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NWQI 200 Report


National Water Quality Inventory

In the US Environmental Protection Agency’s 2000 National Water Quality Inventory, 39 percent of assessed river and stream miles, 46 percent of assessed lake acres, and 51 percent of assessed estuarine square miles did not meet water quality standards in the US.  Most of the impairments were attributed to non-point source pollution, which includes both urban and suburban areas and construction sites.  Non-point source pollution includes, but is not limited to: nutrients, bacteria, metals, and oxygen-depleting substances.  Unaddressed illicit discharges add to this pollution burden.

US Clean Water Act of 1972

The US Clean Water Act of 1972 required the USEPA to pursue and eliminate point sources of pollution, or obvious sources of pollution.  At that time, many pollution problems could be attributed to polluted pipes draining directly to rivers.  The USEPA had addressed most of these point sources of pollution by the 1990s; however, over time, it became clear that non-point source pollution was a persistent water quality problem.

Non-point Source Pollution

Since the late twentieth century, the USEPA has been giving greater attention to non-point source pollution, dedicating funding to research on the origins and solutions to pollutants that are not concentrated in pipes, but dispersed over large watersheds.  These pollutants include stormwater, sediment, and nutrients.  Eutrophication and fisheries losses in the Chesapeake Bay and the Mississippi River Delta areas have spurred greater investments in research and technologies to reduce nitrogen and phosphorous loadings to these very large freshwater systems.  Furthermore, the extraordinary costs to remedy water quality conditions in these two systems has provided a strong incentive to prevent water quality degradation in other important waterbodies.  In North Carolina, knowledge and technology for addressing all forms of non-point source pollution are being applied due to a combination of greater environmental awareness and federal and state regulations.


DWQ Guide to Surface Freshwater Classifications

Designated Uses

The USEPA and the NC Department of Environment and Natural Resources, Division of Water Quality (DWQ) have several lenses through which they can diagnose the sources of pollution to impaired waters (those streams, rivers, or lakes with degraded water quality conditions).  One tool commonly used is the designation of “uses” for waterbodies.  For example, there are human health and ecological health standards that waters must meet in order to meet their uses (e.g. drinking water supply); if they fail to do so, they are considered “impaired” for that use.  Identifying the sources of these impairments is challenging, though the tools and solutions are improving every year.  Along with Florida, DWQ has taken the lead in the Southeast US in developing many tools and supporting new technologies that aim to identify pollution sources and address stormwater and nutrient pollution. 

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