When irrigation canals from the Colorado River jumped their levees near the U.S./Mexico border in 1905 on the desert east of San Diego, millions of gallons of fresh water spilled into the Salton Trough, historically an arm of the Lower Colorado River Delta at the head of the Gulf of California. When the water finally stopped, it filled a trough 45 miles long, 17 miles wide, and 83 feet deep.

The Salton Sea was born. Or was it?

If one looks back beyond 1905, one comes away with a different understanding. The current Salton Sea, which persists today, appears to be far more natural than the accident as it is commonly portrayed. Before levees and pumps reduced the lower Colorado River to a narrow, muddy channel, wet winters would regularly send it careening northwest-ward from Yuma, Arizona, where it would flood the Salton Trough before reaching the ocean at the head of the Gulf of California. Ancient Lake Cahuilla, which persisted until just 500 years ago, was at times even larger than the current Salton Sea – and productive enough to provide a delta fishery for the Indians in the region, whose fish traps are still visible far above the shores of the Sea today.

So, when birds began to flock to the sea during the 1900s, they were actually following ancient migratory paths developed over millions of years. Pelicans, Cormorants and terns began nesting on large islands formed at the southern end of the Sea, and shorebirds and gulls stopped to refuel along its shore. Rafts of Eared Grebes and ducks once again wintered on the open water of the Sea, which now covers 376 square miles (making it larger than Lake Tahoe).

But the Salton Sea isn’t the only important bird habitat in the area dependent on Colorado River water. The marshy irrigation canals and open agricultural fields of the Imperial Valley, immediately to the south, have also emerged as critical wintering and breeding areas for birds, including some that are confined to the pitifully-reduced wetlands of the lower Colorado (e.g. Yuma Clapper Rail). Other species found here have been pushed out of agricultural areas elsewhere in the state (e.g. Burrowing Owl, Mountain Plover), and now thrive in the Imperial Valley, as do thousands of shorebirds that use the flooded fields during late summer and spring migration, and countless songbirds that pour through the Salton Trough en route to northern breeding areas each spring and fall.

Over the past hundred years, a combination of naturally salty soils, high evaporation rates and constant run-off from the Imperial and Coachella valleys have made this now land-locked sea ever saltier, which significantly threatens the entire Salton Sea ecosystem. Meanwhile, increased pressure from urban water users have resulted in proposals for major water transfers away from agriculture (and the Salton Sea) toward growing cities in coastal southern California.