2014-01-29_HYDROLOGY - P2009025 ‎(8)‎

• Permit No: P2009025
• IBM Index Class Name: HYDROLOGY
• Doc Date: 1/29/2014
• Doc Name: Baseline Hydrologic Monitoring Plan
• From: Black Range Minerals
• To: DRMS
• Email Name: TC1
• Media Type: D
• Archive: No

Appendix D — SOP for Stream Flow Measurement — Hansen Project 4
3. FLOW MEASUREMENT PROCEDURES
This section describes the three methods that may be used to measure stream discharge.
3.1 Flumes
3.1.1 Theoretical Considerations
Flumes are specially shaped, open - channel flow sections with a restriction in channel area and, in most models,
with a change in channel slope. Either or both of these shape changes cause velocities to increase and water
levels to change while passing through the flume. Typical flumes consist of three sections:
A converging section to accelerate the approaching flow
A throat section, whose width is used to designate flume size
A diverging section, designed to ensure that the level downstream is lower than the level in the
converging section
The stage of a stream is the height of the water surface above an established datum plane. The datum plane for
a flume is the elevation at the bottom of the throat section. The water - surface elevation referred to some
arbitrary gage datum is called the "gage height." Stage or gage height is usually expressed in feet and
hundredths of a foot.
Ideally, flow rate through a flume may be determined by measurements of stage at a single point some distance
downstream from the inlet and above the throat. The single measurement indicates the discharge rate only if
critical or supercritical flow is achieved in the flume. By definition, critical flow occurs when the ratio of force
due to inertia to the force due to gravity ( Froude number) is unity. Supercritical flow occurs when the Froude
number exceeds unity. If the Froude number is less than one, subcritical flow occurs, commonly due to a
condition referred to as submergence; a second stage reading must be taken in the throat section to determine
the true discharge rate. Additional information concerning the use of flumes under all flow conditions,
including submergence, is found in USGS Water Supply Paper 2175, Volume 2, Chapter 10.
3.1.2 Field Procedures
Overview. Follow the appropriate steps to measure discharge depending on whether a Parshall flume or
portable Cutthroat flume is being used for the site.
Steps to be Followed in Measuring Discharge Using the Parshall Flume
1. The flume should be inspected for level in both directions and proper upstream and downstream
configurations.
2. Remove any material that may have accumulated in the flume.
3. Note any deterioration of the flume; report these conditions to the Project Manager at the conclusion of
daily data collection activities.
4. Measure and record the throat width to the nearest 0.01 feet.
5. Record the time and date of the site visit.
6. Use the staff gage to measure and record the stage in the upstream and throat sections to the nearest
0.02 feet.
7. Calculate discharge as described below.
8. Record the calculated discharge.
Steps to be Followed in Measuring Discharge Using a Portable Cutthroat Flume
The flume should be inspected for level in both directions and proper upstream and downstream
configurations. Make sure the flume captures all water migrating through the channel.
2. Measure and record the throat width to the nearest 0.01 feet.
4153A.140129 Whetstone Associates