Lakes Drawdown Project
What is a lakes drawdown?
For Cravath and Trippe Lakes, a drawdown would be performed by opening the dams and allowing the water level to slowly lower until the water level is down to a stream bed. A lake drawdown is one tool that can be used to manage aquatic weed problems. Most aquatic weeds are found near the shallow shoreline. Lake level drawdowns often start in the fall and continue through the winter when water recreation users are at their lowest.
Why do we need a lakes drawdown?
We are trying to freeze out and control invasive aquatic plants, including Starry Stonewort and Eurasian Milfoil. We currently perform a weed harvest twice a season to reduce the number of weeds in our lakes. An extended drawdown has many other benefits to the lake, including sediment desiccation, which means the silty or much bottom can compress up to 1/3 of its depth when fully dried out. This would result in deeper water in our shallow shore areas. This, along with a dry dredging while the lake is drawn down, would allow for a deeper lake and a navigable channel for recreational use. An extended drawdown would also allow other invasive species to be controlled, while some beneficial native plants that provide excellent fish and wildlife habitat are expected to rebound. The extended drawdown would also give the city and/or DNR an ideal chance to inspect the dam while it’s dry.
What will happen to the fish and other wildlife in the lake?
The drawdown must happen gradually so all fish and wildlife have enough time to locate to deeper water. The fish are expected to move with the water as the lake level goes down. It is possible that some fish may perish if they don’t move up or downstream quickly enough, but this is not expected to be significant. After the drawdown process is complete, there will be a plan in place to restock to allow for a healthier fish population to return.
Will I be able to walk on the lake bottom?
The exposed lake bed should freeze over the winter although there may be soft spots in areas where groundwater enters he lake. The severity of freezing will depend on the weather conditions this winter. Snow cover will insulate the exposed lake bottom and warm weather during the winter will allow water to run under
the snow/ice layer. A cold and relatively dry winter will provide the best conditions for solid and deeper freezing. The DNR will measure the exposed lake bottom surface this winter to determine the depth of sediment freezing.
Will the boat launches be open this fall, winter and spring?
The boat launches will be open, but it will likely be difficult to get boats and trailers to the water edge after the drawdown this fall.
For additional information, more frequently asked questions, and a map detailing the proposed dredging, click here .