Optimal Annual Allocation Model of Large Storage Based Irrigation Project by Multi Level Approach

Abstract

The effective management of water available for irrigation in arid and semi-arid regions has increased in importance due to limited water supply. The need for allocation of water resources optimally in a water limiting condition has already been recognized, and much research has been carried out. In the present study, an annual irrigation planning model is formulated for Nagarjuna Sagar Project command in the semi-arid region of South India dealing with optimal allocation of annual available water among command areas of each main canal taking off from the reservoir and reallocating the available land and water of each command area to different seasons of a year and finally allocating the available land and water of each season among crops grown in that season, maximizing the total annual benefit of the project. The problem is solved in three stages. In the first stage, fortnightly crop water requirements are calculated from the evapotranspiration model by Penman – Monteith method. In the second stage, seasonal crop water production functions are developed using the single crop intraseasonal allocation model for each crop of all seasons. In the third stage, allocations of area and water are made at seasonal, interseasonal and at reservoir levels by deterministic dynamic programming, maximizing the net annual benefit from the project. Optimal cropping pattern and irrigation water allocations are made with full and deficit irrigation strategies for various levels of probability of exceedences of expected annual water available and results obtained are discussed.