Manitowish River/Rest Lake Dam Issue Paper

History

The Chippewa Flambeau Improvement Company (CFIC) owns and operates the Rest Lake Dam on the Manitowish River in Vilas County, Wisconsin. The CFIC is a partnership of the owners of hydroelectric projects in the Chippewa and Flambeau drainage basins. The Rest Lake Dam was constructed in 1887 for use by the logging industry and was acquired by CFIC in 1911. The dam is operated according to conditions established by a July 8, 1937 order of the Public Service Commission of Wisconsin (Wisconsin Commission) and subsequent February 17, 1939 rehearing order. The Manitowish River is classified as Exceptional Resource Water from Rest Lake Dam downstream to the Turtle Flambeau Flowage. The dam impounds the Manitowish Chain of Lakes.

Jurisdiction

The State of Wisconsin Department of Natural Resources (WDNR) has authority over the Rest Lake Dam under Chapter 31 regulations (permit # 2-wp-295). The Federal Regulatory Energy Commission (FERC) ruled on June 1, 2001 that the Rest Lake Dam is not required to be licensed by FERC because it does not benefit hydropower generation at the downstream hydroelectric units of development. FERC also determined that the Rest Lake Dam "is neither used and useful nor necessary or appropriate to maintain or operate the downstream projects and conclude that we have no jurisdiction over this dam or reservoir".

Dam Operation

The drainage area for the Rest Lake Dam reservoir system is about 243 square miles, or 12.9 percent of the Flambeau River drainage area. The dam impounds ten natural lakes (Rest, Stone, Fawn, Spider, Island, Alder, Manitowish, Little Star, Clear and Wild Rice Lakes) with a total surface area of about 4,200 acres and a usable storage capacity of about 15,150-acre feet under current operation conditions.

The following are the existing operation requirements of the Rest Lake Dam:

1. November 1 to Spring Ice Breakup: 5.0' (Gauge reading)
2. Spring breakup to April 15: Minimum of 7.3'
3. April 15 to July 1: 7.3' - 8.6'
4. July 1 to September 1:No lower than 7.3'
5. September 1 to November 1: No lower than 5.0'
6. At no time shall reservoir be lowered at a rate exceeding two inches per day.
7. At no time shall the reservoir be lowered after ice sheet forms.
8. Required to pass 50 cfs base flow minimum.

Annual operation practices are as follows. In Spring, once ice is out (ice 75% off of Rest Lake), CFIC reduces the flow in the Manitowish River down to 50 cfs to fill the chain as quickly as possible (Memorial Day target). During an average year this might take a month but a wet spring may fill the lakes in two weeks while in dry years, the lakes may not fill completely until later in the summer. During the summer CFIC tries to maintain a constant lake elevation between 8’ 4” and 8’ 6”. During some dry years, summer river flows can fall below 50 cfs to maintain this pool elevation. In-flow into the chain at this time of year can also be below 50 cfs. During the fall, they maintain the summer lake elevation (8’ 4”-8’ 6”) through September for fall Colorama and other activities. Fall draw down begins at the end of September/early October to draw the chain down to 5” 0” (3’ 6” draw down). Additional flow from storage is released to draw the lakes down at close to the 2" per day limit until the 5’ 0” elevation limit is reached by November 1st.

Resource Issues

Sturgeon Reproduction/Recruitment

The lake sturgeon population (on Wisconsin's watch species list) in the Turtle Flambeau Flowage appears to be reduced to relatively low numbers of large old fish, with no evidence of natural recruitment documented in the system (Roth, 2002). Radio-tagged fish from the flowage apparently run up the Manitowish River above Benson Lake in Vilas County to spawn. This is also based on observations of other sturgeon in the Benson Lake area. The Turtle Flambeau Flowage Master Plan (WDNR, 1995) states that the reasons for the lack of reproduction are not understood at this time, but this population may eventually disappear if rehabilitation efforts are not successful. Short-term rehabilitation strategies have been implemented. Fingerling sturgeon have been stocked using an egg source from within the same drainage in 1994 and 1998. The department has documented good survival of these fish stocked in 1994 and 1998 (Roth, 2002).

