Public weighs in on extended Lake Ocheda drawdown proposal

Sep. 20—WORTHINGTON — More than 25 people attended a public information meeting Thursday evening regarding a proposed one- to two-year drawdown of Lake Ocheda, south of Worthington. The drawdown is proposed after two winter-time drawdowns failed to achieve goals set for the impaired shallow lake.

Maggie Gross, shallow lakes specialist with the Minnesota Department of Natural Resources, led the meeting, explaining the current state of the lake, management history and what residents and area landowners can expect to see during a full-year drawdown.

Both Gross ( ) and Okabena-Ocheda Watershed District Administrator Dan Livdahl ( ) are collecting public comment on the proposal through Sept. 30.

Comments received Thursday evening, as well as those submitted via email or phone through Sept. 30, will be taken into consideration by the advisory committee before a decision is made. The advisory committee includes Gross, along with representatives from the Minnesota DNR, Okabena-Ocheda Watershed District, Worthington Public Utilities and a local landowner.

Lake Ocheda was designated a managed shallow lake in 2017 by the watershed district as a way to promote good fish and wildlife habitat. The designation also allows for the manipulation of lake water levels.

The average depth of Lake Ocheda is 3 feet, with a maximum depth of 4.5 feet. A water control structure on the south end of the west basin allows for a drawdown that still leaves between a foot and a foot-and-a-half of water in the three-basin lake.

The only way to achieve a complete drawdown is through a pumping system that would likely cost a substantial amount of money. The watershed district previously asked Ducks Unlimited for an estimated cost to pump the basins dry, but it would have cost $60,000 just to conduct the study.

Gross explained Thursday that the goal of the drawdown is to reduce or eliminate undesirable fish, lower the amount of nutrients in the lake and increase aquatic plant life. The watershed's management plan for the lake calls for restocking of predator fish, including northern pike, walleye and yellow perch — all of which would help keep undesirable fish populations under control by feeding on their eggs.

"A clear water state is our goal," Gross said, noting that a clear water goal for Lake Ocheda is to see 2.3 feet below the surface. In 2022, after the last winter-time drawdown, water clarity was less than six inches. "It's currently in a turbid state."

With a drawdown, the goal would be to substantially reduce or eradicate roughfish, which stir up sediment and contribute to turbid waters. By ridding the lake of roughfish, aquatic plants could take root. Once plants are established, they would feed on the excess nutrients that enter the lake, thereby improving water quality.

Livdahl said phosphorus is the most abundant nutrient in Lake Ocheda, with levels four times greater than they should be.

Gross said the benefits of aquatic plants include nesting habitat, food and cover for wildlife, shoreline habitat and protection, clear water, food and cover for fish and being a refuge for invertebrates.

The Okabena-Ocheda Watershed District attempted winter-time drawdowns in both 2020 and 2021, when the area was already experiencing drought conditions. Neither event resulted in a total fish kill, nor did they generate aquatic plant growth. The 2020 drawdown resulted in a "pretty substantial fish kill," said Gross, while the drawdown during the winter of 2021 didn't go as well because of rain events going into winter.

A lake and fish survey conducted in 2022 provided disappointing results, Gross said.

"Water quality was still less than half a foot, and only one point (on the grid) had vegetation at it," she added. The fish survey showed a majority of the species collected were bullheads, fathead minnows and bigmouth buffalo.

"It looks like a wintertime drawdown is not enough to get Lake Ocheda to a clear water state," Gross said as the reason why the advisory committee will be asked to consider a full year to two-year drawdown.

The earliest the drawdown could begin — if approved by the committee — is Aug. 1, 2025. That, however, depends a lot on the weather. A drawdown would not be attempted if it's a wet summer and the lake is at high water levels.

Gross said the drawdown would extend to Aug. 1, 2026, or Aug. 1, 2027, depending on vegetative growth.

"We would host a public meeting after that first year and let (the public know) whether we're going to end or extend that drawdown into the second year," she added.

During the public comment portion of the meeting, one attendee asked if dredging the lake was considered.

"Generally, the cost is very prohibitive for doing dredging," said DNR Area Hydrologist Tom Kresko. "For a lake of this size, it's something that can be done, but the financial hurdle is far too high to consider."

A chemical treatment, such as Rotenone, would also be cost prohibitive — not to mention a concern for people with shallow wells who live around the lake.

"Rotenone also kills turtles, frogs and other animals," Kresko said.

Rolf Mahlberg, chairman of the Okabena-Ocheda Watershed Board of Managers, said with the water control structure on Lake Bella, the cost for a year-round drawdown costs nothing — unlike other options like dredging, pumping or treating the lake with chemicals.

Linden Olson, who lives on the west basin, asked if the drawdown was successful but high nutrients were still a concern, how soon would they consider another drawdown.

Gross said most shallow lakes who do well after a drawdown are able to maintain a clear state for up to seven to 10 years. Another drawdown wouldn't be attempted unless or until there is a notable decline in vegetation and water quality.

Keith Towne, in noting the recent fish kill below the spillway at Lake Bella, asked if there was anything that could be done to reduce the oxygen in Lake Ocheda to promote a fish kill.

DNR Fisheries Supervisor Ryan Doorenbos said he's heard in one instance of people placing dry ice in the water to drop oxygen levels. While it was a success, he said it was also on a one-acre basis. Lake Ocheda spans 1,778 acres and would require many, many semis of dry ice.

Other questions during the meeting pertained to commercial fishermen doing seining, removal and clean up of dead fish following a major fish kill and the frequency of full-year drawdowns.

"You can't be in a drawdown more than you're at full pool," Kresko said. "If we go two full years of drawdown, we need to have full pool for a significant period of time ... five years is good."