Feature - Model Behavior

Experiments being conducted by NU researchers on a scale model of Lake Ogallala could help ensure future success for the popular trout fishing lake.

The model, in Walter Scott Engineering Center, is being used as part of an interdisciplinary study on how the lake’s physical characteristics influence the transport of water, chemicals and dissolved oxygen. Periodic low levels of dissolved oxygen in the lake contribute to fish kills and threaten the lake’s rainbow trout population.

“This is the first lake-modeling study based on water flow and dissolved oxygen that I’m aware of in Nebraska on such a large scale,” said NU lake ecologist Kyle Hoagland.

Hoagland is one of four faculty heading up the project. He and John Holz are supervising the fieldwork, while civil engineering faculty David Admiraal and John Stansbury are directing the physical and computer modeling work.

Lake Ogallala has been Nebraska’s premier public rainbow trout fishery since the 1940s. The lake operated successfully as a trout habitat and recreational fishery until 1984, when a hydropower plant was installed in Kingsley Dam. The dam separates Lake Ogallala from adjoining Lake McConaughy.

In an attempt to increase dissolved oxygen in Lake Ogallala, hydropower plant operators began bypassing water from the turbine to a Howell-Bunger valve. But much of the lake continues to suffer with dissolved oxygen levels, Admiraal said.

To gather the information needed to build the model, researchers sampled water from the lake from four testing platforms and 30 underwater sampling sites. They injected a non-toxic, traceable dye into the lake to collect data on water-flow patterns. The researchers measured water-flow speeds and mapped the lake’s bottom using sonar.

The model was constructed using AutoCAD maps of the lake’s bottom. Details were transferred onto more than 30 16-gauge steel plates that were hand-cut to the contours of the bottom. The plates were spaced from one to three feet apart and the space between the plates was filled with concrete cinder blocks and fill sand. A special blend of cement and vermiculite was then used over the top of the model to give it a smooth, watertight surface. Head gates, where water from the lake flows into irrigation canals and into the Platte River, are reproduced in scale. They are computer-controlled in their opening and closing, just as the real gates are.

Cory Haberman, a civil engineering graduate student from Norfolk, built the model with help from John Hudgens from the Engineering Machine Shop. “It was built as accurately to scale as we could possibly make it within the confines of the building,” Haberman said. The 25-by-40-by-3 foot model holds about 1,000 gallons of water and takes 10 minutes to fill.

The researchers are now testing theories on what can be done to alter flows, aeration strategies or even change bottom contours and features of the 650-acre lake. Cameras and computers will analyze water flow into and out of the model. Dyes can be injected into the water to aid researchers looking for circulation patterns.

The model will be used over the next few months to help researchers gather data for the study. The project is funded in part by the Nebraska Game and Parks Commission, the University of Nebraska–Lincoln and the UNL Water Center.

Lake Ogallala is small as lakes go, a mere shadow of the big, tough Lake McConaughy. The Nebraska Game and Parks Commission calls it a “rag-sweater-and- cup-of-coffee lake, not a sweat and Gatorade lake like its sibling.”

For her size, the little lake can sure pack a punch. Last summer, John Stansbury was one of several who found themselves on the lake in the middle of the night when a storm started brewing. They quickly ran for cover. “There was lightning and it was blowing,” he says, “and the lake was choppy by the time we got to shore. There were surprisingly big waves for such a small lake.”

The little lake poses a bit of a challenge to those who seek to understand its behavior. “There are a lot of different aspects to the problem here,” says Dave Admiraal. “Dissolved oxygen levels, water velocity, possible high levels of sulfur … there’s so much to be studied.”

“What I’ve learned so far,” says Cory Haberman, “is that your design doesn’t always work when you try to build it. You have to learn how to improvise.”

The engineers have their work cut out for them. At first glance, the three men make an unlikely combination. Stansbury’s and Haberman’s roots are in rural Nebraska, while Admiraal is from a small town near Rochester, N.Y. Stansbury taught high school science before going back to school for his Ph.D. when his three children were teenagers. He worked as an environmental engineer for a consulting firm before joining UNL.

“I’ve always been an environmentalist,” says Stansbury. “Engineering is the opportunity to do something — to find solutions to the problems others just talk about.”

Admiraal decided to stay in school after getting his undergraduate degree. He enrolled at the University of Illinois at Urbana-Champaign, received his Ph.D. in 1999 and joined the UNL faculty shortly thereafter. He and his wife, Alicia, have a two-year-old son.

Haberman has worked part-time for the Department of Natural Resources while going to school. He’ll look for a job with the government or in consulting after he graduates.

They all like the outdoors. Stansbury is a novice fly fisherman (he’s taken his rod out to the lake but never had time to fish), while Admiraal enjoys hiking and biking. Haberman enjoys fishing, camping, backpacking and “lots of other outdoor sports.” They are quiet and serious about their work, but not so serious that they can’t joke around and have fun.

“What can a physical model tell us about how this lake behaves?” Admiraal says. “It can’t tell as much as what’s actually going on. But I can change the parameters and see how the adjustments could affect what’s going on in real life. I can run a hundred different scenarios with a relatively inexpensive physical model. I like modeling. It’s fun and it produces useful results.”

Says Stansbury: “No one has developed physical or computer models that will answer all the questions involved with this project. These models will help us determine the directions and velocities of the flows in all parts of the system. Then we can develop some management alternatives.”

The physical and computer models are not only useful for research. They’re valuable teaching tools.

Admiraal uses the model for demonstrations in his classes. “Since I teach water quality modeling,” says Stansbury, “everything I learn is brought back into the classroom.” Eric Dove, manager of water resources at The Schemmer Associates and a graduate student, is helping Stansbury with the computer modeling. “He’s talking to some of the top modelers in the country,” Stansbury says.

“This project is a perfect example of the kinds of problems we have everywhere,” he says. “I think we need to figure out ways to help these systems ecologically. Is there something we can do to make them work right?”

That’s the kind of thinking that gets them up early for a six hour drive to the lake — and lets them be good sports about posing for photographs with fishing poles and waders.