USA Volunteer Water Monitoring Network

Streamflow Monitoring

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Question 1: I’d like to hear from volunteer groups who have experience with measuring flow.

Question 2: Has anyone integrated the head rod velocity method (Volunteer Monitor Newsletter Winter 2004 page 3) with the procedure for calculating stream flow detailed in the EPA Volunteer Stream Monitoring Methods Manual Chapter 5.1?

Question 3: Is anyone using volunteer methods for measuring flow? I would like to talk (e-mail is fine) to anyone who has had success with using volunteers to measure flow.

Question 4: Anyone have any experience (positive or negative) with the ‘Flowatch’ flowmeter? Any other inexpensive flowmeters anyone can recommend?

Question 5: Does anyone have any recommendations of a good Flow Meter that is easy to use in the field by volunteers, low cost (ideally $500 or less), and may (or may not) have other features included (i.e. pH, D.O., etc.) incorporated into the device?

Question 1

Date: Fri, 14 Mar 2003
From: Eleanor Ely
Subject: [volmonitor] monitoring flow

Dear listserv members:

I am preparing an article on “monitoring stream flow” for the next issue of the Volunteer Monitor newsletter. This article was largely inspired by prior discussions on the listserv, which demonstrated a high degree of interest in this topic.

I have a couple of requests:

1. I am trying to find a friendly hydrologist (or two) to answer some of my questions and review the article for technical accuracy.

2. I’d like to hear from volunteer groups who have experience with measuring flow. Questions I’m interested in include: why you decided to measure this parameter, what methods you’re using, how satisfied you are with your methods, any changes you’ve made in your procedures as you learned more about what works and what doesn’t, what you’ve learned from the data, how the data have been used, problems you encountered and what you did about them, and any additional comments that you think would be useful to other volunteer monitoring programs who may be interested in monitoring flow.

Note: If you respond by hitting the “reply” button your message will go to the whole listserv, which may be OK since this topic is probably of wide interest.

Thanks very much.
Ellie

Eleanor Ely
Editor, The Volunteer Monitor Newsletter

Responses to Question 1

From: Phil Emmling
To: VOLMONITOR
Sent: Friday, March 14, 2003 1:38 PM
Subject: [volmonitor] RE: monitoring flow

Ellie,

Let’s see what type of discussion we can get on the subject of flow. Flow measurements are important and USGS has spent a lot of time and money doing it. It seems to me that the value of flow is either for the variable itself (water quantity) or using flow/discharge with concentration information (TSS, phosphorus, nitrate, toxic substances, etc.) to calculate a loading over some time period. I would include the educational value of introducing the concept of flow to students and other citizens. I don’t think volunteers can do flow often enough or well enough to provide more than crude discharge information or loading estimates. Education seems to be the most useful benefit of doing flow. This is my opinion on “why do flow?”

In Midwestern streams the velocity is seldom >1 fps at base flow. The Price Pygmy AA meter works well >0.3 fps. The float method (oranges) is OK for surface velocity on a calm to moderately windy day. The average velocity, however, is at 0.6 depth (from the top) in water 30 inches. I tired it in water that was 34 inches deep and it worked very well (0.6 = 0.2 + 0.8 divided by 2). The standard work on these measurements can be found in a 1964 USGS report by Buchanan and Somers. It is also necessary to apply a correction of 0.9 and 0.8 for smooth or rough bottoms. Most volunteers do not select enough sections across a stream (10 minimum) or enough drift lanes (mid point of sections) for an accurate stream discharge. It is difficult to pick a good section of a slow Midwestern stream that does not contain large rocks, mud on the sides, or weeds. USGS builds weirs in stretches of streams to get around the problem of site selection.

Since it is difficult to pick a good site, obtain a good average velocity, measure an accurate cross section, or obtain an expensive meter, I would suggest following any of the various volunteer protocols and being consistent. It seems important to remember that you want the center of parcels of water and not equally spaced velocity points. For example, if the stream is 12 feet wide, the drift points are NOT at 3, 6, and 9 feet from a shore. If we want 3 velocity measurements across the stream, the parcels are each 4 feet wide (0-4, 4-8, 8-12) and the center of each parcel is at 2, 6, and 10 feet from one shore. If a volunteer did it the USGS way, the person would need a depth at about each foot to describe the area of each parcel and a velocity measurement at the midpoint of each parcel. For any measurement of surface velocity, it is good to have 3 timed runs of about 20 feet long at the midpoint of each parcel.

