A simple method for the optimal spatial and temporal allocation of water shortages

This paper addresses the issue of optimal allocation of irrigation water between competing irrigated areas in case of a shortage. The method is based on the use of penalty functions which penalize for not meeting the demand. Given an irrigation network supplying different irrigated areas with given demands and penalty functions, the method involves going through an upstream sweep of the system during which the penalty functions are aggregated. This process leads to the construction of the minimum penalty curve for the whole system. Knowing the total available supply, one then proceeds downstream to allocate optimally the shortages to the irrigated areas. Extensions of the method to deal with allocation over time is also presented.