American agriculture is noted worldwide for its high productivity, quality and efficiency in delivering goods to consumers. When improperly managed, however, activities from working farms and ranches can impact local and far-field water quality.  The National Water Quality Assessment shows that agricultural nonpoint source (NPS) pollution is the leading source of water quality impacts on surveyed rivers and streams, the third largest source for lakes, the second largest source of impairments to wetlands, and a major contributor to contamination of surveyed estuaries and ground water.  Agricultural activities that cause NPS pollution most generally occur in the absence of a conservation plan. Impacts can be generated from activities such as poorly located or managed animal feeding operations and manure, overgrazing, plowing too often or at the wrong time and improper application fertilizer.

The erosion of shorelines and streambanks is a natural process that can have either beneficial or adverse impacts on the creation and maintenance of riparian habitat. Excessively high sediment loads can smother submerged aquatic vegetation, cover shellfish beds and tidal flats, fill in riffle pools, and contribute to increased levels of turbidity and nutrients.

Runoff controls are essential to preventing polluted runoff from roads, highways and bridges from reaching surface waters. Erosion during and after construction of roads, highways and bridges result in the deposition of sediment that can smother aquatic habitat and clog waterways.

Heavy metals, oils, other toxic substances and debris from construction traffic and spillage can be absorbed by soil at construction sites and carried with runoff water to lakes, rivers and bays.

Runoff control measures can be installed at the time of road, highway and bridge construction to reduce runoff pollution both during and after construction. Such measures can effectively reduce the entry of pollutants into surface waters and ground waters and protect their quality, fish habitats and public health. Pesticides and fertilizers used along roadway rights-of-way and adjoining land can pollute surface waters and ground water when they filter into the soil or are blown by wind from the area where they are applied.

Wetlands and riparian areas typically occur as natural buffers between uplands and adjacent water bodies. They act as natural filters of nonpoint source pollutants, including sediment, nutrients, pathogens and metals, to waterbodies, such as rivers, streams, lakes and coastal waters. It is important to preserve and restore wetlands and riparian areas because these areas can play a significant role in managing adverse water quality impacts. Wetlands, including depressional wetlands, and riparian areas help decrease the need for costly stormwater and flood protection facilities.