Drought-related variables over the Bârlad basin (Eastern Romania) under climate change scenarios

•We assess drought-related climate changes for the Bârlad basin (Eastern Romania).•Ensemble means from regional climate experiments fairly reproduce the observations;•Palmer Drought Severity Index (PDSI) is computed from climate and soil data.•Basin-averaged PDSI components fairly simulate the local water balance.•Present “droughty” summers might be “normal” at the end of the 21st century.

The goal of this study is the assessment of the future evolution of monthly temperature and precipitation and their influences exerted on droughts occurring in the Bârlad river basin (Eastern Romania). We have used recent results of experiments based on regional and global climate models under the Representative Concentration Pathway (RCPs) scenarios (RCP 4.5 and RCP 8.5), which have been made accessible thanks to the EURO-CORDEX initiative. The impact of climate change on drought is assessed by using the Palmer Drought Severity Index (PDSI). The correlations between the observed streamflow at the Bârlad basin outlet and the PDSI-related indices show that the PDSI represents reasonably well the local water balance. The linear trend analysis of multimodel ensemble means reveals that, under climate change, the basin-averaged PDSI will be lower thus indicating a tendence towards drought. The PDSI method applied to the Bârlad basin seems to show low sensitivity to soil characteristics such as available water capacity when drought trends are investigated. On the other hand, model results reveal that, under climate change conditions, the Thornthwaite formula for calculating the potential evapotranspiration will lead to a substantial overestimation of the aridity tendence whenever compared with the Penman-Monteith approach. Depending on the specific climate scenario and parametrization of potential evapotranspiration, droughts that were deemed as incipient, mild or severe towards the end of the 20th century will have been a normal feature towards the end of the 21st century.