Lake Cahuilla High Water Mark

August 17, 2007


Provided and copyright by: David Lynch, Thule Scientific
Summary authors & editors: David Lynch

Lake Cahuilla was an ancient freshwater lake in the Salton Trough of southern California. It covered parts of the Coachella, Imperial and Mexicali valleys and was formed when the Colorado River overflowed its banks or was diverted northwest by its own sediments, which temporarily blocked the flow to the Gulf of California (Sea of Cortez). Although there have been a few smaller incarnations of the lake in historic time, the main high water mark is thought to have occurred sometime between 1,000 and 1,500 AD.

This high-stand is evident many places in the Santa Rosa Mountains west of the Salton Trough. Here on a golf course in La Quinta, California, it's plainly visible as a sharp horizontal boundary separating dark, water-stained rock below and the original lighter-colored rock above. This feature is at an elevation of 12 meters (about 40 feet) above sea level and runs though this area for miles. Indeed, at this same elevation all around the Salton Trough, evidence of the high water mark can be found as travertine deposits, fresh water shells and former Native American settlements. If Lake Cahuilla formed today and reached 12 m elevation, many towns in the area would be submerged including Indio, El Centro, Mexicali, and part of Interstate Highway10.

At present, the Salton Trough is home to the much smaller and lower (-69 m) Salton Sea, a salty, polluted body of water formed during an irrigation accident in 1905. Ancient Lake Cahuilla should not be confused with a modern man-made body of water with the same name in a Riverside County park near La Quinta. See also the Earth Science Picture of the Day for June 5, 2007.

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