中文摘要：

准确估计流域蒸散,掌握其变化趋势和主要影响因子,对科学认识流域水文循环规律以及管理流域水资源具有重要意义。利用傅抱璞年蒸散量公式计算滹沱河上游山区及其子流域1958-2007年逐年蒸散量,并利用Mann-Kendall-Sneyers等方法分析了流域蒸散趋势和突变特征,及其主要影响因子。结果表明在滹沱河流域傅抱璞公式能够较好的拟合蒸散。50 a来全流域及各子流域年均蒸散呈下降趋势。降水对蒸散起控制作用,相对湿度在流域部分地区显著影响蒸散（α=0.05）。

英文摘要：

It is important for both understanding the hydrological rules and managing the water resources to esti- mate the evapotranspiration accurately in a basin as well as master the trends of both itself and the principal in- fluence factors. This paper calculated the annual evapotranspiration in the upstream mountain areas of Hutuo River Basin in North China during 1958-2007 by Fu Baopu formula, and analyzed the trend, the abruption and the principal influence factors of the evapotranspiration. The result shows that the Fu Baopu formula can esti- mate the evapotranspiration satisfactorily. In the past 50 years, the evapotranspiration in Hutuo River basin had a decreasing trend （or=0.05）. Precipitation influenced the evapotranspiration strongly, while the potential evapo- transpiration has little effect on it. In some of the researched area, relatively humidity also had significant influ- ence （or=0.05）, The averaged trends of the studied factors are： annual potential evapotranspiration, annual-aver- aged daily wind speed, hours of sunshine, relative humidity, and atmospheric pressure decreased significantly, annual precipitation decreased non-significantly, annual-averaged daily maximal, mean, minimal temperature increased significantly （o~=0.05）. The factors and the difference between their multi-year averaged values be- fore and after significant abruptions are： annual potential evapotranspiration decreased 70.30mm. Daily wind speed and hours of sunshine decreased 0.53 m/s and 0.52 h/d, respectively. Daily maximal, mean, minimal tem- perature increased 1.09、 0.95, 1.14℃, respectively. Evapotranspiration and precipitation had no abruptions. The sub-basin averaged geological locations, elevations, land cover, and NDVI do not influence the evapotrans- piration significantly within the whole basin.