Tulare Lake used to the largest body of freshwater west of the Mississippi. It disappeared, after farmers and cities diverted its waterflows with dams and canals. But long ago there was an even larger lake in the region. Today on KVPR’s Central Valley Roots – the story of what happened to Lake Corcoran. Imagine a map of the entire Central Valley from Bakersfield to north of Sacramento – all underwater. If you went back, say 1 million years ago that’s pretty much what you would have seen, something geologists today call Lake Corcoran. Back then, the Valley didn’t drain into San Francisco Bay. Instead, geologists believe Lake Corcoran actually drained from the south into the Salinas River, flowing all the way to Monterey Bay.