Gile Flowage, Montreal River Watershed (LS15)
Gile Flowage, Montreal River Watershed (LS15)
Gile Flowage (2942300)
2711.50 Acres
Reservoir
2025
Good
 

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

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