Assessment of precipitation and drought variability in the Weihe River Basin, China

The amount and distribution of precipitation play crucial roles in the occurrence of drought in the Weihe River Basin ( WRB), China. Using the precipitation data ( 1960-2010) of 21 meteorological stations, the spatial and temporal characteristics of short-, medium-, and long-term droughts on 3-, 6-, and 12-month time scales, respectively, were examined using the theory of runs and the Standardized Precipitation Index ( SPI). The trends of the drought characteristics were analyzed by a modified Mann-Kendall ( MMK) test method. Furthermore, comparative analysis of the SPI at different time scales was conducted. The results showed that ( 1) the main drought type was moderate drought, which occurred frequently in July and October; ( 2) the drought intensity and frequency were highest in the 1990s, and the drought severity and drought duration in the northwest was more serious than that in the east; ( 3) an increasing trend of short droughts appeared mainly in the spring and fall; an increasing trend of medium droughts mainly occurred in the 1990s and that of long-term droughts were mainly presented in the northwest region of the WRB; ( 4) SPI-3 can better reflect precipitation in the current month, SPI-6 has an advantage in characterizing drought persistence, and SPI-12 performs well in capturing extraordinary droughts; and ( 5) it was also observed that there is a strong relation between the precipitation distribution and drought zones in the basin, and the drought conditions changed continuously with the seasons depending upon the amount and spatial distribution of precipitation.