Mammoth Pools Hydroelectric Tunnel

[John]

There is actually an underground tunnel that goes all the way from Mammoth Pools Reservoir, down the San Joaquin canyon to the Pumphouse Number 8, about 7 1/2 miles away. It goes right past the toe of Tranquility Dome and pretty much parallels the French Trail. It contains the entire volume of the San Joaquin river within it.

Does this blow anyone else's mind?

[mungeclimber]

Like as in, there is no river in that section of the canyon?  No fishies going upstream at all? 

Doesn't that violate some law or the other?

[John]

There is a relatively small amount of water allowed to flow past the dam compared to what is diverted into the tunnel. There are tributaries between the dam and the powerhouse that add to the flow too. Pretty low otherwise.

[susan]

Well, yeah, it's not probably all the water... There is a bit of flow pictured here down stream of the dam but not much, and is probably fed from other streams meeting there. Yes... sounds like this dam was made long ago? 

Dam Photo


Not much farther downstream of the dam

[NateD]

Yes, all kinds of crazy things with these reservoirs in the hills. For instance, at night, when demand and prices for electricity are low, water is pumped from Wishon Reservoir all the way up to Courtright Reservoir, 1,500 ft. higher, using reversible turbines in the Helms Powerhouse - which, incidentally, was built in a chamber carved out of solid granite a thousand feet underground.

[John]

Yes, all kinds of crazy things with these reservoirs in the hills. For instance, at night, when demand and prices for electricity are low, water is pumped from Wishon Reservoir all the way up to Courtright Reservoir, 1,500 ft. higher, using reversible turbines in the Helms Powerhouse - which, incidentally, was built in a chamber carved out of solid granite a thousand feet underground.

Why don't they just turn off a big 'ol valve at night instead of pumping? I don't get it.

[John]

This is what the dam is for, where 187000kw of power is produced. The tunnel ends at the top of the big pipe above the generators.