Wednesday, March 14, 2018

Dalles Dam on Columbia River near The Dalles, OR

(Satellite, 59+ photos; USACE)
3D Satellite
usgs.gov
usgs.gov
This dam has two fish ladders: north and east. The ladders on this and the other Columbia River dams are designed for adult salmon and steelhead. Fish counters discovered that the east ladder also passed a significant number of white sturgeon. Research as to why the white sturgeon could use the east ladder so much easier than any other ladder on the river determined that the east ladder was 6 feet wider and the submerged orifices were twice the size of those in the north ladder.
Sturgeons...are considered to be among the world’s most endangered and threatened fishes. This research shows that fish ladders can be built to provide upstream passage for white sturgeon, and indicates that ladders can be built for other species as well. In the Columbia River Basin, further research is needed to understand how ongoing changes to operations at hydroelectric dams to benefit migrating salmonids may influence upstream or downstream passage by white sturgeon.
White sturgeon resided within the ladders for periods ranging from 1 minute to nearly 6 months.
[usgs.gov]
Street View
In this photo, the gates are not that much further open than in the street view above, but they are making a bigger splash.  
The design capacity of the spillway is 2,290,000 cfs with 23 tainter gates, each at 50'x42.5'. I wonder how close this dam has gotten to using its design capacity. This spillway should be releasing water only if the power plant is already running at its normal capacity of 312,000 cfs, which is a little less than 2,000 megawatts. The river does have a dry season because sometimes the spillway is closed. [usace-facts]

Street View
usace-facts
Looking at the above street view, either the lock is rather narrow or the dam is rather tall. As it turns out, it is both: 86' x 675' with a lift that ranges between 84'-90.5'. But the lift is normally 88' feet. The extra 75' of lock length allows the tugboat to lock through with a 2x3 tow. The depth-over-sill is minimally 15'.
usace-facts

The Dalles Dam Visitor Center
In the aerial views at the top of this page, I noticed a small spillway on the downstream end of the hydro plant. In the photo on the right, that spillway is near the left side. I read the term "trash spillway." Since each water intake for the 22 turbines has a trash-rack, I assume this spillway is that trash spillway. It allows any trash, and older white sturgeons, blocked by the trash-racks to flow on downstream.

I saw this "trench" labeled the fish channel. But I have not been able to figure out what it does.

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