Excerpt from Chesapeake Bay Program's October press release:

Tidal and Nontidal Water Quality

The U.S. Geological Survey works with partners from D.C. and the watershed states to monitor nitrogen, phosphorus and sediment pollution entering the Chesapeake Bay from its 64,000-square-mile watershed. Stream flow and water quality conditions have been measured at River Input Monitoring (RIM) stations located on the nine largest tributaries of the Bay since 1985. Over time, the monitoring network has expanded to more than 100 non-tidal stations across the region.

Pollution amounts vary from year to year due to a number of factors, including land use, fertilizer and manure use, wastewater and septic discharges, and river flow. Monitoring data from the nine RIM stations represent the amount of nitrogen, phosphorus and sediment that is entering the Chesapeake from 78% of its watershed, while the remaining 22% of pollution entering the Bay is estimated through combining data from wastewater treatment plants and computer-simulated estimates of nitrogen and phosphorus pollution from nonpoint sources.

River Flow, Pollution Loads and Trends

In 2022, average river flow to the Bay measured 47.2 billion gallons per day, a decrease of 7.6 billion gallons per day from the previous year, bringing 253 million pounds of nitrogen, 13.4 million pounds of phosphorus and 14.2 billion pounds of sediment into the Chesapeake. These are decreases from the previous year (2021) of 11.5%, 33% and 20%, respectively.

The U.S. Geological Survey assesses trends in nitrogen, phosphorus and sediment pollution entering the Bay from the nine RIM stations to produce short-term trends. The most recent short-term trends, from 2013-2022, show a mix of improving and degrading conditions throughout the watershed.

• Trends in nitrogen indicate improving conditions at four stations (James, Patuxent, Potomac, Susquehanna), degrading conditions at four stations (Appomattox, Choptank, Mattaponi, Rappahannock) and no trend at the Pamunkey station.
• Trends in phosphorus indicate improving conditions at three stations (Patuxent, Potomac, Susquehanna), degrading conditions at three stations (Appomattox, Choptank, Rappahannock) and no trend at the James, Mattaponi and Pamunkey stations.
• Trends in sediment indicate improving conditions at three stations (Pamunkey, Patuxent, Susquehanna), degrading conditions at four stations (Appomattox, Choptank, Mattaponi, Rappahannock) and no trend at the James and Potomac stations.

The U.S. Geological Survey also analyzes short-term trends in nitrogen, phosphorus and sediment pollution at the non-tidal stations throughout the watershed. The following are the most recent short-term trends, from 2011-2020.

• Thirty-eight percent of 89 non-tidal network stations showed an improvement in the amount of nitrogen pollution, whereas 42% were degrading and 20% showed no change.
• Forty-four percent of 70 non-tidal network stations showed an improvement in the amount of phosphorus pollution, whereas 23% were degrading and 33% showed no change.
• Eighteen percent of 70 non-tidal network stations showed an improvement in the amount of sediment pollution, whereas 46% were degrading and 36% showed no change.

“The River Input Monitoring stations and non-tidal monitoring network are critical to the partnership for documenting how water quality conditions are changing across the watershed,” said Ken Hyer, Chesapeake Bay coordinator with the U.S. Geological Survey. “While the results show progress in many rivers, they also highlight that the partnership has more work ahead of it.”