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Near Record Nutrient and Sediment Loads in the Major Rivers Entering Chesapeake Bay in 2003Prepared by the U.S. Geological Survey (5/18/2004); updated 8/23/2004— Document in PDF Format In 2003, nutrient and sediment loads entering the tidal watershed of the Chesapeake Bay from its principle rivers, were the second highest since 1990, according to the U.S. Geological Survey (USGS). The loads were influenced by near-record river flow to the Bay in 2003. The increased nutrient and sediment loads resulted in less light in the Bay waters, which contributed to a decline of submerged aquatic vegetation (SAV). The increased nutrient loads also contributed to large areas of low dissolved oxygen levels in the Bay during the summer of 2003.
In 2003, the loads at the nine river-input sites were 353.6 million
pounds (Mlbs.) of nitrogen, 30 Mlbs of phosphorus, and 18,169.9 Mlbs
of sediment (see graph and table below). The loads at the River-Input
sites represent about 60 percent of the total load that enter the
tidal waters of the Bay watershed.
In 2003, the loads from the nine major rivers entering the Bay were much higher than in 2002, and contained about 3 times the amount of nitrogen, 5 times the amount of phosphorous, and 11 times the amount of sediment. The loads were higher due to both the near-record river flow and an increase in nutrient and sediment concentrations in the rivers. The increased nitrogen concentrations were a result of higher amounts of nitrogen being flushed from the land and ground water. Increased sediment and phosphorus concentrations were caused by the substantial erosion of sediment from the land and streams. So far in 2004, flow to the Bay has been near average therefore sediment and nutrient loads could be less than in 2003. The USGS has developed statistical techniques to compensate for the natural changes in river flow, so we can better understand progress related to management actions. Using these techniques, preliminary results of trends through 2003 from the nine River-Input sites show improvements in nitrogen and phosphorus concentrations at about half of the sites. There were declines in total nitrogen concentrations at 4 rivers stations, including the Susquehanna, Potomac, and James Rivers, which comprise about 90 percent of the river flow that enters the Bay. Total phosphorus concentrations also declined at four sites, including the Susquehanna and James rivers. More information about USGS activities related to Chesapeake Bay can be found at http://chesapeake.usgs.gov or by contacting Scott Phillips (swphilli@usgs.gov)
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