where the Boulder and Smoky Mountains meet. While not in Sawtooth National Forest, Banner Creek Summit is a mountain pass on State Highway 21 at the northern end of the Sawtooth Mountains, on the border of the Boise and Challis National Forests. Waterways There are over 1,100 lakes covering and an estimated of temporary and permanent streams and rivers in the forest. Over of streams are found in the Fairfield District, over in the Ketchum District, and over in the Minidoka District. The entire northern portion of the forest is in the watershed of the Snake River, a tributary of the Columbia River. The Salmon River's headwaters are in the upper Sawtooth Valley, and this river drains much of the SNRA and follows a tortuous, overall northwesterly course before flowing into the Snake River downstream. The eastern side of the Sawtooth Mountains is drained by the South Fork of the Payette River. The northern Soldier Mountains, southern Smoky Mountains, and much of the Fairfield District are drained by the South Fork of the Boise River, which flows into Anderson Ranch Reservoir just west of the forest. The Ketchum District, part of the SNRA, and the southern slopes of the Fairfield District are drained by the Big Wood River. Much of the Minidoka District is also drained by the Snake River via the Raft River and other tributaries, but portions of the Black Pine and Raft River Mountains drain into the Great Salt Lake. The annual water yield from the forest is estimated just below . Most of the forest's lakes are the result of glaciation and occur in the SNRA in the Sawtooth and White Cloud Mountains, but lakes can be found in most of the other mountain ranges of the forest. There are over 20 lakes in the Fairfield District, 90 in the Ketchum District, and 6 lakes and 3 reservoirs in the Minidoka District. The largest lake on the forest is Redfish Lake, a moraine-dammed lake that is long, wide, and up to deep. Other large lakes include Alturas, Pettit, Sawtooth, Stanley, and Yellow Belly lakes. Seismology The Sawtooth Fault is a long east-dipping normal fault that runs along the base of the Sawtooth Mountains and was discovered and mapped in 2010. It is believed to be capable of producing an earthquake measuring up to 7.5 on the Richter magnitude scale. The most recent earthquake, measuring M5+, occurred