Water quality regulation: Overview

Abstract

Water quality has deteriorated in many parts of the world with intensive agricul- tural practices. Nutrients in agricultural runoffare carried towards streams, lakes and coastal areas and cause there serious eutrophication problems, with fish kills and loss of biodiversity as consequences. Wetlands in agricultural catchments have a robust potential to improve water quality by removing nutrients from the agricultural runoff. Creation and restoration of wetlands in the landscape have reduced nitrogen and phosphorus loads downstream by particle trapping, adsorp- tion and nitrification/denitrification processes. Such wetlands should be designed in a way that connects them with surface and subsurface runoffflows. These wetlands have been shown to enhance biodiversity at the landscape scale because they provide habitat for plants, aquatic macrofauna and birds. The wetlands could potentially result in emissions of nitrous oxide and methane, but these do not constitute a major environmental risk at the catchment scale. The benefits in terms of water purification and biodiversity enhancement by far outweigh these risks.