New investigative monitoring tools for assessing the chemical and ecological state of groundwater within drinking water catchments

The incorporation of the World Health Organisation's water safety plans into German law through the groundwater catchment regulations (Trinkwassereinzugsgebietsverordnung), which will come into effect in 2025, will allow for, but also demand, new investigative groundwater monitoring tools. As part of the BMBF project iMolch, new tools and strategies are being developed to enable sustainable groundwater management. These tools will provide new insights into the ecological and chemical status of drinking water catchments. Two catchments within the Düsseldorf water supply network will be presented as examples. Both are affected by multiple land uses and different proportions of bank filtration from the Rhine. To evaluate the chemical status, non-target analytical methods are compared with hot target analytical methods based on the principle of indicator compounds (over 136 organic micropollutants) and main water chemistry. The ecological status will be investigated using an improved DAC index and beta diversity. Community composition was analysed using 16S rRNA gene sequencing; cell density was measured using flow cytometry; and internal ATP was determined using the BacTiter-Glo microbial cell viability assay. Principal component analysis (PCA) is used to analyse the ecological data and non-target chemical analytics, and the results are presented and discussed. The impact of floods in the Rhine on the groundwater composition was evaluated using both chemical and ecological data. Furthermore, it was possible to calculate the amount of bank filtrate in the individual supply wells based not only on the indicator compounds, but also on the ecological data.