Three Black Hills lakes built from 50 to 90 years ago for their aesthetic and recreation qualities have been degraded by silt that diminishes water quality and encourages thick weed growth.
But the U.S. Forest Service is planning projects to renovate Horse Thief, Bismarck and Lakota lakes, three small reservoirs built to enhance the travel-and-recreation experience along the 68-mile Peter Norbeck National Scenic Byway.
The byway runs through Custer State Park and past Mount Rushmore National Memorial, among other outdoor highlights. Many visitors are likely to see or recreate at one lake or the other along the way, said David Pickford, recreation specialist for the Hell Canyon Ranger District in Custer.
"Basically, anyone who goes through Custer State Park takes the Iron Mountain Road or goes to Mount Rushmore is going by one or the others of these lakes with a lot of folks stopping to visit," he said.
Horse Thief is the most troubled of the three lakes, Pickford said. It has flunked water-quality tests showing pollution that while not threatening to human health reflects the diminished quality of the water.
"It's failing to meet water-quality standards and that's something by law the state has to address," Pickford said.
Over the years, Horse Thief has had problems with dissolved oxygen levels and nutrient loads and consistently high pH levels likely related to algae growth. Like the other lakes, it has not been dredged since it was built.
Rich Hanson, an environmental scientist manager for the state Department of Environment and Natural Resources in Pierre, said the degree of degradation at Horse Thief is "not what I'd call a harmful to anybody" using the lake for recreation. But the lake is considered impaired because of the pH levels and it is monitored by state water specialists.
Lakota and Bismarck lakes have had pH issues in past years. And Lakota was noted in 1998 for fecal coliform levels. Those are not rare issues with South Dakota Lakes, but they do cause trouble for people who use them for recreation, Pickford said.
"It's not a very nice experience when you go to a lake and can't even get your fishing line out because of weeds and cattails," Pickford said. "These lakes are all 50-plus years old. They're in need of help."
Bismarck was built in the 1920s, Horse Thief in the 1930s and Lakota in about 1960.
Help for the lakes is coming through a $700,000 federal grant available for projects along national byway routes. It will be matched by $140,000 from the Forest Service and $150,000 from the state Game, Fish & Parks Department.
Pickford hopes work to clean Horse Thief can begin this winter after the lake has been drained and when it’s easier for crews to get in and scoop out the silt. The other two lakes would be dredged the following winter.
After the lakes are cleaned out and fill with snow melt and spring rains, GF&P will stock them. Initially, those stockings are likely to focus on catchable-sized rainbow trout.
But getting rid of the silt comes first, Pickford said.
"Until you remove the silt, you can't really clean up your water," he said.