Variations in precipitation and runoff from a multivariate perspective in the Wei River Basin, China

Investigation of the variations in precipitation and runoff and possible breakpoints of their relationship is of great value for local water resources planning and management. The Wei River Basin (WRB), as a typical arid and semi-arid region in China, was selected as the case study. The zonal and meridional moisture transport flux from the National Centers for Environmental Prediction (NCEP) reanalysis dataset were used to explore the possible causes of changes in precipitation variability. A Copula-based method was adopted to examine the changing relations between precipitation and runoff variabilities and identify possible breakpoints of their relationship. Results showed that: (1) a roughly decreasing precipitation trend was found for most months, especially in spring and autumn, which was mainly affected by the joint effects of the weakening East Asian summer and winter monsoons; (2) similar to precipitation changes, the runoff in most months in the WRB exhibited significantly decreasing trends, which are highly correlated with those of precipitation at the 95% confidence level; (3) two breakpoints of the relationship between precipitation and runoff were identified at Linjiacun station in 1972 and 1996 and at Zhangjiashan station in 1988 and 1997, whilst only one breakpoint was detected at Huaxian station in 1995, which were well consistent with the extensive human water use and soil conservation practices.