Water: Outreach & Communication
Wetlands and Runoff
Since wetlands are typically the lowest area on the landscape, they often receive runoff from surrounding land. Several of the key programs that address such pollution are discussed in this fact sheet.
Polluted runoff (sometimes called "stormwater" or "nonpoint source pollution") is caused by rainfall or snow melt moving over and through the ground. Runoff carries natural and manmade pollutants into low areas such as wetlands, lakes, streams, and eventually into ground water. In addition, atmospheric deposition and hydrological modifications can contribute pollutants to runoff as well as directly into surface water. The quality of U.S. wetlands and other water resources is related to the quality of the environment contributing to these waters. However, programs have historically focused on single goals or small sets of goals. These programs have succeeded in identifying and controlling, to some degree, the larger point sources of pollution. EPA has expanded its focus to use an approach that addresses the interconnections between water resources and the land, air, and water environment surrounding the resources.
Untreated Runoff Impacts to Wetlands
Untreated runoff from agricultural land, urban areas, and other sources is a leading cause of water quality impairment. Siltation; pollutants; excess nutrients; and changes to water flows, such as more frequent inundation, and increased turbidity, are responsible for most of the impacts to wetlands from runoff.
Impacts to wetlands have resulted in consequences such as changed species composition, increased pollutant loadings (e.g., heavy metals), and replacement of complex wetland systems with less desired open water. Modifications of wetlands associated with some runoff management practices have resulted in significant impacts to wetlands. Some impacts have been particularly tragic, such as in Kesterson and Stillwater Wildlife Refuges, where untreated, contaminated runoff resulted in mortality and deformities of wildlife populations, particularly fish and migratory birds.
EPA has developed technical information that landowners can use to protect the many functions of wetlands, including water quality improvement. In July 2005 EPA developed a guidance document intended to provide technical assistance to state, local, and tribal program managers and others on the best available, economically achievable means of reducting nonpoint source pollution of surface and groundwater through the protection and restoration of wetlands and riparian areas entitled, National Management Measures to Protect and Restore Wetlands and Riparian Areas for the Abatement of Nonpoint Source Pollution, EPA 841-B-05-003 (also available as a PDF (204 pp, 7.16MB)). An issue paper from February 1993 entitled Natural Wetlands and Urban Stormwater: Potential Impacts and Management (PDF) (84 pp, 207K), highlights the impacts of stormwater on wetlands. Other information that can be obtained includes the October 1996 publication, Protecting Natural Wetlands: A Guide to Stormwater Best Management Practices (PDF) (181 pp, 2.2MB), which describes best management practices to pretreat stormwater runoff before it enters a natural wetland. Additional materials on wetlands protection and restoration for nonpoint source benefits will be developed to assist in implementation of the wetlands and riparian areas chapter in the Coastal Zone Act Reauthorization Amendments (CZARA) Management Measures Guidance. Fact sheets entitled Nonpoint Pointer 11 - Managing Wetlands to Control Nonpoint Source Pollution and Stormwater Wetland are also available. EPA will continue to work to address potential opportunities and conflicts regarding wetlands and programs addressing runoff.
To Use or Not To Use Wetlands for Treatment?
Because wetlands have a natural water quality improvement function, there has been a tremendous amount of interest in using wetlands to treat runoff from urban areas, agricultural lands, and other pollutant sources. However, the critical question is, "What can wetlands safely handle before they are contaminated or their functions degraded?" There are significant opportunities to protect and restore wetlands and riparian areas as one part of programs addressing runoff. While wetlands do provide valuable water quality protection for downstream rivers, lakes, and estuaries, the quality of the wetlands, as waters of the United States, should also be protected.
Decisions that might route runoff into wetlands, either inadvertently or by design, should be carefully evaluated, and adequate wetlands protection should be provided, including avoidance of the wetlands, use of best management practices (BMPs), and monitoring to observe how well the BMPs work.
For additional information about the Section 402 stormwater program, visit the National Pollutant Discharge Elimination System (NPDES) Stormwater Program website.