Coolidge Dam: Operations

Coolidge Dam received its sternest, toughest test in January 1993. Rivers all across Arizona surged to record or near-record levels and The Gila River was no exception. San Carlos Reservoir filled quickly and water began to pour over the spillways. The original spillways gates could have prevented the overflow but they had long ago become rusted into place and were completely inoperative.

Once waters begin to spill from any given reservoir, there's really nothing that dam managers can do to mitigate the overflow. They like everyone else have to simply sit back and watch the water flow. The outflow peaked over 29,000 cubic feet per second, a flow not seen in the Gila River since pre-dam days in the teens and twenties. Back before Coolidge Dam was completed, downriver residents well knew the Gila's fury. The peak of the epic 1916 flood was 130,000 cubic feet per second. However, that was generations ago. In the meantime, many people had built and erected structures in the river's old floodplain. Those people thought Coolidge Dam would keep their property safe forever. They were wrong. Winkleman, especially, took a big hit from the 1993 flood which wiped out a mobile home park built beside the river. It was never rebuilt and it now a Winkleman riverside park.

Coolidge Dam was not originally designed specifically for flood control but it served as a de facto flood control structure for most of its service life. Aside from the 1993 fill & spill, very few incidents of higher-than-normal flows have occurred.

The level of San Carlos Reservoir behind Coolidge Dam has fluctuated rather dramatically throughout its life. It has varied between dry and nearly full numerous times. Periods of a stable reservoir level have been few and far between.

Water managers in the Middle Gila have learned to go with the flow. They know and understand the fickle foibles of The Gila perhaps better than anyone.