Horseshoe Dam, on the Verde River 58 miles northeast of Phoenix, is an earthfill structure 202 feet high, with a reservoir capacity of 131,500 acre-feet. Horseshoe Dam was built from 1944-1946 by the Phelps-Dodge Copper Products Corp. for the Salt River Valley Water Users' Association under a water exchange agreement. Spillway gates were added to the dam in 1949 by the city of Phoenix to increase the domestic water supply. In 1952 the dam was raised 4 feet to elevation 2044.
Horseshoe Dam was also modified by Reclamation in 1993 to address concerns about its safety in the event of a Probable Maximum Flood or Maximum Credible Earthquake. Modifications included construction of a fuse plug auxiliary spillway with an erodible embankment and a concrete foundation 2,000 feet west of the existing spillway. In addition, a 148,000 cubic-yard stability berm was constructed at the downstream toe of the dam to help stabilize it in the event of an earthquake, and the dam was raised eight feet to enable the spillway to pass the Probable Maximum Flood. To prevent overtopping of the structure from wave action, an additional 4-foot parapet was built on the dam's crest. Other work included modifying the service spillway gates, and construction of an auxiliary spillway, closure dike and training dike. The dam tender facilities were also relocated and the road to the boat ramp upgraded.