During our lake level discussion at the 1998 annual meeting, we had a questions come up about lake drawdown. What effect would lake drawdown have on the non-native species, the desirable native plants, fish and wildlife, etc.?
I posted this questions and our situation up on the internet into some lake and pond management discussion groups. I received some excellent feedback from many professionals in the field including:
- Scott Seymour, Aquatic Systems Inc., Butler WI, (30 years of Environmental pond and lake management).
- Dr. Mark D. Mattson, Water resources Research Center, University of Massachusetts.
- Steve DeKozlowski, South Carolina Department of Natural Resources.
- Richard S. McVoy, Ph. D., DEP, Office of Watershed Management, Worcester, MA
- Robert Hartzel, Mass DEM, Office of Water Resources, Boston, Ma, Lakes and Ponds Program.
Below is a summary of all their comments:
To have any effect on the nuisance non-native species (Cobomba and WaterMilfoil), you would have to drawdown the lake low enough for the roots to freeze. Because these roots reside in the sediment or “muck”, this would mean a drawdown of 6 to 8 feet. In a lake that’s only 12 to 15 feet deep, this would have adverse effects in many other areas.
The native plant Vallisneria (eel grass), which is very desirable, grows in the shallows and could potentially get wiped out in the process. This plant (which is seed germinating) actually acts as a barrier and helps keep out many non-native species (which reproduce by fragmentation). This much drawdown would also deplete the dissolved oxygen supply resulting in a potential winter fish kill. It would not have any impact on the algae condition since this is a nutrient overload issue.
Many studies show that even after such a drawdown, there’s no guarantee that the non-native plants won’t come back the following year. Your best bet is to keep the lake at it highest maintainable level year round and look into other forms of nuisance plant management control.