The history of the Imperial Valley is driven by its history of water. From its ancient connection to the Gulf of California and the flooding of the Colorado River, to the formation of the Salton Sea and the canals that irrigate our fields today, water has shaped and continues to define the identity of the Imperial Valley. The evidence behind the evolution of the Valley landscape is still visible today, and attests to the various phases of life and activity enjoyed within it across its long history.


The Gulf of California

Ten million years ago, the Imperial Valley did not exist. In its place, the Gulf of California extended inland to the Coachella Valley, well past its current limits south of the border. Beneath the surface of this flooded expanse, ancient corals, shellfish and oysters, and large marine mammals thrived. Then, with the carving out of the Grand Canyon, this reality began to change. Across the Pleistocene glacial age, for 3 million years, the Colorado River, which once emptied into the gulf around the area of the Imperial Valley, began to grow and extend its length through the slow process of sedimentary deposition. Dirt and soil carved out from Grand Canyon became deposited in the Imperial Valley, creating an ever-growing delta fan that slowly came to dam up and separate the Valley from the Gulf. What waters remained became trapped and slowly evaporated, leaving in its place a deep Valley that exists below sea level.

Today, the evidence of this earliest identity is still visible to those who look to find it. In western Imperial County, the town of Ocotillo boasts fossilized oyster beds, shell canyons, and even the remains of an ancient whale, dated to 5 million to 7 million years old. With the damming up of the Valley, the stage was then set for later flooding and the introduction of a new, recurring freshwater lake: Lake Cahuilla.


Lake Cahuilla and the Colorado

For thousands of years, and in a repeating cycle, the Colorado River would burst its natural banks leading it to the Gulf of California, and instead forge a new course. This new course would follow the lowest ground, filling what is now the Imperial and Coachella valleys with water. The resulting body of standing freshwater is today known as Lake Cahuilla. At its largest, Lake Cahuilla was 114 miles long, 33 miles wide, and 315 feet deep. This is roughly two thousand football fields long, 580 football fields wide, and 1 football field deep.

No one knows for sure how long ancient Lake Cahuilla was a feature of the southern California landscape. Geologists can date the shoreline to as early as 26,000 years ago. Archaeologists have evidence of humans living along the lake as far back as 500 BCE (Before Common Era). It would take between 12 to 20 years for the lake to fill and about 60 years to completely empty after the Colorado River re-diverted to the Gulf of California. The lake filled and receded at least five times between 700-1700 CE. The Colorado floodwaters in 1905 which created the Salton Sea were themselves the latest attempt by nature to renew this long-standing body of water, and make the Salton Sea a smaller version of that ancient lake.

Evidence of human adaptation and use around this lake is still part of the modern landscape. Ancient fish traps, set against the ancient shoreline and today sitting isolated on empty hillsides, attest to early activity and innovation to this temporary fixture of the Imperial Valley. The Kumeyaay, one of the local tribes who used the lake, say that Lake Cahuilla may have come and gone, but has always been a part of the land.


A lingering landscape

The traces of this earlier water activity are still visible today. The same river whose water now irrigates our crops once also deposited the fertile topsoil that makes this land one of the most productive farming regions in the county: the Valley thrives on the sediments of the Grand Canyon, first brought here millions of years ago. Driving along I-8, between Dogwood Road and Fourth Avenue, a group of water towers proudly mark sea level with a line set more than a dozen feet off the ground. Driving along Imperial Ave toward Brawley, a similar line on the towers of Spreckels Sugar is even higher.

This Saturday, July 21, the Imperial Valley Desert Museum will celebrate this long history of water in the Imperial Valley at Ocotillo Water Day. Everyone is invited to attend this new event, which runs from 10 a.m. until 4 p.m. and features a variety of educational talks and water-based games and activities. Come learn how desert animals have adapted to live in a low-water environment and how we survive in it today, and get wet with water gun fights and splash pools. Come out to beat the heat of summer, and add your story to our local history.


The Imperial Valley Desert Museum is located in Ocotillo. It is open Wednesdays through Sundays, 10 a.m. to 4 p.m.

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