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Information on the flow of rivers and streams is a vital national asset that safeguards lives, protects property, and ensures adequate water supplies for the future. The USGS operates a network of more than 13,500 streamgages nationwide that provide streamflow information for a wide variety of uses including flood prediction, water management and allocation, engineering design, research, operation of locks and dams, and recreational safety and enjoyment.
The U.S. Geological Survey (USGS) established its first streamgage in 1889, on the Rio Grande River in New Mexico, to help determine if there was adequate water for irrigation, supporting development and western expansion. A streamgage is a hydrological monitoring location on a waterway. It contains equipment to measure and record water levels (gage height or stage). These data, often transmitted via satellite, are typically collected every 15 minutes and converted to streamflow (discharge) using a site-specific stage-discharge relationship developed from onsite water level and streamflow measurements made by USGS hydrographers. The USGS provides these data online through Water Data for the Nation.
Together, USGS streamgages constitute the National Streamgage Network. This network primarily consists of streamgages that provide continuous year-round streamflow data. However, several specialized gage types serve specific monitoring needs:
Measuring streamflow in rivers or streams is like taking the pulse of blood flow in a human body. It is important to measure streamflow so that scientists and water managers can make informed decisions about a river or stream’s health.
Streamgages do not measure streamflow directly. Monitoring streamflow involves several steps.
Stream stage can be measured using a variety of methods. These include the manual reading of staff gages, traditional float/stilling-well method and newer methods that use pressure transducers, bubbler systems or radar sensors.
Staff gages, which appear as measuring tapes permanently installed into rivers, provide visual measurements of stream stage that can be useful to make manual measurements by a hydrologic technician in the field. These are used during storms or to measure high water marks. They are also periodically referenced to visually verify the accuracy of the stage sensors that are published online.
A common approach to measuring stream stage is with a stilling well in the river bank or attached to a bridge pier. Water from the river enters and leaves the stilling well through underwater pipes allowing the water surface in the stilling well to be at the same elevation as the water surface in the river. The stage is then measured inside the stilling well using a float or a pressure, optic, or acoustic sensor. The measured stage value is stored in an electronic data recorder on a regular interval, usually every 15 minutes.
At some streamgage sites, a stilling well is not feasible or is not cost effective to install. As an alternative, stage can be determined by measuring the pressure required to maintain a small flow of gas through a tube and bubbled out at a fixed location under water in the stream (image to the right). The measured pressure is directly related to the height of water over the tube outlet in the stream. As the depth of water above the tube outlet increases, more pressure is required to push the gas bubbles through the tube.
Data collection and transmission follow a dynamic schedule.
Stage measurements are precise, typically accurate to within ±0.01 foot or 0.2 percent of the effective stage.
Streamflow, or discharge, is the volume of water moving down a stream or river over a specific time and is commonly expressed in cubic feet per second (cfs) or gallons per day (gal/d). Because stream discharge cannot be measured directly, it must be computed from variables that can be measured directly, such as stream depth, stream width, and streamflow velocity. It is typically calculated by multiplying the cross-sectional area of water in a stream channel by the average velocity of the water in that cross section (see below). Although streamflow is computed from measurements of other variables, the terms “streamflow measurement” or “discharge measurement” are generally applied to the final result of the calculations.
Numerous types of equipment and methods are used by USGS personnel to make current-meter measurements because of the wide range of stream conditions throughout the United States. Two methods that are primarily used are:
A stage-discharge rating curve depicts the relation between stream stage and stream discharge at a location along a stream, generally at a streamgage. Each point on a stage-discharge graph represents one discharge measurement. Because every stream has a unique channel shape, size, slope, and even channel roughness, every rating curve is site-specific.
Keeping rating curves accurate and up-to-date is important. Key aspects of maintaining rating curves include:
For complex environments, like tidal rivers or flat areas where stage doesn't reliably predict flow, modern instrumentation has made it possible to continuously monitor discharge in these streams using the index velocity method. A hydroacoustic or ultrasonic velocity meter, installed in a river, monitors water speed continuously. These data are paired with cross-sectional area to calculate discharge even when traditional rating curves fail.
Over 135 years of high-quality water data for more than one million monitoring locations are accessible from Water Data for the Nation. Data users include emergency responders, water managers, environmental and transportation agencies, universities, utilities, recreational enthusiasts, and consulting firms. Key applications of USGS water data include:
The USGS can install a streamgage almost anywhere, but in most cases, we do not choose when and where to do that. We typically install and operate streamgages where other entities ask and reimburse us to do so.
USGS selects a suitable site along a river or stream and constructs a gage house to hold equipment that measures and records the height of the water surface (gage height or stage). The gage house also can hold equipment that measures water-quality parameters, such as temperature, pH, dissolved oxygen, and dissolved chemicals, and weather conditions, such as air temperature, precipitation, and wind speed.
