Vol. 122, No. 1 * Pages 1–99 * Januar - March 2018

DOI:10.28974/idojaras.2018.1.2

Evapotranspiration (ET) is one of the most important elements of water balance. Despite its importance, exact determination for a mosaic surface cover is very limited; therefore, there is a demand for relatively simple and cheap methods of determination that work on a small spatial scale.
Water uptake of forest vegetation in groundwater discharge areas generally has a strong influence on the water resources induced diurnal signal in soil moisture, and in the water table. Diurnal methods in a shallow groundwater environment are widely used nowadays for ET estimation.
By modifying the well-known White (1932) method and adapting to soil moisture data, a new technique was developed to calculate ET from soil moisture readings, eliminating the need of specific yield (a weakest point of the groundwater signal based methods). The new method was validated using hydro-meteorological data of the Hidegvíz Valley experimental catchment located in the Sopron Hills at the western border of Hungary.
The 30-min ET rates of the proposed method lag 30-60 minutes behind those of the reference Penman–Monteith method, but otherwise the two estimates compare favorably.
On a daily basis, the newly derived ET rates are very close to PM estimates, but on average, they are 38% higher than the ones obtainable with the original White method. Comparing the ET rates of the proposed method with traditional ET estimates from soil moisture, a significant difference can be ascertained.
The proposed method has potential benefits in groundwater discharge areas, especially in light of the changing climate with its warmer and drier growing seasons, that will likely result in limited water resources.