and, to varying degrees,
implemented in efforts to manage salinity. The main one of interest today was improved
efficiency of irrigation water use.
There is a rudimentary relationship between irrigation and salinity. Irrigation water always
contains at least some salt, derived from the soils and rocks with which it has been in contact.
As the plants use some of this water but not the salt, the concentration of salt in the remaining
soil water is increased. To keep from salting out the soil, there must be drainage and this
drainage water often is returned to a stream for later reuse, or it percolates down to underlying
groundwater that in turn is discharged to a stream. Since irrigation consumes water but not
salt, salt concentrations in the remaining water are always increased by irrigation.
Conceptually, the reason for increasing irrigation efficiency is that any process that
reduces the flow of water through the soil and its underlying formations back to a surface
stream will reduce the mass of salt returned to the stream. This is readily visualized from
the mass balance picture just drawn, but takes on greater significance for at least two reasons.
In many cases, the groundwater that is displaced by drainage water contains substantial
amounts of salts of geologic origin; this is the case, for example, in the Grand Valley of
Colorado where the underlying Mancos shale is extremely saline. Also, as the soil water
content is reduced, some of the salts in solution tend to precipitate and thus to be removed
from the hydrologic system. In contrast, if relatively large volumes of water are passed
through the soil, some salts tend to be dissolved and thus enter the hydrologic system. Thus,
providing just enough water to satisfy crop needs tends to reduce the amount of salt needing
disposal in the drainage system (van Schilfgaarde and Rhoades, 1984).
Water quality and water quantity, it turns out, are intricately linked. As the pressure for
water quantity grows, the concern with water quality increases. Unfortunately, however,
the situation is substantially more complicated, and severe, than indicated so far. As
described at length in a Water Science and Technology Board report (NRC, 1989), our
understanding of the picture just described changed drastically during the 1980s. The
discovery of selenium toxicity in the Kesterson Reservoir in the northern San Joaquin Valley
of California was totally unexpected. That the irrational rapid expansion of the irrigated
base serviced by the Central Valley Project without drainage provisions would encounter
severe problems was widely recognized; that it would take the form of disastrous toxic
effects on fish and fowl caused by trace elements was not anticipated.
In retrospect, we may consider it fortunate that political consideration overruled engineering recommendations and that the use of temporary holding ponds, euphemistically
called the Kesterson wildlife refuge, to store drainage water backfired. This set of events
led to the discovery that, besides total salinity, sodium and boron problems, irrigation could
and sometimes would unleash other, more subtle but potentially more serious, water quality
problems. And indeed, similar situations have since been discovered elsewhere across the
West in studies stimulated by the Kesterson discovery.
Thus, in 20 years we have travelled from a concern with salinity effects on crops, to a
concern with salinity on water heaters and boilers in cities, and similar off-site effects, to
the realization that irrigation-induced salinity may bring about concentration of certain
minor elements to levels that are potentially toxic to various forms of life, especially fish
J. van Schilfgaarde /Agricultural Water Management 25 (1994) 203-219
215
and birds, but in some cases also humans. We have also learned that, as a necessary but
generally insufficient solution, we must improve the efficiency of irrigation water use in the
sense of increasing the percentage of the water diverted that is used directly by the crop.
So far, we have considered various pressures on the water supply that are aggravated as
populations grow, water uses expand, ant thus supplies become relatively more scarce. We
have emphasized irrigation because irrigation is by far the greatest user of water in arid and
semi-arid environments. Superficially speaking, it seems that one could easily make a
mountain out of a mole hill. If irrigation is responsible for over 85% of the water used
consumptively - a figure that is close to reality - then a relatively minor reduction in
irrigation water use would substantially increase the water available for municipal and
industrial purposes, and transfers could be arranged. However, life is not that simple.
It is true that, up to a point, pressures on the water supply can, and are being, resolved
by market transfers, i.e. by letting market forces work and allowing the sale of water rights
from perceived lower to presumably higher valued uses. This solution suffers from a number
of limitations, however, including the obvious fact that our economy is not totally free, and
the concern that there is no entity to bid for certain valid interests.
Consider a few examples. In those irrigation projects that are sponsored by the Bureau
of Reclamation, irrigation water is subsidized heavily, both by the general tax payer and by
the power user. According to Bureau estimates, the total subsidy since establishment of the
Service exceeds $10 X 109 (NRC, 1989, p. 55). Some other projects, such as the California
State Water Project, also deliver subsidized water. The question then is whether the perceived benefits to society justify subsidies in principle, and the specific subsidies provided.
Some level of subsidy was clearly needed in earlier decades and can probably be justified
today. However, these subsidies weaken the ability of free market forces to reallocate water
effectively, and the effect of the subsidies often has been different from the original expectations.