If there is need for a streamgage in your area, reach out to a local government agency and ask them to contact the USGS about entering into an agreement to install and operate a new gage.
Below is other information associated with USGS streamgaging activities.
Below are multimedia items associated with USGS streamgaging activities.
The USGS collects water data daily across the U.S. using sensors that automatically sample the data at set intervals. We have over 11,000 of these devices, known as gages, in our nationwide network.
The data from these gages are used in decision-making at all levels, from recreationists to congresspersons.
The USGS collects water data daily across the U.S. using sensors that automatically sample the data at set intervals. We have over 11,000 of these devices, known as gages, in our nationwide network.
The data from these gages are used in decision-making at all levels, from recreationists to congresspersons.
What is water up to? Keeping the pulse on the Nation’s streams - USGS Streamgaging and the Groundwater and Streamflow Information Program.
What is water up to? Keeping the pulse on the Nation’s streams - USGS Streamgaging and the Groundwater and Streamflow Information Program.
Whether you drink water from your tap, use electricity or canoe down your local river, chances are you benefit from USGS streamgage information. So what is a streamgage and what does it do for you? This CoreCast episode gives you the inside scoop on your silent superhero.
Transcript and captions available soon.
Whether you drink water from your tap, use electricity or canoe down your local river, chances are you benefit from USGS streamgage information. So what is a streamgage and what does it do for you? This CoreCast episode gives you the inside scoop on your silent superhero.
Transcript and captions available soon.
Below are FAQ associated with USGS streamgaging activities.
Information on the flow of rivers is a vital national asset that safeguards lives, protects property, and ensures adequate water supplies for the future. The USGS is the federal agency responsible for operating a network of about 7,000 streamgages nationwide. Data from this network are used by water managers, emergency responders, utilities, environmental agencies, universities, consulting firms...
Streams are like living things and are constantly changing. Sometimes streams erode, becoming deeper, while other times streams deposit sediment, becoming shallower. To understand how those changes can affect streamflow, we need to measure from a reference point that does not change over time, which is why gage datums are chosen to be below the base of a streambed. This means that the gage datum...
The USGS can install a streamgage almost anywhere, but in most cases we do not choose when and where to do that. We typically install and operate streamgages where other entities ask and reimburse us to do so. We operate streamgages for entities such as cities, towns, counties, state agencies, and other federal agencies to assist with their missions and to provide data for general public use...
There can be occasional equipment or database problems where erroneous data are reported for short periods of time until corrections can be made. This is why it is important to look at a record of streamflow (like the 7-day hydrograph plots) rather than a single point in time. However, most of the time the USGS has a high level of confidence in its real-time stage data. During low streamflow...
Stream stage (aka gage height) is an important concept when analyzing how much water is moving in a stream at any given moment. "Stage" is the water level above some arbitrary point in the river and is commonly measured in feet. For example, on a normal day when no rain has fallen for a while, a river might have a stage of 2 feet. If a big storm hits, the river stage could rise to 15 or 20 feet...
Not directly. You cannot say that because a stream rises (doubles) from a 10-foot stage to a 20-foot stage that the amount of flowing water also doubles. Think of a cereal bowl with a rounded bottom. Pour one inch of milk in it. It doesn't take much milk to make it up to the one inch level because the bowl is at its narrowest near the bottom. Now, pour in milk until it is two inches deep -- it...
USGS real-time streamflow data are typically recorded at 15-minute intervals, stored onsite, and then transmitted to USGS offices once every hour, depending on the data relay technique used. Recording and transmission times might be more frequent during critical events (floods, for example). Data from current sites are relayed to USGS offices via satellite, telephone, and/or radio telemetry and...
The USGS usually corrects any equipment or station problems at our streamgages within a few days of their occurrence. Occasionally, replacement parts or equipment might not be readily available, or a station might be inaccessible due to weather conditions. Most USGS streamgaging stations are operated in cooperation with other agencies. At some stations, the stage transmitting equipment is owned...
In order to convert gage height (or "stage", usually expressed as feet) into streamflow (or "discharge", usually expressed as cubic feet per second), USGS hydrographers must establish a relationship between them. This stage-discharge relationship is called a rating curve. It’s developed by making frequent manual discrete discharge measurements at stream gaging stations. The rating curve depends on...
Water Data for the Nation (WDFN) is the home for USGS streamflow, groundwater, and water quality data. Through WDFN you can find different tools to look at historic and real-time streamflow data, find sites of interest, and access using USGS water data application programming interfaces (APIs). State pages (e.g., California) allow you to discover real-time data in your state, or you can create a...
