Past (1971–2018) and future (2021–2100) pan evaporation rates in the Czech Republic

• Published in: Journal of hydrology (Amsterdam) 2020-11, Vol.590, p.125390, Article 125390
• Main Authors: Mozny, Martin, Trnka, Miroslav, Vlach, Vojtech, Vizina, Adam, Potopova, Vera, Zahradnicek, Pavel, Stepanek, Petr, Hajkova, Lenka, Staponites, Linda, Zalud, Zdenek
• Format: Article
• Language: English
• Subjects: Climate change; Drought; Hydrological cycle; Pan evaporation; Vapor pressure deficit
• ISSN: 0022-1694; 1879-2707
• DOI: 10.1016/j.jhydrol.2020.125390

•Pan evaporation has been rapidly growing in the Czech Republic since 1990.•The mean evaporation between 2001 and 2018 was 18% higher than the 1971–2000 average.•Future projections suggest a further increase in evaporation by up to 54%.•Increased evaporation has already enhanced the severity of recent droughts. Evaporation from open water surfaces is often estimated based on the pan evaporation (Epan), which is an essential measure for estimating atmospheric evaporative demand. Within the Central European region, Epan appears to be slightly underestimated in the case of the hydrological balance of water bodies. In the context of the recent multi-year period of drought, significant losses of surface water deposits were observed in countries of Central Europe. In spite of the ‘evaporation paradox’ phenomenon, Epan is not generally decreasing as expected by many studies from past decades. Recorded observations from the Czech Republic show an increase in Epan, which is associated with an increase in global radiation and vapor pressure deficit. The vast majority of meteorological stations show a strong or very strong increase in Epan during April, June, July and August. During the 1971–2018 period, the annual mean Epan has been increasing by an average of 2.97 mm yr−1. For the period 2001–2018, the mean Epan was 18% higher (519 mm) than the 1971–2000 average (440 mm). Our simulations of future scenarios, using regional climate models, predicted a growth in Epan of up to 27–54%. Such an increase in evaporation would cause serious consequences for surface water availability and agricultural production during the periods of drought in the Czech Republic, as the drought period 2014–2018 has clearly demonstrated.