Uses of Streamflow Information

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The U.S. Geological Survey (USGS) has been measuring the amount of water flowing in rivers since the 19th century. Having reliable past and present streamflow information is vital for many reasons, both at the personal and national level. 

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Uses of Streamflow Information

USGS flood-inundation maps for the Saluda River near Greenville, South Carolina.

USGS flood-inundation maps for the Saluda River near Greenville, South Carolina. Streamflow data makes these maps possible.

Credit: Mark R. Newell

Streamflow information provided by the U.S. Geological Survey (USGS) is used in many ways and often the information from any give streamgage is used for not just one of the following but for many of the following purposes:

Water resource appraisal and allocations - how much water is available and how is it being allocated?

For water supply plans

  • Streamflow information is required to determine how much water is available in different locations so the citizens can make informed decisions about growth and to help assure there is an adequate water supply even during periods of drought. Today, the effects of climate change on the water available could become an issue in certain regions of the nation, and accurate long-term streamflow information is required to determine what if any impacts.

 As part of interstate agreements, compacts, and court decrees

  • Because of growing populations, contaminated supplies, and potentially changing supplies, the amount of water crossing political boundaries has come under much more scrutiny in recent years.

 Engineering design

  • Reservoirs
  • Bridges, roads, culverts
  • Treatment plants​​​​​​
    • Streamflow information is used for many of our nation's infrastructure designs. It is important to have accurate information because to over design is very costly, but to under design can be even more costly


  • Reservoirs
  • Power production
  • Navigation
    • Most of the nation's reservoirs relay on streamflow information to know how much water to release and when to release it, whether for flood control or for aquatic habitat. Hydropower producers also rely on streamflow information to regulate the amount and timing of releases.

 Identifying changes in streamflows due to changes in...

  • Land use
  • Water use
  • Climate
    • Major changes in land use can have significant effects on streamflow, as can even more obvious changes in water use. In the near future it will be the effects of climate change on the amount and timing of streamflow that will get the most attention.

 Flood planning and warning

  • Flood forecasts
  • Floodplain mapping
    • Streamflow information is used by the National Weather Service in making flood forecasts. The streamflow information is used to check the model results and to help calibrate the models. The Federal Emergency Management Agency uses streamflow information in delineating flood prone areas to help protect citizens from building or developing in areas that have a high probability of being flooded.

 Streamflow forecasting

  • To help water management agencies do a more efficient job, more are relying on computer models to forecast the amount of water that will be available for different time periods (week, months, seasons). Streamflow information is used to help calibrate the models and to provide verification checks.

 Support of water quality sampling

  • Water quality conditions and trends
  • Contaminant transport
  • Total Maximum Daily Loads (TMDLs)
    • Streamflow information is required to determine the load, or amount, of a contaminant that is moving past a given point.

 Characterizing and evaluating in-stream conditions

  • Habitat assessments
  • In-stream flow requirements
  • Recreation
    • Streamflow information is required to determine the amount and timing of streamflow to assess habitats and to develop in-stream flow requirements. In addition, many boaters, swimmers, and fishermen use streamflow information to decide if the streamflow is appropriate for them to visit their favorite locations.
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Want to know more about uses of streamflow information?  Follow me to the USGS Streamgaging Network website.