Truckee River warm water solution

[craigfalk]

Are there any plans to modify the Truckee River outlet from Lake Tahoe? Currently water is released from surface water which becomes very warm during the summer. The warm water becomes unhealthy for the Truckee River trout and contributes to fish kill. If the outlet was modified to take water from a lower depth the water would be cooler even during hot days. I know from swimming in Lake Tahoe that the water even four or five feet beneath the surface is much colder than the first foot of water. My understanding is a similar modification to the Shasta Lake dam outlet, to improve salmon habitat, is what led to the lower Sacramento's remarkable trout fishery.

[JasonB]

That sounds like a reasonable consideration to me, although I'd be a bit surprised if indeed there was any solid plans to do such a modification. The idea certainly has merit however, and I too am curious if there is any movement to make a change. Perhaps some of the Truckee locals can enlighten us...
JB

[Darian]

Something to consider??? Please don't think I'm trying to rain on your parade but this is one of those things that sounds good on the surface but probably difficult and expensive to accomplish. The annual snow pack in the Sierra's is declining over the long run and the lake already draws down below the level of the outlet during drought conditions. So a modification to draw colder water from depth would have to take that into consideration. It might be easier to try to limit the amount of water released for rafting purposes. Fat chance on that one....

The cost of this could be prohibitive given construction costs and impact of same on the lake itself, permit requirements from multiple, protective local agencies and residents.

The only real benefit that I can see from this would be to reduce fish kills due to low water temps during the summer along the Hwy 89 corridor. Not a bad thing but aren't the fish in that area of the Truckee stocked for the most part??? Where's the audience for this modification??? Fly Fisherman??? Who's going to pay for it???

Since I haven't seen speculation about this anywhere else than on this BB, I wouldn't hold my breath waiting for it to happen. :-|

[JohnD]

Agreed. Most dams you see this done on are large structures where they easily access colder water near the dam. The Truckee/Tahoe dam is a very small structure in a shallow part of the lake. Plus, it would hurt the rafting business so Tahoe City would probably not be on board.

[craigfalk]

Thanks for your comments. I had not considered the fact the lake draws down below the outlet level during drought conditions. It's certainly not a good idea to drain the lake any lower. My thinking was not to release more water, but simply colder water. I'm sure it wouldn't be simple or cheap to accomplish and perhaps the fish kill problem is not sufficient enough to justify the cost. The modification to Shasta dam was done to improve the native salmon and steelhead runs, while the browns and rainbows on the Truckee are not native. I'm sure that's a consideration as well - not to mention the rafters probably prefer the warmer water. :)

[fj40]

If your puling out the colder water out from the bottom wouldnt that raise the temperature of the lake water overall and what implications would that have? No idea.....just thinking

[EricW]

I hadn't seen any data so here's a shot of the gage with flow and temp since Oct 07. Looks like typically approx July-Aug, 200-400 cfs, 65-70°.
http://www.kiene.com/forums/attachment.php?attachmentid=4755&d=1342453091

[Mike O]

Doesn't look like it gets high enough to kill.

And it never seemed to kill the fish directly below at Fanny Bridge...it took otters to do that.

The water may feel warm on the surface of the lake...but have you ever measured it?

According to the USGS:
"The water temperature near the surface generally cools to 40 to 50oF (4.5 to 10oC) during February and March and warms to 65 to 70oF (18 to 21oC) during August and September. Below a depth of 600 to 700 ft (183 to 213 m), the water temperature remains a constant 39oF (4.0oC)."

Lethal temp for rainbows is in the 80s, and cutthroat is in the mid 70s.

Seems like a bit of moot here.

[Dan LeCount]

The temps haven't killed too many fish in my experience. The biggest issues Ive seen with releases is sudden raising and lowering of flows killing macro-invertibrates and leaving nursery areas with juvenile trout high and dry. I could be wrong and just haven't experienced them getting that hot, but Ive encountered trout most of the way down to Pyramid lake amidst very shallow warm water all summer. They move to cold water in-flows, springs, heavily oxygenated water, etc and just survive when it gets very hot, but you don't see many die except when they're caught by fisherman in those conditions and pushed past the brink.