A large number of (organic) micropollutants - comprising hundreds of veterinary and human pharmaceuticals, agricultural pesticides as well as non-agricultural biocides - are a potential threat to the quality of surface water as well as groundwater. Due to the large diversity of compounds and sources their assessment and management at the catchment scale are challenging tasks. For many catchments, modeling approaches and monitoring concepts have to account simultaneously for urban and agricultural sources and transport processes. Often, interpreting measured data suffers from a lack of reliable use data and the fact that monitoring programs can only cover a small selection from the diversity of compounds. Hence, much less empirical data are available compared to e.g., nutrients (N, P). Accordingly, our knowledge is in many cases qualitative and limited to the reporting of substance concentrations at a few selected locations and few moments in time.

Therefore, this session aims at contributions that improve our quantitative understanding of the mass fluxes, the fate and transport of micropollutants at the catchment scale. The latest developments in modeling, process studies and monitoring shall be discussed. Special emphasis shall be put to quantitative approaches integrating urban and agricultural sources. Topics to be discussed cover issues like:

- Novel monitoring concepts like passive sampling.
- Integrated transport modeling for mixed urban and agricultural catchments representing all relevant sources and pathways
- Approaches and data on source quantification of micropollutants at the catchment scale
- Validation of model predictions with empirical data
- Optimal combination of modeling and monitoring to assess water quality with respect to micropollutants
- Uncertainty in the assessment for ungauged or poorly gauged catchments