BACKGROUND 



The Kootenai River enters Montana from British Columbia. It flows south for 

 approximately 50 miles, turns abruptly to the northwest, into Idaho, and eventually 

 into British Columbia again, where it empties into the Columbia River. Its some- 

 what V-shaped journey through Montana is roughly 100 miles long and is entirely 

 within Lincoln County. Its average annual discharge is 12,000 cfs, making it the 

 state's second largest river. Only the Clark Fork of the Columbia River discharges 

 more water out of Montana. 



The Flood Control Act of 1950 (Public Law 515) authorized the construction of 

 Libby Dam on the Kootenai River. Its primary purposes are for hydropower generation 

 and flood control . 



Construction of the dam began in 1966 and the reservoir began filling in 1973; 

 however, it was not until 1975 that power was first generated at Libby Dam and since 

 that time all outflows from the reservoir have passed through the turbines. 



Presently, the powerhouse in Libby Dam has four generators, each with a rated 

 capacity of 105 megawatts (MW). The power operation is characterized as a "load 

 shaping" mode of generation. Load shaping, according to the Corps of Engineers, is 

 a flexible, middle ground between base and peak load generation. When the mode of 

 power generation resembles, or in fact is a peaking operation, outflows from Libby 

 Dam create the most pronounced fluctuations in the river stage downstream. 



Libby Dam was constructed with provisions for eight 105 megawatt generators. 

 With four additional generators (units five through eight), as proposed, peaking 

 capabilities would be increased. However, a total of eight generators, permitting 

 a combined rated capacity of 840 MW, would require a reregulating facility to smooth 

 the great fluctuations that would result from such a peaking operation. 



In January 1970, basic design information regarding the proposed reregulatory 

 facility was presented in the Corps' Design Memorandum 50. The dam would be con- 

 structed 10 miles below Libby Dam. It would be 70 feet high, 1,600 feet long and 

 create a reservoir with a capacity of 30,000 acre-feet of water. The reservoir's 

 maximum surface area would be 1,350 acres. The estimated cost of additional units 

 and a reregulating facility is $225 million and the proposed project was to have 

 been completed in 1933. 



With a reregulating facility, the average daily releases from Libby Dam would 

 be in the range of 5,000 to 9,000 cfs, April through mid-July. With Lake Koocanusa 

 filled by the end of July (maximum elevation, 2,459 feet), outflow into the reregu- 

 lating reservoir would be gradually increased to an average of approximately 20,000 

 cfs. Natural inflow into Lake Koocanusa would normally pass through Libby Dam until 

 it drops below 8,000 cfs. In most years, this occurs during October. Discharge 

 from Libby Dam would average 10,000 to 20,000 cfs through the winter while the re- 

 servoir is lov/ered in the interest of power production and to provide space for the 

 upcoming snovmielt. 



Instantaneous discharge, on the other hand, would vary from almost zero flow 

 to as much as 45,000 cfs. In fact, if its full peaking capacity is utilized, the 

 discharge could rise from almost zero flow to 45,000 cfs in one hour, remain at 45,000 

 cfs for five to ten hours and return to almost zero within an hour. Generally, peak- 

 ing operations would be high during the day time and low at night. At certain times, 

 perhaps v/eekends, the peaking requirements will be less and the discharge could be 

 held relatively costant for several days. 



The minimum discharge from the reregulating dam has been established as 2,000 



