Tolay Lake

Tolay Lake is a shallow freshwater lake in southern Sonoma County, California, United States. The lake, nestled within the southern vestiges of the Sonoma Mountains, is the site of significant Native American prehistoric seasonal settlement. In 2005, Sonoma County acquired the entirety of the lake and virtually its whole drainage basin from the Cardoza family for the sum of $18 million; the County's intention is to utilize the property as Tolay Lake Regional Park for ecological and archaeological preservation, as well as public use and enjoyment. Tolay Lake and its immediate drainage area is home to several nesting pairs of golden eagles, Aquila chrysaetos, and a number of rare, threatened or endangered species including the California red-legged frog, Rana draytonii; Western pond turtle, Actinemys marmorata; and Western burrowing owl, Athene cunicularia.

Tolay Lake was initially altered about 1850 by European settlers who dynamited a natural earth dam on the lake's south side, in order to enable more intensive agricultural cultivation and grazing of the basin; at times thereafter, the lake typically became almost dry in the summer months, when rainfall in this region is at its seasonal nadir. Another modern alteration is the construction of an east-west earthen causeway that effectively bisects the lake, impeding thorough water circulation and fragmenting plant and animal colonies of the lake.