University of Iowa News Release
June 18, 2003
(Photo: A. Jacob Odgaard)
UI Engineers Create Laboratory Model Of California Lake
University of Iowa College of Engineering researchers have created the first model of its kind that successfully imitates the behavior of a large, thermally layered reservoir or lake.
The research team consists of A. Jacob Odgaard, professor of civil and environmental engineering, research engineer at IIHR-Hydroscience & Engineering and project lead principal investigator; Robert Ettema, professor and departmental executive officer of civil and environmental engineering and research engineer at IIHR-Hydroscience & Engineering; Marian Muste, research engineer; Yong Lai, research engineer (currently employed by the U.S. Bureau of Reclamation); Christopher Buren, research assistant; Ozan Abaci, graduate research assistant; and Ahmed Alchhab, graduate research assistant.
The team constructed the model under a $900,000 grant from Pacific Gas and Electric Company (PG&E). Called "The Lake Almanor Cold Water Feasibility Study," the project is an attempt to learn how to withdraw more cold water for use by PG&E's Prattville Hydroelectric Power Plant, located on 27,000-acre Lake Almanor, Calif. (about 120 miles north of Sacramento), without altering the habitat supporting the lake's plant and animal species.
The model, constructed at IIHR, one of the world's premier and oldest fluids research and engineering laboratories, actually consists of two different models. The first is a numerical, or computerized, model of the entire lake, while the second is a physical scale model of a portion of the lake rendered in concrete. The physical model (built with a horizontal scale ratio of 1:220 and a vertical scale ratio of 1:40) occupies a floor space of approximately 50 feet by 75 feet. Researchers construct the thermally distinct and stratified layers of water by slowly filling the basin, first with relatively warm water through inflow manifolds, then with colder water through bottom valves that gently lift the warmer water to a desired elevation. The contoured bottom of the basin is maintained at a given temperature by a sophisticated maze of cooling coils imbedded in the concrete.
Odgaard says that in addition to its usefulness in studying Lake Almonar, the model demonstrates that it is possible to develop models of complex water systems and that complex models can help environmental researchers.
"The project has created the first-ever successful laboratory model of a large, thermally stratified reservoir or lake. It also has involved the development of a unique numerical model. One of the challenges of this project is to fully understand and model the many different environmental and meteorological factors that influence the temperature stratification in the lake and its variation during the year," he says.
At Lake Almanor, the challenge is to design a water intake system that uses cold water only when necessary. Odgaard says that continuous withdrawal of only cold water could deplete the lake's cold water supply, resulting in damage to the lake habitat.
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