Water resource impacts of climate change in southwestern Bulgaria

This study assesses the regional impact of climate change on runoff in a mountainous region of southwestern Bulgaria. A GIS-based distributed hydrologic model and two climate change scenarios - HadCM2 and CCC - were employed for years around 2025 and 2085. Results from both scenarios demonstrate the basin's sensitivity of runoff to climate change, which produce significant spatial and temporal changes in the basin's water yield with maximum runoff shift into early spring and further decreases in summer runoff. There could be no reduction in mean annual runoff, except under the Hadley scenario by 2085. Changes in the magnitude of mean monthly and peak flow are associated with early snowmelt and a reduction in snow cover in spring. Increases in spatial variability of runoff reflect the basin's complex physiographic characteristics. The increase of spatial and temporal variability in runoff points to different strategies for future water resource management.