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Hanna Coy: Today, Fletcher and I are at San Pedro River at Charleston to do a streamflow measurement. We are making this measurement to verify that are gauging station is reading correctly. Today, we’re going to look inside the gauge. Also, we’re going to look at water weight that’s used to reference the stage elevation of the river.
Last, we’re going to do a streamflow measurement. Here comes Fletcher. This is a high-rate data collection platform also known as a DCP. I’m saying that the monsoons are about ready to show up. Maybe, we’ll see some today. Fletcher is getting his pygmy meter ready. We’ll do a spin test.
A spin test is done to make sure that the meter is still in calibration.
Fletcher Brinkerhoff: It should go until for about a minute, 20 minutes, 25 minutes.
Hanna Coy: You’ve got your key.
Fletcher Brinkerhoff: Yes.
Hanna Coy: Flow looks like it’s… what do you think? Half a cfs or…
Fletcher Brinkerhoff: Something like that.
Hanna Coy: 0.6 cfs?
Fletcher Brinkerhoff: I think you were saying something like around 0.6 or 0.5 something.
Hanna Coy: Fletcher is going to get a wire-weight reading now that will reference the gauge with the water surface-elevation rate. This is having a stop gauge, lower this down and get a gauge height.
You can see right next to the wire weight we have the gauge sensor, which is a radar sensor. He is going to get a reading. Again, this is the reference. We got a stage reading from the gauge sensor. This is the way we calibrate it. We get a wire-weight reading and so that will verify the gauge reading. This wire-weight reading should be the same as the gauge reading.
Fletcher Brinkerhoff:: It’s right on.
Hanna Coy: All right. Fletcher is starting his current-meter measurement. He is measuring velocity with the pygmy meter, depth with the wading rod, and distance with the tag line. Fletcher will measure the velocity, depth, and distance in 20 to 25 of these subsections.
Fletcher Brinkerhoff: The depths are about 0.35 in all sections.
Hanna Coy: Well that’s about a third of a foot. All these measurements of velocity, depth, and distance are put into the AquaCalc to give us a final discharge. Measurement we made today was 0.048 cfs, about a half of the cfs.
You can see the radar sensor right next to the wire weight. The gauge pole is this pulled area that is created by a constriction in the stream channel about 80 feet downstream from the gauge. It looks like it’s raining just upstream, so this may be the first day of the monsoons down here.
Title: Streamflow Measurement (San Pedro River - 2008)
Description: USGS streamgagers make a low flow measurement on the San Pedro River at Charleston.
Location: Charleston, AZ, USA
Date Taken: 6/23/2008
Video Producer: U.S. Geological Survey
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