Portage/Base Line Lakes


The Washtenaw County Water Resources Commissioner’s Office operates Flook Dam, just downstream of Portage and Base Line Lakes, as part of a legally established lake level. The dam, constructed in 1965, controls water levels in the lakes through the use of 5 radial gates separated by concrete piers. 

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Flook Dam Informational Meeting 

On October 25, 2023, Washtenaw County hosted a meeting to provide an update regarding the status of the ongoing repairs for the Flook Dam located in the Portage Base Line Lake Level District. 

An overview of the lake level history, how the lake level is managed, and how operational costs are apportioned will also be presented. See the attached map for the special assessment district.

Download the PowerPoint presentation used at this meeting.

A written Q&A will be shared at a later date. 


  1. November 8, 2023
  2. October 26, 2023
  3. August 22, 2023
  4. August 7, 2023
  5. July 27, 2023
  6. July 17, 2023

Since the last update...

Please note that we will be lowering the lake to winter levels starting on November 21, 2023. 

This will involve placing boards upstream of two more gates, with the result that 4 of the 5 bays will be offline at least through the winter months. The middle gate will be used to adjust the lake elevation, which is our normal procedure each year. 

What's Next

Thank you to all the residents for providing input on possible sources of white oak lumber. This will be necessary to help provide a safe working environment in each bay as the gates are removed and replaced. Our office is happy to report we have found a lumber mill to fabricate these boards and expect to take delivery in early December.


Email us at [email protected] or call us at 734-222-6860. 

Lake Levels Reports

2023 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

2022/2023 Portage-Base Line Lake Level Chart - Yearly