Non Linear Optimization Model for Water Allocation under Deficit Irrigation System

A non linear optimization model is formulated in the present study to optimize the deficit levels for different crop growth stages to maximize the net economic return within the available resource constraints. The model determines decade (10 days) optimal withdrawals from canal and ground water, optimal area under different crops and optimal deficit levels for different crop growth stages. The model is applied to Dadu canal command of Lower Indus basin. The result showed an overall increase of 61.7 per cent in the cropped area under deficit irrigation as compared to the full irrigation by using the proposed model. The optimal economic return under deficit irrigation is found to be 18.3 per cent higher than the optimal economic return from the full irrigation. The optimal economic return further increased by 20.3 per cent with an increase of 150 per cent in the tube well capacity under deficit irrigation as the slackness was found in the annual ground water balance constraint at the existing tube well capacity. The model is general and can be used to find out the optimal cropping pattern under deficit irrigation.