Evaporation and the difference between precipitation and evaporation in Bulgaria

Abstract

This study examines the total evaporation and precipitation-evaporation difference in Bulgaria. Data from ERA5-Land reanalysis for the period 1979–2023 were processed using statistical methods. The results show that the main factors for evaporation in Bulgaria are air temperature and precipitation. Evaporation has a positive trend due to the rise in air temperature. This trend is significant only in mountainous regions, which are well-supplied with water. Evaporation is somewhat limited in the other parts of the country because of the water deficits in the warm part of the year. Precipitation is a possible source of water for the earth’s surface, but there has been only an insignificant increase in it in recent decades. Precipitation-evaporation difference remains relatively unchanged during the studied period, which is a favorable trend, as there is no increase in the water deficit in Bulgaria on an annual basis. In addition, most of the country has positive values in terms of the average annual values of precipitation-vaporation difference. However, there is a need to introduce monitoring of actual evaporation, because this study has shown that different calculation methods give different results, which is a significant problem in determining how much precipitation remains in a given area. The exact values of this indicator are extremely important for various sectors of the economy such as agriculture, water supply and sewage, transport, energy, etc.