Joint Dependence Between River Water Temperature, Air Temperature, and Discharge in the Yangtze River: The Role of the Three Gorges Dam

Abstract

The water temperature of rivers is of considerable significance to freshwater ecosystems and human water use. In contrast to traditional regression models or other deterministic statistical models, we present a probabilistic approach to examine the joint dependence structures of water-air temperature and water temperature-discharge in the Yangtze River. Such dependence structures were built based on bivariate probabilistic models with well-fitted marginal distributions of each variable. To investigate the stability of the dependence structures and the effects of the Three Gorges Dam (TGD), three stations (i.e., Cuntan, Yichang, and Datong) located in different sections of the river were involved in comparison between two periods, that is, pre-TGD (1975)(1976)(1977)(1978)(1979)(1980)(1981)(1982)(1983)(1984)(1985)(1986)(1987) and post-TGD (2003-2014) periods (the dam began operating in 2003).Our results indicate that at the three stations the joint occurrence probabilities of the air-water temperature events (e.g., the compound extreme events) tend to be lower for the second period. The dependence structures of water temperature and river discharge were stable between the two periods at the upstream station. For the downstream station relatively close to the TGD (Yichang station), a clear disturbance was observed in the dependence structures of water temperature-discharge. In addition, relying on the established bivariate and trivariate dependence models, we further assessed the risk of different water temperature events under individual and coupled extreme conditions of air temperature and discharge. The trivariate model also revealed substantial changes in the probabilistic difference between the pre-TGD and post-TGD periods at Yichang station, indicating the impact from the TGD.

Comparative Study on Temperature Response of Hydropower Development in the Dry‐Hot Valley

“…The reservoirs have a smaller impact on downstream river temperatures in the dry season than in the wet season because the river runoff caused by reservoir impoundment decreases in the dry season (Liu, Z. et al, 2018;Gou et al, 2020). Additionally, hydrological and meteorological factors also affect the downstream river temperature (Cai et al, 2018;Sun et al, 2019a).…”

Ecological responses of spawning habitat suitability to changes in flow and thermal regimes influenced by hydropower operation

“…As the world's largest and possibly most controversial hydropower project, Three Gorges Reservoir (TGR) has received considerable attention after it began operation in 2003 (Liu et al, 2018; Shen & Xie, 2004; Wang et al, 2021; Xu et al, 2013). In particular, extensive studies have evaluated the potential environmental impacts of TGR impoundment involving runoff alterations (Chai et al, 2019; Dai et al, 2008; Li et al, 2012; Wang et al, 2018), large water temperature fluctuations (Cai et al, 2018; Qiu et al, 2021; Tao et al, 2020), water quality deterioration (Huang et al, 2015; Tang et al, 2018; Xiang et al, 2021) and decreased aquatic habitat suitability (Li & Xia, 2011; Shen et al, 2018; Yi et al, 2010; Zhou et al, 2014).…”

Quantifying the impacts of the Three Gorges Dam on the spatial–temporal water level dynamics in the upper Yangtze River estuary

“…Numerous studies have been conducted to understand the potential environmental impacts of the Three Gorges Dam (TGD), the largest dam in the world, since its operation beginning in 2003 has dramatically changed the downstream hydrology and sediment delivery in the Yangtze River. Key factors influenced by the operation of TGD include hydrodynamics (Cai et al, 2019c), morphological evolution (e.g., Yang et al, 2011Yang et al, , 2014Lai et al, 2017;Yuan et al, 2020), sediment and flow discharges (e.g., Chen et al, 2016;Guo et al, 2018), nutrient transport (e.g., Wang et al, 2020), river-lake interaction (e.g., Guo et al, 2012;Mei et al, 2015), and thermal dynamics (e.g., Cai et al, 2018a;Liu et al, 2018). However, due to the long distance from the TGD to the downstream estuary, quantification of the potential impacts of the TGD (mainly due to its seasonal freshwater regulation) on the spatial-temporal water level dynamics is a challenging task, as flow alterations are generally concurrent with geometric changes induced by natural and anthropogenic factors.…”