Overview

Arthur R. Bowman Dam (formerly Prineville Dam) is an earthfill structure on the Crooked River about 20 miles upstream from Prineville. The dam has a height of 240 feet, crest length of 790 feet, and a volume of 1,424,000 cubic yards of material.

The spillway consists of an uncontrolled-crest inlet structure, chute, and stilling basin. Capacity of the spillway is 8,120 cubic feet per second at maximum water surface elevation of 3,257.9 ft. The outlet works has an intake structure with an 11-foot-diameter circular tunnel upstream from the gate chamber, an 11-foot modified horseshoe tunnel downstream from the gate chamber, and a stilling basin which is shared with the spillway. The capacity of the outlet works is 3,300 cubic feet per second at normal water surface elevation of 3,234.8 ft.

The total capacity of Prineville Reservoir at closure was 154,690 acre-feet (active 152,800 acre-feet). A reservoir sedimentation survey completed in 1998 estimates the total capacity at 150,200 acre-feet (active 148,600 acre-feet).

Geology

The Crooked River drains a mountainous area composed of volcanic tuff and agglomerate beds, and basalt, rhyolite and andesite lava flows ranging in age from early Eocene to Recent. The drainage basin exhibits a wide variety of topographic forms owing to variation in the resistance of volcanic beds and the varying degree of folding in the area. Depth of overburden at the damsite is not uniform. In the areas where bedrock exposures are common, overburden ranges from several feet deep.

General

Dimensions

Hydraulics & Hydrology