Approximately 30 percent of Wisconsin's wetlands are connected or adjacent to lakes and streams. Because wetlands are a principal conduit for precipitation flowing to lakes and streams, their contributions to water quality, water supply, flood control, erosion control, flora and fauna and overall importance to the food chain are significant. The water quality of the wetland itself will determine other important values such as wildlife habitat and aquatic life support. Three functions important to water quality are sediment trapping, nutrient retention and removal, and flood water attenuation and storage. Sediment Trapping Sediment trapping is the process by which particulate matter of any size is retained and deposited within a wetland.
Water running off upland areas picks up particles of soil and other debris as it moves downhill.
Important factors in wetland sediment trapping are the location and size of the wetland. Wetlands adjacent to streams and lakes, near the mouth of a drainage basin or downslope from nonpoint sources of pollution have a greater opportunity to trap sediments than wetlands high in a drainage basin. Nutrient Retention and Removal Wetlands help protect surface water from nutrients and other pollutants which degrade surface water quality. Phosphorus and nitrogen are taken up and stored in the plant. Nitrogen is also retained by the biochemical process of denitrification and is removed from wetlands by conversion to its gaseous form.