[puzzlr]

I've tried searching and asking around to find out the answer to this question. Why do some wilderness lakes have small dams built at the outlet? The two I'm thinking of are

Snow Lake

My guess here is that at one time the USFS wanted a bridge that stock could cross. A point against that theory is the positioning of the dam right next to steep walls of the ravine. The old CCT went down the Rock Creek trail which separates before this point, however.

Snoqualmie Lake

Snoqualmie Lake

My guess here is that this was somehow related to plans to build a highway through here. By raising the level of the lake it would provide more water for more of the season. It was a lot of work to put in the cribbing and rocks, and there's clearly logs and debris that show it used to stretch all the way across the outlet. As far as I know, there was never a trail on the other side of the outlet here. As late as 1946 there was a FS cabin near the outlet, in case there are any ideas related to that.

[Conrad]

From 100 Hikes in Washington's Alpine Lakes (1993), re the Snow Lake leading to the Enchantments:

[puzzlr]

Yes, the Snoqualmie Snow Lake. But thanks for the info on the other Snow Lake. I didn't know that's why there's a dam there either until you posted, but it's exactly the kind of reason I'm looking for.

[contour5]

I don't have the answer exactly, but I remember seeing tiny ruined dams on alpine lakes above Owens Valley in the Sierra. They were built to trap water for agriculture and mining, long before the current water schemes were devised. I'd imagine it's the same scenario locally. There's an old dam at the outlet of Square Lake if I remember correctly. Somebody (maybe BPJ) posted a photo of it...

[BirdDog]

I don't for sure about Snow Lake; but loggers way back when would build log/earthern damns. They would log the slopes and slide the logs downhill into the creek/river. Then they would bust the damn and wash the logs downstream. Also miner built dams for water storage used for sluicing. You can often see the remnants of miles of old iron pipe running out of lakes. Kind of answers the question as to why we have environmental regs now.

[dave allyn]

I believe the snow lakes dam (enchantments) was built well before the fish hatchery, and is used for irrigation. Obviously it was built before it was "wilderness". If i remember correctly that and six other lakes are dammed by the irrigation district, including Colchuck,Eightmile, and Klonaqua.

[polarbear]

I will have to inspect the Snow Lake outlet more closely the next time I am there.

[HitTheTrail]

This is the tunnel above Nada Lake in the Enchantments that was built up under Snow Lake to let water out from the bottom of the lake. The upper one goes to the gate valve control room and the lower held the gate valve and 30" sleeve valve.

Snow_Lake_Outlet_Valve

As I understand it the project was for the fish hatchery and built as part of the Grand Coulee Dam effort to compensate for loss of fish runs. Grand Coulee was built without a fish ladder of any kind and stopped all salmon getting up the Columbia River into Canada. No wonder they have always been mad at us.

[Schroder]

According to the Spokane Daily Chronicle on March 21 1939, the Nada bore was built for the fish hatchery. Here's an older thread on this also. There were several dams contemplated on Foss Lakes and Lake Dorothy also to generate power for the electric cars that pushed the Great Northern trains through the Stevens Pass tunnel. The dam was built in Tumwater Canyon instead.

[Ringangleclaw]

Lake Isabel has a small wooden dam at its outfall

[HitTheTrail]

[Kim Brown]

[NacMacFeegle]

There are a lot of alpine lakes with small dams in Idaho, most were built for irrigation, and all have resulted in reservoirs that really aren't worth visiting. One particular lake comes to mind: Twin lake (two lakes once separated by a narrow peninsula) is set in a deep granite-cliffed bowl in central Idaho, the setting is spectacular, but the dam turned the shoreline into mud, and the forest service routinely clears the trees from the area around the dam, resulting in a permanent clear cut. To top it all it is often used as a watering hole for cattle, and thus the already muddy shore is often a veritable morass of stinking goo. There isn't even any good fishing since they planted non-native tiger muskie to kill the non-native brook trout (and every other living thing within the lake). Apologizes for the rant- I have a great dislike for all dams, but those installed on alpine lakes are particularly disgusting to me!

[jinx'sboy]

It may not be evident, now, but many years ago I was at Big Hidden Lk In the Pasayten. There is/was a dam there. I heard at one time that is was irrigators downstream, either in BC, or in WA where the Pasayten enters the Similkameen and flows back into the US who impounded the water.

[pianodirt]

A few years ago a friend and I were staying at the lower of the two Klonoqua lakes. While there, I stood dumbfounded as a helicopter landed next to the concrete dam, a helicopter in a Wilderness area! My friend talked to the pilot, who said he was there to open/close the valve to the dam, something he did once or twice a year. He said it was for the irrigation district in Leavenworth. The dam was unlike other alpine lake dams I have come across. The one at Square Lake (I was there a couple years ago and it's still standing) is fairly rustic, but the Klonoqua one has real cement and a large metal plate-valve with a large metal wheel to activate the valve. Like others have said, the dam/irrigation existed before the area was designated as Wilderness.