Why is my lake water lowered in the winter?
Water drawdown is one tool that can be used to manage aquatic weed problems. Lake level drawdowns often start in the fall and continue through the winter when water recreation uses are at their lowest.
Some riparian owners hate seasonal drawdowns on lake or reservoir because it restricts recreation access and can look unsightly for a time. However, there are several reasons for this practice. The practice of water level lowering is not new and had historically been done to control increased rain and winter snow melt runoff from late fall through early spring. This also helped to reduce shoreline erosion during these heavy flooding periods.
Other reasons besides shoreline protection include:
- Aquatic weed control. Most aquatic weeds are found near the shallow shoreline. Drawdowns during the winter can dry and freeze the offending plants helping to control invasive species.
- Reduce ice damage to shorelines from ice push during the winter.
- Water storage level and flow regulation
- Shoreline access for clean-up and sediment removal
- Allows access to docks, seawalls and other installations for inspection and repair
There are some detrimental impact that a drawdown can have as well, including:
- May not kill the desired invasive plant
- Exposed sediments may release nutrients once exposed to rain events
- Invertebrates may not be able to migrate quickly enough with the changing water conditions and die
- May restrict access to mammals and birds
When lake managers decide to lower water levels in a lake or other detention system, they take into consideration the many effects that may occur from this practice. One of the most motivating factor is to use this chemical free method to control Eurasian watermilfoil. Drying out this plant from lake lowering exposure is an effective organic approach to managing this aquatic invasive plant.
For more information about the Clean Boats, Clean Waters program and aquatic invasive species contact Beth Clawson, MSU Extension Educator. To learn more about invasive organisms and invasive aquatic plants contact Michigan State University Extension Natural Resources educators who are working across Michigan to provide aquatic invasive species educational programming and assistance. You can contact an educator through MSU Extension’s “Find an Expert” search tool using the keywords “Natural Resources Water Quality.”