Gibson Dam, the principal structure of the Sun River Project, is on the Sun River, 70 miles west of Great Falls, Montana. It is a concrete arch dam and contains 167,500 cubic yards of concrete. The reservoir, with 1,296 surface acres and 15 miles of shoreline, offers fair fishing for rainbow trout, cutthroat trout, and brown trout. Recreation is managed for Reclamation by the U.S. Forest Service as part of the Lewis and Clark National Forest which can be reached at 406-791-7700. Current Reservoir Levels