Catchments in Saxony differ regarding their physiographic characteristics (topography, geomorphology, geology, land use, soils, etc.) and their climatic boundaries. Both factors influence the flow behavior and the water balance components of catchments. How sensitive the water balance of catchments responds to current and future changes in the climatic boundary conditions is difficult to predict for each catchment and is associated with significant uncertainties. In Saxony, the pronounced drought in groundwater and surface water from 2018 to 2020 led to considerable regional problems in water supply and quality.

Schwarze et al. (2017) already investigated trends of the observed discharge and variables derived by hydrograph separation (e.g. baseflow) in a sensitivity study. In this presentation, we show the results of an extension of this analysis with current observation data until 2020. The following research questions are investigated: (i) Are catchments in Saxony already responding to changing climatic conditions? (ii) Which regions show the most significant changes in discharge behavior relative to other water balance components? (iii) What are the factors and drivers of changes in the water balance in Saxonian Catchments?

The study is based only on observational data for precipitation, temperature, and discharge in the period of 1961 to 2020 in Saxony. Break point analysis, hydrograph separation, and sensitivity analysis of hydrological signatures are performed for different sets of climate periods to quantify changes and elasticity of the water balance components. As a result, a decreasing trend for the mean flow can be seen for almost all 88 investigated and undisturbed catchments in Saxony. This trend is more pronounced in the mountainous regions than in the lowland of Saxony. Despite the slight increase in the mean annual precipitation, the temperature rise of about one °C from 1991-2020 compared to 1961-1990 in all catchments leads to an increasing evapotranspiration, reduced discharge, and groundwater recharge.