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Sediment Loads and River Flow to the Chesapeake Bay

During the 2014 water year (October 2013 to September 2014), approximately 3.62 million tons of sediment reached the Chesapeake Bay. This is below the long-term average of 5.32 million tons per year. River flow averaged 53 billion gallons per day during this time, which is close to the long-term average of 51 billion gallons per day.





September 13, 2011

Scientist Allen Gellis with the U.S. Geological Survey (USGS) visits Linganore Creek in Maryland to describe how he conducts studies of sediment sources in the Chesapeake Bay watershed.

Sediment forms when rocks and soil weather and erode. There are two major sources of sediment: eroding land and stream banks—called watershed sources of sediment—and eroding shorelines and coasts—called tidal sources of sediment. An estimated 2.7 million tons of sediment was delivered to the Chesapeake Bay in 2013 and an average of 5.2 million tons comes in each year. Too much sediment can cloud the waters of the Bay and its tributaries, harming underwater grasses, fish and shellfish.

Importance

Each day, billions of gallons of fresh water flow from rivers and streams into the Chesapeake Bay. The amount of water flowing from these tributaries into the Bay has a direct impact on pollution: as snowmelt or rainfall increase river flow, more nutrients and sediment are pushed into the estuary. In other words, precipitation and river flow are factors affecting pollution loads and water quality.

Sediment pollution is one of the leading causes of the Bay’s poor health. While loose particles of sand, silt and clay are natural parts of the environment, too much sediment can cloud the water and harm underwater grasses, fish and shellfish.

Goal

In 2014, the Chesapeake Bay Program adopted a goal to reduce pollution loads and achieve the water quality necessary to protect human health and support the region’s underwater resources.

The amount of sediment delivered to the Chesapeake Bay can change dramatically from year to year and is influenced by changes in land use, land management and river flow. This complicates our efforts to determine trends in sediment loads over time.

During the 2014 water year (October 2013 to September 2014), approximately 3.62 million tons of sediment reached the Bay. This is below the long-term average of 5.32 million tons per year and 760,000 tons more than the 2013 load. River flow averaged 53 billion gallons per day during this time, which is close to the long-term average of 51 billion gallons per day.

Additional Information

Scientists use water samples collected at River Input Monitoring (RIM) sites to estimate sediment loads to the Chesapeake Bay.

This indicator helps us understand and explain trends in sediment loads and water quality. Another indicator—Reducing Sediment Pollution—reports computer-simulated estimates of the amount of sediment delivered to the Bay following the implementation of efforts to reduce pollution. These estimates are generated with the Chesapeake Bay Program’s Watershed Model (Phase 5.3.2), and help us understand the effects of our management actions on pollution loads and develop “what-if” scenarios that project the future impacts of our actions on water quality. Because of the differences in the data behind these indicators, it is possible for them to report different pollution load amounts in a particular year.

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