Ecotechnological measures to control nutrient losses from catchments

Ecotechnological measures allow to use different natural and seminatural ecosystems to control nutrient losses from intensively used watersheds. The most effective means are buffer strips, buffer zones and constructed wetlands. In southern Estonia a 31 m wide buffer zone of wet meadow and grey alder forest removed 50% nitrogen and 78% phosphorus, while in a 51 m buffer zone, also containing a grassland strip in addition to wet meadow and alder forest, 87 % N and 84 % P was retained. The outflow of total - N was 4.9% and outflow of total - P was 4.8% lower in well-buffered watershed in comparison to similar watershed with lower buffering ability. Three constructed wetlands in southern Estonia were studied. The removal efficiency was 76 - 84% for BOD5, 39 - 70% for total-N, 73 - 83% for total-P. All results show that compared to other seasons the winter performance was not reduced.