Southwest Crown Stream Monitoring Project
SWCC Protocol: Measuring Streamflow
Stuff you’ll need:
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Rebar/stakes
Hammer to set stakes
River tape measure (measures in tenths of feet, rather than in inches.)
Clips to attach tape to stakes
Flow meter
Top-setting rod
Data sheets, clipboard, and pencils
You'll need a team of three people. Two can do it in a pinch. Choose one person to record data, one to
measure depth with the top setting rod and hold the propeller in place to measure velocity, and one to
set and read the velocity on the flow meter. If you have only two people, the person in the stream must
measure depth, hold the propeller and use the flow meter. Switch off periodically if possible so that
everyone gets to perform and learn each job.
1. Select a cross section for the flow estimate. The best sites will have relatively uniform flow and
minimal turbulence, boulders or other obstructions that disrupt the flow or make
measurements more difficult. You can clear cobbles and debris from the cross section to make a
more uniform site before you begin. It’s helpful to use the same site on repeated
measurements, but sometimes you will need to change sites as flows come up or down.
2. Set stakes near water’s edges and attach tape so that it is perpendicular to the banks, with the
start end of the tape on the side of the stream you will start on.
3. Fill out the top of the data sheet, making sure you include the time, the gage height, and the
names or initials of the people collecting the information.
4. Assemble the top setting rod with the propeller inserted at the bottom, being careful not to
bump or torque the propeller directly. Tighten with the small Allen wrench until snug but the
propeller still moves on the shaft. Blow on the propeller to make sure it spins easily.
5. Practice reading the depth with the top setting rod by placing the bottom on the streambed and
sliding the rod up until the nose of the propeller is right at the surface of the water. Read the
depth on the large rod, counting the lines from the top until you reach the top of the white
clamp. Remember that each line represents 0.1 foot, and estimate the hundredths. Then adjust
the rod until the smaller rod reads at the same level; this will automatically set the propeller at
60% of the total depth.
6. Put the flow meter strap around your neck. Attach the cable from flow meter to the cable on
the rod. These should twist lock easily. Turn the black knob on the meter to Calibrate. The
display should be close to 188 (e.g.185-189). Then turn the knob to the left to the Velocity
Display Averaging line in the middle, between Max and Min. This sets it to average the velocity
every 40 seconds.
7. Looking straight down read the tape distance (in tenths of feet) at the starting water’s edge and
the ending waters edge. Calculate the total distance and the distance between observations
needed generate 20 to 25 observations across the stream.. E.g., if the stream is 40’ wide you
could measure at every 2.0 feet to end with at least 20 observations.
Southwest Crown Stream Monitoring Project
8. Look at the cross section and see if you can tell whether a disproportionate amount of the flow
occurs in some part of the cross section (i.e. is there an area where depth and/or velocity is
substantially higher than the rest of the stream). If so you should plan to add more
measurements by shortening the distance between measurements in that part of the stream.
(e.g., from 2.0’ to 1.0’)
9. Record the distance at waters edge and then find your first measurement spot on the tape by
adding the distance determined in Step 7. Place the rod next to the tape with the bottom of the
rod resting on the stream bed. Call out the distance (e.g., 0.8 feet) to the recorder. Always call
out feet and tenths of feet. The recorder should repeat it back to make sure it was recorded
correctly.
10. Call out the depth to the recorder; again the recorder should repeat it back.
11. Adjust the small rod to the same spot and hold the rod vertical and perpendicular to the tape.
Hold both rods to make sure they don’t slip, but don’t press down excessively hard. The person
carrying the flow meter can help the person setting the rod by observing whether the rod is
vertical.
12. When the rod is set the holder should say “ready”, and the meter reader should press the Reset
button on the meter. Keep rod still while reading. When the average velocity reading appears,
call it out to the recorder, who will repeat it back. Remember to always report and record
velocity in feet and hundreths of feet per second.
13. The recorder checks the numbers. If nothing seems out of whack, repeat steps 9-12 adding the
correct distance to find the next point. If you are in the portion of the stream where flow
increases substantially reduce the distance as described in step 8.. Continue across the stream
until you reach the far side. Record the time and gage height when you finish.
14. Carefully check the data to make sure measurements are complete and nothing seems odd or
out of place. Check to make sure you have recorded all necessary information on the data
sheet, including gage height at start and end.
15. Copy data sheet and enter data into spreadsheet ASAP!!
MORE THINGS TO REMEMBER:
1. You can clear large obstacles like rocks from under the tape before you start the measurement
process, but once you start you shouldn’t move things in the streambed or it will alter the flow.
2. Don’t let anyone stand upstream of the tape or let your foot be above or alongside the
propeller, as this will also affect the flow.
3. If the water is too shallow at the edges for the propeller to move, you can move it slightly to get
a reading or just call it zero; it will have a negligible effect on the overall flow.
4. When data are entered and the calculations proofed and complete, review the proportion of the
flow associated with each measurement point. This will show you whether a disproportionate
part of the flow was in any one of the measurement cells. The best estimates will have less than
10% of the flow in any cell. If any are close to or higher than that number make a note to adjust
the measurement distances to minimize that next time.