Use of wetlands, ponds and buffer zones in Finland

Summary in the original language of the document

Main purpose of the CWs (constructed wetlands) for the treatment of runoff from agricultural areas is to reduce nutrient loading to surface waters and hence combat eutrophication.
The most important single design parameter controlling retention effectiviness of a CW is its area in relation to the catchment area.
Input concentrations, catchment properties(soil type!), hydraulic efficiency and CW soil properties also have a significant influence on the effectiviness.