Analysis of drought conditions and their impacts in a headwater stream in the Central European lower mountain ranges

Abstract

Headwaters represent a significant fraction of the global stream length and are important for streamflow quality and quantity. Since climate change is predicted to affect runoff generation processes fundamentally, it is essential to understand potential consequences for the water availability in headwater catchments. The Lehstenbach catchment, located in the Fichtel Mountains (Germany), represents many headwater catchments in the lower mountain ranges in Central Europe. This study’s primary objective is to predict and analyze potential shifts in the catchment’s water balance, estimate periods of hydrological drought conditions, and their characteristics. For this purpose, we used an integrated process-based hydrological model to represent surface/groundwater interactions and runoff generation mechanisms for the Lehstenbach catchment until 2100, using a Regional Climate Model Ensemble. The simulations indicate decreased water availability in summer and autumn, mainly due to increased evapotranspiration rates. The Minimum Environmental Flow (MEF), a quantitative measure of aquatic species’ exposition to abnormally low streamflow conditions, implies an increase of low flow conditions towards 2100. A first estimate indicates a possible increase of hydrological drought duration and intensity in the future. These findings suggest severe impacts on ecosystem health and services, such as decreasing water availability, leading to consequences like forest and wetland degradation and declining biodiversity. These findings can be used to implement suitable mitigation strategies to reduce climate change effects on the headwater ecosystems, such as water shortage for irrigation and drinking water supply and loss of flora and fauna.