This book presents a Linear Programming (LP) model developed for the conjunctive use of surface water and ground water to obtain the optimal operating policy for a multipurpose single reservoir. The present study explains how to maximize the net benefit from the command area under consideration. The constraints imposed on the objective function are maximum and minimum irrigation demands, reservoir storage and canal capacity. The model takes into account the continuity constraint which includes inflows in to the reservoir, releases for irrigation, releases for hydro-power generation, evaporation losses, feeder canal releases, initial and final storage in the reservoir in each time period. The developed model is applied to the case study of Jayakwadi reservoir stage-I built across river Godavari, Maharashtra, India. Initially the model is solved for the availability of surface water which results in net benefit of 3373.45 million rupees with irrigation intensity is 57.07%. Next themodel solved by considering the availability of surface water and available potential of groundwater in the area, which results in net benefits of 3590.02 million rupees with an intensity of irrigation.