Black Canyon Diversion Dam, on the Payette River near Emmett, Idaho, is a concrete gravity type dam with an ogee overflow spillway. The dam has a structural height of 183 feet and serves to divert water to the Payette Division through Black Canyon Canal. The original capacity was 44,700 acre-feet but heavy siltation has reduced the capacity. At full pool there is now a volume of 31,200 acre-feet. Water is diverted at Black Canyon Diversion Dam by gravity into the Black Canyon Main Canal on the south side of the Payette River and by two direct connected turbine-driven pumps, located in the powerhouse, to serve the Emmett Irrigation District Canal on the north side of the river. The two unit powerplant had an initial total capacity of 8,000 kilowatts. The unit’s electrical components were upgraded to 5,100 kilowatts each in 1995 to provide the capability of generating 10,200 kilowatts with further upgrade of the turbines. Present generating capacity however, is limited to about 10,000 kilowatts. The plant supplies power to the Southern Idaho Federal Power System for Bureau of Reclamation project uses and for non-project purposes.
In 1998, a six-inch raise in Black Canyon Reservoir water surface was implemented by modifying the spillway drumgate and the radial gate at the Black Canyon Main Canal headworks. This was done to improve regulation of irrigation diversions from Black Canyon Reservoir to the Black Canyon Main Canal and to conserve the amount of stored water released from upstream reservoirs to meet fluctuating irrigation demands.
Foundation: Primarily basalt flow ranging in thickness from about 100 feet at the left abutment to founded on sedimentary units (which underlie the basalt) at the right abutment.