Assessment of hydro-meteorological drought in the Danube Plain, Bulgaria

Abstract

The purpose of this study is to evaluate occurrences of hydro-meteorological drought in the Danube Plain territory, located in northern Bulgaria. As a natural hazard, drought is best characterized by multiple climatological and hydrological parameters. In this study, meteorological drought is analyzed with the Standardized Precipitation Index (SPI), and hydrologic drought is defined by the Streamflow Drought Index (SDI). Both indices are calculated on a time scale of 6 to 12 months over the 1993–2009 period. Future drought occurrence probability is analyzed for two periods: 2021–2050 and 2051–2080 by downscaling the data from regional model KNMI. The results based on the SPI and SDI showed that almost all the investigated areas suffered from mild to moderate droughts during the study period. It is expected that there will be an increasing frequency of occurrences of moderate drought during the second half of 21st century.