There are quite a few reservoirs and artificial lakes in and around the Bay Area that are open to the public for a variety of recreational acitivities. Following is a listing of many of these which, while not necessarily comprehensive, gives you a range of places to get wet this summer and beyond.
East Bay Reservoirs
San Pablo Recreation Area
East Bay Municipal Utilities District (EBMUD)
Mid-Feb to Mid-Nov, 6am-9pm
Fishing, biking, playground, picnics, hiking, row & motor boats
Entry fee $6, fishing fee $3
Between Orinda and El Sobrante
Lafayette Recreation Area
All year, 6am-9pm
Boating, hiking, trails, playground, fishing, picnics
Entry fee $6, fishing fee $3, rents row & pedal boats
Off of Highway 24, near Lafayette BART
Los Vaqueros Reservoir
Contra Costa Water District (CCWD)
(925) 371-2628
All year, 6am-8pm
Fishing, biking, hiking, 55 miles of trail, picnics
Entry fee $6, fishing fee $3
South of Brentwood
Contra Loma
East Bay Regional Parks District (EBRPD)
(510) 562-PARK
5am-10pm
Swimming, sandy beach, picnics, fishing
Entry fee $4, dog fee $1
Antioch
Del Valle Reservoir
(510) 562-PARK
8am-10pm
Camping (150 sites), swimming, fishing, lake tours
Entry fee $6, dog fee $1. Rents row/paddle/motor boats and canoes
Livermore
Lake Anza
(510) 562-PARK
Call for hours
Swimming, fishing, sandy beach
Fee for swim area, call for info
Tilden
Lake Temescal
(510) 562-PARK
4am-10pm
Swimming, fishing
Entry fee $4, dog fee $1
Oakland
Lake Chabot
(510) 562-PARK
Call for hours
Fishing, swimming, boating, seasonal lake tours
Entry fee $4, dog fee $1. Rents canoes and boats
Castro Valley
Cull Canyon Reservoir
EBRPD
(510) 562-PARK
Call for info
Swimming, sandy beach, picnics, fishing, hiking, horseback riding
No fees
Castro Valley
San Luis Reservoir State Recreation Area
(209) 826-1197
All year, sunrise to 10pm
Camping, boating, fishing, picnics, hiking, swimming, horseback trails
Camping fees, call for info
San Joaquin Valley, near Gilroy
Bethany Reservoir State Recreation Area
(209) 874-2056
Call for hours
Bike trails, fishing, picnics, windsurfing, windmills
Call for info
Northeast of Livermore
Santa Clara County Reservoirs (no swimming in any)
Almaden Reservoir
Santa Clara Valley Water District (SCVWD)
(408) 355-2215
All year, 8am to sunset
Fishing
No fees
San Jose. 1,553 acre-ft. of water
Anderson Reservoir/ Anderson Lake County Park
(408) 779-3634
*Currently closed. Normally: All year, 8am to sunset
Boating, fishing, hiking, paved trails
Entry, lake use, group picnic, and boat launch fees, call for info
Morgan Hill. Largest manmade lake in Santa Clara county, 89,073 acre-ft.
Calero Reservoir County Park
SCVWD
(408) 268-3883
All year, 8am to sunset
Backcountry trails, fishing, powerboats, jet skiing
Vehicle entry and boat launch fees, call for info. Horse rentals: (408) 268-2567
San Jose. 10,050 acre-ft.
Chesbro Reservoir / County Park
(408) 779-9232
All year, 8am to sunset
Fishing, non-powered boats, picnics
Lake use fee, call for info
Morgan Hill. 8,952 acre-ft.
Coyote Reservoir / Coyote Lake County Park
(408) 842-7800
All year, 8am to sunset
Camping (64 sites), boating, fishing, picnics, hiking trails
Entry, camping and boating fees, call for info
Gilroy. 22,925 acre-ft.
Lexington Reservoir/County Park
(408) 356-2729
All year, 8am to sunset
Surf area, electric powered & rowboats, picnics
Lake use fee, call for info
Los Gatos. 19,834 acre-ft.
Stevens Creek Reservoir/County Park
(408) 867-3654
All year, 8am to sunset
Archery, kayaking, hiking, horseback riding, picnics, fishing
Lake use and group picnic fees, call for info
Cupertino. 3,465 acre-ft of water
Uvas Reservoir/County Park
SCVWD
(408) 779 9232
All year, 8am to sunset
Camping (25 sites), hiking, waterfalls, picnics, fishing, non-power boating
Lake use fee, call for info
West of Morgan Hill. 1,935 acre-ft
Vasona Reservoir/Vasona Lake County Park
(408) 356-2729
All year, 8am to sunset
Fishing, non-power boating, picnics,
Entry fee, lake use and group picnic fees, row and paddle boat rentals, call for info
Los Gatos. 400 acre-ft
Marin County Reservoirs
Lagunitas Reservoir
Marin Municipal Water District (MMWD)
(415) 945-1455
Sunrise to sunset
Fishing, hiking, dog walking, horseback riding, picnics
Call for info
On Mt. Tamalpais
Alpine Reservoir
(415) 945-1455
Sunrise to sunset
Fishing, hiking, dog walking, horseback riding, picnics
Call for info
On Mt. Tamalpais
Bon-Tempe Reservoir
(415) 945-1455
Sunrise to sunset
Fishing, hiking, dog walking, horseback riding, picnics
Call for info
On Mt. Tamalpais
Kent Reservoir
(415) 945-1455
Sunrise to sunset
Fishing, hiking, dog walking, horseback riding, picnics
Call for info
On Mt. Tamalpais
Phoenix Reservoir
(415) 945-1455
Sunrise to sunset
Fishing, hiking, dog walking, horseback riding, picnics
Call for info
On Mt. Tamalpais
Nicasio Reservoir
(415) 945-1455
Sunrise to sunset
Fishing, hiking, dog walking, horseback riding, picnics
Call for info
West Marin
Soulajule Reservoir
(415) 945-1455
Sunrise to sunset
Hiking, dog walking, horseback riding, picnics
Call for info
West Marin