Irrigation Societies Research Paper

1. Overview Of Irrigation Systems

It is estimated that humanity now uses 26 percent of total terrestrial evapotranspiration and 54 percent of runoff that is geographically and temporally accessible. Most of this water is used for irrigation. The average water application rate in 1990 was estimated at 12,000 cubic meters per hectare for 240 million hectares of irrigated lands worldwide (Postel et al. 1996). In the past three decades, there has been an enormous expansion of new irrigation systems. According to the World Bank, an average of 885 large dams (>15 m high) were constructed per year between 1950 and the 1980s. During the same interval, the total area of irrigated agriculture in the world increased by about threefold (Cernea 1985, p. 23). Recently, the rate of construction of large dams has begun to decline, averaging no more than 500 per year, and this number is expected to decline further because of rising economic, social, and environmental costs (Postel et al. 1996).

Meanwhile, small-scale, hand-built, gravity-flow canal systems managed by small groups of farmers still account for about 85 percent of the world’s irrigated cropland, according to World Bank estimates. Small- scale systems operated by local irrigators are still used to grow most of the crops in Asia. For example, more than 15,000 systems of less than 50 hectares are managed by farmer’s associations in Korea (Oh 1978). In southern India (Andhra Pradesh, Karnataka, Kerala, and Tamil Nadu), more than 125,000 com- munity tanks provide water for 30 percent of the irrigated croplands (Sakthivadivel and Shanmugham 1987). More than six million small tanks and reservoirs are managed at the village level in China (Yu and Buckwell 1991). Similarly, in Morocco 830,000 hectares are irrigated by locally managed systems utilizing perennial flows and seasonal floods, which range in size from 50 to 3000 hectares (Abdellaoui 1989). About a million hectares are cultivated in Nigeria using traditional irrigation or flood-recession systems, while an estimated quarter million hectares of pre-Hispanic Peruvian terraces are still irrigated in the Andean highlands (Mabry 1996).

Small-scale irrigation systems are also found in the developed world. Fifty thousand local irrigation systems exist in Japan, some in continuous operation since the early seventeenth century, and together constitute about a quarter of Japan’s total irrigated area (Takeuchi 1980). Centuries-old irrigation systems also thrive on the Mediterranean coast of Spain (Glick 1970), in the Swiss Alps (Netting 1981), and in the Southwestern USA (Mabry 1996).

2. Environmental Constraints On Irrigation

The physical environment constrains the kinds of irrigation systems that can be constructed. Wittfogel’s thesis was based on the demands imposed by large-scale, pre-modern canal irrigation systems, fed by large rivers. Such systems, typical of arid and semiarid regions such as those adjoining the Tigris, Euphrates, and Indus rivers, required the coordinated labor of thousands to be constructed and maintained. Tropical, semitropical, island, and desert environments impose quite different constraints, leading to different technical and managerial solutions. Scarborough (1998) has proposed an ‘accretional’ model for the modification of tropical and semitropical environments, where there is great species diversity but little abundance of one specific species in any single niche or patch. Archaic civilizations evolving in these settings adapted to this dispersed resource base in a manner markedly different from that of early states located in semiarid settings with access to large rivers. According to Scarborough, the political economies of tropical archaic states adapted to the interconnectivity of dispersed resources, discovering and refining the ecological pathways that made useable resources accessible to humans. For example, the civilizations of the archaic Lowland Maya, and in many regions of South and Southeast Asia developed irrigation systems based on tanks designed to capture wet-season flows and release them in the dry season. Such tanks are still in use in southern India and Sri Lanka.

Oasis civilizations of Central Asia, China, and Arabia developed tunnels called qanats to capture the snow melt from the Himalayas and other mountain chains, transporting the flow for great distances under the deserts. In parts of North Africa, including the Nile Valley and the American Southwest, flood recession systems were invented to capture and control scarce seasonal rainfall. Mandelbrot and Wallis (1968) showed that data on the annual flood of the Nile River exhibits chaotic behavior. Using this historic data from the Nile as well as modern data from the Senegal river basin, Park (1992) has argued that farmers adapted to the risks of too much or too little water by creating institutions to reallocate land among cultivators annually, fostering control by the elite and class stratification long before population pressure reached significant levels.

3. Management Of Irrigation

The relationship between the technical and social aspects of irrigation is an ongoing topic of research. There are two major schools of thought. One tradition, emanating from Wittfogel and pursued primarily by archaeologists, is concerned with the power-centralizing effects of large-scale irrigation systems. A second tradition approaches small-scale irrigation systems from the perspective of common property management (or ‘common-pool resources’). A key issue for both research traditions is the relationship between the scale of irrigation systems and the structure and complexity of management institutions. Hunt (1989) distinguishes between ‘irrigation communities’ and ‘water-user associations’: the former are autonomous, self-contained organizations that are supported by consensual, mutually beneficial institutional arrangements while the latter are units within larger bureaucratic structures that require communication and coordination across organizational levels.

