Analysis of temporal trends in potential evaportranspiration over Heihe River basin

Based on the Penman-Monteith formula recommended by FAO (Food and Agriculture Organization), calculated the potential evapotranspiration of all stations in Heihe River basin in 49 years. The research data included he monthly average temperatures, average maximum temperature, average minimum temperature, wind speed, relative humidity, wind speed, hours of sunshine and solar radiation from 1960 to 2009. The change characteristics of evapotranspiration were analyzed by using trend analysis and Mann-Kendall abrupt tests. The results showed that the ET₀ is increasing in the upper reaches and fluctuating in middle and lower reaches. The abrupt point is 1979 in middle reaches and in 1983 in middle reaches. While there is no obvious abrupt point in upper reaches.