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A stream gauge, streamgage or stream gauging station is a location used by
hydrologists Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and environmental watershed sustainability. A practitioner of hydrology is call ...
or environmental scientists to monitor and test terrestrial bodies of water. Hydrometric measurements of water level surface elevation (" stage") and/or volumetric
discharge Discharge may refer to Expel or let go * Discharge, the act of firing a gun * Discharge, or termination of employment, the end of an employee's duration with an employer * Military discharge, the release of a member of the armed forces from serv ...
(flow) are generally taken and observations of
biota Biota may refer to: * Biota (ecology), the plant and animal life of a region * Biota (plant), common name for a coniferous tree, ''Platycladus orientalis'' * Biota, Cinco Villas, a municipality in Aragon, Spain * Biota (band), a band from Color ...
and
water quality Water quality refers to the chemical, physical, and biological characteristics of water based on the standards of its usage. It is most frequently used by reference to a set of standards against which compliance, generally achieved through ...
may also be made. The locations of gauging stations are often found on
topographical maps In modern mapping, a topographic map or topographic sheet is a type of map characterized by large- scale detail and quantitative representation of relief features, usually using contour lines (connecting points of equal elevation), but historic ...
. Some gauging stations are highly automated and may include telemetry capability transmitted to a central data logging facility.


Measurement equipment

Automated direct measurement of streamflow discharge is difficult at present. In place of the direct measurement of streamflow discharge, one or more surrogate measurements can be used to produce discharge values. In the majority of cases, a stage (the elevation of the water surface) measurement is used as the surrogate. Low gradient (or shallow-sloped) streams are highly influenced by variable downstream channel conditions. For these streams, a second stream gauge would be installed, and the slope of the water surface would be calculated between the gauges. This value would be used along with the stage measurement to more accurately determine the streamflow discharge. Improvements in the accuracy of velocity sensors have also allowed the use of water velocity as a reliable surrogate for streamflow discharge at sites with a stable cross-sectional area. These
sensor A sensor is a device that produces an output signal for the purpose of sensing a physical phenomenon. In the broadest definition, a sensor is a device, module, machine, or subsystem that detects events or changes in its environment and sends ...
s are permanently mounted in the stream and measure velocity at a particular location in the stream and related to flow in a manner similar to the use of traditional water level. In those instances where only a stage measurement is used as the surrogate, a rating curve must be constructed. A rating curve is the functional relation between stage and discharge. It is determined by making repeated discrete measurements of streamflow discharge using a velocimeter and some means to measure the channel geometry to determine the cross-sectional area of the channel. The technicians and hydrologists responsible for determining the rating curve visit the site routinely, with special trips to measure the hydrologic extremes (floods and droughts), and make a discharge measurement by following an explicit set of instructions. Once the rating curve is established, it can be used in conjunction with stage measurements to determine the volumetric streamflow discharge. This record then serves as an assessment of the volume of water that passes by the stream gauge and is useful for many tasks associated with hydrology. In those instances where a velocity measurement is additionally used as a surrogate, an index velocity determination is conducted. This analysis uses a velocity sensor, often either magnetic or acoustic, to measure the velocity of the flow at a particular location in the stream cross section. Once again, discrete measurements of streamflow discharge are made by the technician or hydrologist at a variety of stages. For each discrete determination of streamflow discharge, the mean velocity of the cross section is determined by dividing streamflow discharge by the cross-sectional area. A rating curve, similar to that used for stage-discharge determinations, is constructed using the mean velocity and the index velocity from the permanently mounted meter. An additional rating curve is constructed that relates stage of the stream to cross-sectional area. Using these two ratings, the automatically collected stage produces an estimate of the cross-sectional area, and the automatically collected index velocity produces an estimate of the mean velocity of the cross section. The streamflow discharge is computed as the estimate of the cross section area and the estimate of the mean velocity of the streamflow. A variety of hydraulic structures / primary device are used to improve the reliability of using water level as a surrogate for flow (improving the accuracy of the rating table), including: * Weirs ** V-notch, ** broad-crested, ** sharp-crested and ** combination weirs *
Flume A flume is a human-made channel for water, in the form of an open declined gravity chute whose walls are raised above the surrounding terrain, in contrast to a trench or ditch. Flumes are not to be confused with aqueducts, which are built to ...
s ** Parshall flume Other equipment commonly used at permanent stream gauge include: * Cableways - for suspending a hydrographer and current meter over a river to make high flow measurement * Stilling well - to provide a calm water level that can be measured by a sensor Water level gauges: * Staff (head) gauges - for a visual indication of water depth * Water pressure measuring device (Bubbler) - to measure water level via pressure (typically done directly in-stream without a stilling well) * Stage
encoder Encoder may refer to: Electronic circuits * Audio encoder, converts digital audio to analog audio signals * Video encoder, converts digital video to analog video signals * Simple encoder, assigns a binary code to an active input line * Priority e ...
- a potentiometer with a wheel and pulley system connected to a float in a stilling well to provide an electronic reading of the water level * Simple ultrasonic devices - to measure water level in a stilling well or directly in a canal. * Electromagnetic gauges
Discharge Discharge may refer to Expel or let go * Discharge, the act of firing a gun * Discharge, or termination of employment, the end of an employee's duration with an employer * Military discharge, the release of a member of the armed forces from serv ...
measurements of a stream or canal without an established stream gauge can be made using a current meter or Acoustic Doppler current profiler. One informal methods that is not acceptable for any official or scientific purpose, but can be useful is the float method, in which a floating object such as a piece of wood or orange peel is observed floating down the stream.


