Impacts of climate change on reference crop evapotranspiration in Shiyang River basin

Based on the meteorological data collected from six weather stations in recent 50 years in Shiyang River Basin, the reference crop evapotranspiration(ET₀) was calculated with the Penman-Monteith equation recommended by FAO in 1998. The change characteristics of monthly and annual ET₀ were analyzed. ET₀ values were decreasing year by year in other regions except Wuwei and Sunan. The average ET₀ values in 1990s were greater than those in 1980s in all stations, which showed that impacts of climate change on ET₀ were large. The correlations of average temperature, average maximum temperature, annual sunshine hours, average wind speed, average relative humidity, annual rainfall, annual evaporation and altitude with ET₀ were analyzed. The coefficient of correlation of ET₀ with average relative humidity was greatest. Spatial variation of ET₀ values was obvious and the value was increasing from mountainous area to oasis plain in Shiyang River Basin.