Although the number of impaired waterways on a draft list prepared by the Iowa Department of Natural Resources climbed ever higher this year, the number in Scott County remained constant.

The Mississippi River, Duck Creek and Lake of the Hills in Scott County’s West Lake Park remain on the list, which is updated every two years to comply with provisions of the federal Clean Water Act.

The DNR identified 445 rivers, streams and lakes across the state on the draft list released Thursday that are polluted and are in need of water quality improvement plans. That number is up from the

225 water bodies that were listed by the state in 2006.

The larger number does not necessarily mean more of Iowa’s waters are polluted, said John Olson, the DNR’s specialist on water quality assessments. Instead, more monitoring is being done.

“The majority of impairments in Iowa are not severe,” Olson said. “But they do indicate that our waters are not as good as they could or should be for Iowa’s aquatic life and for Iowans to swim in, to play in and use as a source for drinking water.”

The three top reasons rivers and streams are on the impaired list are because of bacteria, biological factors and fish kills, Olson said. The top three reasons for lakes are algae, turbidity (cloudy water) and bacteria.

Lake of the Hills has a longstanding turbidity problem, said Roger Kean, executive director of the Scott County Conservation Board, which runs the 620-acre park west of Davenport. The lake covers 57 acres. Runoff from nearby agriculture and home construction have been the chief causes of the problem.

“The problem we have is that there is not a lot of buffer around the park,” Kean said of farms that are adjacent to its western edge. “Turbidity affects the dissolved oxygen levels in the lake and makes it difficult to raise caged fish. We’ve tried to work with some of the farmers to do some things to eliminate runoff, and we’ve had some success. We’re also interested in working more with the state to find programs and assistance to correct the problem.”

Duck Creek has serious bacteria contamination problems, according to the draft list. Last month, DNR officials presented results of 29 continuous weeks of testing of water samples in the creek taken from April through October and told those present at a public meeting in Bettendorf that 2009 will see development of a plan agreeable to the federal Environmental Protection Agency to clean it up.

“What you see in Duck Creek is typical for an urban stream,” Mary Skopec, of the DNR’s watershed and monitoring section, said at the meeting. “It has a great delivery system for stormwater runoff. Its chloride levels are atypical even for an urban stream.”

The Mississippi also has a longstanding contamination problem from bacteria, nutrients, aluminum and arsenic brought by agricultural and urban runoff.

Tom Saul can be contacted at (563) 383-2453 or