Abstract Background Heavy rainfall causes not only high water levels and discharge but can also lead to the mobilization of sediments and pollutants to rivers. In contrast, droughts with low discharge can impair water quality due to minimized dilution. Both extremes—heavy rainfall as well as droughts—are aggravating under climate change; thus, it is important to understand the processes as well as the meteorological and hydrological preconditions that lead to elevated concentrations of sediments and pollutants. This study aimed at identifying event types that cause high discharges, and increased concentrations in suspended sediment and changing pollutant concentrations in a large river. We use a long-term (2010–2022) data set of high-resolution precipitation, discharge, suspended sediment concentrations as well as 14-day composite sample concentrations of six organic micropollutants (OMPs) in the central European Moselle River. Results By means of principal component analysis and cluster analysis, we identified typical as well as atypical events with high suspended sediment concentrations. The cluster analysis clearly identified a cluster of high-magnitude events with high discharge, precipitation amounts and high suspended sediment concentrations, which mainly occurred in winter. However, single atypical high-magnitude events such as the one associated with the July 2021 floodings in Western Europe also occurred in summer. For OMPs, the cluster analysis showed less clear results. Yet, general differences in concentrations dynamics related to high discharge regimes were identified for the herbicide metabolite metazachlor ESA and the pharmaceutical carbamazepine. Conclusions Our results show that the methodology is a powerful tool for the identification and characterization of high-magnitude suspended sediment transport and discharge events. However, it is limited by data availability for most OMPs. Nonetheless, the data set helped us to identify relevant time periods of high OMP concentrations in line with observations made in smaller catchments or for shorter observation periods.
Uber et al. (Tue,) studied this question.