Protecting river eco-hydrological processes: insights from water temperature studies.

Water temperature (T_w) plays a critical role in the aquatic ecosystem of rivers. Studying the response process and mechanisms of T_w to climate change and human activities is crucial for assessing the sustainable development of river ecological environments. In this study, we conducted a multi-time scale analysis of T_w using mathematical and statistical models and a vector autoregressive model. We analyzed hydrometeorological data collected from 1961 to 2019 to understand the evolutionary characteristics of T_w under different meteorological conditions and reservoir operation stages. Our findings reveal a significant mutation in T_w in 1994, with the warming rate changing from 0.007 to 0.032 °C/year. Among the various meteorological factors examined [runoff, evapotranspiration, air temperature (T_a), rainfall, duration of sunshine, wind speed, air pressure, and solar radiation], T_a and runoff were found to have the greatest influence on T_w, accounting for > 30% of the observed changes. Conversely, the wind speed had the weakest impact. Furthermore, the Three Gorges Dam (TGD) exerted a substantial influence on T_w. The presence of the TGD elevated winter T_w compared to the non-impoundment condition. Additionally, the completion of the TGD significantly weakened the correlation between runoff, Ta, and Tw, resulting in a 25–34 day delay in the Chinese sturgeon's target spawning time. This delay could have negative ecological implications for the lower reaches of the TGD. These findings offer essential support for guiding water resource management, protecting river eco-hydrological processes, and understanding the impact on aquatic ecology in the Yangtze River. [ABSTRACT FROM AUTHOR]