Journal Issue

Irrigation and the Environmental Challenge

International Monetary Fund. External Relations Dept.
Published Date:
January 1991
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Proper management of water can protect the environment

Shawki Barghouti and Guy Le Moigne

Chief, Agriculture Production and Services Division

Senior Advisor

Agriculture and Rural Development Department, The World Bank

Irrigation projects are facing increasing challenges from concerned groups that see potential harm to the environment. These groups have recently blocked the construction of major water development projects in India, China, Thailand, and the United States. The reasons given by them are many: dams and irrigation systems, they contend, result in waterlogging, salinity, disruption of water tables, damage to fisheries, plant, wildlife, and water supply systems downstream, and the displacement of people inhabiting areas submerged by the new reservoirs and irrigation schemes.

Up to the early 1970s, environmental costs were hardly considered in the design of irrigation systems. Irrigation schemes were viewed as highly effective means of transforming traditional agricultural systems into commercially oriented and scientifically based productive enterprises; indeed, in the 1960s, water development projects seemed to be a fairly straightforward process. With few exceptions, damming rivers to store water for irrigation, urban uses, and hydroelectric power production was not regarded as seriously detrimental to the environment.

Rising criticisms

It was not until the early 1970s that the trade-offs between relieving today’s poverty and hunger through massive manipulation of the water cycle and its natural systems and the attendant environmental and ecological costs of doing so came under scrutiny. Public and private environmental organizations began demanding action and lobbied to enact laws to protect the environment.

As failures of large-scale irrigation schemes to protect and enhance the environment came to light, there was growing skepticism that irrigation and drainage projects could be justified solely on the basis that they provided significantly increased opportunities for food production, trade, water management, flood control, electricity, and sustaining water supplies to growing populations in both urban and rural communities. Those benefits could be offset by damage to the environment and the social disorientation caused by resettlement of affected peoples.

Helping to buttress this growing anti-irrigation bias, weak policies in many developing countries—or lack of a clear direction in water management policy—have encouraged misallocation of water resources, including the use of greater amounts of water than the actual requirements for crops. Widely varying water-pricing policies and inadequate systems and methods for recovery of the cost of irrigation enforce a commonly held fallacy of water application: If a little of it is good, then more must be better. Such inadequate water policies have aggravated the environmental consequences of water projects, especially in areas where problems of water scarcity are dominant, such as the Middle East, China, and India. In many cases, lack of incentives for proper use of water, compounded by technological problems, have adversely affected system performance, resulting in poor maintenance, and leading countries to defer modernization.

Although it is difficult to quantify all the social, environmental, and ecological costs related to human interventions in freshwater systems, it cannot be denied that imprudently developed, badly designed, and, poorly managed irrigation schemes have had substantial negative effects on the environment. Irrigation projects do modify the environment by reshaping the land surface and changing its hydrological regime—sometimes with harmful side effects. The construction of dams and irrigation channel networks, while providing water for irrigation and power, affects soil moisture, changes the depth of groundwater, and alters water quality. Often some of these effects show up in even the best-managed irrigation schemes in ways that scientists are just now beginning to understand.

Problems of irrigation

Salinity, resource degradation, and wider damage. Data collected from large irrigated areas in China, Egypt, India, Mexico, Pakistan, the Union of Soviet Socialist Republics, and the western part of the United States indicate that irrigated lands are losing productivity, as a result of progressive deterioration of soil caused by waterlogging and salinity. This “twin menace” of waterlogging and salinity can be largely attributed to lack of drainage and poor water management. Productivity on about 25 million hectares (about 7 percent) of the world’s irrigated land is seriously affected by these problems, and the salinization of fertile croplands is running between one million and one and a half million hectares a year. The intensification of irrigated cropping, for example, damaged the ecosystem in the rice-growing areas of the humid zones of Asia and led to the salinization of areas in the region’s arid and semi-arid zones.

According to a recent study conducted by the World Bank, waterlogging and salinity have reduced yields of major crops by 30 percent, both on the 15 million hectares of irrigated croplands in Pakistan and the 3.5 million hectares in Egypt. In India, about 20 percent of the 40 million hectares of irrigated agriculture is reported to suffer from this problem.

In many parts of Asia, following the lead of Japan, drainage is being introduced as part of a crop diversification program and as a way to control waterlogging and salinity. Studies of irrigation systems are currently underway in areas that have not maintained a balance between production, water conservation, and environmental protection. But progress is slow.

The environmental damage around the Aral Sea in Soviet Central Asia is a good illustration of the harmful effects of ill-planned irrigation on the environment. Water from two rivers feeding the Aral Sea—the Syrdarya and the Amudarya—was diverted to irrigate about seven million hectares. The 1,450 kilometer-long Karakoum Canal was built to transfer considerable quantities of water from these two rivers toward the Caspian Sea to help develop agriculture in the dry republic of Turkmenistan. Because of this large-scale water transfer, the Aral Sea has begun to die, as water volume has fallen to one third of what it was in 1960. While the Aral Sea has sharply diminished in size, its once fresh water has become increasingly saline, threatening the livelihood of thousands of people living nearby who depend on it for fishing, water supplies, and transportation. Vast salty flat-lands remain as the sea pulls back. Strong winds deposit this salty residue on prime agricultural land, not only in the vicinity of the sea, but also as far away as Afghanistan, causing severe ecological damage.

