بررسي اثرات تغييرات اقليم بر كيفيت آب ذخيره شده در مخزن سدها (مطالعه موردي: سد مارون)

Providing the water with quality for drinking, agriculture, an‎d environmental uses is a fundamental challenge in water resources management. Climate change can affect the water quality an‎d the thermal stratification phenomenon in dam reservoirs by changing precipitation an‎d temperature patterns. Therefore, investigating this phenomenon in dam reservoirs is essential. In this research, the two-dimensional CE-QUAL-W2 model is used to simulate thermal stratification an‎d qualitative changes (dissolved oxygen) in the Marun Dam reservoir, located in Khuzestan Province. The model is calibrated for the period December 2019 to December 2023 an‎d validated for the period from December 2023 to December 2024. The obtained results indicate that the model can successfully predicte temperature variations in the reservoir, with Mean Absolute Error (AME) an‎d Root Mean Square Error (RMSE) values for the calibration (validation) period being 1.09 (0.79) an‎d 1.34 (1.06) °C, respectively. For dissolved oxygen modeling, the AME an‎d RMSE values during the calibration (validation) period are 2.21 (1.37) an‎d 2.50 (1.68) mg/L, respectively, which are within the acceptable range. Subsequently, to investigate the impact of climate change, daily precipitation data for the period from December 2024 to December 2029 are extracted by combining the MPI-ESM1.2-HR an‎d NCEP models under the SSP3-7.0 scenario an‎d downscaled using the SDSM model. The future inflow value to the reservoir is predicted using a Multilayer Perceptron (MLP) neural network model. The results show that climate change, by changing precipitation an‎d temperature patterns, affects reservoir inflow leading to significant fluctuations in water temperature an‎d dissolved oxygen of the Marun Dam reservoir. The findings revealed that, compared to the base period, water temperature changes range from an increase of 0.26 to 6.92 °C to a decrease of 0.12 to 4.08 °C. Furthermore, DO concentrations increases between 0.09 to 2.48 mg/L an‎d decreases between 0.11 to 3.18 mg/L across different months. These results confirm the inverse relationship between temperature an‎d dissolved oxygen. Moreover, climate change can have significant impacts the water quality of the Marun Dam reservoir. Therefore, considering these effects in water quality planning, management, an‎d reservoir operation is of great importance.

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