Marin Water maintains seven reservoirs – five in the Mount Tamalpais Watershed and two others in the hills of west Marin County. The oldest, Lake Lagunitas, was built in 1872, before the District was even chartered. The District’s only concrete arch dam, at Alpine Lake, was built in 1919 using the bond funding approved by voters who originally agreed to establish the District.
Six others were built, and some expanded, in the decades that followed, with the last significant modification to the District’s reservoirs coming in 1985. Together, these reservoirs are capable of holding 79,566 acre-feet of water – enough for three years’ worth of drinking water for the residents in Marin Water’s service area. Alpine, Bon Tempe, Kent, Lagunitas, and Phoenix Lake are located on the north slope of Mt. Tam. The other two – Nicasio and Soulajule – are outside the District’s service area in western Marin County.
Alpine Lake
- Type: arched concrete dam
- Year built: 1919, raised in 1923 and 1941
- Storage Capacity: 8,891 acre-feet
Bon Tempe Lake
- Type: earth-fill dam
- Year built: 1948
- Storage Capacity: 4,017 acre-feet
Kent Lake
- Type: earth-fill dam
- Year built: 1953, enlarged in 1982
- Storage Capacity: 32,895 acre-feet
Lake Lagunitas
- Type: earth-fill dam
- Year built: 1872
- Storage Capacity: 350 acre-feet
Phoenix Lake
- Type: earth-fill dam
- Year built: 1905,modified in 1968 and 1985
- Storage Capacity: 411 acre-feet
Nicasio Reservoir
- Type: earth-fill dam
- Year built: 1960
- Storage Capacity: 22,340 acre-feet
Soulajule Reservoir
- Type: earth-fill dam
- Year built: 1979
- Storage Capacity: 10,572 acre-feet
Every day, water from the reservoirs is pumped to one of the District’s treatment plants before passing through pump stations, storage tanks and a portion of Marin Water’s massive, 908-mile pipeline network en route to one of 61,900 service connections.