I monitored 7 sites in a day and did not have time to do a good flow measurement. When you sample events, it is even more difficult in flashy systems to coordinate the water chemistry and bacteria sample with the rising or falling stage height and discharge. I used stage height relative to a 1.00 foot mark and rapid sampling (15 minutes) in order to match sample with discharge. I saw the stream drop 0.5 inch in about 15 minutes. Conductivity can be used to estimate the amount of event runoff in the stream at the time of sampling. If the base flow conductivity is usually 600uS and it is 400uS during an event, I would estimate that 1/3 of the stream is runoff. It seems valid to assume that any pollutant concentration was 3 times as the event measured level due to dilution by the base flow.

Any comments?

Phil Emmling
Environmental Chemistry & Technology Program
660 N. Park St.
Madison, WI 53706
Phone: 608 262-2899
FAX: 608 262-0454

 

Date: Fri, 14 Mar 2003
From: Dale Banks
Subject: [volmonitor] RE: monitoring flow

Phil,
We have not been gathering flow data on our streams in our volunteer program to date. We plan on implementing a strategy to do so this sumer, to help understand the nutrient and turbidity and conductivity data we are collecting, and to simply identify the discharge rates. I think that volunteers are certainly capable of being trained to use a flow meter and to follow a procedure that will produce usable results, at least on the streams here, not simply crude information as you suggest. You said ” Since it is difficult to pick a good site, obtain a good average velocity, measure an accurate cross section, or obtain an expensive meter, I would suggest following any of the various volunteer protocols and being consistent.” The biggest difficulty I see for our program is purchasing the meter. The site can be selected with guidance from our tecnichal advisory committee, and by following established guidelines for site selection for flow. The other difficulties can be addressed through volunteer training and quality control measures. We have a sampling design that calls for site visits twice monthly in the summer and once monthly in the winter, totalling 16 site observations/year. With a trained volunteer using a flow probe and established transect methods, a volunteer would be capable of collecting valuable flow data on the streams we monitor. I think that volunteers will be receptive to the idea of being trained to measure flow with a more advanced method than floating an orange, and will be ok with the extra time on site. We expect to begin with this approach in the next couple of months on a limited number of sites to work out the kinks. Any suggestions anyone might have regarding this strategy would be appreciated.

Cheers,

Dale

Dale Banks
Volunteer Monitoring Coordinator
Cook Inlet Keeper
3734 Ben Walters Lane
Homer, Alaska 99603
(907) 235-4068
dale@inletkeeper.org
www.inletkeeper.org

 

Date: Fri, 14 Mar 2003
From: mark a kuechenmeister
Subject: [volmonitor] Fw: monitoring flow

my name is mark kuechenmeister. i’am the leader of stream team 888 (mo. stream teams) and i monitor a little creek named maline creek in st. louis, mo.for the last 6 years. the mo. dnr has guidelines for monitoring. we go through many training levels. i;am level 3 certified. this is the highest you can get. level one you get training in the classroom and at a creek. level 2 is a review after you have monitored a few times. level 3 a conservation agent goes out to your creek and watches you work. he uses his instruments to test the creek and compaires his results with you. when we did stream flow measurements, my measurements were exactly the same as his sophisticated instruments read. i used a tape measure, a measuring stick in tenths of a foot incraments, a ten foot rope, and a tennis ball. we have a worksheet in wich we plug in all the missing numbers that we get from our monitoring. then we know what the stream discharge is in cubic feet per second. our last monitoring trip 3/9/03 our discharge was 1.86 cubic feet per second. i hope this helps out
Monitoring and helping
Maline Creek,
your friend
Mark K.

 

Date: Mon, 17 Mar 2003
From: Phil Emmling
Subject: [volmonitor] RE: monitoring flow

Dale,

I am going to recheck my flow information since I pulled the note to Ellie out of my head and made a few typo mistakes. Our southwest WI streams have lots of agricultural problems hampering flow measurements. There are cow trails producing back eddies, large amounts of mud extending about 3 feet on each bank in a 12 foot wide section, extensive vegetation mats in shallow runs, and some large sandstone, limestone, chert boulders or rock piles in the stream. It is impossible to get into some areas with waders due to muck or depth. In the rocky areas, undercut banks and vegetation make in difficult to obtain a good cross section measurement. I am certain there are streams with rather regular cross sections, but our streams in SW, W, S, E, and NE Wisconsin seem to either have lots of mud, or weed beds, or rocks. There are sandy streams in central Wisconsin.

