The power of Open Data – Using free data for a preliminary screening of impact from urban wet-weather discharges on Danish streams

Integrated management of urban water have been promoted for decades at the European level, promoted by legislation such as the Water Framework Directive (2000/60/EC). Given the challenges to monitor the impact of urban wet-weather discharges (SSSO -Separate Storm Sewer Outlets and CSO - Combined Sewer Overflows) by using current protocols and techniques, complex integrated models have been proposed as effective tools for planning and implementing integrated solutions and for achieving the desired quality status (e.g. Gill et al., 2019). The implementation of these complex models, however, requires large resources for data collection, model implementation and validation. Thus, these tools are not suited for preliminary screening activities, where urban water managers need to identify critical areas for prioritizing their investments.
This study exploits data that are freely available in the Danish context (modelled flows in natural streams, and wet-weather discharges, measured concentrations) to perform screening of the potential threat posed by micropollutants to the chemical status of Danish natural streams. A simple river model, based on dilution and advection, allowed to identify stream stretches were Environmental Quality Standards (EQS) could potentially be exceeded as consequence of wet-weather discharges.
Although benefitting from a “rich data” context, the proposed approach can be adapted to the measured/modelled data in other countries to provide a first indication of the areas negatively affected by wet-weather discharges. This will allow a prioritization of available resources, enabling the implementation of integrated modelling and management approaches in the most critical areas.