The ecohydrological approach, SWAT modelling, and multi-stakeholder engagement - A system solution to diffuse pollution in the Pilica basin, Poland.

The reduction of diffused nutrient pollution from agriculture is one of the defining challenges of our time, demanding system solutions. A nitrogen and phosphorus (N&P) reduction strategy at the catchment scale is the most realistic and effective long-term approach to eutrophication management. In this study, a voluntary programme for the reduction of diffuse pollution was developed for the Pilica catchment and the Sulejów Reservoir in Poland. The Action Plan was based on the ecohydrological approach, which strives to use ecosystem processes as a management tool. One fundamental element of the Plan was a SWAT model, used to estimate N&P emissions and to determine the priority areas in the catchment. Strong cooperation between water managers, interdisciplinary researchers, and stakeholders helped to catalyse the capacity-building process of public participation, through dialogical interaction including a critical exchange of knowledge. Finally, a list of selected spatially-targeted mitigation measures was generated based on the modelling results and following measure acceptance by stakeholders. The key assumption in the creation of the measure list was that ecohydrological nature-based solutions (NBS) should be used complementarily to good agricultural practices. Such an approach has contributed to a faster achievement of 'good ecological status' of water bodies.