California's largest lake was created by accident when an irrigation canal failed
In 1905, flood water on the Colorado River burst into an irrigation canal and did not stop. For about two years the whole river poured into a dry desert basin in Southern California, drowning a railway town and half a reservation. The Salton Sea it created is still there, saltier and shrinking.
The basin has flooded before. Over three million years the Colorado's growing delta cut the northern end off the Gulf of California, and ever since the river has swung between emptying into the gulf and filling the basin with a freshwater lake. Wave-cut shorelines record the cycle. The last version, Lake Cahuilla, filled three or four times in 1,300 years; the Cahuilla people remember one that dried soon after 1700. Before the modern sea, the dry Salton Sink was a major salt-mining site.
From 1900 the California Development Company dug canals to water Imperial Valley farms, but silt clogged the Alamo Canal within two years. Under financial pressure, engineer Charles Rockwood had a new cut made in the riverbank about 4 miles below the existing gates, without headgates and without asking Mexican authorities. When the river swelled in 1905 it tore through, running down two dry gullies that became the New and Alamo rivers. A waterfall carved its way back up the canal, growing from 15 to 80 feet, and engineers feared it would reach the main channel. The Southern Pacific Railroad finally sealed the breach on 11 February 1907.
The lake should then have evaporated, but farm runoff kept it topped up. A wildlife refuge opened in 1930 as fish thrived and migrating birds gathered. In the 1950s and 1960s it became a resort, with yacht clubs, golf and entertainers such as Frank Sinatra at Bombay Beach, drawing over 1.5 million visitors a year at its peak.
With no outlet, though, the water grew steadily worse. Runoff carried salts, selenium and fertiliser, desert heat concentrated them, and by the late 1970s fish were dying and bird numbers falling. After 1999 more efficient farming sent less water in, the shoreline retreated, and wind lifted toxic dust from the exposed bed into nearby towns. A 2023 report put its surface at 318 square miles.
Source: Salton Sea
