Simultaneous design an‎d operation of conjunctive use systems of surface an‎d groundwater resources under hydrological uncertainties

7/8/2026 12:00:00 AM

Conjunctive use of surface an‎d groundwater resources refers to the optimal allocation of these resources to improve planning objectives compared to managing them separately. The main aim of this study is to develop a simultaneous operation–design model for a cyclic conjunctive use system under inflow uncertainty. In such a system, surface reservoir an‎d groundwater aquifer are treated as two physically interconnected parallel storages that allow for regulated water exchange while maintaining their individual characteristics. This research consists of three components: an operation model, a design model, an‎d a hybrid design an‎d operation model. The operation model employs a stochastic dynamic programming (SDP) framework in which the aquifer is modeled as a lumped system. Solving the model provides seasonal operational policies (rules) that maximize the expected value of a water allocation sustainability index for agriculture, defined as a function of reliability an‎d vulnerability. The design model is developed with the objective of minimizing design an‎d operational costs, using the particle swarm optimization (PSO) algorithm. Finally, the design an‎d operation models are integrated in an iterative information-exchange process, forming the hybrid operation–design model. The only constraint applied at this stage is convergence error, which can be adjusted depending on computational limitations. To account for inflow uncertainty in the SDP model, seasonal transition probability matrices are derived using the K-means clustering method. To reduce the computational burden of the SDP, a novel approach is introduced an‎d applied, demonstrating high performance. In addition to the expected value of the sustainability index (objective function), the expected values of other system characteristics are also computed directly from the SDP optimization model without requiring a separate simulation model, providing a broader understan‎ding of the rule performance. The operational rules derived from the SDP model are compared with those obtained from the M5 decision tree algorithm as one of the algorithms used in the implicit stochastic method, highlighting the superiority of the explicit stochastic method. By implementing the hybrid SDP–PSO model for different initial design components, sustainability index-cost Pareto solutions were identified. Finally, the proposed method was compared with the conventional approach for the design an‎d operation of conjunctive use systems. The SDP results indicate that the expected sustainability index would be 0.85 for the system developed using the conventional method an‎d 0.97 for the system developed using the proposed approach, highlighting the effectiveness of the hybrid SDP–PSO framework.

بهره‌برداري تلفيقي از آب‌هاي سطحي و زيرزميني , قواعد بهره‌برداري , عدم قطعيت

Conjunctive use of surface an‎d groundwater , Operational rules , uncertainty

Mina khosravi

Dr abbas Afshar