Optimal Sizing of On-Farm Reservoirs for Supplemental Irrigation

Abstract

A model was developed for prediction of the optimal size of an on-farm reservoir (OFR) so as to provide supplemental irrigation to rice in monsoon season and presowing irrigation to mustard in winter for a rainfed farming system of eastern India. Daily simulations of water balance parameters of both the cropped field and the OFR, economic analysis, and irrigation management practices were inputs to the model. The study predicted an OFR of depth 2 m requiring 12% of the 800 m2 farm area with a volume of 61 m3 to be optimum. The above-mentioned optimal size of the OFR gave a benefit-cost ratio (BCR) of 1.22, internal rate of return (IRR) of 15%, and pay back period (PBP) of 15 years. Simulated results were verified by conducting three years of field experiments to justify the investment in the OFR irrigation system. The observed BCR, IRR, and PBP from the experimental study were 1.17, 14.8%, and 16 years, respectively. There was an increase of 39 and 15% in the yield of rice grain and mustard seed over rain...