Developing a framework for assessment of climate change impact on thermal stratification of dam reservoirs

Abstract

According to the impact of climate change on the thermal stratification which results in a quality change of dams outflow, this study aims to present a framework to assess the impacts of climate change on altering thermal regimes of dam reservoirs. Therefore, five Atmosphere–Ocean Global Circulation Models (AOGCM-AR5 models) under two emission scenarios (RCP2.6 and RCP8.5) are used to investigate the change of air temperature, precipitation, wind speed, relative humidity, dam inflow and water temperature in 2020–2039. To quantify these impacts, three models are used, namely rainfall–runoff IHACRES, hydrodynamic model CE-QUAL-W2 and a downscaling model of LARS-WG. The efficiency of the proposed framework was evaluated in Latian Dam in Iran. Results show an increment of long-term air temperature average by 0.7 °C and, consequently, water surface temperature by 0.59 °C in 2020–2039 relative to the baseline period (1990–2009). Precipitation, wind speed and relative humidity decrease due to climate change in the future by 57%, 17% and 11%, respectively. The simulated dam inflows show that the maximum of 89% of the dam inflow decreases in the future period relative to the baseline period. The results indicate that the water temperature will increase in the coming period as the air temperature increases and this will lead to the extension of thermal stratification period up to 52 days.