Dams aren't all evil. They provide flood control, a source of power ( some ), irrigation for millions of acres of otherwise unfarmable lands, transportation and recreation.
Without the dams, most people in the northwest would be paying 10 times as much for there electricity. Rolling black out would be a regular occurance.
If the farmers in the midwest/west were not able to get irrigation water from the dammed up rivers, the majority of them would fail. Food shortage would hit the country and food prices would go through the roof.
Lewiston, Idaho would die. Lewiston is one of the furthest in land 'sea ports' all made possible by the transportation along the Columbia.