Lake restoration project drops water level

For those wanting one more fun time on 3 Mile Lake before fall weather arrives, they are encouraged to pay closer attention to water levels.

Late last month, water levels at Three Mile Lake were started to be lowered as a part of a restoration project.

According to the Iowa Department of Natural Resources, managers will maintain the lake at approximately 8 feet below normal lake levels until fall 2024, when the water will be lowered up to 11 feet to expose areas of shoreline and lake bed for construction. Water being released through the lake’s outlet structure will be released slowly to avoid downstream impacts.

Construction activities will begin this fall and be completed in spring 2025, when managers will allow the lake to refill. The lake will remain open for boating and recreation throughout the project with boat access maintained at the main boat ramp. Boaters should use caution with the lower water levels as tree stumps, cedar tree brush piles and underwater reefs may be at or near the water’s surface.

Preventing additional sediment from entering the water is the foundation for various improvements planned at Three Mile Lake. A silt dam, on the north end of the lake, takes in soil that flows with water entering the lake. The eroded soil within the water is left in layers on the north end and not enter the entire body of water. Research has shown the silt dam is nearing capacity and additional silt will eventually flow into the rest of the lake without restructuring.

In 2007, the lake itself was about 810 acres and had about 13,000 acre feet of water. An acre feet of water is the amount of water one foot in depth over one acre. When measured in 2019, it had reduced to 793 acres and closer to 12,000 acre feet of water because of the silt accumulation. The watershed for the lake is about 23,700 acres.

The lake is used for recreation and as a public water source.

Dredging the lake, which is physically removing silt build up on the lake floor, was not financially feasible.

Other work includes strategic shoreline improvements and fish habitat. The entire project is estimated at $4.5 million which has been benefited by the state, many grants and a contribution from Union County. The lake is a tourist attraction for Union County bringing in people from across the state and others.

George Antoniou, from the DNR’s lake restoration office, said weather will play a factor considering extensive rain or snow during the winter and spring runoff. Refilling the lake is scheduled to begin in February 2025.

Another factor is when Southern Iowa Rural Water Association’s water treatment plant will be operational. It is under construction east of Creston along U.S. Highway 34 and will acquire water from Three Mile. The plant is expected to begin use in early 2024.

Creston Waterworks, which supplies water for its customers and SIRWA using 12 Mile Lake, is still researching its system for a quantity issue. Since June, Creston Waterworks has noticed its not producing the desired hourly amount. The goal is to have about 4,500 gallons ready a minute, but it is only reaching the 4,100 level. That is still an adequate amount of water for normal usage.

Staff has replaced filters that are part of the process but no additional water is measured. Creston Waterworks has acquired additional devices to analyze its entire system but officials said weeks of time are needed for results.

Creston Waterworks and SIRWA have asked their respective customers to voluntary conserve water in addition to the dry summer as lakes are not being replenished as often.