"The Disappearance of California's Largest Freshwater Lake" Did you know that California’s Central Valley was once home to a massive freshwater lake? Over 600,000 years ago, Lake Corcoran covered much of the region, fed by rainfall and glaciers from the Sierra Nevada mountains. However, as the climate warmed, the lake overflowed and drained into the Pacific, leaving behind Lake Tulare. By the 1800s, Lake Tulare, also known as "Pashi" by the Tachi Yokut tribe, became the largest freshwater lake w