Water Leadership Institute

Arizona Water History

Despite being a desert in the current era, there are multiple fossil beds in Arizona that preserve the multitudes of life that inhabited the bodies of salt and freshwater now absent. 

The grand canyon for example was formed during the permian period tens of millions of years before the dinosaurs, and contains aquatic fossils ranging from the sponges, crinoids, and trilobites since the precambrian. The grand canyon’s fossil records do not reveal only aquatic life as ferns, reptiles and insects were also present primarily discovered during the Permian alongside sharks and saltwater life.

After the Permian, the Mesozoic age of dinosaurs had a blend of terrestrial and aquatic animals indicating that both habitats were present. Although water levels fluctuated then decreased during the paleozoic, Triassic arizona still had respectable water levels into the age of the dinosaurs, with the 26 foot long crocodile relative Rutiodon and the semi aquatic marine predator tanystropheus indicating the presence of large aquatic bodies. 

As the age of the dinosaurs continued the waterways of the Jurassic receded and became far more dry. However the Cretaceous had brought forth the Western Interior Seaway which hosted mosasaurs, plesiosaurs, and a plethora of marine life.

The end of the dinosaurs had also brought about the end of much of the water in Arizona, however that doesn’t mean that the state was a complete desert. The presence of alligators and mammoths indicate a far more water and floral rich ecosystem.

Most of the water lost in Arizona is due to human intervention with the Rillito river being removed due to damming.