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Non-tidal areas in the Chesapeake Bay region are defined as areas where water is not affected by the tides of the Atlantic Ocean. These freshwater areas are located above the fall line: the physical barrier west of the Bay that’s marked by waterfalls and rapids. The major tributaries on the western shore that cut a path through the fall line include the Potomac, Patuxent, Rappahannock, York and James rivers. All of these tributaries have both tidal and non-tidal portions. One river in particular – the Susquehanna north of the Bay -- is entirely non-tidal. This tributary alone contributes approximately 50% of the freshwater flow to the mainstem Bay. Because so much freshwater flows into the Bay, the water quality in non-tidal areas is of extreme importance. Freshwater flows carry nutrients (nitrogen and phosphorus) and sediment to the Bay. Though this is a natural process, the actions of people on land can increase the amounts of these Bay stressors. Nutrients can reach the non-tidal portions of rivers either through point sources (industrial or municipal wastewater facilities) or nonpoint sources (runoff from urban, suburban and farm lands). Besides the reduction of actions that contribute to nutrient pollution, another defense that can help to protect rivers is a forest buffer. Vegetation near water can consume nutrients. Sediment can reach non-tidal areas through many sources. Of particular concern is the capacity of the Susquehanna River’s hydroelectric dams to continue to trap sediment and prevent it from flowing downstream. These dams are in danger of completely filling in sometime within 20 years. Because of the importance of non-tidal areas in the health of the Bay, the Chesapeake Bay Program in partnership with agencies including the USGS and the Susquehanna River Basin Commission measure water flow and nutrient concentration, load and yield. These measurements are made at the fall lines of each of the major rivers, as well as at a few stations farther up into the non-tidal portion of each tributary, and they help the Bay partners in making management decisions. To bookmark this page, please use this URL: http://www.chesapeakebay.net/nontidal.htm For more information, contact the Chesapeake
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