Gile Flowage, Montreal River Watershed (LS15)
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Gile Flowage, Montreal River Watershed (LS15)
Gile Flowage (2942300)
2711.50 Acres
Natural Community
Reservoir
Year Last Monitored
2025
Good
 
Iron
Trout Water 
No
Outstanding or Exceptional 
Yes
Impaired Water 
No

Fish and Aquatic Life

Current Use
Shallow Lowland
Attainable Use
Default FAL
Designated Use
Default FAL

Overview

The Gile Flowage on the West Fork Montreal River is a headwater storage reservoir essential to the operation of the two hydropower projects downstream on the Montreal River. Norther States Power draws and refills the Gile Flowage to provide seasonally uniform streamflow for maximum generation at its Superior Falls and Saxon Falls hydro projects. The flowage is gradually lowered in winter in anticipation of collecting and storing spring runoff. That stored water is then gradually released to maintain flows during summer. Between 1974 and 1993 the maximum winter drawdown depth at the flowage ranged between 5.7 and 15.6 feet, averaging 9.9. It is possible such winter drawdown can affect the fish community in the impoundment by decreasing the winter survival of walleye fingerlings. WDNR fisheries staff have at least a decade of walleye density data for fingerling and yearlings, along with concurrent winter water levels. While fingerling densities showed the natural variation expected, yearling densities were low in all years. Fisheries managers suspect the drawdown may affect survival over their first winter by reducing the available shoreline habitat in the impoundment. An eight-foot drawdown reduces the surface area of the impoundment by about 46 percent and the volume by 58 percent.

WDNR asked the Federal Energy Regulatory Commission (FERC) to analyze the effects of winter drawdowns as part of the cumulative impacts analysis for the Superior Falls Hydro licensing decision. FERC denied the request, citing that it had no authority at the Gile Flowage. FERC subsequently initiated an investigation of its jurisdiction at the Gile Flowage, but has yet to make a decision on its authority. WDNR suggested a moderation of the drawdown over a three-year test period to see if there is any change in walleye fingerling survival. If no evidence came from the study showing that modified drawdown altered walleye survivability, the traditional operating procedures could resume. Northern States Power declined to participate in the study, citing economic concerns, regulatory uncertainties and increased liabilities as a result of flooding, and has suggested the fingerling survival might be related to other factors such as entrainment in the works of the dam.

From: Turville-Heitz, Meg. 1999. Lake Superior Basin Water Quality Management Plan. Wisconsin Department of Natural Resources, Madison, WI.

Date  1999

Author   Aquatic Biologist

Natural communities (stream and lake natural communities) represent model results that use predicted flow and temperature based on landscape features and related assumptions. Ranges of flow and temperature associated with specific aquatic life communities (fish, macroinvertebrates) help biologists identify appropriate resource management goals. Wisconsin Natural Communities.
This is the most recent date of monitoring data stored in SWIMS. Additional surveys for fish and habitat may be available subsequent to this date.
Trout Waters are represented by Class I, Class II or Class III waters. These classes have specific ecological characteristics and management actions associated with them. For more information regarding Trout Classifications, see the Fisheries Trout Class Webpages.
Wisconsin has designated many of the state's highest quality waters as Outstanding Resource Waters (ORWs) or Exceptional Resource Waters (ERWs). Waters designated as ORW or ERW are surface waters which provide outstanding recreational opportunities, support valuable fisheries and wildlife habitat, have good water quality, and are not significantly impacted by human activities. ORW and ERW status identifies waters that the State of Wisconsin has determined warrant additional protection from the effects of pollution. These designations are intended to meet federal Clean Water Act obligations requiring Wisconsin to adopt an 'antidegradation' policy that is designed to prevent any lowering of water quality - especially in those waters having significant ecological or cultural value.
A water is polluted or 'impaired' if it does not support full use by humans, wildlife, fish and other aquatic life and it is shown that one or more of the pollutant criteria are not met.
The use the water currently supports. This is not a designation or classification; it is based on the current condition of the water. Information in this column is not designed for, and should not be used for, regulatory purposes.
Shallow lowland lake describes the depth and location of the lake in a watershed. These variables affect the lakes response to watershed variables.
The use that the investigator believes the water could achieve through managing "controllable" sources. Beaver dams, hydroelectric dams, low gradient streams, and naturally occurring low flows are generally not considered controllable. The attainable use may be the same as the current use or it may be higher.
Fish and Aquatic Life - Default Waters do not have a specific use designation subcategory but are considered fishable, swimmable waters.
This is the water classification legally recognized by NR102 and NR104, Wis. Adm. Code. The classification determines water quality criteria and effluent limits. Waters obtain designated uses through classification procedures.
Fish and Aquatic Life - Default Waters do not have a specific use designation subcategory but are considered fishable, swimmable waters.