Water management scenario simulation for decision support in multiobjective planning

A mathematical model has been developed for the Simulation of Water management in the Arab Republic of Egypt (SIWARE). The model predicts the effect of changes in irrigation water management, hydraulic and hydrologic conditions, cropping pattern, and crop characteristics on the quantity and salinity of drainage water. The model also calculates the effect on other decision parameters such as crop yield as a function of evapotranspiration and soil salinity. It is a tool for supporting water management decisions aiming at multiple objectives such as improving water use efficiency, saving on water supply quantities, reclaiming land for agriculture, use of other conventional and nonconventional water resources, and providing more farmer freedom in crop selection. This paper presents how a simulation model such as SIWARE can be used for simulating different water management scenarios for the sake of selecting the most favorable option. Planning of water resources on a regional scale involves multiple objectives that need to be achieved by the existing water supply system. Two water management scenarios are evaluated as examples of steps in the decision-making process. The first scenario deals with the reduction of total water supply to the Middle Nile Delta with the objective of saving water or coping with a shortage in water supply. The second scenario deals with the shift to a so called "free cropping pattern" policy with the objective of providing more freedom to the farmer in selecting crops that he wishes to cultivate depending on his vision of the local and international market prices. The impact of these scenarios on crop evapotranspiration and soil salinity are evaluated.