Evaluation of the effects of climate change on thermal stratification of reservoirs

Abstract

Many water needs are provided by reservoirs. Increasing water retention time in reservoirs leads to thermal stratification and, consequently, affects the water quality of reservoirs. This situation can be exacerbated under climate change. The objective of this study is to assess the climate change effect on thermal stratification of the Aidoghmoush reservoir (East Azarbaijan, Iran) for baseline (1987–2000) and climate change (2026–2039) periods. For this purpose, future temperature and precipitation were estimated by HadCM3 under the A2 emission scenario, and inflow of the reservoir in 2026–2039 was simulated by IHACRES. Results show that the average annual reservoir inflow in climate change decreases about 1% relative to the baseline. In addition, CE-QUAL-W2 was calibrated and used to simulate the thermal stratification of the reservoir. Results show that on average, the surface and bottom water temperatures of the reservoir during the climate change period respectively increase by 1.69 and 1.24 °C compared to those of the baseline. The maximum and minimum surface water temperatures under climate change are respectively 0.14–3.98 °C higher than those in the baseline. Under climate change, thermal stratification mainly occurs in shallow water of the reservoir in spring and summer, but it is extended to deeper water in autumn. In winter, however, complete mixing may occur.