Irrigation Essay ⋆ Environment Essay Examples ⋆ EssayEmpire

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Irrigation is the artificial application of water to land for the purpose of supplying moisture essential for plant growth. Although irrigation is an old art, its importance has increased in recent times with the increased demand for food to meet the needs of a growing population. Today, irrigation accounts for 70 percent of all water used by humans. Although irrigation works are found almost everywhere, they are most important in arid and semiarid regions, where the quantity and timing of rainfall are not inadequate for crops. For instance, in those parts of Asia where rainfall is seasonal, and most precipitation occurs in three to four months of the year, irrigation is highly critical to agriculture.

The importance of irrigation is evident from the fact that, historically, the development of human civilizations has followed the development of irrigation. For instance, Egypt claims to have had the world’s oldest dam, 355 feet long and 40 feet high, built some 5,000 years ago to store water for drinking and irrigation. In fact, basin irrigation introduced in the Nile valley around 3000 B.C.E. still plays an important part in Egyptian agriculture. Similarly, in the valley of the Euphrates and the Tigris (the two rivers which pass through Turkey, Syria, and Iraq, and which defined what was once called Mesopotamia), there are remains of the largest irrigation canals built around 2200 B.C. Historical references to the practice of irrigation from wells, tanks, and canals are also found in countries such as China, India, Iraq, the former U.S.S.R., Mexico, and Peru.

The importance of irrigation has grown further since the 19th century, particularly with the application of modern engineering technology. The 19th century saw the world’s irrigated area increase from 8 million hectares to about 40 million hectares, of which the single largest share was that of India (17 million hectares). Considerable irrigation development also took place in the western United States and Italy in the latter half of the 19th century. Irrigation development continued in the 20th century, particularly after World War II, when the use of irrigation technology, along with other inputs, led to the so-called Green Revolution in many parts of Asia. But since the late 1970s, irrigation expansion has slowed markedly due to a number of reasons such as low commodity prices, high energy costs, and economic conditions that discourage agricultural production.

Currently, the Asian continent accounts for nearly 70 percent of the irrigated area in the world, and the Americas for 15 percent. The three countries with the largest areas under irrigation are India, China, and United States, in that order.

According to estimates by the Food and Agriculture Organization, the share of irrigation in world crop production is expected to increase in the next decades, although the rate of increase will slow down. Irrigated land will expand by 45 million hectares to reach a total of about 242 million hectares by 2030, at a projected annual growth rate of 0.6 percent compared with the 1.9 percent observed in the period from 1963-99. The expansion of irrigation is projected to be strongest in south Asia, East Asia, and Near East/North Africa. Rising economic and environmental costs, along with declining public investments in irrigation, means that a significant increase in the rate of addition of irrigated areas is unlikely in the future; therefore, irrigation’s contribution to food production will have to come from improving existing systems rather than from expanding them to new lands.

Methods and Classification

Irrigation systems can be classified in a number of ways. The most common mode of classification is by the characteristics of the water and power source. The water source can be surface (canals and tanks) or groundwater (wells). In some parts of the world, such as South Asia, most of the recent expansion in irrigated area has been through private investments in wells to exploit groundwater. Wells in turn can be open wells (where water is pumped up by manual or animal labor or motors) and shallow and deep tubewells (which are almost exclusively operated by diesel engines and electric motors). Further, water can be conveyed by gravity flow or lifted via pumps, depending on whether the irrigated area is located downhill or uphill of the source of water.

Other criteria for classifying irrigation systems include capital labor ratio, scale, institutional arrangements (whether water is directly appropriated by the user, acquired via contract, or allocated by a community or a bureaucracy), and degree of farmer control over availability and timing of irrigation.

The method of water application also varies. Irrigation water can be applied to crops by flooding it on the field surface, by means of furrows, applying it beneath the soil surface, spraying under pressure (sprinklers) or applying it in drops (drip irrigation). Of these, drip and sprinkler irrigation are water-saving techniques, but drip irrigation involves high initial investment and sprinkler irrigation involves high level of power. Ultimately, the choice of method is dictated by a number of factors such as the available water supply, type of soil, topography of the land, and the crop to be irrigated. Irrigation can be intensive or extensive. Intensive irrigation is usually used when the motive for irrigation is increasing production per unit area, and extensive irrigation is used when the motive is to protect crops from droughts by expanding the cultivated area.

Multidimensional

Irrigation is a subject that has a number of dimensions. The science and engineering dimension includes the construction and maintenance of structures and channels for the conveyance of water, as well as the adequate application of water to maintain plant growth. The economic dimension of irrigation arises from the fact that water is a primary input in agriculture, as well as one that increases the benefits from other inputs and makes possible the use of high-yielding varieties of seeds and fertilizers. Another important economic aspect of irrigation is its profitability. The unit cost of irrigation development varies with countries and types of irrigated infrastructures, ranging typically from $1,000 to $10,000 per hectare, with extreme cases reaching $25,000 per hectare. The lowest investment costs are in Asia, which has the bulk of irrigation and where scale economies are possible. The most expensive irrigation is found in sub-Saharan Africa, where irrigation schemes are usually smaller and development of land and water resources is costly.

