Diurnal Method for Evapotranspiration Estimation from Soil Moisture Profile

Abstract

Abstract Water use of plants can be manifested in diurnal signal of soil moisture changes, and also of water table fluctuations in shallow water table environments. The signal can be especially strong in case of groundwater dependent forest vegetation with high water demand, where the water uptake is partly happening across the capillary zone. A new technique for water uptake estimation was elaborated on the basis of high frequency soil moisture profile data taking into account diurnally changing replenishment rate. The method is of great benefit to provide sufficient accuracy without soil specific calibration. The method was tested on the soil moisture dataset of a riparian alder forest in Hidegvíz Valley experimental catchment. Using this new method significantly higher and more realistic water uptake can be calculated compared to the traditional soil moisture method. The method is taking into account soil moisture replenishment from groundwater, which can provide high portion (up to 90%) of evapotranspiration in dry periods. For the above mentioned reason the new technique is recommended to be used for evapotranspiration estimation in groundwater discharge areas, where the traditional methods and simple one-dimensional hydrological models generally work inaccurate.