indeed an awesome spectacle. I had the good fortune to go there about a year and a half ago and I was duly impressed. It is America's largest dam by far with about three times the generating capacity of Hoover Dam which might be our most famous dam.
The Columbia River has other dams on it as well as the Grand Coulee. The Bonneville Dam is huge and impressive too plus it has an interesting arrangement for fish to move up and down the river.
There are quite a few other dams on the Columbia River system so I expect that further hydro-power may not be too profitable, plus the dams do have some considerable effects upon the ecology.