Information on the flow of rivers and streams is a vital national asset that safeguards lives, protects property, and ensures adequate water supplies for the future. The USGS operates a network of more than 13,500 streamgages nationwide that provide streamflow information for a wide variety of uses including flood prediction, water management and allocation, engineering design, research, operation of locks and dams, and recreational safety and enjoyment.
The U.S. Geological Survey (USGS) established its first streamgage in 1889, on the Rio Grande River in New Mexico, to help determine if there was adequate water for irrigation, supporting development and western expansion. A streamgage is a hydrological monitoring location on a waterway. It contains equipment to measure and record water levels (gage height or stage). These data, often transmitted via satellite, are typically collected every 15 minutes and converted to streamflow (discharge) using a site-specific stage-discharge relationship developed from onsite water level and streamflow measurements made by USGS hydrographers. The USGS provides these data online through Water Data for the Nation.
Together, USGS streamgages constitute the National Streamgage Network. This network primarily consists of streamgages that provide continuous year-round streamflow data. However, several specialized gage types serve specific monitoring needs:
Measuring streamflow in rivers or streams is like taking the pulse of blood flow in a human body. It is important to measure streamflow so that scientists and water managers can make informed decisions about a river or stream’s health.
Streamgages do not measure streamflow directly. Monitoring streamflow involves several steps.
Stream stage can be measured using a variety of methods. These include the manual reading of staff gages, traditional float/stilling-well method and newer methods that use pressure transducers, bubbler systems or radar sensors.
Staff gages, which appear as measuring tapes permanently installed into rivers, provide visual measurements of stream stage that can be useful to make manual measurements by a hydrologic technician in the field. These are used during storms or to measure high water marks. They are also periodically referenced to visually verify the accuracy of the stage sensors that are published online.
A common approach to measuring stream stage is with a stilling well in the river bank or attached to a bridge pier. Water from the river enters and leaves the stilling well through underwater pipes allowing the water surface in the stilling well to be at the same elevation as the water surface in the river. The stage is then measured inside the stilling well using a float or a pressure, optic, or acoustic sensor. The measured stage value is stored in an electronic data recorder on a regular interval, usually every 15 minutes.
At some streamgage sites, a stilling well is not feasible or is not cost effective to install. As an alternative, stage can be determined by measuring the pressure required to maintain a small flow of gas through a tube and bubbled out at a fixed location under water in the stream (image to the right). The measured pressure is directly related to the height of water over the tube outlet in the stream. As the depth of water above the tube outlet increases, more pressure is required to push the gas bubbles through the tube.
Data collection and transmission follow a dynamic schedule.
Stage measurements are precise, typically accurate to within ±0.01 foot or 0.2 percent of the effective stage.
Streamflow, or discharge, is the volume of water moving down a stream or river over a specific time and is commonly expressed in cubic feet per second (cfs) or gallons per day (gal/d). Because stream discharge cannot be measured directly, it must be computed from variables that can be measured directly, such as stream depth, stream width, and streamflow velocity. It is typically calculated by multiplying the cross-sectional area of water in a stream channel by the average velocity of the water in that cross section (see below). Although streamflow is computed from measurements of other variables, the terms “streamflow measurement” or “discharge measurement” are generally applied to the final result of the calculations.
Numerous types of equipment and methods are used by USGS personnel to make current-meter measurements because of the wide range of stream conditions throughout the United States. Two methods that are primarily used are:
A stage-discharge rating curve depicts the relation between stream stage and stream discharge at a location along a stream, generally at a streamgage. Each point on a stage-discharge graph represents one discharge measurement. Because every stream has a unique channel shape, size, slope, and even channel roughness, every rating curve is site-specific.
Keeping rating curves accurate and up-to-date is important. Key aspects of maintaining rating curves include:
For complex environments, like tidal rivers or flat areas where stage doesn't reliably predict flow, modern instrumentation has made it possible to continuously monitor discharge in these streams using the index velocity method. A hydroacoustic or ultrasonic velocity meter, installed in a river, monitors water speed continuously. These data are paired with cross-sectional area to calculate discharge even when traditional rating curves fail.
Over 135 years of high-quality water data for more than one million monitoring locations are accessible from Water Data for the Nation. Data users include emergency responders, water managers, environmental and transportation agencies, universities, utilities, recreational enthusiasts, and consulting firms. Key applications of USGS water data include:
The USGS can install a streamgage almost anywhere, but in most cases, we do not choose when and where to do that. We typically install and operate streamgages where other entities ask and reimburse us to do so.
USGS selects a suitable site along a river or stream and constructs a gage house to hold equipment that measures and records the height of the water surface (gage height or stage). The gage house also can hold equipment that measures water-quality parameters, such as temperature, pH, dissolved oxygen, and dissolved chemicals, and weather conditions, such as air temperature, precipitation, and wind speed.
