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Speaker: OK. What we're looking here is the gauge pole at the Charleston at San Pedro gauge. The gauge pole extends downstream to a point where there is a change in velocity or a flow regime.
You can see during these under-low flow conditions, we're looking at an area that is about 1.1 feet wide. It shifted the deepest point of this riffle is going to be right about here, 1.11.
Our flume section is just about 30 feet downstream.
We have here an area that has been used previously for a Parshall Flume measurement. What I'm going to do right now is I am going to fill it in a little bit with some very fine sediments and it's going to settle. I'm going to fill in around the flume.
This truss right here is 3-inch Parshall Flume. It's constructed in such a way that it has a very precise throat. The dimensions inside the Parshall Flume are very precise. It has been computed using a rating table that at different elevation and flowing through the Parshall Flume, a discharge would be associated with that elevation.
We actually measure the elevation in the stilling well of the Parshall Flume. This is the stilling well, this part here.
The purpose is at very low flow conditions, like we have here at the San Pedro Charleston gauge, we have an accurate method for determining and computing the discharge using the rating table.
Title: Measuring Low Flow in San Pedro River
Description: Measuring low flow in the San Pedro River with flume.
Location: Charleston, AZ, USA
Date Taken: 3/22/2010
Video Producer: U.S. Geological Survey
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