Mono Lake sits above 6,000 feet, just east of the Sierra Nevada Mountains and not far from the eastern edge of Yosemite National Park. It is among the oldest lakes in the United States: at least 760,000 years old, possibly as old as 3 million years. But Mono Lake is a landscape caught on the edge: Growing Los Angeles, thirsty for more water, began tapping the streams that feed the lake in 1941, using only gravity to send the water through culverts, tunnels and pipes to the Los Angeles Aqueduct, 350 miles south to the city.