I am certain that most volunteers can do anything an agency tech can do to measure flow. It isn’t a matter of IQ; it is a matter of training and some sixth sense of scientific precision. In addition to the cost of the meter, you may have a problem keeping a meter working. I have experience with the Price Pygmy AA. The cat whisker wire and pivot pin can be abused easily when the meter is used by several people. If you buy a meter, it would be good to use the orange and get an idea of the range of velocity to be measured. I found that my meter was rated for an accuracy of 0.1fps but it needed 0.3 fps to initially turn the cups. In shallow water you can watch the cups. My advice is to talk to some USGS field workers in your area. You may be able to obtain USGS Water Yearbooks in your area that can provide discharge information for your streams. I assume you know about the Real-Time website at USGS. Our Middleton, WI USGS people are very helpful and have a librarian and lots of free publications.

I wouldn’t condemn the orange, but I would like people to consider the assumptions and limitations of the float technique. There is a curve in the USGS Buchanan and Sommers (1964) publication showing average flow at either 0.6 or (0.2 + 0.8)/2 of the depth. I don’t think any volunteer protocols make this correction for average velocity. Most volunteer protocols do not measure enough cross section parcels or stress the value of matching a parcel to a velocity. For example, the USEPA manual uses 3 or 4 depth measurements. I am not certain that volunteers appreciate the effects of wind on the orange measurement. The orange measurement requires a minimum of two people to do it. However, the orange is cheap and dependable and perhaps the only option in water less than 12 inches deep. I sent out my meter for a tune-up this winter (perhaps it will work in less than 0.3 fps) and I will try it against the orange in some well chosen location. Then I will try it in a few other less optimal locations and distribute the information. Has anyone else done a detailed comparison using the orange and a Pygmy Price AA or any other type of meter?

Thanks for your comments,

Phil Emmling
Environmental Chemistry & Technology Program
660 N. Park St.
Madison, WI 53706
Phone: 608 262-2899

Question 2

Date: Wed, 13 Apr 2005
From: Jane Herbert
Subject: head rod method and calculating flow

Hello,

Has anyone integrated the head rod velocity method (Volunteer Monitor Newsletter Winter 2004 page 3) with the procedure for calculating stream flow detailed in the EPA Volunteer Stream Monitoring Methods Manual Chapter 5.1? I’m wondering if you can substitute the head rod “jump” readings for float trials. This would eliminate the need to calculate cross-sectional area for two transects as the length (L) factor would be removed. Seems like it would also remove the drag coefficient (C).

If this makes sense, does anyone have an idea what the equation would then be for calculating stream flow? I’ll take a stab at it:

Flow = the square root of (2gh) x A, meaning the average velocity in m/second multiplied by channel cross sectional area in square meters would give you flow in cubic meters per second.

Please feel free to comment…

I like the idea of using the head rod method for calculating flow in Michigan streams. We have a lot of overhanging riparian vegetation where oranges can hang up. It would seem that the head rod method would eliminate the bias of only being able to do float trials down the middle of the channel where the water runs faster.

Thanks in advance for any thoughts, suggestions or experiences you’d like to share on this.

Jane
_____________

Jane Herbert
District Water Quality Agent
Michigan State University Extension Land & Water Program
Kellogg Biological Station
3700 E . Gull Lake Drive
Hickory Corners, MI 49060
Phone: 269-671-2412 x 222 or 800-521-2619 x 222
Fax: 269-671-4485
Email: jherbert@msu.edu

Responses to Question 2

Date: Wed, 13 Apr 2005
From: Eleanor Ely

Dear Jane et al.:

It sounds fine to me to multiply the cross-sectional area by the average velocity. If you look in the Summer 2003 Volunteer Monitor article on measuring flow, page 22, under “Calculate flow,” you will see that it directs you to multiply the cross-sectional area by the average velocity. (For those who don’t have the Winter 2004 Volunteer Monitor handy and are wondering what “g” and “h” stand for, the head rod method calculates average velocity as the square root of (2gh) where g is the gravitational constant and h is the average head.)

