Comparison of evapotranspiration variations between the Yellow River and Pearl River basin, China

Based on daily meteorological data at 43 gauging stations in the Pearl River basin and 65 gauging stations in the Yellow River basin, we analyze changing properties of actual evapotranspiration (ET_a), reference evapotranspiration (ET_ref) and precipitation in these two river basins. In our study, Pearl River basin is taken as the ‘energy-limited’ system and the Yellow River basin as the ‘water-limited’ system. The results indicate decreasing ET_a in the Pearl River and Yellow River basin. However, different changing properties are detected for ET_ref when compared to ET_a. The middle and upper Yellow River basin are characterized by increasing ET_ref values, whereas the Pearl River basin is dominated by decreasing ET_ref values. This result demonstrates enhancing drying force in the Yellow River basin. ET_a depends mainly on the changes of precipitation amount in the Yellow River basin. In the Pearl River basin, however, ET_a changes are similar to those of ET_ref, i.e. both are in decreasing trend and which may imply weakening hydrological cycle in the Pearl River basin. Different influencing factors are identified behind the ET_a and ET_ref in the Pearl River and Yellow River basin: In the Pearl River basin, intensifying urbanization and increasing aerosol may contribute much to the evapotranspiration changes. Variations of precipitation amount may largely impact the spatial and temporal patterns of ET_a in the Yellow River basin. The current study is practically and scientifically significant for regional assessment of water resource in the arid and humid regions of China under the changing climate.