Groundwater recharge and baseflow as products of climate: example of Southeast Bulgaria

The study area is located in Southeast Bulgaria. The main factors affecting climate in Burgas lowland are the proximity to the Black Sea and to mountains. The aim of the study is to quantify the long-term value of the baseflow and other water balance elements. The methods include Turc-Radiation equation, equation relating baseflow coefficient with the aridity index, regression set for Conterminous USA based on climatic parameters, etc. All water balance elements are estimated as reasonable, as compared with available data from previous studies. Therefore, the methods applied are recognized as suitable for the study area. The results show that the baseflow varies from 20 to 70 mm per year, and the baseflow coefficient ranges from 5 to 10 percent in respect to the proximity to the Black Sea coast. Possible impact of the climate change on the groundwater recharge and baseflow is evaluated based on the climate scenario for the period between 2040 and 2070. The expected decrease of baseflow as a result of the increased aridity is up to 50% in comparison to the baseline state.