Droughts can adversely affect water quality by e.g. leading to algal blooms, increased water temperatures, lowered dissolved oxygen concentrations or increased salinity and nutrient levels (Mosley 2015). While such negative influences have been documented for different case studies (e.g. Zwolsman & van Bokhoven 2007; Nosrati 2011; Van Vliet & Zwolsman 2008), little is known about spatial variations of drought effects on water quality depending on climate and catchment characteristics. New large-sample datasets providing information on water quality and quantity for a large number of catchments with a variety of climate and catchment characteristics might help to improve our understanding of variations in the impacts of droughts on water quality. This thesis aims to leverage a new dataset on water quality and quantity for Germany (Ebeling et al. 2022) to better understand the links between catchment characteristics, climate, drought occurrence, and water quality.

The analysis of spatial variations in the impacts of droughts on water quality relies on a novel dataset providing data on water quality and quantity at monthly resolution for 140 catchments in Germany (Ebeling et al. 2022). In a first step, it determines the effect of drought on different water quality parameters, e.g. nitrogen and phosphorus concentrations, for all catchments in the dataset to understand spatial and temporal variability in the relationship between droughts and different water quality parameters. In a second step, it tries to explain the spatial variations in drought-water quality relationships by climatic and physical catchment attributes and temporal variations by climatic drivers (also provided by the Ebeling et al. (2022) dataset). In a third step, the most important factors influencing the impact of drought on water quality will be identified.

You will improve your data management, visualization, statistical and R-programming skills by working with large-smaple datasets, producing informative maps, performing statistical/machine learning analyses, and adapting existing and developing new R-code.

Dr. Manuela Brunner (University of Freiburg, manuela.brunner@hydrology.uni-freiburg.de)

Manuela Brunner manuela.brunner@hydrology.uni-freiburg.de

English or German

1. Ebeling, P., Kumar, R., Lutz, S. R., Nguyen, T., Sarrazin, F., Weber, M., Büttner, O., Attinger, S., & Musolff, A. (2022). Water quality, discharge and catchment attributes for large-sample studies in Germany-QUADICA. Earth System Science Data Discussions, under review. https://doi.org/10.5194/essd-2022-6

2. Mosley, L. M. (2015). Drought impacts on the water quality of freshwater systems; review and integration. Earth-Science Reviews, 140, 203–214. https://doi.org/10.1016/j.earscirev.2014.11.010

3. Nosrati, K. (2011). The effects of hydrological drought on water quality (Vol. 348). IAHS Publ.

4. van Vliet, M. T. H., & Zwolsman, J. J. G. (2008). Impact of summer droughts on the water quality of the Meuse river. Journal of Hydrology, 353(1–2), 1–17. https://doi.org/10.1016/j.jhydrol.2008.01.001

5. Wolff, E., & van Vliet, M. T. H. (2021). Impact of the 2018 drought on pharmaceutical concentrations and general water quality of the Rhine and Meuse rivers. Science of the Total Environment, 778. https://doi.org/10.1016/j.scitotenv.2021.146182

6. Zwolsman, J. J. G., & van Bokhoven, A. J. (2007). Impact of summer droughts on water quality of the Rhine River - A preview of climate change? Water Science and Technology, 56(4), 45–55. https://doi.org/10.2166/wst.2007.535