But I’m not sure about the correction factor. The explanation we used in the newsletter (Summer 2003, page 22) was “Because the float travels along the water surface, rather than being submerged at the 6/10-depth point like a meter, the number you obtain is actually average surface flow, which is higher than the overall average flow. Therefore you need to multiply the result by a correction factor to get a closer approximation of average flow. Most protocols suggest a correction factor of 0.8 for rocky-bottom streams and 0.9 for smooth-bottom streams.” I am not sure whether the head rod method is (like the float method) measuring surface flow or whether it’s giving a better indication of overall average flow.

By the way, I think this would be a good query for the volunteer monitoring listserv.

Ellie

Eleanor Ely
Editor, The Volunteer Monitor Newsletter

Question 3

From: BrownSt1@cs.com
To: Multiple recipients of list
Subject: measures of flow

Is anyone using volunteer methods for measuring flow? I would like to talk (e-mail is fine) to anyone who has had success with using volunteers to measure flow. Thanks and happy holidays…

Stacey Brown
Staff Scientist
Virginia Save Our Streams Program
7598 N. Lee Highway
Raphine, Va. 24472
brownst1@cs.com
540 377 6179 or
434-466-2613

Responses to Question 3

From: Eleanor Ely
Subject: Re: measures of flow

Dear Stacey and other listserve subscribers:
I am very interested in this topic as the possible subject of a future article in The Volunteer Monitor newsletter. I would appreciate it if anyone who replies to Stacey could either send their response to the whole list (volmonitor@unixmail.rtpnc.epa.gov) or else cc me (ellieely@earthlink.net).
I have heard about several programs that measure flow. Some of this information may be a little outdated, but here’s what I’ve got:

Napa County (California) Resource Conservation District uses a “wire weight gage” to measure depth and an orange peel to measure velocity; contact them at 707-252-4188, or staff@naparcd.org (Website:www.naparcd.org).
Missouri Stream Team also collects depth and velocity measurements (using whole orange for velocity). Contact Tim Rielly; I don’t have his direct number but he is at MO DNR; you can call Stream Team Coordinator Priscilla Stotts, also at DNR, at 573-526-3406, or Donna Menown, 573-526-1595.

Finally, I believe several Massachusetts groups have been very interested in collecting flow data. I think Geoff Dates (gdates@rivernetwork.org) would have information about them.

Hope this helps.
Ellie

Eleanor Ely
editor, The Volunteer Monitor Newsletter

 

From: “Donna Menown”
Subject: Re: measures of flow

Thanks, Ellie! Actually, we currently use a wiffle golf ball to measure stream flow (discharge) rather than an orange. Although the orange is nice because if it gets away from you it’s biodegradable, it is often too heavy to use to measure very shallow stretches (bumps off bottom), so we now give out wiffle golf balls to volunteers.

If you want more info on what we do, please feel free to contact any of us in Missouri who train volunteers to monitor water quality on streams.

Me — see contact info in signature block;

Priscilla Stotts, my Missouri DNR, Water Pollution Control Prog. coworker at the phone number Ellie lists below, or nrstotp@dnr.state.mo.us;

Tim Rielly, MoDNR, Environmental Services Program, 573/526-8998, nrrielt@dnr.state.mo.us; OR

Chris Riggert, Missouri Dept of Conservation, 573/882-9880, ext. 3301; riggec@mail.conservation.state.mo.us

We are glad to help! — Donna

Donna Menown
Volunteer WQ Monitoring & Stream Team Coord.
WPSC Division/Water Pollution Control Prog.
Mo. Dept. of Natural Resources, Jeff. City
(573) 526-1595; FAX [526-5797]
Internet e-mail: nrmenod@dnr.state.mo.us

 

From: Arleen Feng
To: Multiple recipients of list
Subject: Re: measures of flow

Stacey,

A new guidance document on flow measurement, with examples of some flow protocols, is on the California volunteer monitoring website at: www.swrcb.ca.gov/nps/flow.html

It includes a brief description of the “wire weight” protocol mentioned by Ellie, as used by the Sonoma Ecology Center; see also their site at http://www.vom.com/sec/svws/stream_stewards/ss_intro.htm

Hope this helps. Email me if you would like contact info for other volunteer groups mentioned in the guidance doc.


