Näringsläckage från åkermark inom Brååns dräneringsområde : lokalisering och åtgärdsförslag

The river of Bråån is heavely polluted by nutrient leakage from arable land. The aim of this study is to propose measures designed to reduce nutrient transport within the dranaige basin (165 km2). Leaking areas of the arable land were located and measures were suggested where they would be most effective. The west part of the basin tends to leak more through the soil profile as a result of very intense farming on land mostly drained by covered drains. Leakage caused by overland flow is mainly due to rill erosion in the western part of the basin, were the slopes are long and without obstacles to the eroding water. In the eastern part, by contrary, the topography is more complex and the land use of more various kind, which reduce rill erosion. However, the fields of the east are often closely adjacent to open diches. The risk for leakage by sheet erosion is consequently great. The methods suggested in order to reduce the pollution of nutrients are mostly "natural nutrient traps", such as wetlands, ponds and riparian zones. In fields where the leakage is assumed to be very severe agricultural measures are suggested, e.g. regulated manuring, cultivation of grass or capture crops and the use of special cultivation methods. In all 27 ponds, 20 horseshoe wetlands, 2 moorland forests, 6 areas of submerged meadow-land, 82 km of riparian zones and 17 km2 with agricultural measures are suggested to be introduced within the Bråån drainage basin.