Portage/Base Line Lakes

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The lake level at Portage and Base Line lakes will be lowered beginning on November 22, 2022. The legally established winter lake level range is between 850.04 feet and 850.29 feet above sea level. The lakes will reach the winter range by December 5, 2022, weather conditions permitting 

The information on this site is updated weekly.

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2021/2022 Portage-Base Line Lake Level Chart - Weekly

Portage and Base Line lakes are located in Dexter and Webster Townships. The Lake Level District includes lands in both Washtenaw and Livingston County. Washtenaw County includes approximately 545 parcels in the assessment district. The Water Resources Commissioner’s Office actively monitors the level of the lake. 

Established Lake Levels

Daily weather conditions affect the lake level and a 1-3 inches fluctuation outside of the established level is common. Low inflows from the watershed into the lakes are a result of minor drought conditions, while an increase of water into the lakes comes from quick or heavy rain.  Any fluctuations outside of this norm are addressed within hours of notification.  

The Portage Base Line Lake sensor gauge is located near the Flook Dam.  This gauge is monitored by a Dam Operator 24/7. It is common to see higher lake levels upstream of this point during the wet seasons.  

The lake level is drawn down each winter to reduce the ice damage to the shoreline. Lowering of the lake level is scheduled in coordination with the closing of the Department of Natural Resources boat launch on Portage Lake.  Typically, the drawdown to the winter level begins mid-November.   

Raising the lake level is dependent on the weather.  The water must be free of ice cover and weather must remain consistently above freezing.  Typically, the change to the summer level begins in late March or early April.  

  • The legally established summer lake level is 851.54 feet.
  • The legally established winter lake level is a range between 850.04 feet and 850.29 feet.

Lake Level Reports

2021/2022 Portage-Base Line Lake Level Chart - Yearly