Might be a stupid question, but what's a CFS?
I would stay away from below Whitney right now. Dealing with 5000 CFS isn't a refreshing thing to do.
Power generation Not stupid at all and I should have expanded on my comment. As Sitex said thats cubic feet per second. Thats a 5000 cubic foot wall passing you every second. Normally this time of year the flow is 100cfs or less. That's a really low flow that you'll have to drag between the pools. You can't even tell there is flow unless you're in a narrow section. At 5000cfs the water will rise about 6 foot and make the water line go up into the trees in sections. Not really class 5 rapids but such a massive flow it's extremely difficult to paddle against. Go with the flow you'll move what seems like 20mph and its hard to control a kayak. Me and another very experienced paddler have done it because we got caught down river from Dicks. It took us 4 hours to paddle back 1 mile. We would look up river for a spot that wasn't getting swept by tree limps and paddle to it then rest. At times I was paddling as hard as I could but when I looked at the bank I wasn't even moving. I'll never forget that day!