Over the past 10 years, nitrogen concentration trends are downward at about half (16 out of 33) monitoring sites within the Bay watershed. The trend results indicate that in many locations, management actions, such as improved wastewater treatment and nonpoint-source pollution controls (i.e. urban stormwater runoff and agricultural runoff controls), have reduced nitrogen concentrations in streams. In addition, in the last 5 years, higher yields indicate a tendency to be located in the northern half of the watershed, conversely. lower yields are more numerous in the lower half of the watershed. The short-term flow-adjusted trends and yields indicator is calculated, and results and maps are published annually by the U.S. Geological Survey as part of a larger effort to determine loads and trends in nutrient and sediment concentrations and streamflow in the Chesapeake Bay watershed.
Date created: Mar 10 2011 / Download ( 4.32 MB )