Maximizing Reliability of Supplying Drinking Water with Conjunctive Operation of Groundwater and Water Transfered from Salman-Farsi Dam

Drinking water supply to Larestan region in Fars, Iran, is fulfilled from Salman-Farsi Dam, which is not reliable all the times due to drought and presence of other stakeholders. On the other hand, there are many well fields available to Fars Water and Wastewater Company with varying discharge capacity and total dissolved solids concentration. Optimum mix of the trensfered water from well-fields’ pumping and the transferred one from the dam by the pipeline is the main question of the decision makers for maximizing the reliability of the drinking water while fulfilling the water quality constraints. Therefore, conjunctive use of dam’s release and pumping is selected as managerial approach to be optimized under water quality constraints with the target of maximum drinking water supply to demands. The conjunctive use of the water released from dam and withdrawn from the wells is a candid strategy selected by the decision makers among many other strategies for water supply in the region. The conjunctive water use model is formulated in GAMS environment and solved by nonlinear optimization solver MINOS. The conjunctive water use strategy is planned and optimized for three stages of short-term, mid-term and long-term Operation, and operation rules for dam’s release and pumping rates are presented. Current midterm water supply reliability from dam is 63% while with conjunctive use it becomes 90%. In emergency cases (malfunctioning of water transfer system) the reliability without conjunctive water use is 49% while conjunctive water use increases it to 77%.