Coordinators
Tips for teaching Flow Measurement
Pre-training thoughts:
- WAV's methods to determine stream flow have been adapted from the Missouri Stream Teams. These methods were introduced to WAV during the summer of 2002 and differ from those previously used by most WAV monitors (former methods can be found at: EPA's Volunteer Stream Monitoring Methods Manual); therefore, please be sure to review methods for this procedure prior to training session.
- To save time during training, it is a good idea to visit the site of the training in advance and to measure the width of the stream at the location where flow will be taught. Using this information, you can pre-assemble the mid-site transect line for the flow measurement with 1 foot (or greater if stream is wider than 20 feet) increments marked.
- Be sure to use a site that can be safely waded across and that is uniform in width along at least a 20-foot length.
- Also be sure the stream is not braided (numerous channels) at the site where you will measure flow (although such a site can also provide a good teaching point in that not all flow is being estimated if the channel is braided).
- You might consider marking the handles on the D-frame nets (or other poles) to be used in the training session with tenths of feet, so they can be used to measure depth when assessing flow. (Hint from a local coordinator: If you write the numbers upside down on the pole, you can read them more easily when standing looking down at it to read it when in the stream.)
- Be sure to give monitors a copy of the data sheet for use at the training as well as for use at their own sites. All data sheets can be printed from the WAV website: here
Teaching tips:
- Discuss the connection between stream flow and other parameters being monitored by WAV volunteers. The link between land use and stream flow is a critical aspect for monitor trainees to understand. You may choose to discuss how flow patterns are altered with increased impervious surface in a watershed (lower base flows and quicker, higher peaks flows with storms than in an undeveloped watershed).
- Please be sure that monitors understand site selection requirements for monitoring flow:
At least a 20 foot length of stream that is uniform in width along that length
Not a braided stream
Must be safe to wade across the entire width of the stream where flow monitoring is done.
If the stream is wider than 20 feet, rather than assessing depth at every foot across the width, please have the monitors divide the stream into 20 equal increments across its entire width and assess depth at each of these intervals
- For consistency among sampling groups, please have everyone enter a depth of 0 feet for their first depth measurement. Newer versions of the data sheets should have this value pre-entered onto the form.
- The more the merrier in assessing stream flow. You might ask someone to act as a timer, a float dropper, a float catcher, and a data recorder.
- Remember that data calculations must be completed using depth in tenths of feet (NOT feet and inches). The recording form was designed to accept measurements in either feet and inches or tenths of feet. Please point out that distinction to trainees (left hand column is for feet and inches, right hand column is for tenths of feet conversion).
- If measurements are initially recorded in feet and inches on the recording form, it is designed to be folded over to reveal a chart that converts feet and inches to tenths of feet.
- As noted in the methods, if the float gets caught on an obstruction or in a backwater area, it should be removed and the time trial should be redone.
- If you are short on time during training and will have more than one group cycle through sessions, you might consider doing flow calculations as a group after all cycles have passed the station. Further, you might choose to have each group assess velocity only one time in their session, averaging their velocity measurements to determine flow as a group later in the training. A similar 'sharing' of data might be done with depth measurements along the transect.
- A great idea in assessing the stream's velocity across the transect is (thanks to Raccoon Creek trainer Tom) to describe the stream like a multi-lane highway, in which there are different amounts of traffic in the different lanes, so it is necessary to try to measure velocity in the various lanes of the stream and take an average. (The flow directions ask monitors to assess velocity at least 3 times.)
- Kinkos or other copy shops will enlarge and laminate the stream flow data sheet for a few dollars. It can then be used to determine streamflow with a group in the field, sing a Vis-a-Vis wet-erase marker to record the data on the form.
- Flow Measurement Fact Sheet Series pdf