Quantifying the Impacts of Climate Change and Vegetation Variation on Actual Evapotranspiration Based on the Budyko Hypothesis in North and South Panjiang Basin, China

Actual evapotranspiration (E-a) plays a key role in the global water and energy cycles. The accurate quantification of the impacts of different factors on E-a change can help us better understand the driving mechanisms of E-a in a changing environment. Climate change and vegetation variations are well known as two main factors that have significant impacts on E-a change. Our study used three differential Budyko-type equations to quantify the contributions of climate change and vegetation variations to E-a change. First, in order to establish the relationship between the parameter n, which usually presents the land surface characteristics in the Budyko-type equations, with basic climatic variables and the Normalized Difference Vegetation Index (NDVI), the stepwise linear regression method has been used. Then, elasticity and contribution analyses were performed to quantify the contributions of different numbers of climatic factors and NDVI to E-a change. The North and South Panjiang basin in China was selected to investigate the efficiency of the modified Budyko-type equations and quantify the impacts of climate change and vegetation variations on E-a change. The empirical formal of the parameter n established in this study can be used to simulate the parameter n and E-a for the study area. The results of the elasticity and contribution analyses suggest that climate change contributed (whose average contribution is 149.6%) more to E-a change than vegetation variation (whose average contribution is 49.4%). Precipitation, NDVI and the maximum temperature are the major drivers of E-a change, while the minimum temperature and wind speed contribute the least to E-a change.