Estimation of natural water body’s evaporation based on Class A pan measurements in comparison to reference evapotranspiration

Abstract

Abstract⎯ A Class A pan (C) evaporation (E p ) study was conducted at the Agrometeorological Research Station of Keszthely, in the growing season of 2016. Some of the evaporation pans were implemented with freshwater aquatic macrophytes (Myriophyllum sp., Potamogeton sp., and Najas sp.) (P s ) and sediment covered bottom (S). The applied macrophytes were the predominant species of Keszthely Bay (Balaton Lake). Reference (E o ) after Shuttleworth and reference evapotranspiration (ET o ) after PenmanMonteith (FAO-56 formula) were also included for the E study. Of pre-selected four investigated variables, air temperature and air humidity impacted E p of treated Class A pans the most. Cumulative E p values for 2016 were 363.1, 427.7, and 461.5 mm in C, S, and Ps, respectively. There was no difference in measured cumulative E p of P s (461.5 mm) and computed ET o (472.1 mm) during the studied season.On the basis of a simplified water budget, E rate of Keszthely Bay increased with 16.9%, when macrophytes and sediment cover were accounted. It is equivalent to 264,000,000 m 3 water in Keszthely Bay's E estimation. Simple E approach -when lake's components, such as submerged macrophytes and sediment cover were also accounted -could extend the accuracy of natural lake's E estimation in a broader circle than earlier.