Laserfiche WebLink
Appendix D — SOP for Stream Flow Measurement — Hansen Project 2 <br />Cutthroat Flume. The cutthroat flume is similar to the Parshall flume except that it has a horizontal (non - <br />sloping) floor with an entrance section and exit section, but no throat section (Bennett, 1972). The principals of <br />operation are similar to that of the Parshall flume. <br />Depth- Measuring Device. Parshall flumes will be equipped with standard UnitedStates Geological Survey <br />(USGS) style vertical staff gages. The staff gages will be used to measure gage height to the nearest 0.02 feet. <br />2.2 Materials Required for Velocity -Area Measurements using a Flow Probe <br />The Global Water® Flow Probe is the current velocity meter most commonly used at the Hansen Project for <br />stream flow measurement using the area - velocity method. The following equipment is required: <br />• Current meter and depth measuring device (Global Water(& Flow ProbeTm or similar device) <br />• Width - measuring devices, either engineer's tape or tagline <br />- Steel or fiberglass (non - stretchable) <br />- Engineer's measuring tape or graduated line in tenths and hundredths <br />• Fieldbook and field data sheets <br />• Flat headed screwdriver (optional, recommended) <br />• Waders <br />2.3 Materials Required for Velocity -Area Measurements using a AA or Pygmy Meter <br />The Price AA or Pygmy meter are older technologies, and no longer commonly used. However, the materials <br />and equipment are specified in this SOP in the event that it is necessary to use such equipment. <br />Equipment. Current meters, timers, depth and width measuring devices, and a means of counting meter <br />revolutions are needed for measurement of discharge by the velocity -area method. The equipment includes: <br />• Depth- measuring device, the wading rod <br />• Current meter <br />• Width- measuring devices, either engineer's tape or tagline <br />• Headset <br />• Stop watch <br />• Fieldbook or field data sheets <br />• Waders <br />Depth - Measuring Device. The depth- measuring device that will be used is the top- setting 1/2 -inch diameter <br />hexagonal wading rod. The current meter is attached to the wading rod. The top- setting wading rod consists of <br />a 1/2 -inch hexagonal main rod for measuring depth and a 3/8 -inch diameter round rod for setting the position <br />of the current meter. <br />Current Meter. A current meter is an instrument used to measure the velocity of flowing water. The <br />principle of operation is based on the proportionality between the velocity of the water and the resulting <br />angular velocity of the meter's rotor. By placing the current meter at a point in a stream and counting the <br />number of revolutions of the rotor during a measured interval of time the velocity of water at that point is <br />determined. <br />The number of revolutions of the rotor is obtained by an electrical circuit through the contact chamber. Contact <br />points in the chamber are designed to complete an electrical circuit at selected frequencies of revolution. The <br />contact chambers selected for discharge measurements have contact points that will complete the circuit once <br />per revolution. The electrical impulse produces an audible click in a headphone. The intervals during which <br />meter revolutions are counted are timed with a stop watch. <br />Engineer's Tape or Tagline. Fiberglass tapes or pre - marked taglines are used for stream channel width <br />measurement. Tapes or taglines can be accurate with proper precautions. Orientation normal to the flow <br />4153A.140129 Whetstone Associates • <br />