In the Sub-Saharan region, the development of irrigation has raised concern about the environmental consequences of irrigation on upstream swamp and delta regions. For instance, the Niger River and Senegal River swamplands are valuable wintering sites for migratory Western European birds. The rivers’ wetland regions support from one and a half to two million head of cattle, and fishermen catch some 100,000 tons of fish annually in the Niger’s inner delta.

Before Sub-Saharan irrigation projects move forward, environmentalists say they will need convincing answers to questions on hydrological, economic, and ecological issues relating to these deltas and swamps.

Bilharzia and malaria. Other potential harmful effects of irrigation arise from habitats served by stagnant water in canals and drainage areas leading to public health problems like bilharzia, malaria, yellow fever, and other diseases. People living and working near canal water supplied through irrigation stand an increased risk of contracting such diseases associated with water development projects.

The most serious threat is bilharzia, also known as Schistosomiasis, since the carrier vector is released from an aquatic snail and penetrates human skin that comes in contact with disease-infected water. Bilharzia, which is widespread in the savannah and semi-arid regions of Africa, the Middle East, and South America, is characterized by disorders of the liver, bladder, lungs, or central nervous system, and it affects physical growth and endurance. It has also appeared in Southeast Asia, China, the Philippines, and Sulawesi, and significant increases in the incidence of bilharzia have been documented in Sub-Saharan Africa as a result of irrigation development in Ethiopia, Kenya, and Sudan.

In most of these countries, bilharzia infestations have increased among the population at risk at rates from less than 5 percent to 10 percent after the introduction of irrigation schemes. But the incidence of occurrence rose to over 80 percent of the population at risk after irrigation in some extreme cases, such as the Gezira in Sudan. A recent study by the World Health Organization concluded that the spread of bilharzia in island nations, such as the Philippines, was facilitated by the removal of natural barriers to the snail’s migration, because of irrigation project development and construction of roads through rain forests.

Schistosomiasis has substantially reduced labor productivity in China, Egypt, Sudan, and Tanzania. In Egypt, for example, labor output dropped as much as 35 percent among infected groups; whereas in China, an average loss of adult capacity to work of about 40 percent has been reported. Studies of sugar plantations in Tanzania and Sudan show that infected workers produce 10 to 15 percent less than non-infected workers. As the demand for greater amounts of food grows, better design and control of irrigation systems becomes imperative.

Toward food security

World population is expected to grow from five billion today to at least eight billion by 2015, and indications are that average annual growth rates in yield of over 2 percent in agriculture as a whole—and about 3 percent in irrigated agriculture—will be necessary to achieve food security and improve the quality of life in developing countries. We are faced with the challenge today of either continuing investment in well-conceived and environmentally sound irrigation projects to capitalize on unexploited agricultural potential, or slowing down such investment because of environmental and ecological concerns that cannot be met.

Supporters of more irrigation programs point to a recent study on the impact of irrigation in Thailand, which states that the benefits of irrigation to the environment were substantial because it attracted large segments of the population away from the “slash-and-burn” culture that destroyed the forests and damaged the environment in the hills of Thailand. Irrigation allowed these people to settle in the newly irrigated lands on the plains.

Irrigation is also identified as a key to the success of the Green Revolution. Its supporters contend that today the roughly 300 million hectares of irrigated land account for only about 20 percent of all land under cultivation and yet produce nearly 55 percent of the global output of rice and wheat. These proponents also note that over the last 20 years, irrigation projects have helped several developing countries—for example, China, India, Indonesia, and the Philippines—effectively pursue agricultural programs that have significantly reduced the number of people living below the poverty line. The high-yielding, irrigation-dependent varieties of rice and other grains have turned many Asian nations from food importers to surplus producers.

But with about $250 billion already invested in irrigation systems and another $100 billion expected to be invested by the year 2000, the environmental and other costs associated with such projects need to be clearly identified and weighed carefully.

Better evaluations

Many irrigation projects built in the past 25 years appeared to be economically attractive only because they did not include expensive subcomponents, such as proper drainage. It did not take long, however, before such “savings” produced costly results. Lack of adequate drainage systems, for example, were found to be the main cause behind the deteriorating environment and declining yields in the Indus Basis in Pakistan and Egypt’s Nile Delta.

Because of emerging concerns, the costs of supplying water—the key input in the production of major cereals—may become greater than the value of the crops and services it provides. This is the basis of the emerging “water problems crisis.” To forestall such problems, we must first put into place a plan for water management that views human intervention in the hydrological cycle not as an isolated act, but rather in terms of the action’s systemwide consequences.

The water sector must be seen as part of the whole economy and as a part of the national and regional environment. Reallocation of water resources, whether made by custom, law, regulation, or the market, is becoming increasingly difficult. In many instances, market forces alone cannot be counted on to produce optimal allocation. A well-articulated water investment strategy should provide a framework for analyzing the environmental and other implications of human interventions in the hydrological cycle over the long term.

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