May is the month to visit Shoshone Falls. The amount of water cascading over one of Idaho’s most well-known scenic attractions will pick up this week and could exceed 2,500 cubic feet per second (cfs) by Thursday morning. Those aren’t high flows by historical standards, but enough to make the drive down into the Snake River Canyon northeast of the city of Twin Falls worthwhile. And it’s as good as it’s likely to get this year.
A dry spring throughout the Snake River Basin means, until this week, virtually all of the water in the Snake River was being diverted for agricultural irrigation at Milner Dam, east of Twin Falls. Springs and irrigation return flows account for the small amount of water visitors have seen going over the falls recently. Although Idaho Power can divert some water to generate electricity through the Shoshone Falls Power Plant, the company is required to allow at least 300 cfs to go over the falls from April 1 through Labor Day.
This month’s boost in volume comes from the U.S. Bureau of Reclamation’s annual flow augmentation – water released from upstream reservoirs to help young salmon and steelhead make their way down the Snake and Columbia rivers to the Pacific Ocean. For the next few weeks, tourists visiting Shoshone Falls will also benefit from the sight and sound of that additional water.
The Shoshone Falls Power Plant, visible on the north side of the river from the Shoshone FallsPark viewing platform, was originally built in 1907. Idaho Power acquired the plant in 1916 and rebuilt it in 1921. After an upgrade completed last year, the plant can generate up to 14.7 megawatts of electricity, enough to power more than 11,000 homes.