Study on response of water temperature characteristics in reservoir-river systems to climate change

Abstract

[Objective] With the intensification of climate change, the effects of thermal stratification in reservoirs and water temperature fluctuations in downstream river channels on aquatic ecosystems have become critical issues in water resource management. This study examines Longyangxia Reservoir to investigate the effects of climate change and reservoir operations on the stability of water temperature stratification and the ecological impacts of discharge water temperatures on the ecosystems of downstream river. [Methods] Using the CE-QUAL-W2 hydrodynamic model, simulations were conducted based on four socio-economic pathways representing future climate change scenarios and two reservoir operation strategies. These simulations examined the water temperature and discharge water temperature of Longyangxia Reservoir. [Results] The result showed that:(1) under climate warming and low water level operations, the average thermocline thickness of Longyangxia Reservoir was 15.57 m, with an average thermocline strength of 0.55 ℃/m and a stable stratification period lasting from 244 to 281 days. Under high water level operations, the average thermocline thickness was 20.57 m, with an average thermocline strength of 0.37 ℃/m and a stable stratification period lasting from 251 to 288 days.(2) Under the conventional pathway(SSP-8.5), the temperature difference index between the discharge water temperature and the downstream river water temperature before reservoir construction was 45.66 ℃·d and 12.39 ℃·d under different operation strategies, both showing the minimum values.(3) Under the conventional pathway(SSP-8.5), the discharge water temperature reached the optimal reproduction temperature for Gymnocypris eckloni approximately one month earlier. [Conclusion] The result highlight that climate change significantly affects the water temperature characteristics of the reservoir-river systems, suggesting that effective operation strategies are essential for addressing climate change.

Keywords

climate change / reservoir-river systems / thermal stratification / discharge water temperature / Longyangxia Reservoir / influencing factors