The 248 km2 Mondsee catchment, close to the Austrian city Salzburg, is located at the border between the European Alps and the hilly alpine foreland with a dozen of mid-sized lakes. The grassland and forest dominated catchment is characterised by a very dense river system of approximate 2 km/km2 (490 km rivers and ditches), embedded in steep slopes and heavy soils causing fast surface runoff, especially during extreme weather events (thunderstorms, snow melting). Due to the fast response time, villages like Thalgau along the Fuschler Ache, or St. Lorenz close to Lake Mondsee are at risk of being flooded. During extreme events wide floodplains trigger nutrient runoff, causing a water quality challenge for Lake Mondsee. The current trophic status of Lake Mondsee is oligo-mesotrophic, but it repeatedly failed to reach the 'good ecological status' requested by the European Water Framework Directive.