water flow rate in stream / ditch

[osh]

Does anyone have any suggestions as to how to measure the flow rate / volume of water flowing within a ditch.

Preferably something home made (i.e. cheap!).

I have a few ideas but thought I would ask the group!

[Clanad]

I've used this method for measuring water flow rates in irrigation ditches here on the ranch (western U.S.) It works well...

http://www.epa.gov/volunteer/stream/vms51.html

[newtron]

Clanad suggests a good simple method. I've done a lot of stream gaging and the orange method provides a decent flow rate estimate (within 10%) if the stream is straight and flow is uniform across the stream. How big is your ditch? If the ditch is very small, then you could build a small earthen dam so that the water flows freely over it in a water fall type fashion. Then you can get a container of a known volume and time how long it takes to fill the container. Again this should be done several times and the results should be averaged. Other more accurate methods of flow rate measurement include the construction of a flume or weir. A V notch wier is not to difficult to build. You should be able to find instructions for building one by googling 'weirs'.

[Clanad]

Good to see you again, newtron ... how are things in N.M.?

[newtron]

Hi Clanad, Things are going well. It's been rather cool for this time of year. It just started warming up considerably the last couple of days. How are things going in AZ?

[Muppit]

Really easy: if you not too bothered about being completely accurate and your ditch is fairly uniform!

You will need 4 things:

1. A stick (or something else that floats and is smaller than your ditch!

2. A stopwatch (or anything else that can measure time - a sundial might not be appropriate)

3. A measuring tape

4. A calculator (you seem to have a computer, so I guess you'll have a calculator!)

You'll need to perform these 4 easy steps......

1. Measure a length of your ditch, and call this length 'L'. (The longer 'L' is, the greater the accuracy will be)

2. Measure the cross sectional area of your ditch. (If you don't know how to do that, look it up on google or something). (For increased accuracy, measure the cross section in several locations and take the average). Call the area 'A'. (If you measure the length in meters, then you should measure the secional area in meters^2, if L = feet, then A should be feet^2 etc etc.

3. Throw the stick or floaty thing into your ditch (something non toxic and bio-degradeable is preferable!). Use the stop watch or sun dial to time how long it takes to travel the length of your measured section of ditch. Call the amount of time taken 'T'.

4. Get out your calculator and multiply the length by the area, this gives you a volume. That is the volume of water that flows through your ditch per 'T', (if you measured T in seconds it will be the volume per 'T' seconds). Divide the volume by 'T', this will give you the volume of water flow per unit time. If you measured the volume in meter cubes, and time in seconds, you will get meter cubes per second. If you measured v in nano feet, and t in light years then you will have a really big answer in nano feet cubes per light year!

I hope this helps, and if anyone reads it, I know water flow varies trough a section, but this is the