A multi-objective simulation-optimization approach for water resource planning of reservoir-river systems based on a coupled quantity-quality model

摘要

The allocation of Limited water resources, water quality, and environmental impacts are issues that necessitate proper planning for the exploitation of water resources. In the present study optimal operation of surface water resources system is studied in the term of quantity and quality simultaneously, using Non-Dominated Sorting Genetic Algorithm-II (NSGA-II) algorithm. For this purpose, the WEAP-QUAL2K coupling model was developed for the simulation of water quality and quantity. Dez dam reservoir and Dez dam downstream sub-basin in Dez river-basin, from Dez dam to BandeGhir (Dez river), in Iran is used as study site. The simulation and optimization period is considered to be 5 years (2018-2022). Given that in the verification stage of the QUAL2K and WEAP models, it can be concluded that the model has high accuracy in simulating the parameters of water quality (Temperature, pH, EC, DO, BOD, N-NH4, and N-NO3) and quantity. Two scenarios are considered. The first scenario is used for dynamical coupling of quantity-quality model (reference scenario) and the second is optimization of coupled model (optimal scenario). In optimal scenario, decision variables, environmental flow rate at BandeGhir in different months, are optimized based on multi-objective function within the range of 27.7-86.2 m(3)/s. The results show that, in the optimal scenario, optimal operation of surface water resources, considering the maximum demand site coverage causes to increase the water supply reliability of all demands in the Dez plain. Average water supply reliability increase from 84.46% in the reference scenario to 92.92% in the optimal scenario. Also, the results of optimal scenario compared with reference scenario show that not only the river water quality was improved, but also in river withdrawal points, especially in the agriculture withdrawal points, there is a least violations of river water quality standards.