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Pollution Loads and Trends in Rivers: The U.S. Geological Survey (USGS) monitors nutrient and suspended sediment pollution loads delivered from the large watersheds located upstream of nine river input monitoring (RIM) stations to the Chesapeake Bay. Together, these stations—which are located on the Appomattox, Choptank, James, Mattaponi, Pamunkey, Patuxent, Potomac, Rappahannock and Susquehanna rivers—reflect loads delivered to the Bay from 78 percent of its 64,000-square-mile watershed. According to data from the program, nutrient and sediment pollution loads measured in water year 2013 (which took place between Oct. 1, 2012, and Sept. 30, 2013) were below long-term averages.

Water Quality Standards Achievement in the Tidal Chesapeake Bay: The Chesapeake Bay Program measures progress toward the achievement of water quality standards in the Chesapeake Bay and its tidal tributaries using three environmental factors: dissolved oxygen, water clarity or underwater grasses, and chlorophyll a. These data are assessed in three-year periods and combined into a single environmental indicator that tracks changes in Bay health over time. After more than a decade of steady improvement between 1989 and 2002, the attainment of water quality standards has seen mixed results. Changes seen in the past 10 years have shown no statistically significant patterns, fluctuating between 29 and 40 percent. Results of the 2011 to 2013 assessment period indicate that 29 percent of the water quality goals for the Bay were met during this period.

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