P.O. Box 283
Manitowish Waters, WI 54545

Historic Dam Operations

The Rest Lake Reservoir Dam near Manitowish Waters in Vilas County has been in existence since 1887 and in its present configuration since 1926. The original Rest Lake Reservoir Dam was constructed in 1887, primarily for use in logging operations. The Chippewa and Flambeau Improvement Company (CFIC) took over ownership of the dam in 1912. In 1926, the dam was replaced with the existing structure.

Adding or removing stop-logs from the four spillway bays controls the headwater levels of the reservoir and the river flows downstream from the dam. Required winter drawdown and specified minimum and maximum pool maintenance are achieved with manual manipulation of the four stop-log bay spillway system. The normal water surface elevation of Rest Lake is 1,601.0 (NGVD) and the normal hydraulic head at the dam is approximately 10 feet. There is no hydroelectric generation at the Rest Lake Dam.

After acquisition by the Chippewa and Flambeau Improvement Company, the Railroad Commission in 1914 established a maximum head of 8 feet and a minimum of 5.5 feet. The newly empowered Public Service Commission increased that maximum to 8.5 feet in 1915. The 5.5 feet minimum head was maintained, but a drawdown minimum of 2.5 feet was allowed when the reservoir was ice-covered.

In 1937, in an attempt to minimize winter kill of aquatic animal and plant life, the Public Service Commission (PSC) increased the drawdown minimum to 5 feet from November 1 through spring break-up. From spring break-up until April 15, the PSC required the filling to 7’3″ on the gauge, and then to 8’6″ until September 1 at which time it could be drawn down to no lower than 5’0” by November 1. Additionally, the drawdown rate was established at no greater than 2” per day.

The final regulation was put in effect by the PSC in 1939. That regulation requires the 5’0” minimum winter drawdown level (elevation 1597.5), the 7’3” minimum (1597.75) and 8’6” maximum (1,601.0) operating levels following the dates listed previously. The drawdown rate of 2” per day was also reinforced.

Today, the dam is operated following the 1939 PSC ruling. The dam operator operates the spillway to comply with the headwater requirements and the 50 cfs minimum discharge requirement. Daily modifications to the stop-logs allow slow reservoir level fluctuation and control during the seasonal fluctuation periods.

The drawdown does not begin until late-September or early October each year to allow property owners to maintain their docks along the shoreline of Rest Lake and to accommodate the Muskie Festival, Colorama, and other recreational interests.

The following table summarizes the operations of the Rest Lake Dam as required by the PSC’s order of 1937 and subsequent rehearing order of 1939. The table also includes the CFIC’s water level practices instituted to satisfy public recreation interests on the reservoir.

 

Date Head Level in Feet on Dam Staff Gage
November 1 to spring break-up (when ice is 75% off of the Rest Lake Chain) 5’0″
Spring break-up to April 15 Water level shall be raised to a minimum of 7’3″ on the gage, provided the minimum discharge required by law, and rainfall and runoff will permit*
April 15 to July 1 7’3″ to 8’6″ (8’6″ is the maximum allowed pond level at any time) – provided the minimum discharge required by law, and rainfall and runoff will permit**
July 1 – September 1 Water levels may be drawn down not lower than 7’3″ (routine operations are to maintain summer pond levels between 8’4″ and 8’6″)
September 1 – November 1 Water levels may be drawn to a level of 5’0″. Drawdown does not begin until late-September to accommodate recreational activities (Musky Festival and Colorama)

* The required minimum discharge from the dam is 50 cfs.
** The rate of drawdown cannot exceed 2″ per day