It appears that many small-scale systems of irrigation management are self-governing. Hunt (1988) compared fifteen irrigation systems in industrialized and developing countries, ranging from 700 to 30,000 hectares in extent, and found no strong relationship between system size and the structure of authority. But he predicted that any system larger than about 100 hectares has a ‘very high probability’ of being managed by a ‘unified administrative authority structure’ (Hunt 1988, p. 347). Netting has argued that water scarcity can be a stimulus for the centralization of decision making, when it threatens widespread conflict that will seriously reduce the efficiency of the system. Kappel identified 5,000 as the upper limit of the number of people who can be supported by local self-governing systems, based on a study of 17 historic and contemporary cases. However, Uphoff found that irrigation systems with command areas of up to 40 hectares tend to be managed by the entire group of irrigators; those between 40 and 400 hectares are managed by a central official, either elected by the irrigators or appointed by the state, and systems between 400 and 4,000 hectares often have three layers of management (cited in Mabry 1996).

Turning to the dynamics of management in small-scale irrigation systems, Ostrom (1992, p. vii) notes that ‘a self-governing irrigation system is a prime example of a public enterprise in which a segment of society governs itself for itself.’ A frequent starting point for the analysis of irrigation communities is Hardin’s (1998) ‘tragedy of the commons’ thesis, which holds that rational self-interest will motivate individuals to take as much of a common resource as possible. This is linked to the ‘tail-ender’ problem in irrigation systems: irrigators closer to the source can control the flow to their downstream neighbors, so the farmer at the tail end is always vulnerable. How then are sustainable cooperative systems of water sharing possible?

One answer is suggested by game theory, specifically the iterated Prisoner’s Dilemma, which shows how it can be in one’s interest to cooperate with other users if there is an expectation that such cooperation will result in continuing access to a valuable, shared resource. Irrigation systems do not only provide benefits, they often entail high labor costs, and this can also be a motive for cooperation. Ostrom (1992) found that in negotiations over the rules of water use between the members of a local water-user association, the bargaining power of tail-enders is greater if their labor is needed to maintain the system.

Ecological factors may also influence patterns of cooperation. Rice farmers on the Indonesian Island of Bali must cope with a suite of rice pests, including rats, insects, and bacterial and viral diseases. The traditional method for controlling these pests is to plant large blocks of rice terraces at the same time. After harvest the fields are flooded, depriving the pests of their habitat, and in some cases killing them outright. Thus upstream farmers, who control the flow of water, may benefit by cooperating with their downstream neighbors. In this way, the scheduling of irrigation can be used to manage pests (Lansing 1991).

4. Irrigation And Agro-Ecology

Salinization resulting from over-irrigation and poor drainage has significantly reduced yields on more than 60 million hectares, about a quarter of the total worldwide, and 25 million hectares have been abandoned because of salt accumulation (Mabry 1996, p. 229). Annually, for every additional hectare brought into production by new irrigation projects, another goes out of production because of salinization (Umali 1993).

Flowing water can pick up and transport mineral nutrients needed by plants, such as nitrogen, phosphate, and potassium. Traditional Asian rice paddies use irrigation systems to bring these nutrients, as well as water, to the plants. For example, volcanic ash from Indonesian volcanoes contains about 1 percent potassium, and relatively high levels of phosphate. Until the advent of the ‘Green Revolution’ in rice in the 1970s (the spread of high-yielding crops designed to rely on chemical fertilizers), most of the nutrients needed in Asian rice paddies were supplied by this process of mineral leaching. In Western Europe and the USA, the spread of ‘Green Revolution’ farming techniques has created an over-abundance of nutrients: too much of a good thing. Worldwide, between 1960 and 1980 the application of nitrogen fertilizers increased more than five-fold, and in the decade that followed, more synthetic fertilizer was spread on land than had been applied in the entire previous history of agriculture. Rivers like the Mississippi and the Colorado acquire heavy loads of nutrients like phosphate, and generate enormous pollution problems downstream. Every summer, approximately 18,000 square kilometers of the deep waters of the Gulf of Mexico become a ‘dead zone.’ European countries like The Netherlands have begun to implement strict regulations restricting fertilizer use in order to protect freshwater ecosystems, but meanwhile pollution problems have scaled upwards from lakes and streams to the Baltic and North Sea. Worldwide, virtually all coastal zones are experiencing rapidly increasing pollution from agricultural runoff and domestic waste (Nixon 1998). Archaeologists generally agree that environmental problems associated with the expansion of irrigation systems led to the decline of many ancient states. Today, the spread of irrigated agriculture on which the continuing expansion of the human population depends poses a ‘tragedy of the commons’ problem on a global scale.

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