The hyrdroelectric station, owned by SaskPower, contains three 62 MW generators with a total capacity of 186 MW. Construction of the power station spanned a period of three years at a cost of $40 million. It became operational in 1969, two years after construction of Gardiner Dam was completed.
Under normal operating conditions, the release rate of water through the power station ranges from 60 to 150 m3/s. The maximum flow the station can accomodate is 360 m3/s. Real-time water out-flow rates can be found here courtesy of the Water Security Agency. The outflow rates have a direct impact on the speed of the river and should be checked before beginning any canoe or kayak trips down the river!
Although it is preferable to have all water flow through the hydroelectric station, water levels in Lake Diefenbaker are monitored very closely for both saftety and wildlife habitat reasons. There are circumstances where anticipated inflows to the lake are greater than can be accomodated by the power station, pushing water levels higher than desired, or potentially even higher than the reserve's capacity. Under these circumstances, the potential revenue from flowing water through the power station is forfeited in the interest of public (or wildlife habitat) safety, and the relief spillway at Gardiner Dam is opened. If this is the case be sure the visit becuase the open spillway is a great sight to behold!
Why not run the hydroelectric station at its full capacity to avoid using the spillway? If the station was to run continually at full capacity, the reserves in the lake could be depleted althought it may take several months. Typically the lake is preferred to be close to its maximum capacity coming into the winter months when electricity is in peak demand. This may mean decreasing outflow throughout the remainder of the year to ensure the water supply is built up and ready.
Thanks to the Water Security Agency for permission to place this geocache!