Spatiotemporal Characteristics of Drought in China’s Nine Major River Basins under Climate Change

Based on the monthly precipitation and temperature data interpolated by using ANUSPLIN from meteorological stations in China from 1961 to 2020, this study employed methods such as the standardized precipitation evapotranspiration index (SPEI), Mann-Kendall (M-K) test, Morlet wavelet analysis, and Hurst exponent to obtain the spatial and temporal characteristics, frequency, periodic changes over the past 60 years, and future trends of droughts in the nine major river basins of China. The spatial and temporal characteristics of droughts in these river basins was systematically conducted. The results show that, except for the Haihe River and Yellow River basins, where precipitation tends to decrease, the other basins exhibit an increasing trend, with the southeast river basins showing the largest increase. The SPEI index of most basins shows a downward trend, indicating an intensification of drought. The inland river and southwest river basins have not experienced any abrupt changes over the past 60 years, whereas other basins such as the Haihe River, Huaihe River, Pearl River, Yangtze River, and Yellow River basins have undergone abrupt changes between 1980 and 2000. After the change, the UF shows a declining trend, with an intensifying drought. Seasonal trends of drought are ranked as autumn > summer > spring, with some basins showing a trend towards wetness in winter. Since 1991, drought events have increased, with significant rises in moderate and light droughts in the 21st century, particularly in the inland river and Haihe River basins. All basins generally exhibit a dominant oscillation cycle on the medium and long-term scales, with multiple oscillation cycles in each. The Hurst exponent (H) is greater than 0.5 for all basins, indicating that, with the exception of the southeast river basins, the historical drought trends will continue in the future.