Optimal Dynamic Water Allocation for Irrigation of Multiple Crops

A dynamic irrigation scheduling method was developed for optimal water allocation from an irrigation reservoir and maximum net benefit from multiple crops under wet, average, and drought conditions. The model integrates two control volumes: (i) the plant root zone, which demands water, and (ii) the reservoir, which supplies water. The FAO Penman-Monteith Method was used to compute the reference crop evapotranspiration (ET0). Optimal allocation of water supply in the reservoir was determined by a dynamic programing method. The model allows for variable decision intervals for each crop. Since soil moisture exhibits a dynamic structure, various scenarios were developed for probable soil moisture deficit ratios. The objective function of the model developed in this study consists of the yield sensitive factor (Ky), the actual evapotranspiration (ETa), the potential evapotranspiration (ETm), the maximum crop yield (Ym), the benefit of unit yield in unit area (UB), the unit cost of unit yield in unit area (UC), is the unit cost of water of unit yield in unit area (UCW), and the crop area (AREA). The applicability of the method was demonstrated through a case study of Cavdarhisar Dam irrigation field (5000 ha) in Kutahya, Turkey. From the commonly grown crops in the area, wheat, maize, sunflower, potato, onion, sugar beet, beans, tomato, chickpea, and melonwatermelon were selected to be planted. Optimum water allocation scheduling of available water in the reservoir was determined based on maximum net benefit from multiple crops under wet average, and drought conditions.