S-R photo by Jesse Tinsley
That's the question I asked Bruce Howard, knower of all things dams for Avista Corp., and one of our River Dialogues experts.
He e-mailed me some good information:
The dams don't all hold water back. Only Post Falls and Long Lake actually "store" water. The other dams operate as "run of river."
At Post Falls, we can't "store" water above 2128 feet (the summer elevation). However, the lake has gone up to over 2137' because of the natural control point for the lake -- the outlet near North Idaho College that is the start of the Spokane River. That natural restriction controls the lake elevation and river flows about half the year, and always during high flows.
Right now, well over 50,000 cfs (cubic feet per second) are pouring into Coeur d'Alene Lake from the St. Joe and CdA rivers...but the natural outlet is only letting around 35,000 cfs out.
At the PF dam, we pass, or spill all water that the natural outlet delivers.
CdA Lake, because it buffers the high inflows, is a sort of natural flood control reservoir for the Spokane River and for Spokane. We have had no control over lake levels or river flows for months. We've just been passing by whatever mother nature has been delivering.
Spokane used to experience flooding in early days leading to the railroad berms from downtown upstream, road construction, filling of the shorelines. From Upriver Dam all the way downtown is mostly a man-made shoreline. Spokane Falls Blvd. is partly built on an old channel that was filled after the Spokane fire with the debris.
At Long Lake, we can also spill all the water that comes down. That's why there's not flooding around the lake though our parking lot below the dam is flooding now, and we have to watch water coming in to our facilities there too.
Howard signed off with this reminder about Mother Nature.
Since it's been about 10 years since we had high water, this is a good reminder of who's in charge.
By the way, as Bruce told us in the River Dialogues, "there are seven dams on the Spokane River, starting with Post Falls, which (Avista) operates. And then downtown there is Upper Falls and Monroe Street, which we operate. And then between the downtown and Post Falls is Upriver Dam, where Boulder Beach is, and that is operated by the city of Spokane. Downstream is Nine Mile Falls, which we operate, and Long Lake Dam, which creates Lake Spokane, and Little Falls and we operate those two as well."
Any thoughts flooding your way about the flooding today? Blog lines are open.