Informing Chesapeake Bay Watershed Management by Monitoring Trends in River Nutrient and Sediment Loads
The USGS has computed nutrient and suspended-sediment loads and trends through water year 2023 in Chesapeake Bay rivers. These monitoring-based estimates help federal, state, and local managers evaluate and plan water-quality restoration strategies.
Issue
Watershed managers are working to reduce the load, or amount, of nutrients and suspended sediment in Chesapeake Bay rivers to meet the region’s clean-water goals. These restoration efforts rely on accurate information about the load of nutrients and suspended sediment in Chesapeake Bay rivers. The Chesapeake Bay nontidal monitoring network (NTN) addresses this need by measuring the load of nutrients and suspended sediment in rivers at 123 stations throughout the watershed. With at least ten years of monitoring data, trends are computed to determine if nutrient and suspended-sediment loads are getting better or worse over time.
USGS Study
The USGS partners with federal, state, and local agencies to collect more than 2,000 water-quality samples from 123 NTN stations each year. Every other year, the USGS uses these samples and daily streamflow measurements to compute nutrient and suspended-sediment loads and to assess trends in how these loads have changed over time. The most recent load and trend assessment includes monitoring data collected from water years 1985 through 2023 (a water year is from October 1 through September 30 of the following calendar year). Long-term trends are computed using this full range of data. Short-term trends are computed on the most recent 10-year window, in this case, from water years 2014 through 2023. Trends are categorized as “improving” if loads have decreased over time and as “degrading” if loads have increased over time. Stations are assigned a “no trend” result if there is no statistically meaningful change in load over the period. Trends are computed from “flow-normalized” loads to remove most year-to-year variability in load caused by streamflow.
Major Findings
- Loads: After accounting for differences in load caused by watershed area, nutrient and suspended-sediment loads were typically higher in agricultural and/or urban watersheds than in forested areas.
- Long-Term Trends: Most long-term trends of total nitrogen and total phosphorus improved. Long-term trends were calculated for total nitrogen at 43 stations and for total phosphorus at 16 stations. Long-term suspended-sediment trends were calculated at 15 stations; suspended-sediment improved at 7 of these stations.
- Short-Term Trends: Improving short-term trends of total nitrogen, total phosphorus, and suspended sediment were detected at less than half of all stations (figure 1).
Management Implications
- NTN stations with elevated nutrient and/or suspended-sediment loads may represent areas that require focused water-quality conservation efforts.
- NTN stations with improving trends may provide insights about the drivers of reduced nutrient and suspended-sediment loads.
- Additional nutrient and suspended-sediment load reductions may be needed to meet the region’s clean water goals.
- The USGS will continue to work with Chesapeake Bay partners to evaluate and explain NTN loads and trends in a way that addresses the needs of watershed managers.
For More Information
- Visit the Chesapeake Bay water-quality loads and trends website to learn more about these results
- Explore the interactive NTN data mapper to see load and trend results in more detail: Loads and Trends in the Chesapeake Bay Nontidal Monitoring Network
- Download the load and trend data: Nitrogen, phosphorus, and suspended-sediment loads and trends measured at the Chesapeake Bay Nontidal Network stations: Water years 1985-2023 - ScienceBase-Catalog
Chesapeake Bay Water-Quality Loads and Trends
The USGS has computed nutrient and suspended-sediment loads and trends through water year 2023 in Chesapeake Bay rivers. These monitoring-based estimates help federal, state, and local managers evaluate and plan water-quality restoration strategies.
Issue
Watershed managers are working to reduce the load, or amount, of nutrients and suspended sediment in Chesapeake Bay rivers to meet the region’s clean-water goals. These restoration efforts rely on accurate information about the load of nutrients and suspended sediment in Chesapeake Bay rivers. The Chesapeake Bay nontidal monitoring network (NTN) addresses this need by measuring the load of nutrients and suspended sediment in rivers at 123 stations throughout the watershed. With at least ten years of monitoring data, trends are computed to determine if nutrient and suspended-sediment loads are getting better or worse over time.
USGS Study
The USGS partners with federal, state, and local agencies to collect more than 2,000 water-quality samples from 123 NTN stations each year. Every other year, the USGS uses these samples and daily streamflow measurements to compute nutrient and suspended-sediment loads and to assess trends in how these loads have changed over time. The most recent load and trend assessment includes monitoring data collected from water years 1985 through 2023 (a water year is from October 1 through September 30 of the following calendar year). Long-term trends are computed using this full range of data. Short-term trends are computed on the most recent 10-year window, in this case, from water years 2014 through 2023. Trends are categorized as “improving” if loads have decreased over time and as “degrading” if loads have increased over time. Stations are assigned a “no trend” result if there is no statistically meaningful change in load over the period. Trends are computed from “flow-normalized” loads to remove most year-to-year variability in load caused by streamflow.
Major Findings
- Loads: After accounting for differences in load caused by watershed area, nutrient and suspended-sediment loads were typically higher in agricultural and/or urban watersheds than in forested areas.
- Long-Term Trends: Most long-term trends of total nitrogen and total phosphorus improved. Long-term trends were calculated for total nitrogen at 43 stations and for total phosphorus at 16 stations. Long-term suspended-sediment trends were calculated at 15 stations; suspended-sediment improved at 7 of these stations.
- Short-Term Trends: Improving short-term trends of total nitrogen, total phosphorus, and suspended sediment were detected at less than half of all stations (figure 1).
Management Implications
- NTN stations with elevated nutrient and/or suspended-sediment loads may represent areas that require focused water-quality conservation efforts.
- NTN stations with improving trends may provide insights about the drivers of reduced nutrient and suspended-sediment loads.
- Additional nutrient and suspended-sediment load reductions may be needed to meet the region’s clean water goals.
- The USGS will continue to work with Chesapeake Bay partners to evaluate and explain NTN loads and trends in a way that addresses the needs of watershed managers.
For More Information
- Visit the Chesapeake Bay water-quality loads and trends website to learn more about these results
- Explore the interactive NTN data mapper to see load and trend results in more detail: Loads and Trends in the Chesapeake Bay Nontidal Monitoring Network
- Download the load and trend data: Nitrogen, phosphorus, and suspended-sediment loads and trends measured at the Chesapeake Bay Nontidal Network stations: Water years 1985-2023 - ScienceBase-Catalog