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

Abstract

As global warming produces dramatic climate changes, water management is facing increasingly serious challenges. Given to the process of climate change and its complex effects on watershed hydrology, this paper investigates the spatial and temporal variation characteristics of major climatic factors (i.e., precipitation and temperature) over the upper Yangtze River basin (UYRB), China. The statistical analyses are based on annual and seasonal scales during 1951–2020 with a recorded period of seven decades. The Mann–Kendall nonparametric test and R/S analysis are used to record the temporal trends (past and future) of climate variables; the Pettitt test, standard normal homogeneity test and Buishand test are used to detect the homogeneity in climate series. The sensitivities of the streamflow to climatic parameters are assessed at the watershed scale, especially considering the Three Gorges Dam’s (TGD) effect on changing runoff. The results of the study indicate that the annual precipitation of 29 out of 34 series indicate homogeneity, while 31 out of 34 annual mean temperature series show heterogeneity, with jump points around 1997 in the mean temperature of 20 sites. Detectable changes in precipitation were not observed during 1951–2020; however, the temperature increased significantly in the whole basin on annual and seasonal scales, except for several stations in the eastern part. The magnitude of increase in air temperature in high altitudes (Tibet Plateau) is higher than that in low altitudes (Sichuan Plain) over the last seven decades, and future temperatures continue to sharply increase in high altitudes. The TGD plays an important role in explaining the seasonal variations in streamflow at Yichang station, with streamflow experiencing a sharp increase in winter and spring (dry season) and a decrease in summer and autumn (rainy season) compared to the pre-TGD period. The streamflow variation at an annual scale is mainly regulated by climate fluctuation (variation in precipitation). During the last seven decades, increasing air temperature and decreases in rainfall and runoff signify reduced water resources availability, and the climate tends to be warmer and drier over the basin. The sensitivity of the streamflow to watershed precipitation is higher than that to temperature, with variation in annual rainfall explaining 71% of annual runoff variability.

Evidence for Intensification in Meteorological Drought since the 1950s and Recent Dryness–Wetness Forecasting in China

“…This study performs a relative long-term assessment of drought behavior based on a time window of 71 years from 1951 to 2021, providing independent evidence for climate variations on interannual to interdecadal scales in China. The statistical period of the datasets forms a favorable foundation for trend and variability analysis [70]. This paper provides a reference framework to the climatic attribution of dry-wet variation and plentiful evidence for describing the spatio-temporal pattern of the drying-wetting transition.…”

“…In the MMK test, the modified variance of the MK statistic is used to replace the original one if the lag-i autocorrelation coefficients are significantly different from zero at the 5% significant level [102]. The MMK statistic limits the possible influence of serial correlation on the significance of trends [38] and has been widely used in hydroclimatic studies concerning trend detection (e.g., [14,17,38,70]). In this study, the statistical significance of drought variations was tested using the MMK statistic at the 95% confidence interval (p < 0.05).…”

“…The Pettitt test [107] was performed on annual climate factors and the SPEI to identify any possibility of a significant shift. This method is a rank-based non-parametric statistical test whose null hypothesis assumes no significant transition in meteorological time series exists [70]. The alternative hypothesis is that there is a transition (i.e., change-point) in meteorological time series [31].…”

The Characteristics of Precipitation During the Flood Seasons in Heilongjiang Province Over the Past 53 Years

“…As an important point in the water cycle, precipitation is the direct or indirect replenishment source of various water bodies, and its long-term evolution has a decisive influence on regional water resources [6]. The change in precipitation pattern and water cycle process intensifies the complexity of water resources change, resulting in increased uncertainty of precipitation and its spatio-temporal distribution [7]. Flood season is the precipitation concentration period in a year, and it is also the peak period of disastrous weather such as strong convection and heavy precipitation [8].…”

Variation of heat flux and ecological impact on fish reproduction in the middle reaches of Yangtze River

“…In recent years, river flow and water temperature (WT) have been impacted by global warming and the construction of hydraulic engineering structures [1][2][3] , and the river heat flux (HF) situation has undergone a significant transformation. Changes in HF and their impacts on the ecological environment have received a great deal of attention at home and abroad [4][5] .…”