Sizing Farm Reservoirs for Supplemental Irrigation of Corn. Part 11. Economic Analysis

ABSTRACT A procedure is presented for determining the optimum reservoir size, based on economics, for water supply for supplemental irrigation. The procedure can also be used to evaluate the risk involved in investing in sup-plemental irrigation. The Duncan-SIMAIZ model is used to calculate crop yields under irrigated and nonir-rigated conditions as well as daily irrigation water re-quirements. The Haan water yield model is used to calculate daily water yields into a water supply reservoir. These models are used along with a reservoir water balance and a present worth economics procedure to defme the economics of investing in supplemental irriga-tion as well as determining the optimum reservoir size. The procedures are described and example computations presented.