Stream gauging
How do we measure the discharge passing through a river?
Learning Goals
- Know what river discharge is and some basic methods for measuring it.
- Recognize that stream gauging is typically a two-step process involving (1) measuring the height (stage) of the flow and (2) converting this stage into a discharge using either measurements and some understanding of flow mechanics.
Videos
Ways to measure river discharge
This lesson from Ohio University goes over the methods of stream gauging quite thoroughly! If you wonder why they are taking measurements at 20% and 80% of the flow depth, just wait to learn a bit about flow mechanics and the boundary-layer turbulent velocity profile given by the Law of the Wall.
How a USGS gauge works for measuring river stage
Example of measuring discharge in small stream
Oh, the Geography Men. Don’t let the initial jingle fool you; these two guys do a really professional job of explaining how river-discharge measurements work in practice.
US Geological Survey method for stream surveying and gauging
The United States Geological Survey has an official way to measure flow within a stream cross section, which involves splitting the cross section into 20 smaller sections and measuring the velocity within each one to obtain the discharge.
Image: USGS.
Indeed, the USGS webpage containing this image is an excellent reference for how streams are gauged, and I suggest that you read it if you are interested in hydrology water resources.
And if you are really into this and think that you might do this for your research and/or be interested in working for the USGS (for example, at one of their water science centers) or a related state agency, here’s their their full handbook in PDF: USGS Techniques and Methods 3-A8: Discharge Measurements at Gaging Stations.
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