A multilevel approach for optimizing land and water resources and irrigation deliveries for tertiary units in large irrigation schemes: 2. Application.

The resource allocation model, Area and Water Allocation Model (AWAM), incorporates the concept of deficit irrigation through a variable depth irrigation approach, VDI. It uses this to allocate land and water resources optimally to different crops in a heterogeneous irrigation scheme with limited water under rotational water supply. This model was applied to a medium irrigation scheme in India as a case study, to obtain the land and water allocation plans. These optimal allocation plans were compared to those obtained by using the model with the existing approach (full irrigation with a fixed irrigation interval of 21 days in Rabi and 14 days in summer season). The allocation plans were obtained taking account of the different parameters that were included in the model such as crops and cropping pattern, soils, irrigation interval, initial reservoir storage volumes, efficiencies and the outlet and canal capacities. The total net benefits were compared for the two cases of fixed cropping distribution and free cropping distribution and a sensitivity analysis was conducted on other parameters. Summaries of the allocation plans with the VDI approach are presented for the two cases. The total net benefits obtained with the VDI approach introduced in the model were found to be 22% higher than those obtained with the existing approach. The results of this study are thus indicative of the benefits of deficit irrigation and its application within irrigation schemes that have limited water supply. 1 Academic Visitor, Water, Engineering and Development Centre, Loughborough University, Loughborough, Leics., LE11 3TU, UK 2 Director, Water, Engineering and Development Centre, Loughborough University, Loughborough, Leics., LE11 3TU, UK