Over the past 10 years, 49 percent of sites show little change while 41 percent show degrading flow-adjusted sediment concentrations. Between 2003 and 2012:
For more information go to the U.S. Geological Survey's webpage, Summary of Trends and Yields Measured at the Chesapeake Bay Nontidal Network Sites: Water Year 2012 Update
Sediment concentrations are highly variable, depending on the amount of water flowing in streams and rivers throughout the Bay watershed. Therefore, scientists calculate flow-adjusted trends to determine whether concentrations have changed over time. By removing the effects of natural variations in streamflow, resource managers can evaluate the changes in stream health that may result from erosion and runoff controls or other changes within the watershed.
The goal is to observe downward trends in flow-adjusted sediment concentrations at monitoring sites across the Bay watershed.
The U.S. Geological Survey (USGS), works with partners in the Chesapeake Bay Program (CBP) to operate the Nontidal water-quality monitoring network. This network is designed to measure changes in nutrients and sediment in the Chesapeake Bay watershed. The nutrient and sediment data are updated and interpreted each year. The update of 2012 information includes:
Because the goals of Bay restoration efforts are to reduce nitrogen, phosphorus and sediment reaching the Bay, downward trends in concentration are considered improving conditions, while increasing trends are considered degrading conditions. The major findings for nutrient and sediment concentration trends and yields in the Chesapeake Bay watershed through 2012 are:
US Geological Survey