The economics of water lifting for small scale irrigation in the third world: traditional and photovoltaic technologies
Author(s)Tabors, Richard D.
Much of the non-traditional, irrigated, agricultural land in developing nations utilizes pumping technologies which have been adapted from the developed nations. These technologies are adaptable to the medium and large scale farms (individual farms in excess of 2 hectares) but are not adaptable to smaller farms. It has been these larger third world farmers who have been able to take the fullest advantage of the benefits of new seed varieties in wheat and rice combined with fertilizer and water, the ingredients of the "green revolution." This short paper summarizes the experience to date of developing water pumping systems for small farms in selected deltaic areas of the 'third world,' those areas in which irrigation water is available at depths between 1.5 and 4.5 meters (m). These areas include the Nile, Euphrates, Indus, Ganges, Irrawaddy, and Mekong River Basins which combined encompass 50 million hectares of the earth's surface (less than one percent of the earth's land area) and contain roughly 250 million people (nearly 7 percent of the world's population). The analyses evaluate water supplied by traditional means--human and animal--by conventional systems--diesel, gasoline and electric--and by renewable resource systems, in particular photovoltaic powered systems. A review of previous studies indicate that the value of water for irrigation is in the range of two to three cents (U.S.) per cubic meter (m3). The methods of lifting water, available to farmers on land areas of one hectare or less, provide water at costs in excess of this two to three cents (U.S.) per m3. Investigations of the Shadoof systems of North Africa and Asia show costs of water as high as seven cents (U.S.) per cubic meter. An evaluation of animal power used to operate a Persian wheel resulted with water costs that varied with the amount of feed required by the animal from 1 to 4/m3. Four pumping systems were investigated using conventional power systems: two diesel, one gasoline, and one electric. Since pumping systems have relatively fixed sizes and prices, the costs generally exceed the benefits for the small farmer. The cost per cubic meter for irrigating one hectare averaged: 3.5¢ (U.S.) for diesel in Chad; 4.0¢ (U.S.) for gasoline in Chad; 3.5Q (U.S.) for diesel in India; and 3.0t (U.S.) for electricity in India. In each of these instances, the cost of supplying small scale farmers with water using conventional systems was greater than the economic value of the water supplied. A fifth pumping system investigated herein utilized a high technology power system, photovoltaic cells combined with efficient electric motor and pump devices. The cost of providing water utilizing the photovoltaic power system resulted in costs of 2.8t/m3 (U.S.) to lift the water 1.5m and 5.44/m3 (U.S.) for lifting heads of 4.5m, at today's cell prices ($10/Wp). If photovoltaic power system costs are reduced to $4.00 per peak watt (Wp), the cost of irrigation water for a lift of 1.5m would be 1.2¢/m3, and for a lift of 4.5m would be 2.3*/m3.
Previously issued as MIT Energy Laboratory Working paper # MIT-EL-78-015wp, August 1978.
MIT Energy Laboratory
Developing countries |x Irrigation.
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