National stream gauge networks


United Kingdom

The first routine measurements of river flow in England began on the Thames and Lea in the 1880s, and in Scotland on the River Garry in 1913. The national gauging station network was established in its current form by the early 1970s and consists of approximately 1500 flow measurement stations supplemented by a variable number of temporary monitoring sites. The Environment Agency is responsible for collection and analysis of hydrometric data in England, Natural Resources Wales in Wales, whilst responsibility for Scotland and Northern Ireland rests with the Scottish Environment Protection Agency and Rivers Agency respectively.


United States

In the United States, the U.S. Geological Survey (USGS) is the principal federal agency tasked with maintaining records of
natural resources Natural resources are resources that are drawn from nature and used with few modifications. This includes the sources of valued characteristics such as commercial and industrial use, aesthetic value, scientific interest and cultural value. ...
. Within the USGS, the Water Resources Division carries the responsibility for monitoring water resources. To establish a stream gauge, USGS personnel first choose a site on a stream where the geometry is relatively stable and there is a suitable location to make discrete direct measurements of streamflow using specialized equipment. Many times this will be at a bridge or other stream crossing. Technicians then install equipment that measures the stage (the elevation of the water surface) or, more rarely, the
velocity Velocity is the directional speed of an object in motion as an indication of its rate of change in position as observed from a particular frame of reference and as measured by a particular standard of time (e.g. northbound). Velocity i ...
of the flow. Additional equipment is installed to record and transmit these readings (via the Geostationary Operational Environmental Satellite) to the Water Science Center office where the records are kept. The USGS has a Water Science Center office in every state within the United States. Current streamflow data from USGS streamgages may be viewed in map form at


Zimbabwe

In
Zimbabwe Zimbabwe (), officially the Republic of Zimbabwe, is a landlocked country located in Southeast Africa, between the Zambezi and Limpopo Rivers, bordered by South Africa to the south, Botswana to the south-west, Zambia to the north, and Mozam ...
, the national stream gauge network is the responsibility of the
Zimbabwe National Water Authority Zimbabwe (), officially the Republic of Zimbabwe, is a landlocked country located in Southeast Africa, between the Zambezi and Limpopo Rivers, bordered by South Africa to the south, Botswana to the south-west, Zambia to the north, and Mozam ...
. This is an extensive network covering all major rivers and catchments in the country. However, a review of existing gauges raised serious concerns about the reliability of the data of a minority of stations, due in part to ongoing funding problems.


Bangladesh

The largest stream gauge network in Bangladesh is maintained by Bangladesh Water Development Board (BWDB). At few other locations, Bangladesh Inland Water Transport Authority maintains a few gauges to provide advisories for navigational purposes.


Czech Republic

In the Czech Republic, in some measuring places (profiles) are defined three levels which define three degrees of flood-emergency activity. The degree I is a situation of alertness, the degree II is a situation of readiness, the degree III is a situation of danger.


Canada

Canadian Canadians (french: Canadiens) are people identified with the country of Canada. This connection may be residential, legal, historical or cultural. For most Canadians, many (or all) of these connections exist and are collectively the source of ...
streams and rivers are monitored by the
Water Survey of Canada The Water Survey of Canada (WSC) is a scientific branch of Environment and Climate Change Canada, responsible for monitoring the nation's freshwater resources. ThWSCmaintains Canada's hydrometric data network, widely referred to as HYDAT. Previous ...
, a branch of Environment and Climate Change Canada. As of 2021, it operates or collects data from more than 2800 gauges across Canada. This data is used by provincial and territory governments to inform flood predictions and water management.


Sri lanka

In sri lanka stream and rivers are monitored by Hydrology and Disaster Management Division a branch of
Irrigation Department Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has been develo ...
.it operated nearly 40 gauging station around the island.


See also

* *
Willow Beach Gauging Station Willow Beach Gauging Station is a gauging station located within Lake Mead National Recreation Area. The Willow Beach Gauging Station was listed in the National Register of Historic Places on March 21, 1986. The cables, catwalk, trail and gaugin ...
* * * * * * * * * *


References


Further reading

* World Meteorological Organization (2010) Manual on Stream Gauging. ** Volume I - Fieldwork

** Volume II - Computation of Discharge


External links


''Contoocook River Streamflow-Gaging Station'', Water Resources of New Hampshire and Vermont"USGS Surface-Water Data for the Nation"UK Hydrometric Register (pdf)
A catalogue of river flow gauging stations and observation wells and boreholes in the United Kingdom together with summary hydrometric and spatial statistics.
"Radio Gauge Warns of Flood as Water Rises" ''Popular Mechanics'', July 1935
{{Authority control Hydrology instrumentation