Temporal and spatial characteristics of precipitation and droughts in the upper reaches of the Yangtze river basin (China) in recent five decades

Drought is one of the most harmful natural hazards in the Upper Reaches of the Yangtze River basin (URYR) in the mid-west part of China. Alterations in precipitation will affect the severity of drought. The nonparametric Mann–Kendall (MK) test was used in this paper to examine the trend of precipitation and the standardized precipitation index (SPI) was adopted to analyze the spatial–temporal variations of meteorological drought over different time scales in the last 50 years. The MK test value of precipitation indicated that, for most of the URYR showed an increasing trend of precipitation in the months of January, February, March and June, mainly in the Min-Tuojiang, Jialingjiang and Wujiang sub-basins and a decreasing trend was observed in August to December. The most obvious decreasing trend of precipitation occurred in the Jialingjiang, upper mainstream and Wujiang sub-basins in September, with a rate ranging from –7.89mm/10 years to –39.36mm/10 years. The results show that the SPI is applicable in the URYR basin. The number of severe droughts differed among the six sub-basins, i.e., a more obvious 3-month drought takes place in the middle of the upper mainstream, Wujiang sub-basins and the southeast of Jialingjiang sub-basin and other droughts in 6, 9 and 12 month timescales have the same effect in these three sub-basins. The outcomes of the paper could provide references for droughts mitigation, local water resources management and agriculture decision making.