Streamflow Gaging Station and Measurement on San Pedro River, AZ

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Detailed Description

USGS employee, Hanna Coy, talks about stream gauging.


Date Taken:

Length: 04:20:00

Location Taken: Tucson, AZ, US


-So I read the staff plate down there, and I got a read of about 3.43. So what Iím doing is just checking. 
The data logger is up here,  and its recordingóSo we have the flow inside the stilling well, 
-and thatís connected to a shaft encoder, which is being recorded. And then there is also a pressure 
transducer up here, 
-and there is a long line of tubing, and it comes out--  You can see it on the other side of the door there.  
What happens is that line is pressurized, and as the water goes up or down it changes the relative 
pressure in the line.  And that can be translated to a change in water level as well. So Iím checking those 
two values to see if they correspond with what I read directly from the staff plate.  If they are in 
agreement, then everything is good and I can start the measurement.  If they are not, then I will 
probably need to purge the orifice line, and check to make sure everything is functioning properly. 
-For this right here, the control is pretty much this section of water right here. So there are these two 
little branches, and this one is kind of falling in sideways,
-  and where it comes in sideways, that's kind of acting as a control on the stage for this little section 
that is flowing right by the gauge.
- And so Iím just noting how far it is from the stilling well and whether itís got derby it in, that kind of 
-That's better.
- [grass rustle] 
-Its turbulent right here by the edge, so Iím getting velocity numbers that are jumping around like crazy. 
-[stream trickle] 
-There are six cites total, where I do discharge measurements, either along the San Pedro or I guess one 
of them is,
- at the Babocomari River right before it comes into the San Pedro.  So Iím able to compare up and down 
stream. Right by the gauge, the water very shallow and there are some little islands that appear in the 
middle, and the flow is kind of braided.
- So it's not a very good place to get a measurement section. What happens is as it flows down here, the 
flow all kind of gets condensed here on the left bank, and so there is a nice straight even section here, 
and thatís a lot better for measuring. 
- I'm going to make larger sections starting here. There was more flow over here so I wanted smaller 
sections so I could capture a smaller percentage of the total flow of each section.  And here since the 
flow is less the sections, then the section donít have to be so small. Typically, we rate measurements 
-good, fair, or poor. And those correspond to the amount of air in percentage that we associate with it. 
An excellent would be  2%, good would be 5%, fair would be 8%, and poor would be more than 8%. So 
Iím probably going to rate this measurement fair, because the water was kind of pulsating and there was 
a little bit of turbulence so the velocity measurements were fluctuating a lot.
-I was doing a measurement the other day and I was standing in one birds territory, and it kind ofÖit 
seemed to me that it was doing the bird equivalent of  [throat clearing noises]
Please get out of here." 
[small laugh] You know that's funny.