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STREAM GAUGING INSTALLATION
How to Install a Stream Gauging Station Using the Flow Probe (FP101), the Water Level Logger, and Microsoft Excel
For single-event monitoring of flows in open channels, we recommend using the Global Water Flow Probe. With the Flow Probe, you can measure the average velocity of a channel's cross-section by moving the
probe smoothly and uniformly throughout the flow profile until you obtain a steady average reading. The flow can then be obtained using the following equation: Flow (Q) = V (average velocity) x A (cross-sectional
area).
For continuous flow monitoring of free-flowing open channels, you can use both the Flow Probe and the Water Level Logger to establish a stream gauging station. First, using the Flow Probe as described in
the paragraph above, you will need to determine the flows (Q's) at your gauging station while the channel contains several different depths of water. To measure the flows of various water depths, you will either need
to manually manipulate flows (in a controlled setting) or measure flows over time (in an uncontrolled setting). Using this data, you can develop a conversion table reflecting the channel's depth/flow relationships. You
can then use the Water Level Logger to record water depth in the channel over time, and you can convert Water Level Logger depth data to flow using Excel as described below.
EXCEL LEVEL TO FLOW CONVERSION
Obtain Rating Equation
Using the Flow Probe depth/flow relationship data obtained for your gauging station site, enter water level (h's) in Column A and flows (Q's) in Column B (h1 opposite Q1, etc).
Highlight all Q’s and h’s.
Click on Graph icon.
Click on “X-Y (Scatter)”.
Click on image with curves and dots. Then click “Finish”.
Right click on an point on the curve.
Select “Add Trendline”.
Under “Type”, pick “Power”
Under “Options”, check “Display equation”
Click "OK" or “Complete” and your rating equation will be displayed. The equation is represented as "y" = a function of "x",
where "y" is your "Q" data trend and "x" is your "h" data trend.
Apply Rating Equation to Convert Water Level Logger Data
Apply your rating equation to "h" data downloaded from the Water Level Logger data to calculate corresponding “Q” flow.
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