Spatial variability and temporal stability of actual evapotranspiration on a hillslope of the Chinese Loess Plateau

Actual evapotranspiration (ETa) is a key component of water balance. This study aimed to investigate the spatial variability and time stability of ETa along a hillslope and to analyze the key factors that control the spatiotemporal variability of ETa. The potential evaporation, surface runoff and 0–480 cm soil water profile were measured along a 243 m long transect on a hillslope of the Loess Plateau during the normal (2015) and wet (2016) water years. ETa was calculated using water balance equation. Results indicated that increasing precipitation during the wet water year did not alter the spatial pattern of ETa along the hillslope; time stability analysis showed that a location with high time stability of ETa could be used to estimate the mean ETa of the hillslope. Time stability of ETa was positively correlated with elevation (P<0.05), indicating that, on a hillslope in a semi-arid area, elevation was the primary factor influencing the time stability of ETa.