Dakota County maintains the Lake Byllesby reservoir winter and summer water levels. A permit from the Minnesota Department of Natural Resources establishes the summer and winter elevation requirements.
The Lake Byllesby reservoir summer elevation is 856.7 feet from mid-May to early October. The winter elevation is 853.7 feet from early October to mid-May. The fall drawdown gradually lowers the water by three feet to just below the sill of the Byllesby Dam. This lowers nearby groundwater levels accommodating local agricultural needs. Annual refilling of the reservoir begins on May 15.
Byllesby Dam Drawdown Schedule Chart
Lake conditions
Lake Byllesby becomes a no-wake zone when the water levels reach 858.2 feet and above.
Flood events
Precipitation and runoff contribute to the changing water level of the reservoir. Snow and rain falling on the surface contribute water to the reservoir. Several factors affect the amount of runoff that drains into the reservoir:
- The condition of the soil (frozen to unfrozen, dry to saturated)
- The water level in nearby ponds and wetlands
- The state of trees and vegetation (active or dormant)
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The amount of porous surface in the area.
The watershed of the Cannon River covers portions of nine counties. Areas as far away as the Waseca and Blooming Prairie drain to the dam.
Lake Byllesby's surface elevation is controlled by the Byllesby Dam. The elevation of the lake level can be somewhat controlled by the dam's discharge structures. By opening or closing the discharge structures, the lake is kept near the appropriate level.
Natural forces sometimes exceed human designs. Excessive precipitation and runoff can cause the lake to rise to undesirable levels. Persistent dry weather and evaporation can cause lower than desired lake levels.
Get up-to-date weather and water level information
River gages track water levels and measure stream flow. They are installed on bridges or other fixed objects. River levels are checked on a regular basis. Staff trigger emergency plans should major flooding appear imminent.
For updates, you can call the Byllesby Dam Hotline at 651-438-4626.
The public can also access information generated from these river gages.