If there is need for a streamgage in your area, reach out to a local government agency and ask them to contact the USGS about entering into an agreement to install and operate a new gage.
Below is other information associated with USGS streamgaging activities.
Below are multimedia items associated with USGS streamgaging activities.
The USGS collects water data daily across the U.S. using sensors that automatically sample the data at set intervals. We have over 11,000 of these devices, known as gages, in our nationwide network.
The data from these gages are used in decision-making at all levels, from recreationists to congresspersons.
The USGS collects water data daily across the U.S. using sensors that automatically sample the data at set intervals. We have over 11,000 of these devices, known as gages, in our nationwide network.
The data from these gages are used in decision-making at all levels, from recreationists to congresspersons.
What is water up to? Keeping the pulse on the Nation’s streams - USGS Streamgaging and the Groundwater and Streamflow Information Program.
What is water up to? Keeping the pulse on the Nation’s streams - USGS Streamgaging and the Groundwater and Streamflow Information Program.
Whether you drink water from your tap, use electricity or canoe down your local river, chances are you benefit from USGS streamgage information. So what is a streamgage and what does it do for you? This CoreCast episode gives you the inside scoop on your silent superhero.
Transcript and captions available soon.
Whether you drink water from your tap, use electricity or canoe down your local river, chances are you benefit from USGS streamgage information. So what is a streamgage and what does it do for you? This CoreCast episode gives you the inside scoop on your silent superhero.
Transcript and captions available soon.
Below are FAQ associated with USGS streamgaging activities.
Information on the flow of rivers is a vital national asset that safeguards lives, protects property, and ensures adequate water supplies for the future. The USGS is the federal agency responsible for operating a network of about 7,000 streamgages nationwide. Data from this network are used by water managers, emergency responders, utilities, environmental agencies, universities, consulting firms...
Streams are like living things and are constantly changing. Sometimes streams erode, becoming deeper, while other times streams deposit sediment, becoming shallower. To understand how those changes can affect streamflow, we need to measure from a reference point that does not change over time, which is why gage datums are chosen to be below the base of a streambed. This means that the gage datum...
The USGS can install a streamgage almost anywhere, but in most cases we do not choose when and where to do that. We typically install and operate streamgages where other entities ask and reimburse us to do so. We operate streamgages for entities such as cities, towns, counties, state agencies, and other federal agencies to assist with their missions and to provide data for general public use...
There can be occasional equipment or database problems where erroneous data are reported for short periods of time until corrections can be made. This is why it is important to look at a record of streamflow (like the 7-day hydrograph plots) rather than a single point in time. However, most of the time the USGS has a high level of confidence in its real-time stage data. During low streamflow...
Stream stage (aka gage height) is an important concept when analyzing how much water is moving in a stream at any given moment. "Stage" is the water level above some arbitrary point in the river and is commonly measured in feet. For example, on a normal day when no rain has fallen for a while, a river might have a stage of 2 feet. If a big storm hits, the river stage could rise to 15 or 20 feet...
Not directly. You cannot say that because a stream rises (doubles) from a 10-foot stage to a 20-foot stage that the amount of flowing water also doubles. Think of a cereal bowl with a rounded bottom. Pour one inch of milk in it. It doesn't take much milk to make it up to the one inch level because the bowl is at its narrowest near the bottom. Now, pour in milk until it is two inches deep -- it...
USGS real-time streamflow data are typically recorded at 15-minute intervals, stored onsite, and then transmitted to USGS offices once every hour, depending on the data relay technique used. Recording and transmission times might be more frequent during critical events (floods, for example). Data from current sites are relayed to USGS offices via satellite, telephone, and/or radio telemetry and...
The USGS usually corrects any equipment or station problems at our streamgages within a few days of their occurrence. Occasionally, replacement parts or equipment might not be readily available, or a station might be inaccessible due to weather conditions. Most USGS streamgaging stations are operated in cooperation with other agencies. At some stations, the stage transmitting equipment is owned...
In order to convert gage height (or "stage", usually expressed as feet) into streamflow (or "discharge", usually expressed as cubic feet per second), USGS hydrographers must establish a relationship between them. This stage-discharge relationship is called a rating curve. It’s developed by making frequent manual discrete discharge measurements at stream gaging stations. The rating curve depends on...
Water Data for the Nation (WDFN) is the home for USGS streamflow, groundwater, and water quality data. Through WDFN you can find different tools to look at historic and real-time streamflow data, find sites of interest, and access using USGS water data application programming interfaces (APIs). State pages (e.g., California) allow you to discover real-time data in your state, or you can create a...