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By Heidi Glaus

O'FALLON, Mo.(KSDK) - Chances are you've driven past them and not even noticed. Gauges old and new, manual and automated measure the river and creek levels.

"This is the automated gauge and this is what we call a pressure transducer," explains Mark Fuchs, service hydrologist at the National Weather Service. He's a man who knows these gauges well.

"That tube runs all the way down to the bottom of the channel. There's a gas inside the tube and the water exhorts a pressure at the bottom of that tube and that pressure is measured with instrumentation on the inside of the gauge," Fuchs goes on to explain.

The data is accumulated and then transmitted via satellite to a collecting station in Virginia. Walk a little farther along Highway K, and you'll find slightly older gauges, gauges that require someone to come out and read them.

"This is a crest stage gauge and it's a very simple piece of equipment. All it is Heidi, is a piece of wood with markings on it," Fuchs says pulling the stick from a metal tube.

The other one in a little metal box hanging over Dardenne Creek is a wire weight gauge that has to be lowered down to touch the water surface. And there's another, newer gauge at another point along the creek.

"This is some of the newest technology we have, locally anyway. This is a radar gauge and what this thing does is bounces electromagnetic pulses off the water surface," Fuchs says.

All of these gauges measure basically the same thing, but surprisingly the bottom doesn't equal zero.

"Zero is kind of arbitrary," Fuchs points out.

It's something that dates back to the 1800s.

"They had some idea to how low the river might get and how high it could get so they had never seen it any less than what they established as zero," Fuchs says.

So zero varies from site to site, and in case you were wondering, gauges are placed in certain areas for a variety of reasons.

"Some of these gauges are here because of the potential impact, some of them are here for scientific reasons," Fuchs goes on to say.

They also help withresearch on water quality or urban runoff.

Whatever the reason they're around, maybe now you'll notice them.

If you have a Hey Heidi question, email Heidi at hglaus@ksdk.com.

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