Agricultural Water Demands: Preliminary Results of Silistra Case Study

Preliminary results of the Silistra Water for Irrigation Model (SWIM) for determining agricultural water demands in the Silistra region of Bulgaria are presented. For various areas of irrigated and non-irrigated land, and various volumes of water supply, SWIM uses linear programming to select the optimal combination of crop areas and production inputs so as to maximize annual net benefits from crop production in excess of target production quantities of each crop. Both normal and dry weather conditions are examined. The region's import-export balance is investigated for areas of irrigated land between 10,000 and 50,000 hectares, and it is shown that total costs of crop production are minimized when the region is just self-sufficient in crop production. By means of demand curves it is demonstrated that the marginal values of land and water for irrigation are greater than their unit costs of development so that it is optimal to develop irrigation to the maximum area considered by the model