Evapotranspiration Study Based On Budyko Coupled Water-energy Balance Theory In Nenjiang River Basin

Evapotranspiration is the result of water balance and energy balance, which is affected by climate and characteristics of underlying surface comprehensively, its process is complex, the spatiotemporal differences are larger, many scholars have been devoted to estimating actual evapotranspiration over the years, and the achievements were distinguished. In recent decades, with the continuous increase of temperature, the phenomenon of evaporation paradox has appeared in multiple regions, which leads to great contradiction between the observation based on the phenomenon of evaporation paradox as well as the study on hydrological cycle response to global warming, and prediction on actual evapotranspiration change trend by evapotranspiration theory based on water balance and energy balance, the phenomenon results in production of Budyko coupled water-energy balance theory, which provides a new approach for the estimation of actual evapotranspiration.For half a century, temperatures of Nenjiang river basin continuously elevated, runoff reduced, evapotranspiration enhanced, drought phenomenon was serious, flood and drought occurred frequently, all the above-mentioned factors affected hydrological cycle of river basin immediately, finally, water shortage occurred. Therefore, the study on evapotranspiration provides a scientific basis for prevention of flood and drought disasters in Nenjiang river basin and exploitation, utilization and protection of water resource.Nenjing river basin is the study area in this paper, the study starts from Budyko coupled water-energy balance theory, estimates actual evapotranspiration combining with hydro-meteorological data from 1956 to 2000. Firstly, the study analyzes the evolution of climatic factors, researches the relationship among the amount of precipitation, actual evapotranspiration and potential evapotranspiration, the results show that the phenomenon of evaporation paradox exists in Nenjiang river basin, there is a negative correlation between the amount of precipitation and potential evapotranspiration, while the amount of precipitation is positively correlated with actual evapotranspiration, ~ curve analysis proves that actual evapotranspiration is mainly controlled by the amount of precipitation. Subsequently, the study utilizes Fu’s equation to estimate the actual evapotranspiration yearly in Nenjiang river basin and typical collection area, then the study estimates and validates the result in July, the study shows that Fu’s equation has high precision for estimating evapotranspiration yearly in Nenjiang river basin, the correlation between estimation of collection area with high dryness and result of water balance is good. Furthermore, the study analyzes the distribution regularity of underlying surface, which decreases with the decrease of vegetation coverage from upstream to downstream. Finally, the study investigates the laws of time evolution and spatial distribution of both actual evapotranspiration and potential evapotranspiration in Nenjiang river basin, under the significance level of α =0.05, actual evapotranspiration and potential evapotranspiration have no trend variation; what is more, the distribution of actual evapotranspiration is contrary to potential evapotranspiration in space, the former shows a decreasing trend from upstream to downstream gradually. PETPPETa/...