Estimating Shallow Groundwater Evaporation Based on Surface Evaporation and Ambient Air Temperature

【Objective】 Evaporation loss via capillary rise is an important component of groundwater cycle but difficult to measure in situ. This paper presents an empirical formula to estimate it using surface evaporation and ambient air temperature, based on long-term experimental data obtained from a hydrological experimental station. 【Method】 Groundwater evaporation from phreatic surface of shallow groundwater was measured from lysimeters with cross section of 0.3 m2 at Wudaogou Hydrological Experiment Station, and the meteorological data were measured from a weather station installed at the station. There were two soils, a fluvo-aquic soil and a lime concretion black soil. For each soil, we established a regression model using temperature and surface evaporation, either separately or in combination, to estimate groundwater evaporation. 【Result】 For the lime concretion black soil, the average R2 of the models using single or two meteorological factors was 0.88, and its associated average absolute error (MAE) and root