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Ririe Dam

Ririe Dam
 
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Ririe Dam is located on Willow Creek, a minor tributary of the Snake River, in Bonneville County of eastern Idaho. The dam is 15 miles northeast of the city of Idaho Falls and about 4 miles southeast of the town of Ririe. Constructed by the Corps of Engineers, the dam is an earth and rockfill structure, 253 feet high and 1,070 feet long. The reservoir impounded by the dam has a total capacity of 100,500 acre-feet (active 90,500 acre-feet).

 

Geology

Ririe is located in the Willow Creek Drainage on the western flank of the Caribou Range of the Middle Rocky Mountains. The stream flows from the southeast to the northwest and enters the adjoining Snake River Plain about three miles below Ririe Dam. The upper watershed is an area underlain by Paleozoic and Mesozoic age rocks, mainly of sedimentary origin. The lower watershed near the damsite is an erosion-dissected plateau surface, which is slightly tilted toward the northeast. The plateau into which Willow Creek is entrenched is comprised of Pleistocene volcanic flows and intercalated sediments which, in turn rest with angular unconformity on the regional widespread Salt Lake Formation. This formation, identified locally as "basalt sediments", is a Pliocene age unit of continental origin with highly variable lithology. The surface of the volcanic rocks is often overlain by a variable thickness of unconsolidated, windblown silt deposits. At the damsite Willow Creek has entrenched itself 250 feet below the surrounding plateau surface. The floor of the river valley under normal conditions is about 550 feet wide and nearly level at elevation 4,960, with the meandering stream channel incised about 5 to 10 feet into alluvial deposits.  The valley alluvium is about 70 to 90 feet deep and is underlain by the canyon wall basalt sequence, except where erosion and faulting have exposed the underlying basal sediment formation.


Last updated: Oct 25, 2012