Hydrological projections in the upper reaches of the Yangtze River Basin from 2020 to 2050

Abstract

Understanding the impact of climate change on runoff is essential for effective water resource management and planning. In this study, the regional climate model (RCM) RegCM4.5 was used to dynamically downscale near-future climate projections from two global climate models to a 50-km horizontal resolution over the upper reaches of the Yangtze River (UYRB). Based on the bias-corrected climate projection results, the impacts of climate change on mid-twenty-first century precipitation and temperature in the UYRB were assessed. Then, through the coupling of a large-scale hydrological model with RegCM4.5, the impacts of climate change on river flows at the outlets of the UYRB were assessed. According to the projections, the eastern UYRB will tend to be warm-dry in the near-future relative to the reference period, whereas the western UYRB will tend to be warm-humid. Precipitation will decreases at a rate of 19.05–19.25 mm/10 a, and the multiyear average annual precipitation will vary between − 0.5 and 0.5 mm/day. Temperature is projected to increases significantly at a rate of 0.38–0.52 °C/10 a, and the projected multiyear average air temperature increase is approximately 1.3–1.5 ℃. The contribution of snowmelt runoff to the annual runoff in the UYBR is only approximately 4%, whereas that to the spring runoff is approximately 9.2%. Affected by climate warming, the annual average snowmelt runoff in the basin will be reduced by 36–39%, whereas the total annual runoff will be reduced by 4.1–5%, and the extreme runoff will be slightly reduced. Areas of projected decreased runoff depth are mainly concentrated in the southeast region of the basin. The decrease in precipitation is driving this decrease in the southeast, whereas the decreased runoff depth in the northwest is mainly driven by the increase in evaporation.

Hydrological Extremes in the Upper Yangtze River Over the Past 700 yr Inferred From a Tree Ring δ18O Record

“…It has been suggested that under the global warming scenario, land‐ocean temperature contrasts and the low‐level monsoon circulation will progressively strengthen and thus generate more precipitation (Bhowmick et al., 2021). Similar projections have been reported for the UYR (Gu et al., 2018; Huang et al., 2021); for example, Gu et al. (2018) suggested that the annual mean precipitation will increase by 3.62% under RCP4.5 (1.81°C) and 7.65% under RCP8.5 (2.26°C) over the Yangtze River basin, including the UYR.…”

“…The Yangtze River is the third largest river system in the world, accounts for nearly 40% of China's mean annual discharge, and supports the livelihoods of millions of people. The upper reaches of the Yangtze River (UYR) supply ∼46% of the multiyear average annual runoff and possess abundant water and hydropower resources (Huang et al., 2021). The large interannual and decadal variations in the monsoon precipitation leave the basin vulnerable to droughts and floods (S. L. Yang et al., 2015).…”

Spatio-Temporal Variability in Hydroclimate over the Upper Yangtze River Basin, China

“…The spatial mean annual rainfall and air temperature variation across the UYRB is shown in Figure 3. The difference in rainfall between the northwest and southeast of the watershed seems to be considerable, as seen in Figure 3a, which is in accordance with the analysis of [62,67]. As reported by [62], the spatial distribution of precipitation over the UYRB is extremely heterogeneous, and in general, the rainfall decreases from the southeastern to the northwestern part of the basin.…”

Bias Correction for Precipitation Simulated by RegCM4 over the Upper Reaches of the Yangtze River Based on the Mixed Distribution Quantile Mapping Method

“…The data used in this study include precipitation data sets from a RegCM4 simulation and observational data sets. The precipitation that has been simulated by RegCM4 for the period from 1989 to 2012 was based on the model configuration scheme from Huang et al [26]. In addition, the EAR-Interim reanalysis data were used as initial and boundary conditions to perform dynamic downscaling with a resolution of 50 km.…”