It's hard to believe that a place as hot and dry as El Morro could sustain such a large source of water. Averaging about twelve feet deep, the pool holds about 200,000 gallons of water, depending on yearly rainfall.
It was once thought to be replenished by a spring, but it is entirely fed by snowmelt and rain runoff from the top of the cuesta. After a heavy monsoon, there are often temporary waterfalls as water pours from the top of the cliff!
Then and Now
The pool has changed since its use by Ancestral Puebloans and Spanish conquistadors. Historically, the pool would have been more of a catchment basin, with clear water and a sandy bottom. Visitors looking for a drink of water could walk or ride their horses around the pool's sandy perimeter.
In the 1920s, the first custodian of El Morro Evon Vogt deepened and dammed the pool to provide a better source of water to visitors, farmers, and ranchers. The pool continued to serve as a water source for area ranchers until 1939. In 1942, a rockfall destroyed the previous dam and filled the pool with debris. When the pool was dredged for repairs, evidence of older attempts to dam the water was discovered. It also served as the main water source for the park until 1961, when a well was dug on the north side of the monument.