Arleen Feng
Alameda Countywide Clean Water Program
arleen@acpwa.mail.co.alameda.ca.us
ayfeng@alum.mit.edu

 

Question 1: Anyone have any experience (positive or negative) with the ‘Flowatch’ flowmeter?

Question 2: Does anyone have any recommendations of a good Flow Meter that is easy to use in the field by volunteers, low cost (ideally $500 or less), and may (or my not) have other features included (i.e. pH, D.O., etc.) incorporated into the device?

Question 4

From: Dale Banks
Subject: [volmonitor] Flow meters
To: VOLMONITOR

Hi,
Anyone have any experience (positive or negative) with the ‘Flowatch’ flowmeter? Any other inexpensive flowmeters anyone can recommend? These would be used for stream flow monitoring.

Thanks!

Dale

Dale Banks
Volunteer Monitoring Coordinator
Cook Inlet Keeper
(907) 235-4068
dale@inletkeeper.org
www.inletkeeper.org

Responses to Question 4

From: Dennis
Subject: [volmonitor] Re: Flow meters
To: VOLMONITOR

Hi Dale,

I have seen the Flowatch flow meter, and considered using it on a monitoring project, however, the company doesn’t have a way to calibrate it. For our DEP to accept the results of our monitoring, I need to show how we are going to calibrate our equipment, and apparently the Flowatch does not have a method for the customer to do that. If you don’t need to calibrate it, however, it seems like an easy to use and straightforward meter.

Hope this helps,
Carolyn

Carolyn W. Sibner
Water Quality Coordinator
Housatonic Valley Association

 

From: Phil Emmling
Subject: [volmonitor] Re: Flow meters
To: VOLMONITOR

Flow meters:

Perhaps a nearby university civil engineering department has a small hydrology flume to calibrate meters. If they have a course, they usually have a flume.

You should make certain that any meter can read down to your expected base flow velocity. For example, the Price Pygmy meters AA used by some professionals are rated at 0.1 ft/s. I have found, however, that it takes about 0.3 ft/s to start the cups moving and then the resolution is fine at 0.1 ft/s increments. I don’t think there are too many units that do well between 0.1 and 0.5 ft/s.

If anyone knows of any units that are accurate to 0.05 ft/s (0.05-1 ft/s), I would be interested in them.

Phil Emmling
Environmental Chemistry & Technology Program
660 N. Park St.
Madison, WI 53706
Phone: 608 262-2899
FAX: 608 262-0454

 

From: Revital Katznelson
Subject: [volmonitor] Re: Flow meters
To: VOLMONITOR
Cc: Raquel Gutierrez…snip… xhernand.RB4Post.Region4@rb4.swrcb.ca.gov>

Phil and Carolyn –

I am not really clear what you mean when you use the word “calibrate” – are you referring to adjusting the output of the instrument, or only to checking whether it shows the “true” value?
Our Clean Water Team (the Citizen Monitoring Program of the California State Water Resources Control Board) is now using two separate terms, defined below for water quality (rather than flow):

Calibration: The action of adjusting the readings of an instrument to have it match a “true” value as represented by known natural conditions (e.g., freezing point) or by a Standard Solution (e.g., Standard pH buffer).
Accuracy Check: Comparison of the reading, or output, of a measurement device with a value believed the “true” value (see above). An “Accuracy Check” is different from a Calibration, since it is only a
comparison and does not result in an adjustment of an instrument or procedure.

I have encountered many instruments that have been calibrated by the manufacturer prior to sale, and are not amenable to any adjustments by the user. If your flow meter is one of those, you can use the flume (or the apron&bucket method for very low flow discharge) to conduct an “accuracy check” and provide that information with your flow data. “Accuracy check” results – i.e., the difference between the “true” value and what your instrument actually reads – can then be used to either “correct” your measurement Results or to compute the inaccuracy of your measurement.

