The impact of climate change on water evaporation in Romania

Climate change indicates an acceleration of some components of the water cycle in nature, including evaporation and evapotranspiration. Worldwide evaporation measurements are relatively few and have a low degree of coverage, especially in areas exposed to drought. Observations from around the world have indicated a general trend of decreasing evaporation over the last 50 years, attributed to changes in the air temperature regime and atmospheric precipitation. The objective of this study is to evaluate the changes in the evaporation regime in the context of climate change supported by the modifications identified on air temperature and precipitation values in Romania, as well as the prediction of evaporation rates for the time horizon 2100 based on the HIRHAM5 regional climate model (according to the ICHEC-EC global model -EARTH) of the DMI Climate Modelling Centre (Danish Meteorological Institute). To achieve this objective, direct measurements of evaporation and other climatic parameters were extracted from 44 evaporimeter stations, during the period 1981-2010. The correlations between evaporation and air temperature are strong and direct, with coefficients between 0.6-0.9, whereas lower relations were obtained for stations located in the mountainous area. The evaporation projection in the near future (2021-2050) and far future (2071-2100) time horizon was carried out based on the regression equations obtained between evaporation and air temperature. For the reference period 1981-2010, in Romania evaporation indicated an increasing trend, with the exception of some remaining areas of the south and central area of the country. Regarding the near and far future, due to the increase in air temperature values, the predictions over the evaporation rates indicate also an intensification (compared to the reference period 1981-2010), which may vary between +60 and +130 mm in the near future (2021-2050), or exceed +200 mm in the far future (2071-2100). In conclusion, in Romania, the increase of air temperature by up to 2.0°C, can have a significant impact on the evaporation rates, generate an increase in the average evaporation up to approximately 800 mm/year (prediction for the year 2100), a fact that would have consequences on the water resource.  Keywords: climate change, climate projection, evaporation, water resource