The social aspect of irrigation stems from the fact that it often necessitates collective action, for which it may draw upon existing institutions and organizations, as well as cultural practices. For example, the Indonesian subak is an irrigation institution where there is a strong interrelationship between water and religion. Each subak or irrigation group has two temples-one dedicated to the goddess of fertility, the other to the god of water-and there is a complex, albeit synchronized, relationship between rituals in the temple and agricultural activity. Irrigation projects that do not take into account preexisting local social structures, or social and cultural practices, can result in conflict.

There is also a political aspect to irrigation. This is because irrigation is not just an economic resource, but also a source of power and patronage at the local, regional, and national levels. In fact, the relationship between irrigation and general political authority has been the subject of considerable discussion among social scientists. The most well-known theory in this regard is Wittfogel’s (1957) theory of Oriental Despotism, which hypothesized that agriculture in arid regions required the building and operation of large-scale irrigation works, the control and management of which gave rise to a highly centralized and elite bureaucracy; this in turn provided the base for the emergence of despotic, “agro-bureaucratic” states in ancient China, India, Egypt, and Mesopotamia. In other words, hydraulic societies have an inherent tendency to become centralized, despotic states. Wittfogel’s thesis has been critiqued on a number of grounds, such as the presence of local autonomy in irrigation management in many countries and the lack of systematic correlation between the existence of irrigation and the nature of the overall political authority.

Cautions and Caveats

There is no doubt that irrigation is important not only in food production, but in the multiplier effect of creating employment opportunities and bringing about development via linkages with other economic activities. Further, irrigation can also help to bring about social change because of its linkage with social and political power. But in spite of its importance, irrigation has also resulted in a number of problems. For instance, lack of adequate drainage and lack of knowledge of the appropriate relationship between soil, crop, and irrigation, have given rise to serious problems of waterlogging, salinity, and alkalinity in many irrigated projects in India, Pakistan, China, the United States, and Central Asia. This has resulted in once-fertile land becoming unfit for agriculture. Similarly, overpumping of groundwater in many regions is beginning to make continued irrigation too costly-as well as resulting in drying up of aquifers-thereby forcing land out of agriculture. For instance, about one-fifth of U.S. irrigation is achieved by pumping groundwater at rates that exceed the water’s ability to recharge, which means that aquifers like the Ogalla in the Midwest are being rapidly depleted.

Apart from environmental problems, there are also problems of underutilization of existing systems (due to inefficiencies such as leaky pipes and unlined canals) and low rates of cost recovery, as well as social problems (for instance, as a result of displacement due to big dams). There are also pressures on irrigation water due to growing demands for water from other sectors, the most important among these being industry and increasing urban populations. Shifting water from farms to cities is already being done in a number of places such as the western United States, China, Mexico, and India. Water-scarce countries often satisfy the growing needs of cities and industry by diverting water from irrigation, then importing grain to make up for lack of production. This practice has now come to be called trade in “virtual water”; the water used to produce an agricultural commodity.

The multifaceted nature of irrigation means that a wide variety of factors, such as geography, agrarian structure, population pressure, cultural factors, the role of the state, and the vision of development, determine the direction and pace of irrigation development. This, in turn, has led to considerable differences in the way irrigation development has taken place. For instance, in many parts of the world (such as in South Asia), the state has played an important role in undertaking irrigation development. In others (like Australia, Canada, and the United States), governments have encouraged irrigation development by private individuals or groups.

There have been a number of changes in the nature of irrigation development since the 20th century, and particularly in the last two decades. First, irrigation has been extended even to areas of sufficient and abundant water supply. Second, there has been considerable interest in the science of irrigation techniques and works, resulting in changes in the way irrigation is conceived. For instance, the concept of single-purpose irrigation projects first gave way to multipurpose projects (which include water supply, hydroelectric power and flood control), then to river basin planning and to the integrated development of a river basin. Third, there has been greater emphasis on the necessity of learning from traditional water management systems. Fourth, there is a trend toward privatization and user participation in irrigation systems.

Bibliography:

James K Boyce, “Technolgical and Institutional Alternatives in Asian Rice Irrigation,” Economic and Political Weekly (v.23, 1988);
K. Framji, B.C. Garg and S.D.L. Luthra, Irrigation and Drainage in the World: A Global Review (International Commission on Irrigation & Drainage, 1981);
M. Michael, Irrigation: Theory and Practice (Vikas Publishing House, 1978);
Sandra Postel, “Water and Agriculture,” in Water in Crisis: A Guide to the World’s Fresh Water Resources, Peter Gleick, ed., (Oxford University Press, 1993);
UNESCO-WWAP, The United Nations World Water Development Report (UNESCO and Berghahn Books, 2003).