When Engineers designed Coolidge Dam to form San Carlos Lake behind it, they dramatically underestimated the flow of the Gila River and other regional runoff. They had assumed that the water flow would be about 460 thousand acre feet per year. They based their calculation on runoff they had observed in recent years. However rainfall was unusually plentiful during this time. As the dam was being built, rainfall in the region decreased. The actual flow was closer to 200 thousand acre feet per year. When the dam was dedicated in March 1930, San Carlos Lake, which was supposed to be a massive 1,3000,000 acre-foot reservoir, looked more like a shallow, weed-choked swamp.
Humorist Will Rogers, who attended the ceremony, looked out over the lake and quipped, “If this was my lake, I’d mow it.
It would take almost 50 years for the lake to reach capacity.
Source: Arizona, A History – Thomas Sheridan. Photo credit: US Bureau of Reclamation