Does the development of large irrigation projects, with or without subsidies, lead to
economic development the benefits of which are shared equally and equitably? As observed
earlier, both in Sudan and in Asia, the benefits of irrigation tend to accrue unequally to a
relative few. In the U.S., Goodall and Sullivan (1985), in a study involving Fresno and
Imperial Counties in California, concluded that in the area served by the two largest Bureausponsored irrigation projects, substantial wealth was unevenly distributed and unemployment levels were extraordinarily high. More generally, Worster (1985) developed the theme
that large-scale irrigation development inevitably leads to a concentration of power and
wealth through the development of a hierarchical system of management and, thus, social
structure. The evidence, such as it is, suggests that irrigation, if it requires managing and
transporting large volumes of water over substantial distances, results in the creation of a
severely stratified society with inequitable distribution of benefits, characterized by great
wealth in the hands of a few and serious poverty for many. Should this be of concern, or
should it be accepted as a "natural" law? Should this apparent fact influence how society
views subsidies?
Possibly more important, water development has had, and continues to have, serious
adverse effects on a number of values that are less readily translated into economic terms.
In the Central Valley of California, less than 10% of the wetlands there originally remain.
This and similar changes elsewhere have resulted in tremendous pressure on migratory
216
J van S~hi!/]~aarde / Agrlcuhural Wawr Mana,vement 25 (1994) 203 21 ~
birds, as one example. Who speaks for the birds, or for the salmon? For that matter, who
speaks for the rafters and the recreationists? In recent years, legislation and court decrees
have tended to develop means for protecting instream flows. In principle, the public trust
doctrine should provide for those legitimate water uses not represented in the market; the
system, however, is far from perfecl.
An entirely different issue emerges when one recognizes that water development can
greatly alter the nature of society and, even if the abstract total economic benefit is substantial, the impact on certain sub-groups of people can be devastating. An example of this is
the Truckee-Carson Irrigation District near Reno, Nevada, and its surroundings, which,
along with several other situations described below, are treated in detail in a recent NRC
report concerning water transfers (NRC, 1992).
As the first development under the 1902 Reclamation Act, the Newlands Project presents
a complicated case that illustrates a number of significant conflicts. Originally intended
primarily as an irrigation project, developments in recent years have made irrigation far less
important to the local economy than municipal and industrial uses of water. The severe
demands on the available water supply, in terms of quantity as well as quality, resulting
from a booming regional economy have led to extreme stresses on the natural ecosystem as
well as on the lifestyle and livelihood of two native Indian tribes. The Paiute Indians have
always depended on fishing in Pyramid Lake for their existence. This lake is fed by the
Truckee River. As more water was consumed, and water was also diverted from the Truckee
to the Carson River to satisfy another tribe near the Carson Sink, the water level in Pyramid
Lake dropped precipitously and, aggravated by stream morphology, the lower inflow
prevented migration of the cui-cui and Lahontan cutthroat trout for spawning. Thus, irrigation development, plus municipal growth, resulted in serious harm to a natural asset and
to a people dependent on this asset, Pyramid Lake.
At the same time, the Fallon Indians, who depended on water from the Carson River for
irrigating their land, felt they were given short shrift; and downstream from them, the
Stillwater Wildlife Refuge continued to shrink in volume and suffer from water quality
degradation as upstream water use increased. Wetlands in the Stillwater Marsh area shrank
from some 16 000 ha originally to less than 2400 ha, placing severe stress on this wildlife
habitat.
Numerous suits, countersuits, and court decrees have made lawyers rich and, to some
extent, abated the worst of the insults. The fact remains that, in an arid area short of water
resources, development of an unproductive irrigation economy has led to disruption of an
ecological and cultural system with severe consequences for both nature and native populations. Part of this disruption is the price we pay for progress; part of it may be seen as the
price of greed and ignorance.
A quite different situation prevails in northern New Mexico where Indian, Hispanic, and
Anglo cultures compete and coexist. Without developing the case in any detail, one key
observation seems pertinent. The Hispanic agricultural communities depend on a community-shared and community-operated irrigation system, admittedly of a subsistence nature
and on a small scale. When water rights are transferred or reallocated using "white face"
logic, no rational harm is done and efficiency is increased. However, long established
cultural ties are broken and values related to social stability, maintaining a cultural heritage
and protecting a way of life are placed in jeopardy. To what extent, and by what means,
J. van Schilfgaarde /Agricultural Water Management 25 (1994) 203-219
217
should values such as these be cherished and protected? Clearly, a pure market economy
provides no answer to such questions.
The various examples used illustrate that, with the development of irrigation projects and
their clearly beneficial increases in agricultural production and communal growth, there
also are associated disbenefits, or insults to nature and insults to human traditions and values.
