4/26/01

Contacts:
Al Farris, Iowa Department of Natural Resources, (515) 242-5948
John Downing, Animal Ecology, (515) 294-2734
Karen Bolluyt, Ag Communications Service, (515) 294-3701

CLEAR LAKE COMMUNITY LEARNS RESULTS OF RESEARCH ON LAKE QUALITY

AMES, Iowa -- In its first 10,000 years, Clear Lake's depth decreased 3 feet due to sedimentation. In the last 65 years, sediment reduced the average depth of Clear Lake by another foot. And in the last 50 years water clarity has decreased from 5 feet to 1 foot.

In a community meeting Thursday, an Iowa State University scientist outlined results of studies done in the 12,000-acre Clear Lake watershed. Researchers were particularly interested in sources of phosphorus entering the lake. Phosphorus promotes algae growth, and too much algae results in green water and algae blooms. Some algae also produce toxins harmful to fish, wildlife and humans.

John Downing, Iowa State limnologist (lake scientist), headed the study, which was funded primarily by the Iowa Department of Natural Resources. He characterized the research as "the most thorough assessment of lake-water quality ever done in Iowa." Part of the credit, he said, goes to many citizen volunteers and faculty and student volunteers from Iowa State.

Downing and a team including agronomists, geologists, economists and a landscape sociologist identified the sources of sediment and phosphorus entering the lake.

The researchers used models to calculate how much nutrient reduction is possible and what might be the impact. They calculated that more than a 60-70 percent reduction will be difficult because of the nutrients carried in rain and ground water.

"The rain is dusty and soil particles carry phosphorus," Downing says.

But a 60-percent reduction could return water clarity to 3 feet, Downing said. How much less phosphorus is that? Nearly 7,000 pounds, or close to the weight of two Corvettes.

Studying the feasibility of various water-quality-improvement strategies is part of the study. Downing expects the feasibility study to be completed by the end of July. Area residents will choose what to do to regain a clearer, healthier lake.

Downing said there probably will be something for everyone, urban and rural residents, to do. He noted that community support for corrective action is high and the DNR and other agencies will help the community develop plans for lake improvement.

Even children who fish in Little Clear Lake may play a role. Team members watched with interest as youngsters caught carp, carried them across the road and threw them into Ventura Marsh, where carp populations have proved difficult to suppress.

The final report is heavy on such things as secchi dish readings (for water clarity) and wave velocity measurements, but the research team also documented human activity. And that will be the focus of the next step.

"Collecting and making sense of the data is the first step. People in the community, with support from several state and federal agencies, are ready to take it from here," Downing said.

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