Irrigated Agricultural Expansion Planning in Developing Countries: Investment Scheduling Incorporating Drainage Water Reuse

Abstract

Agricultural expansion planning in developing countries where there is extensive government involvement in the planning process can be defined in a two‐level hierarchy. At the first level, the role of the agricultural expansion investment in achieving the strategic goals of the sector is to be determined. At the second level, analysis of the agricultural expansion is to be carried out in such a way that the strategic decisions from the first level can be implemented. The focus of this paper is on the analysis of investment scheduling, the major issue of the second level. A mathematical optimization model is built to aid in analyzing the scheduling problems of land development, crop selection, drainage water reuse, and capacity expansion of the irrigation and drainage networks. A minimum cost criterion is used, where costs of land development, farming, irrigation and drainage infrastructures, maintenance and operations, and pump stations are considered. The model has a nonlinear objective function to account for economies of scale and linear and nonlinear constraints. A fixed charge approximation is used for the nonconvex cost functions, and a mixed integer programming algorithm along with an enumeration procedure is used for solving the model. The solution procedure guarantees global optimality for the approximated problem. A hypothetical expansion of 70,000 acres (28,350 ha) based on data from the Nile Delta in Egypt is used as a case study to illustrate the procedure under different conditions of irrigation water quality.