This raises the question, in the jargon of the day, whether irrigation is sustainable. A great
deal has been written about sustainability in recent years; often, the debate has generated
more heat than light. With special reference to irrigation, the following is observed. Irrigation
always results in degradation in water quality. Irrigation, by its nature, uses pure water
consumptively, leaving less water to transport salts and other contaminants. Irrigation may
be viewed as the intensification, or acceleration, of a natural process. Even without irrigation,
salts were transported from the landscape into the oceans and into inland seas. Evaporation,
without which we would have no precipitation, concentrates these salts.
Using good irrigation and drainage practices, one can maintain an irrigated agriculture
indefinitely. To do so, we must sacrifice some downstream values. As an example, consider
the Salton Sea in southern California. This sea was formed by man's diversion of Colorado
River water for irrigation in the Imperial and Coachella Valleys. Drainage from this irrigated
area into a natural sink forms the Salton Sea. A secondary benefit of irrigation is that the
Salton Sea, which would be dry were it not for irrigation, provides a habitat for fish and an
opportunity for recreation. Over time, the salinity in the Salton Sea will continue to rise,
causing it to lose biological value. Is irrigation in Imperial County sustainable? It is if we
are willing to give up, in time, fishing in Salton Sea. If irrigation is stopped, and with it the
diversion of Colorado water, the S alton Sea will dry up. The question of sustainability, then,
must be reworded into the terms of a social contract. Do we wish to maintain irrigation?
The answer may be yes, recognizing that the ultimate use of the Salton Sea is drainage water
disposal, and not recreation; or, to use another example, the answer could be no, if the cost
to a wildlife haven is seen as too great (van Schilfgaarde, 1990).
10. Conclusions
Irrigation has made major contributions in the past, continuing through this day, to feeding
the world and to rationalizing the use of limited natural resources for the common weal; but
in the process, warts have arisen n inequities have appeared and unneeded insults to the
environment have occurred.
These problems have been identified before and, in most instances, work is underway to
find solutions or, at least, to minimize the problems. An elaborate list of technologies has
been developed to increase the quality of management in irrigation and thus optimize the
benefits while constraining the insults. For example, highly sophisticated and carefully
controlled subsurface drip irrigation can increase typical crop yields manyfold while minimizing adverse off-site effects; cynicism about this "pie-in-the-sky" technology is slowly
yielding to the realization that its adoption not only helps the environment but also can put
money in the farmer's pocket. Water reuse technologies that take advantage of the fact that
some crops in some stages of growth can make effective use of brackish water generally
considered of no agricultural value are beginning to be adopted to improve overall resource
218
,1. valt Schi!tl,4aarde / A~,,ri,'utmral Water Management 25 (1994) 203-21'~
use effectiveness. Similarly, a growing literature describes institutional innovations to
enhance the distribution and use of water resources, through market mechanisms and in
other ways, and to enhance societal returns. The public trust doctrine is invoked increasingly
to help protect water uses of value to society hat are not readily represented in the market.
Ruttan ( 1991 ), in a recent report on sustainable agricultural growth, acknowledged that
we are far from having developed the necessary institutional and technical responses for
responsible resource use. He stressed the need to internalize the cost of pollution prevention
and/or remediation, an idea whose time has come. Numerous critics, including voices in
Congress, have raised the question whether expiring Bureau of Reclamation contracts ought
to be renewed without major fundamental revision.
Progress is being made, but we have a long way to go. Increased demand will place
increasing pressures not just on water, but on the institutions that govern its use. The current
public interest in the environment or in sustainability is not a temporary nuisance that will
pass. It represents an awakening of a social consciousness that recognizes that mankind
cannot continue to ignore the limits to the earth's ability to absorb and correct man's errors
and his foibles, whether committed in malice or in ignorance.
Two years ago, Schad ( 1991 ) lamented the lack of a meaningful national water policy.
At about the same time, Luna Leopold (1990) spoke of the need for an ethos to guide us
in water resource management.
Irrigation is vital for the well being of man. Irrigation has contributed substantially to the
stability and the variety of the supply of food and fiber in the U.S. Many other nations
depend on irrigation to a much greater extent than do we. In the future, irrigation worldwide
will gain further in importance, and better water management is essential for human survival.
We can learn from our errors. We should acknowledge our mistakes. There are clear
limits to the insults the environment can absorb; in some instances, these limits have been
reached or even exceeded. We should face up to the fact that equity has suffered, that third
parties often have not been served well, and resolve to do better.
We should rejoice that a sense of stewardship has reawakened. As water professionals,
we should take the initiative towards strengthening the irrigation industry in a manner that
is equitable to all parties, compatible with greater social goals, in deliberate balance with
environmental needs and sustainable for generations to come.
The technology is there, or waiting to be discovered. The need is there. The potential is
there. Do we have the will?
Acknowledgement
This paper is based on The Abel Wolman Distinguished Lecture presented June 29, 1992
at the National Academy of Sciences, Washington, D.C.
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