Assessment of the hydrological drought risk in Lithuanian sub-basins
by Serhii Nazarenko (Lithuanian Energy Institute)
Hydrological drought is becoming an increasingly prevalent issue in our modern world, with climate change and human activities exacerbating the frequency and severity of these events, and its consequences are: leading to water scarcity, food insecurity, and economic losses. To solve these consequences, it is critical to know the territories that are most under the hydrological drought influence. A hydrological drought risk assessment map can solve this problem and detect potentially vulnerable sub-basins.
The object of investigation is Lithuania, whose area is 65,200 square kilometers and includes more than 22,000 rivers. Lithuania is divided into three hydrological regions (Western, Central, South-Eastern) and 15 main basins, but the main analysis was based on over 550 small sub-basins.
Hydrological drought risk consists of drought hazard and drought vulnerability components. In this study, both components consist of eight sub-basin variables (four in each). Hazardous variables include the number of short-term and long-term hydrological drought, precipitation, river dependence on precipitation and vulnerability components are land cover, slope, dominant soils of sub-basins, lake percentage. For drought hazard analysis, variables based on point data from water gauging stations and meteorological stations were used, which were interpolated in GIS software. The variables from the drought vulnerability component were divided into classes, depending on their influence. Rescaling was applied to all variables to bring them to one scale, and each sub-basin was assigned the average value of the variable. To combine all spatial layers of the variables, overlapping was used in GIS. The hydrological drought risk assessment map of the sub-basins was considered at three levels: large scale (sub-basins), medium scale (15 main basins), and small scale (three hydrological regions).
The results show that the sub-basins in the central hydrological region of Lithuania have the highest degree of risk compared to those in the western and southeastern regions. The obtained results will enable measures to be taken in advance to increase the resistance of sub-basins to future hydrological droughts.