Solar-Powered Drip Irrigation Systems in the Sudano-Sahel
Program on Food Security and the Environment, Stanford University
Most of the world's poor populations live in rural areas, depend on agriculture for their livelihoods, and spend the majority of their incomes on food. Improved agricultural productivity in the developing world is thus critical for food security and poverty alleviation. At the same time, agriculture is currently responsible for 10-12 percent of global greenhouse gas emissions (not including land-use change, which adds an additional 10-12 percent) and approximately two thirds of the world's annual water withdrawals, along with a host of environmental ills, including eutrophication, biodiversity loss, and soil degradation. Meeting the food needs of a growing population under tightening climate and resource constraints (or meeting mitigation targets while eliminating global poverty) will therefore require new technologies and strategies that significantly improve rural livelihoods at minimal environmental cost. This project quantifies the impact of emissions-free distributed water delivery and irrigation technologies in the dry tropics. Most rural, poor farmers depend on rain-fed production of staple crops for their livelihoods. These smallholder production systems are typically limited to a 3-6 month rainy season, and are often high-risk and relatively low-return; in addition, despite producing grain crops, these farmers are nevertheless net consumers of food across food groups, particularly in non-staples. Promotion of irrigation is frequently cited as a strategy for both poverty reduction and improved food and nutrition security in developing countries, as it can enable year-round cultivation, promote increased yields, and facilitate the introduction of new crops in regions where they could not be sustained by rainfall alone. In remote locations far from the grid, the most reliable and cost-effective energy option for irrigation is solar power. A recent evaluation of the pilot phase of a novel solar-powered drip irrigation project in northern Benin, West Africa, demonstrated strong and significant poverty-reduction and food security impacts for farmers using this technology, and showed that solar pumps are cost-effective, especially in rural areas where fuel access for liquid fuel pumps may be sporadic at best. Building on this work, I optimize the solar-powered water pumping system in future installation villages to minimize cost and maximize system efficiency and lifetime for both surface and groundwater sources. Solar-powered pumps and drip irrigation are well-matched technologies, as both pump speed and crop evapotranspiration scale with incident solar radiation. A properly designed system thus passively self-regulates and can be implemented in a direct-coupled configuration, eliminating the need for batteries, which reduce system lifetime, cost-effectiveness, and performance in the developing world. The optimization of solar-powered drip irrigation systems has potential global application as an efficient water use technology.