Abstract:Using meteorological observation data at weather stations in China from 1960 to 2012, the trend of dryness/wetness changes and its reasons were analyzed based on SPEI (Standardized Precipitation Evapotranspiration Index). Over the past 52 years, the dryness/wetness changes showed a "+-+" spatial distribution from northwestern to southeastern China. Most of the northwestern River Basin (NWRB) and western Huaihe River Basin (HaRB) significantly tend to be wet, while the Yellow River Basin (YRB), western Changjiang River Basin (CJRB), southeastern southwestern River Basin (SWRB) and western Pearl River Basin (PRB) have significant increase in dryness. The contribution of referenced evapotranspiration (ET0) and precipitation to dryness/wetness changes were quantitatively calculated by several numerical experiments. Results show that the average annual ET0 significantly offsets the drying trend caused by the decrease in annual precipitation, showing a trend of slight wetting. Precipitation is still the dominant factors for the dryness/wetness changes in most regions (the central YRB CJRB, SWRB, PRB and SERB). The impacts of ET0 on dryness/wetness are worth attention. The contribution of ET0 to the dryness/wetness trend in Liao River Basin (LRB), Hai River Basin (HRB), HaRB and NWRB exceeds that of precipitation.