ITRC Report October 1, 2019.
In arid environments, streamflow enhancement in low flow channels is common. It is challenging to assess enhancement project effectiveness in these channels because of uncertainties in metering (regarding both meters and procedures). The basic equation for flow is:
Q = VA (Eq. 1)
Q = channel flow rate (e.g., cubic feet per second, CFS)
V = cross sectional average velocity (e.g., feet per second, fps)
A = cross sectional area (e.g., square feet, ft2)
There are three main factors that impact flow measurement uncertainty in natural channels:
1. Flow meter velocity measurements (V)
2. Depth and area measurements (A)
3. Lack of continuous measurements over time
Items 1 and 2 above are directly shown in Eq. 1. However, the third point is important to also understand because point flow measurements are difficult to utilize, since flow changes over time. The work outlined in this report only focuses on the first two factors (V and D). The last factor is typically overcome by somehow continuously measuring the flow or relating point flow measurements to water depth (stage discharge relationship).
The objectives of this study were to evaluate several meters under laboratory and semi-laboratory conditions in order to:
1. Determine the most effective meter to use under low flow conditions
2. Identify constraints in the metering process or with meters themselves
3. Utilize the results to identify improved methods or recommendations for improving low flow measurement accuracy
Bioresource and Agricultural Engineering
© 2019 ITRC.
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