There are many suspected reasons why spawning success is a continued failure in the Turtle Flambeau and Manitowish River. For one, the sturgeon in the Manitowish River have spawned as late as the first two weeks of June. Typical sturgeon spawning takes place (Wolf and Wisconsin Rivers) in late April. Why spawning occurs so late is a mystery, but it could be water flow or temperature related. Attraction flows have been shown to be important in triggering Lake Sturgeon spawning migrations at other locations (Martini, personal communication, 2002). Low flows (< 50 cfs) in April May and June would likely inhibit spawning activity and contribute to reproductive failure. The water temperature may be to warm for proper egg development, hatching and embryo survival. Lack of water or fluctuation water levels in the Manitowish River at the time sturgeon spawn could be another factor. The rusty crayfish also inhabits the Manitowish River. They could be feeding on sturgeon eggs. Another unique situation that could be limiting recruitment is predation by redhorse suckers. As indicated earlier, the sturgeon spawn later than usual and at the same time as the redhorse are spawning.

Any work conducted at the Rest Lake Dam to look at operational impacts on the Lake Sturgeon would be supported by the Wisconsin Lake Sturgeon Management Plan (WDNR, 2000). This plan identified the following objectives as crucial to the future of sturgeon management.

1. Maintain and enhance current sturgeon population assessments.
2. Identify critical habitats and habitat requirements for various life cycles.
3. Use proper flow management at dams to benefit sturgeon.
4. The Manitowish River system is priority water for sturgeon rehabilitation.
5. Develop and implement standardized exploitation assessments.

Public Interest Flow (Flow Requirements for species diversity down stream)

At the present time the minimum flow at the Rest Lake Dam is 50 cubic feet per second (cfs). Is this flow suitable for downstream wildlife, fish and aquatic life requirements? There has been no water flow gauging by USGS or others to establish a Q7, 10-flow value (seven-day low flow that occurs once every 10 years). Major fluctuations in water flow can occur on a daily basis in spring and fall. Long periods of minimum flow (50 cfs) releases have extended into late spring (i.e. 4/08/00 until 6/26/00). There is concern that major water level fluctuations in the Manitowish River could harm aquatic organisms including threatened and endangered species. Minimum flows in the spring may limit sturgeon and other fish species spawning. A public interest flow needs to be evaluated. Downstream navigation concerns also need to be addressed. Another issue is the accuracy of flow monitoring at the dam and flow forecasting in the basin.

Manitowish Chain of Lakes (Winter Drawdown)

The chain is drawn down 3’.6” starting on September 1st (starts in October in many years) and is held at an elevation of 5’.0” (gauge reading) from November 1st until spring ice break up. The reason for this drawdown is to protect property from ice damage. What effect does this have on the establishment of a littoral zone? Is ice damage a valid concern today? If there is little flood control or hydropower benefit is there a need to drawdown the chain? What impact does this operating practice have on the fishery in the chain?

Fish Passage

The dam at Rest Lake clearly prevents fish migration upstream. The Rest Lake Dam was once equipped with a Barr Fishway (installed in 1931) that moved spawning fish from the bottom of Rest Lake Dam up into Rest Lake. It no longer exists. Fish Passage is a major concern. The building of the Turtle Flambeau Dam in 1926 has prevented the movement of sturgeon from the lower Flambeau River system into the Turtle Flambeau Flowage. The same can probably is said about the Rest Lake Dam. Fish passage is also important for the colonization of mussel communities in the river system. The Turtle Flambeau Master Plan recommends that a potential long term solution could be to construct a Fishway at the Turtle Flambeau Dam which would allow sturgeon from the healthier down stream population to access the Flowage and up-river areas that they were once able to reach before dam construction. This should be investigated. The Wisconsin Lake Sturgeon Management Plan recommends providing passage at dams where feasible and where passage would benefit the sturgeon population. Sturgeon passage structures are being planned at three sites on the Menominee River. The structures are being modified to pass most warm water species in addition to sturgeon.

Rest Lake Dam Inspection

The Rest Lake Dam has been inspected periodically over the years and maintained. Another inspection was conducted on July 25 2002 by department staff. Overall the dam was in good shape and well maintained.

Manitowish River/Rest Lake Dam Work Group