Level Measurement in Dam

How accurate do you need to be? Fish finders will typically read to one foot, if more accurate than this best use a weight on a tape measure or just a line.

Do you want to:

1. Measure the water level (depth)at the dam?

2. Measure the levelness of the dam?

3. Measure the level of the dam above sea level (elevation)?

4. Measure the level of the top of the dam to the top of the water?

5. Measure the level of the water behind the dam above sea level (elevation)?

Use pressure measurement at the base and avoid reinventing wheels. S.M.

How do you propose getting a pressure sensor down there. Buying fish finder would be cheaper as would weight on a string.

Easiest way is to put a weight on the end of an open, 1/2" silicone tube connected firmly to a pressure sensor located at the top of the dam, or any other location that works.

Water pressure on the open tube will compress air in the tube and pressure sensor output can be set for feet of water, accurate to 0.01 feet.

cost of silicone tube 60 meters long $10

Cost of pressure gauge $10- $20

Cost of rock on a string $0.00

Cost of measurement - priceless

Borrow a tape to measure lenght of wet string with accuracy good as graduations on tape.

Dear energygod,

This will not provide a direct water column pressure measurement due to the compressability of the air in the tube the pressure will be equal to the feet of water differential between the level of water in the tube and the reservoir level.

However if you supplied a small purge flow you would have created a dip tube and the pressure in water column would then be equal to the differential from the bottom of the tube to the reservoir level.

Alberto,

Are you looking for a loop powered 4-20ma instrument, or digital, or wireless, etc..?

What is the range of the level (fluctuation)?

Are there environmental considerations (wind, waves, ice, rain...)?

What accuracy and response do you need?

For the information that you have provided I think a tape measure with a weighted end is the best answer, but I suspect there is more to it.

I recommend that you call an instrumentation sales rep or two and let them have a look at your application. They will gather the necessary application information and make an excellent recommendation to you for free. They get payed when you buy something from them.

I am looking a loop powered 4-20mA. Level fluctuation is 5 to 60 meters of deep51 centigrades maximum-11 centigrades minimum1 meter accuracy
is for a big pump station Thank's Ace!

Based on this information I would recommend that you look into non contact radar level instruments. The angle of energy dispersion is narrower than ultrasonics, and where ultrasonic velocity is affected by atmospheric pressure and temperature radar technology is not. Look at Ohmart Vega "The stick" and/or Magnetrol "Pulsar".

Thank you Ace!
I will to considered your proposal for my project.
Thanks' again!
Bye!

I also voted GA, and it definitely is a relatively low cost, effective "measurement" tool. But, I got the impression (perhaps incorrectly) that the OP's issue was how to measure depth dynamically so that some "process" could maintain water level below the defined MAX- likely by opening a sluice gate.

Assuming that the level would be manually controlled, you would likely also need a camera to broadcast the level to the operator (who is likely NOT on the "active" side of the dam.

IF there is no constantly present "operator", I have just thought of another very low cost, simple, reliable way to control water level.

Install a float switch, like those used for sump pumps, on the "active" side of the dam, set to activate at- say- 59.9 feet. For added "safety", install two switches set for 59.9 and 60.0 feet. If you are really paranoid, install a third set at 59.8 feet. Connect them through a double acting relay connected to the contactor controlling the sluice gate drive motor- "ON" = open gate, "OFF" = close gate.

Just to be totally accurate- I accidentally used "feet" instead of "meters"- sorry

Brilliant!

Damn Tornado you beat me to it.

To the OP (Original Poster) as you can see there are as many solutions as there are people willing to help. The reasons for choosing between the various solutions have been fully scripted by other posters .

I would say the most important would be

1. Do you need to be able to continuously read the level and supply the value electronically to other users (if yes this rules out the numbers on the dam or the weight on a string - btw there is a risk with the weight on a string of the stone getting stuck on submerged trees, rocks etc before reaching the bottom. Original plans will show the height of the dam so you can just measure down fromt he parapet), from your suggestion of ultra sonics I guess this is the case and that would be a good solution imho

2. How do you accomodate surface effects - wind, ice, waves trees

3. How accurate do you need the measurement

How fast can a level change? Go with the markings on the inside face.

But, if yo really got to get fancy, there is no need to reinvent the wheel. Every modern washing machine has a water pressure sensor in it for level setting. A member of that family will do fine.

You can use sonar level gauges like in ships, you can use a tape type level gauge, you could use radar, ultrasonic, etc. It all depends on the accuracy, response speed and repeatability that you need, since you have not mentioned them, there is no way to suggest anything

Why don't you keep this KISS?

I question why didn't the dam designers, builders, and owners include a vertical graduated sounding board up along the entire height of the dam, so that it would be very easy to see the actual water depth at a glance?

By introducing pressure transponders and ultra-sonics into the mix you're going to need to calibrate the instrument on a routine basis, plus you will be required to do extensive maintenance on it. Then, we're also talking about the great expense of purchasing an electronic toy, installing it, and finally operating it. Finally, what diver in his right mind will be diving down 180 meters to install this gizmo? Have you even considered that? There are not too many certified deep divers out there that would contemplate such a folly, and for what, peanuts? Do this on the cheap? I don't think so! f you do, you'll end up with an experienced diver who'll get the "bends" and die on you if you don't supply a depressurizing chamber.

My experience over the years that a lot of ultrasonic measuring devices my not work correctly in murky water....as well as in pristine clear water, so choose very carefully after discussing your options with several manufacturer's tech reps!

Opppps, my bad. I meant to type 60 meters, or roughly 180 feet, not 180 meters in my previous posting! Sorry for the confusion!!!

Both of us goofed in similar way at nearly same time- must have been a sunspot.

More than likely the original dam builders did in fact provide water level measuring boards and likely several more options not mentioned in this thread. Trouble is today's generation of engineers are not trained to think of these choices or methods. For instance every dam has to have a spillway. Right there is a very accurate and measuerable location to determine water level behind the dam.

Even a quick perusal of the original civil construction drawings should reveal enough data to enable some means of determining static water level measurements. For dynamic levels more sophisticated means are needed. .

Many years ago when I was still involvd in hydrographic survey work including water depth behind dams, depth of water in channels etc. I proposed using radio controlled model boats to survey resevoirs to determine siltration extent without the expenditure of placing a full sized survey vessel or having people walking along the crest of dams that lacked safety railings. this method is now pretty standard.

At one time I worked for a company that designed and built remote monitoring equipment. One large hydro-electric power company wanted us to design a system for measuring water level ata dam then control the sluice gates and turbines for power generation. The manual methods wa considered old fashioned and they wanted some operator sitting miles away in an air conditioned office to do the job.

Therin lies the real problem. Too often the new generation of engineers seldom get out of the office into the real world.

It would be nice if OP got back to us to clarify what was intendd with the question.

submersible head pressure level sensors are off-the-shelf commercial items, in various ranges with cabling and vent tube cut to order; loop powered 4-20mA.

http://www.lesman.com/unleashd/catalog/level/level_WIKA_LS-10_LH-10_Submersible.html