Soil and Water Conservation

Johnston County, North Carolina

Wetlands and Water Quality

Wetlands help regulate and maintain the hydrology of our nation's rivers, lakes and streams by storing and slowly releasing flood waters. They help maintain the quality of water by storing nutrients, reducing sediment loads and reducing shoreline erosion.

Runoff from agricultural lands after the application of fertilizers and animal wastes is a major source of phosphorus and nitrogen contamination of surface waters of the United States. Phosphorus and nitrogen input to lakes and reservoirs can degrade water quality in these systems by promoting algal blooms and nuisance aquatic plant growth. Concentrations of nutrients can be altered, by uptake, cycling and dilution. For example, nitrogen and phosphorus cycle from the water to the plants to the sediment in the wetland ecosystem. Wetlands, because they are found between agricultural lands and water bodies often intercept runoff, thus capturing the nutrients in the wetland and preserving the water quality of the receiving waters.

One of the major functions of wetlands is the removal of suspended sediment from water traveling through the wetlands. Flow velocity of the water is decreased as its movement changes from channel flow to sheet flow in the wetland. The decrease in velocity and the presence of vegetation promote fallout of suspended particles. Deposition of sediment can result in removal of nutrients and toxins from an environment.

These substances are taken up by plants in the wetland. Substances such as pesticides undergo a variety of physical, chemical and microbial processes which break down their molecular structure.

It is possible for moving sediment to tie up dissolved nutrients and toxins in addition to that which it is already carrying from its origination point. Substances not readily decomposed by chemical or microbiological processes, may ultimately be removed from interaction with the water column when buried by sediment.

Wetlands are transitional lands between terrestrial and aquatic systems where the water table is usually at or near the surface, or the land is covered by shallow water. The water saturation plays a major role in determining the nature of soil development and the types of plants and animals that make wetlands their home.

With their strategic locations between bodies and high ground, wetlands buffer shorelines from erosion and act as a sediment trap from upland erosion. Wetlands, because of their interrelationship with both the land and water, are of increasing importance.

With many ways that wetlands act to preserve the environment, a new outlook on the value of wetlands has evolved.

For more information on protecting and enhancing wetlands in your community, contact your local soil and water conservation district or the Conservation Technology Information Center, 1220 Potter Drive, Room 170, West Lafayette, IN 47906-1383.

(Information provided by: Soil and Water Conservation)