Published: January 01, 2000
The major factors affecting the trends were changes in nutrient sources and natural variations in streamflow. The dominant source of nitrogen and phosphorus from 1985 to 1998 in six of the seven tributary basins to Chesapeake Bay was determined to be agriculature. Because of the predominance of agricultural inputs, changes in agricultural nutrient sources such as manure and fertilizer, nutrient sources such as manure and fertilizer, combined with decreases in agricultural acreage and implementation of best management practices (BMPs), had the greatest impact on the trends in flow-adjusted nutrient concentratons. Urban acreage and population, however, were noted to be increasing throughout the Chesapeake Bay Watershed, and as a result, delivered loads of nutrients from urban areas increased during the study period. Overall, agricultural nutrient management, in combination with loads and the phosphate detergent ban, led to downward trends in flow-adjusted nutrient concentrations at many of the monitoring stations in the watershed.
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Originator: US Dept of Interior/USGS