To Develop a Crop Water Allocation Model for Optimal Water Allocation in the Warabandi Irrigation System

Abstract

The water allowance for canal systems of Pakistan was designed considering the average values of cropping intensity and irrigation area. However, water allowances would be different if estimated on the basis of real cropping intensities, cropping pattern and actual evapotranspiration. This inequity of water allocation results in decreased agricultural production. Hence, optimal water allowances for given canal commands need to be developed to maximize the efficiency of the existing irrigation system. Therefore, present study aims to assess the difference between the available water supplies and those required on the basis of real field conditions. Crop Water Allocation Model has been used for this purpose. Discharge at the head of each watercourse was predicted on the basis of the actual evapotranspiration, cropping patterns, cropping intensity, the number of days of canal flows in a year and the irrigation efficiency. The predicted optimal water requirements and the design flow rate were also compared for Kasur minor and found that 59 watercourses out of 61 require less water for optimal operation than the designed flow rate. Only two watercourses require more water for optimal conditions than the designed flow rate. Sensitivity and scenario analysis were also performed to evaluate the impact of different agricultural and climatological parameters on the reference crop evapotranspiration and design discharges.