Abstract: With the data of observed monthly evaporation at 44 meteorological stations in Xiangjiang River basin from 1960 to 2006. Changes in pan evaporation and their causes are analyzed. The main results are as follows: pan evaporation decreased by 21.29 mm per 10 year (90% confidence level) in Xiangjiang River basin during the recent 47 years. Significant decrease of annual pan evaporation occurred at 75% of meteorological stations. As for the seasonal pan evaporation, especially in summer, it decreased by 15.58 mm per 10 year (99% confidence level). Spatially, the pan evaporation declined from the southwest to the northeast, the significant decrease of pan evaporation occurred in the downstream. The decrease of pan evaporation is mainly attributed to the decrease of vapor pressure deficit and the significant decrease of wind speed at most of the meteorological stations in Xiangjiang River basin.

Key words: pan evaporation, trends, analysis of cause, Xiangjiang River basin