Optimal crop planning model for an existing groundwater irrigation project in Thailand

A monthly irrigation planning model is formulated for determining the optimal cropping pattern and the groundwater abstraction requirement in an existing groundwater development project. Two objectives, maximisation of net economic benefit and maximisation of irrigated area, aspired to by both the irrigation authority and the individual farmers in the Sukhothai Groundwater Development Project in Thailand are considered, To account for uncertainty in water resources availability, the model is solved for three levels of reliability of rainfall and groundwater resources (80, 50 and 20%). The effects of deficit irrigation on the net benefit and cropping intensity as well as on the yield of crops are also assessed by considering three levels (no deficit, 25% deficit and 50% deficit) of water application to the crops, To select the best alternative plan, a multi-objective analysis is carried out using the Analytic Hierarchy Process considering the preference of the decision makers, including farmers and irrigation project managers, The selected decision makers in the Sukhothai Project collectively allocate almost half of the total weight to reliability (or risk) factors, while the remaining preference is almost equally divided between the two objectives listed above. On average, they seem to prefer the planning alternative corresponding to average (hydrologic) conditions and full irrigation without any deficit.