Reliability-Based Design of Conjunctive Use Water Resources Systems: Comparison of Cyclic and Non-Cyclic Approaches

Conjunctive use of surface and groundwater has received growing attention since the introduction of sustainable development of water resources. Cyclic storage system is an extension to conjunctive use of surface and groundwater in which the surface water bodies and groundwater aquifer(s) satisfy the prespecified demands in an interactive loop. Cyclical exchange of regulated water between groundwater aquifer and surface reservoir is the key element of a cyclic storage system that differentiates it from the conjunctive use of surface and groundwater systems as usually practiced. In the present study, reliability-based design of the cyclic and non-cyclic storage systems models is formulated as a multi-objective programming and intends to minimize the construction and operation costs and maximize the reliability of water allocation to the agricultural sector. Results show that the performance of cyclic storage system significantly improves by more efficient storing of surface water in a groundwater basin in wet seasons (years) and using it during dry periods. So, in order to fully meet the present demands in cyclic strategy, we had to pay just under 90.4 billion rials, compared to the non-cyclic strategy. It is also shown that, for any given cost, the reliability with cyclic strategy well exceeds that of non-cyclic strategy. In addition, the cyclic design of the system implicitly reduces the probability of flooding downstream significantly rather than the non-cyclic strategy.