The Cultural Effects of Conveyance Loss in Gravity-Fed Irrigation Systems

Abstract

Anthropological analyses of power in hydraulic and hydroagricultural societies have tended to concentrate on the larger issues of state development and maintenance of power (see Adams 1966; Butzer 1976; Harris 1977; Wittfogel 1957). For the most part these discussions have glossed over issues vital to the particular forms of nondespotic irrigation societies that evolved despite their hydraulic infrastructural base. One such vital issue is that of conveyance loss. Conveyance loss refers to the water that is lost as irrigation water travels from its source to the fields. The factors that lead to conveyance loss include evaporation, evapotranspiration, seepage, and spillage. The phenomenon of conveyance loss in gravity-fed systems has implications for the evolution and structuring of societies reliant on the delivery of water for agriculture. This essay is a comparative study of conveyance loss in gravity-fed irrigation systems. After a critical consideration of some of the relevant ethnographic literature and theoretical issues, some field data from the Egyptian Fayoum are analyzed in relation to what is known of the effects of conveyance loss in other societies. During the past decade there has been an increasing realization that as a result of limited water sources and conveyance loss, unlined gravity-fed irrigation systems favor irrigators whose plots are located toward the top of the canal network (Bromley et al. 1980; Moore 1980; Skold et al. 1984; Wade 1988). The unequal access to water, if unchecked, leads to differential agricultural returns that are translated into differential economic and social benefits for top-ended system members. In both hydraulic and hydroagricultural societies, conveyance loss affects agricultural productivity. In societies that have private property, the effects of conveyance loss have a special importance. In irrigation societies without private property, conveyance loss affects the overall productivity of specific lands and the system as a whole, but it does not necessarily differentially reward individuals. The combination of conveyance loss and private property results in differential agricultural returns favoring up-canal irrigators who can convert these elements into personal gains. There are other factors besides conveyance loss that are responsible for water shortages in irrigation systems and up-canal monopolies on water use; not all scarcity in irrigation systems is caused by conveyance loss. Conveyance loss is but one factor affecting water scarcity in irrigation systems around the world. The general limited nature of water in irrigation systems around the world of course has a profound effect in determining up-canal and down-canal relationships. While analysts such as Wade (1988:72) stress that up-canal water users must follow rules of restraint and allocate water in an equitable manner, a complete understanding of the nature of water allocation cannot occur without accounting for conveyance loss. Conveyance loss accentuates the inherent inequalities of upstream/downstream relationships. There are countless statements testifying that conveyance loss seriously diminishes agricultural returns. Wade (1988:163) writes that in the South uplands of India towards the tail-end of an irrigation distributary tend to have a less adequate, more unreliable water supply than villages higher up. The up-canal advantages for these farmers are many: With water, those owning land closest to the canal outlet have first access and under simple common rights cannot be prevented from taking as much as they wish by those lower down who see themselves disadvantaged by excessive use higher up-no more than a driver on a road can be excluded by later arrivals who find the road congested. Because of this, top-enders are inclined to waste water and to skimp on maintenance of field channels, and may dispose of their drainage water in ways inconvenient to tail-enders. …