Analysis of the impacts of droughts on the water quality of the transboundary German-French Lauter catchment with SWAT

Current state-of-art studies have been largely focusing on analysing how headwater catchment characteristics influence the sensitivity of the water yield in response to climate change. However, there has been little research combining both hydrological analysis with in situ water quality assessment and understanding how extreme climate events could influence the water quality of the headwater catchment, especially under anthropogenic stress. Therefore, this research aims at understanding the mechanisms of how different types of droughts modify the water quality of an anthropogenically impacted catchment.

The research is performed on the Lauter river, which takes its source from two headstreams, the Scheidbach and the Wartenbach in the Palatinate Forest, Rhineland-Palatinate and flows between the French-German border and ultimately flow into the Rhine River. The discharge time series of 59 years and water quality data of 48 years are being analysed. We will present the methodology of the research and current updates on the progress. The research is planned to proceed in three steps, 1) understanding the water partitioning mechanism and defining different drought types by using the SWAT (The Soil & Water Assessment Tool), 2) studying the water quality behavior under different hydrologic scenarios by conducting in situ water quality monitoring experiments, 3) predicting the water quality trend under future climate change and anthropogenically impacted scenarios. Current results include water quantity trend analysis based on the daily flow rate data at the Salmbacher Passage measuring station on the Lauter river and a primary catchment modeling result with the SWAT.

Keywords: Drought, Water quality, SWAT model, Headwater catchment