I hope this is useful –
Revital

=======================================================
Revital Katznelson, Ph.D.
Regional Citizen Monitoring Coordinator
State Water Resources Control Board

 

From: Dale Banks
Subject: [volmonitor] Re: Flow meters
To: VOLMONITOR

Thanks for the useful comments. One possible way to check accuracy of the Flowatch would be to measure flow on a stream alongside USGS or someone else who is using an approved method. This might satisfy QC requirements in Carolyn’s case, but not sure what you would do if the results were bad and the meter can’t be calibrated…

Dale

 

From: Bob Williams
Subject: [volmonitor] Re: Flow meters
To: VOLMONITOR

Well, if nothing else works for measuring flow then the old orange or lemon in the water does an adequate job of determining stream flow. I stop by the supermarket and pick up the old oranges, lemons and limes (for free) and lay out a 10 meter strip along shore. A student at the top and bottom and a stop watch is all that is needed. This method could also be used to calibrate a device. All this is outlined in chapter 3 of Rivers Chemistry, the curriculum developed by the Rivers Project.
Dr. Bob

Question 5

Date: Thu, 24 Jul 2008 11:02:30 -0400
From: River Info
Subject: [volmonitor] Flow Meters

Greetings! Some of our Hoosier Riverwatch volunteers expressed an interest in purchasing Flow Meters, but after an initial search of options, found quite a variety of models and price ranges. Does anyone have any recommendations of a good Flow Meter that is easy to use in the field by volunteers, low cost (ideally $500 or less), and may (or my not) have other features included (i.e. pH, D.O., etc.) incorporated into the device?

Any information is appreciated! Thanks!!

Katie Hodgdon
Hoosier Riverwatch Volunteer Coordinator
Fort Harrison State Park – NREC
5785 Glenn Road
Indianapolis, IN 46216
317.541.0617
www.hoosierriverwatch.com

Responses to Question 5

Date: Thu, 24 Jul 2008 10:20:18 -0500
From: Don Snethen
Subject: Re: [volmonitor] Flow Meters

Katie, Have you consided the float method? It is inexpensive and probably more accurate than current meters for small streams.

Don Snethen

 

Date: Thu, 24 Jul 2008 11:29:55 -0400
From: Bruce Gorrill

Using vernier software stream flow sensor at $129 (http://www.vernier.com/probes/flo-bta.html) with their golink (http://www.vernier.com/go/golink.html) for $61 hooked to a computer gives good results. Using the golink saves needing to purchase an interface between the computer and the stream flow sensor.

Date: Thu, 24 Jul 2008 12:36:48 -0700
From: Erick Burres

FlowProbe seems to be the least expensive, relatively maintenance free, and easy for volunteers to use.

Erick Burres
Citizen Monitoring Coordinator
SWRCB- Clean Water Team

Visit the Clean Water Team at: http://www.waterboards.ca.gov/water_issues/programs/swamp/cwt_volunteer.shtml

Contact me at:
Desk (213) 576-6788
Cell (213) 712-6862
Fax (213) 576-6686

LA-RWQCB
320 West 4th Street, Suite 200
Los Angeles, CA 90013

 

Date: Fri, 25 Jul 2008 09:17:22 -0500
From: Kris Stepenuck

Hi

There may be some useful responses to a similar question that was asked a while back on this list posted at: http://www.uwex.edu/ces/csreesvolmon/Special/EPAListserv/FlowMeters.html

Also, I’ve heard from USGS people in a few states that most of them have moved on to using acoustic methods for monitoring flow, so a trusted volunteer group may be allowed to use a pygmy meter that a local USGS office has but isn’t using any longer.

Kris Stepenuck

 

Date: Mon, 28 Jul 2008 09:14:54 -0400
From: Tim Craddock

I’ve had good luck with Global Water’s Flow Probe, which is about $700-$800

http://www.globalw.com/products/flowprobe.html

Also I would try others methods such as the float. I use a styrofoam practice golf ball, which can be purchased at K-mart etc. They are about $4.00-$6.00 for a package of four; or the velocity head rod (VHR) method. For the VHR method I use a 2″ wide 4′ feet long aluminum straight edge. This can be purchased at Lowes or local hardware stores. I’ve also used an MJP student stream flowmeter, which is about $300.00.

The disadvantage to any alternative is of course comparability. However, as long as you are consistent with your methodology you can easily collect data that will show trends, even without purchasing high-cost equipment.

Tim Craddock, Citizen’s Monitoring Coordinator
West Virginia Save Our Streams Program
601 57th Street, SE
Charleston, WV 25304

Office: (304) 926-0499 Ext. 1040
Mobile: (304) 389-7630
Email: tcraddock@wvdep.org

 

Date: Mon, 28 Jul 2008 11:06:25 -0400
From: Jerry Iles

Kris,
My experience is that cheap flow meters are not accurate. You need to pay about 1200 to get something that USGS will consider accurate.
Jerry

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