# What is a stream gage and what is it used for?

## What is a stream gage and what is it used for?

A streamgage contains instruments that measure and record the amount of water flowing in the river or stream, or its discharge. Generally, these measurements occur automatically every 15 minutes or more frequently in times of flooding.

What does a stream gage measure?

What is Stream Gaging? Stream gaging is a technique used to measure the discharge, or the volume of water moving through a channel per unit time, of a stream. The height of water in the stream channel, known as a stage or gage height, can be used to determine the dischage in a stream.

### How do you read a stream gauge?

Between the tenths are 4 hash lines used for measuring hundredths of a foot. The top of the hash is one hundredth and the bottom of the hash is another. The pointed hash represents 5 hundredths (0.05). To read the gauge, you note the foot and tenth labels above the water line, and then count hashes down for hundredths.

What is streamflow analysis?

Streamflow data are a recorded sample from a much larger period of flows, most of which were not “observed. �� We use streamflow statistics to mathematically manipulate discharge data in order to generate ideas about the larger (longer) “population” of streamflow at a site based on the record (sample).

#### What is a gage station?

Gauging station, site on a stream, canal, lake, or reservoir where systematic observations of gauge height (water level) or discharge are obtained.

How do you calculate stream flow?

Multiply the average depth of the stream by the width of the stream to find the area in ft2. Divide the distance traveled by the average travel time to find the velocity of the stream in ft/sec. Multiply the velocity of the stream by a correction factor. This is the corrected velocity of the stream.

## How do you read water levels?

You can measure the depth of water by lowering a wetted steel tape to into the well until the lower part of the tape is under water. A chalk coating on the last few feet of tape indicate the exact water level.

What is river gage height?

Stream stage (also called stage or gage height) is the height of the water surface, in feet, above an established altitude where the stage is zero. The zero level is arbitrary, but is often close to the streambed.

### Why are stream gauges so important?

Stream gages measure the quantity and variability of our surface water resources. In addition, the analysis of streamflow data in combination with groundwater data helps us understand the relationships of the hydrologic cycle.

What unit is flow rate measured in?

Introduction. Flow is the volume of fluid that passes in a unit of time. In water resources, flow is often measured in units of cubic feet per second (cfs), cubic meters per second (cms), gallons per minute (gpm), or other various units.

#### When to use stream gauge data for highway drainage?

For highway drainage design purposes, a statistical analysis of stream gauge data is typically applied only when adequate data from stream gauging stations are available. The definition of adequate data comes from USGS practice and is provided in Table 4-3. USGS National Water Information System (NWIS).

How is stream flow calculated in the USGS?

Streamflow (also called discharge) is computed from measured water levels using a site-specific relation (called a stage-discharge rating curve) developed from onsite water level and streamflow measurements made by USGS…

## How are streamgages used in the National streamflow network?

(Credit: Tim Merrick, USGS.) Most USGS streamgages are used to generate continuous streamflow information year-round. Together these gages constitute the National Streamflow Network. Some gages, however, only record the water level (gage height or stage) of a stream, lake or reservoir; no streamflow (discharge) is computed.

How often does a streamgage measure a stage?

The accuracy of the measurements generally is ±0.01 foot or 0.2 percent of the effective stage. A streamgage usually measures stage every 15 minutes. When intense rainfall and runoff cause a stream or river to rise quickly, however, the time intervals can be as short as every 5 minutes.