Analysis on hydrological drought characteristics based on standardized runoff index: a case study in the Tarim River Basin

Monthly runoff and precipitation in the headwaters of the Tarim River were analyzed from standardized runoff index and standardized precipitation index. Applicability of drought index and related changing properties of droughts were investigated using historical observations and run theories. SPI and SRI on a 3-month time scale reflect well the changing properties of droughts within the Tarim River Basin. Correlation between SPI3 and SRI3 is more significant in the Hotan and Yerqiang River Basins than in other river basins Occurrence frequency of droughts in Hotan and Yerqiang River Basins is larger than in Arkasu and Kaidu River Basins. However, the duration of droughts in Hotan and Yerqiang River Basins is shorter than in Arkasu and Kaidu River Basins. The number of light droughts in headwater regions of Tarim River Basin after 1987 is smaller than that before 1987, due to increased temperature and precipitation and massive construction of hydraulic facilities after 1987. In addition, substantially increase of crop lands after 1987 is a major contribution factor behind lengthening drought duration and intensified droughts compared to before 1987. This study sheds new light on the understanding of drought changes in a warming climate in arid river basins in China and also in similar river basins in other regions of the globe.