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 May 15 to Oct. 1. The winter elevation is 853.7 feet from Oct. 1 to May 15. The fall drawdown gradually lowers the water by three feet to just below the sill of the Byllesby Dam. This lowers adjacent groundwater levels accommodating local agricultural needs. Annual refilling of the reservoir begins on May 15.
Changing water levels
Precipitation and runoff contribute to the changing water level of the reservoir. Snow and rain falling on the surface directly contribute water to the reservoir. The amount of runoff from the watershed (area that drains into the reservoir) is affected by several factors: 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) and the amount of porous surface in the area.
Lake Byllesby’s surface elevation is controlled by the Byllesby Dam on the Cannon River. The elevation of the lake level can be regulated to some extent by the dam’s discharge structures. By opening or closing the discharge structures, the lake is kept at or near the appropriate seasonal pool elevation.
However, 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 as well.
Get up-to-date water level information
River gages, installed on bridges or other fixed objects, monitor water levels and measure stream flow. Public safety employees evaluate river levels on a regular basis and trigger emergency plans should major flooding appear imminent.
The general public can also access information generated from these river gages.