Los Vaqueros Reservoir sits in the northern Diablo Range in eastern Contra Costa County, reached from Vasco Road between Brentwood and Livermore. The Contra Costa Water District runs it as a drinking-water reservoir that is also open for day-use recreation.

Hours and fees

The district says Los Vaqueros is open every day, including holidays. Hours are 7 a.m. to 6 p.m. in October and 7 a.m. to 5 p.m. from November through February. Gates lock on time, and late departures get citations. Parking is $6 for the general public, $5 for seniors and $4 for residents of the district's service area. Fishing costs $6 per person per day. The Los Vaqueros Interpretive Center is open weekends, 9 a.m. to 4 p.m.

Rules

Watershed rules are strict. No pets, swimming, alcohol or outside watercraft are allowed, and smoking is limited to one designated area at the marina. The district says the pet ban protects wildlife and water quality, and it also covers the neighboring Round Valley Regional Preserve. Visitors who want to hike with a dog can use Morgan Territory Regional Preserve above the marina. Park only in designated areas, or you may be cited. Pack out your trash, and ask marina staff before using a barbecue during fire season.

Instead of private boats, the marina rents 16-foot and patio-style electric boats. The district warns that storms, fog or high winds can shut the dock, fishing pier and rentals. The marina sells snacks and some limited hot food.

Why it exists

Wikipedia says salty water pushing into the Sacramento-San Joaquin Delta has worried the district since its founding in 1936. A 1977 drought pushed salinity past public health standards and forced rationing. Voters approved the project in 1988, and construction began in 1994. Filling started in February 1998 and finished in January 1999, a year ahead of schedule. The American Society of Civil Engineers named it the nation's outstanding civil engineering achievement of 1998.

The name comes from the 19th-century Rancho Cañada de los Vaqueros; vaquero is Spanish for cowboy. Wikipedia says an expansion begun in 2010 raised the dam to boost storage from 100,000 to 160,000 acre-feet.

Neighboring parkland: Round Valley Regional Preserve and Morgan Territory.