Anyone who has driven Highway 17 over the Santa Cruz Mountains has seen Lexington Reservoir. Valley Water says the reservoir and its dam sit on Los Gatos Creek about three miles south of the town of Los Gatos.

A dam with three names

Valley Water says the dam was built in 1952. During planning it went by several names, mainly Windy Point Dam, after an obscure spur near the site. In 1947, water district directors decided to name the dam and reservoir after Lexington, a small nearby community that was sacrificed when the reservoir was built. The district renamed the dam in 1996 for James J. Lenihan, who had served as a director for 37 years.

Valley Water lists the reservoir as 2.5 miles long, with room for 19,044 acre-feet of water and a surface area of 412 acres. It calls Lexington its second-largest reservoir. Wikipedia describes Lenihan Dam as an earthen dam 195 feet high.

The towns under the water

According to Wikipedia, the reservoir covered the towns of Lexington and Alma. Each had about 200 residents at its peak in the mid-1800s. Lexington declined after 1880, when the railroad from Los Gatos to Santa Cruz bypassed it. Alma declined after Highway 17 bypassed it in 1940.

When the water drops, old roads from the reservoir's construction and the towns can reappear. Wikipedia says a 1926 bridge over Black Creek and a few house foundations were exposed in 2008, when the reservoir was drained for dam maintenance. That work was the district's Lenihan Dam Outlet Project, which began in September 2007 and replaced the old 48-inch outlet pipe at the base of the dam.

Visiting

Wikipedia notes that Alma Bridge Road runs along the eastern side of the reservoir and connects with Highway 17 at the north end. The reservoir is part of a Santa Clara County park, and the Los Gatos Creek Trail starts at the dam and heads downstream from the dam toward town. Wikipedia lists rowing, paddling and fishing among the uses. Swimming is not allowed.

Valley Water also posts inundation maps for a hypothetical failure of Lenihan Dam on its reservoir page, alongside maps for Austrian Dam upstream.