Damming the salmon by Mary Caperton Morton Thursday, September 3, 2015 Salmon used to be plentiful in the Snake River; today, wild salmon populations are less than 10 percent of their pre-European settlement numbers. Credit: Mary Caperton Morton. In the 1940s, the state of Idaho decided that the Salmon River would be left to flow freely while the Snake would be developed for hydroelectric power to become Idaho’s workhorse river. To date, a total of 15 dams have been built along the Snake for a variety of purposes, from irrigation to flood control to hydroelectricity. Hells Canyon is home to three hydroelectric impoundments: the Brownlee, Oxbow and Hells Canyon dams, built in 1959, 1961 and 1967, respectively. Together they have a maximum capacity of 391 megawatts of power production.