The impact of irrigation on production and income variability: Simulation of diversion irrigation in the Philippines
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Irrigation not only contributes to increased crop production but may also reduce variability in production through improved control of the crop environment. However, the dependence of modern seed-fertilizer technology on irrigation and fertilizer, which are subject to unreliable supply, may contribute to increased variability in production. This paper examines this issue using an irrigation system simulation model to analyze the impact of irrigation on the variability in area, yield, production, and farm income in diversion irrigation systems in the Philippines. The results show that irrigation more than doubles crop-year rice production and income. However, because of the dependence of diversion irrigation systems on highly variable dry-season streamflow, irrigated dry-season production and income are highly variable compared with those of wet-season rainfed production. On a crop-year basis, production and income variability under irrigated conditions are slightly higher than under rainfed conditions. Although improved management of irrigation systems can reduce income and production disparities among farmers within the system, it has little impact on system-wide variability. Investments in irrigation infrastructure and management are not substitutes for other policies that will offset the adverse effects of production instability, such as buffer stock or import management.
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