Twin Falls, ID

Twin Falls, on the Snake River a little over five miles upstream from the eponymous city (and about two and a half miles upstream from Shoshone Falls), consists of similar-sized falls in chutes on either side of a stubby basalt pillar. Hence the name was particularly appropriate.

In 1935, however, Idaho Power built a hydropower plant in the south channel, completely blocking it. Hydroelectric power and rural electrification were priorities at the time, and no doubt job creation during the height of the Great Depression was another primary motivation for the project. The powerplant is still in use, and after an upgrade in 1995, the plant capacity is just under 53 megawatts. Although the aesthetic loss is regrettable, the plant has provided clean and sustainable energy for almost a century.

The north channel is now effectively a spillway. A low, submerged arch dam (weir) completely crosses the north channel on the upstream side and provides an even level over which the current now falls.