South Tufa State Reserve. Mono Lake is an ancient lake in Mono County, Eastern Sierra. The lake is 760,000 years old and lost 40 feet of water exposing 17,000 acres of lakebed when water was diverted to Los Angeles in the 1940's. The tufa towers you see here were formed underwater over the course of hundreds of years. Directly ahead is a small tufa island referred to as Pirate Island. The tufa all the way to the left is currently the home of an Osprey.