Future projections of thermal regimes and mixing characteristics in a monomictic reservoir under climate change

Haoyu Wang; Yun Deng; Yanjing Yang; Min Chen; Xingmin Wang; Youcai Tuo

doi:10.1016/j.scitotenv.2023.167527

Future projections of thermal regimes and mixing characteristics in a monomictic reservoir under climate change

Sci Total Environ. 2024 Jan 1:906:167527. doi: 10.1016/j.scitotenv.2023.167527. Epub 2023 Oct 1.

Authors

Haoyu Wang¹, Yun Deng¹, Yanjing Yang², Min Chen¹, Xingmin Wang¹, Youcai Tuo³

Affiliations

¹ State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu 610065, China.
² PowerChina Chengdu Engineering Corporation Limited, Chengdu 610072, China.
³ State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu 610065, China. Electronic address: tuoyoucai@scu.edu.cn.

PMID: 37788776
DOI: 10.1016/j.scitotenv.2023.167527

Abstract

Stratified structures are basic physical characteristics of lakes and reservoirs, which play important roles in vertical convection and mixing processes. Global warming is expected to alter the thermal regimes and stratified characteristics of lakes and reservoirs, leading to potential environmental risks and ecological problems. In this study, we used a two-dimensional hydrodynamic model to explore the response characteristics of the thermal regime to climate change in the Xiluodu Reservoir. The study is conducted based on four representative concentration pathways (RCP 2.6, RCP 4.5, RCP 6.0, and RCP 8.5). The results show that the projected surface water temperature of the reservoir will significantly increase (0.13 °C/10a-0.34 °C/10a) from 2022 to 2099, and the warming rate of the water in the epilimnion and thermocline will be greater than that in the hypolimnion, leading to enhanced vertical stratification in the reservoir. The stratification stability index (SI) will increase by 14.4 % under RCP 8.5 compared to that under RCP 2.6. The main responses of the reservoir to climate change are earlier start date and later end date of stratification, which may increase the duration of hypoxia in the hypolimnion and promote the succession of planktonic algal communities. The withdrawal water temperature in the reservoir will significantly increase under the climate warming scenarios (0.03 °C/10a-0.22 °C/10a). Furthermore, our research results indicate that selective withdrawal is still needed to mitigate the adverse effects of cold water from the reservoir during the fish spawning period under the strongest warming scenario, and can also be an effective adaptive management strategy to regulate thermal stability in the reservoir. This study provides a scientific and theoretical reference for the sustainable management of similar deep monomictic reservoirs under climate change.

Keywords: Climate change; Reservoir management; Selective water withdrawal; Thermal regime; Two-dimensional hydrodynamic model.