Undoing The Handiwork of Centuries Past

Sharing data, devising ways to make river systems cleaner, more hospitable habitats

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This segment is part of the Engineers of the New Millennium: The Global Water Challenge Special Report.

Transcript:Sensors to Determine Health of Streams


Harry Goldstein: Is that a giant clam? What is that?

Art Parola: Yeah, it is. It’s a mussel, and actually it’s—oh, this one’s dead.

Harry Goldstein: Are they edible?

Art Parola: I believe that the Native Americans ate them. I’m not sure they’re all that good to eat.

Harry Goldstein: We’re standing in a stream called the South Fork of Curry’s Fork. The water burbling around our boots eventually feeds into Floyd’s Fork, which empties into the Salt River and ultimately the Ohio River, 50 miles [80 kilometers] to the southwest. My guide is Art Parola, a civil engineering professor at the University of Louisville and director of the Stream Institute. He’s not entirely sure what kind of mussel we’re chucking back into the water. But it could be one of Kentucky’s 20 endangered species of mussel, with exotic names like orangefoot pimpleback, rough pigtoe, and fat pocketbook. Just like frogs, fish, and waterfowl, freshwater mussels depend on clean water to thrive.

Art Parola: But the Floyd’s Fork system, which this is a tributary to, has some endangered mussels in it. And they are sensitive, actually, to the supply of this fine material that can clog up the system they use to eat and breathe.

Harry Goldstein: Parola and his colleagues worry that these little waterways are depositing sediments into larger rivers and that fertilizer chemicals such as phosphorus are hitching a ride. The problem is that banks of streams that pioneers dug out 200 years ago are eroding, loosening fine-grain sediment that eventually winds up in major rivers like the murky brown Ohio. But the most obvious impact of this process can be seen right here, where the food chain of this wetland begins, with the bugs.

Art Parola: And what we’d like is the gravel to be loosely packed so the water can flow underneath and around the gravel. That lets a lot of the insect life that we’d like to have that lives in these gravels to exist. If it gets clogged up, then these animals can’t exist in these rivers.

Harry Goldstein: Parola and his team are in the first stages of undoing the handiwork of centuries past. Over the next several months, they will bulldoze the land surrounding this stream down to about a foot above the current water level. The stream will spread out, allowing it to filter sediments and exchange nutrients with the surrounding vegetation. But first, they need to understand how the stream flows now and what kind of sediments are in the water.

Art Parola: What we need to know is what those dynamics are.

Harry Goldstein: To help Parola read the stream, fellow U. of L. professor Cindy Harnett is pitching in with the low-cost wireless sensor systems that she and her students are developing. Harnett’s system is basically a stack of wireless sensors housed in 3-foot-long [1-meter-long] PVC pipes you can find at the hardware store. The pipe is placed in the water, and the sensors inside collect data about chemicals, water flow rates, and turbidity and transmit it wirelessly to a low-cost computer that she’ll plant about 50 feet [15 meters] away. Most of the system uses off-the-shelf parts.

Cindy Harnett: What I’d really like to do is put the designs out on the Web so that you could build these from commonly available parts. A long-term goal of mine is to get just regular citizens—maybe starting with some of the people that are a little geeky, that would put weather stations in their backyard—get people to kind of have a stake in their environment by measuring water conditions in their backyard, if they have streams or a well.

Harry Goldstein: Harnett is now deploying her first few sensor-filled pipes to monitor the South Fork of Curry’s Fork. Even as she puts the first ones in, she and her students are developing new sensors to detect chemical vapors, particularly oxygen.

Cindy Harnett: We’re gonna start out with multiwalled nanotubes.

Harry Goldstein: The concept is pretty simple. First, Harnett’s team makes batches of cylindrically shaped carbon molecules. These are arrayed on a chip, where they are connected to some minuscule pipes. When a chemical flows through the pipes and into the nanotubes, it will react with the catalyst. That interaction will produce an electrical signal, which will be processed by a computer.

Cindy Harnett: We’re using it first to flow catalyst solution through, then we’re getting thousands, if not millions, of catalyst iron nanoparticles all over the channel.

Harry Goldstein: She’s mindful of the untested nature of the carbon nanotubes she uses to construct her sensors.

Cindy Harnett: People don’t want to be cooking up something that turns out to be the next asbestos, so there is a lot of incentive for us to look into health effects.

Harry Goldstein: That’s an awareness those fat mussels might appreciate and which was absent among 18th-century pioneers whose do-it-yourself terraforming she and Parola are now actively de-engineering. I’m Harry Goldstein.