Water

MMWD manages a complex water system that provides high quality drinking water to 186,000 customers in central and southern Marin. Two unique features of this system stand out: the drinking water provided is very pure, and our unique geography and topography means our distribution system is very complex, similar to agencies ten times larger than ours, such as EBMUD.

Reservoir and Rainfall Levels



Water Watch (daily updates on rainfall, reservoir storage, consumptions levels, and more)

Daily Rainfall Levels (this year vs. last year)

Rainfall History (since 1880)

Reservoir Diversion Data

Marin County Sources
Nearly 75% of MMWD's water comes from 21,635 acres of protected watershed on Mt. Tamalpais, and in the grassy hills of west Marin. These areas are mostly forested MMWD-owned lands and other undeveloped rural lands. Rainfall from these watershed flows into MMWD's seven reservoirs. Water from these reservoirs is treated and filtered before delivery.
Reservoir Capacities
Reservoir Capacity in Acre Feet % of Total Capacity Year Built
Lagunitas 350 0.4 1872
Phoenix 411 0.5 1905
Alpine 8,891 11.2  *1918
Bon Tempe 4,017 5.1 1948
Kent 32,895 41.3 **1953
Nicasio 22,430 28.2 1960
Soulajule 10,572 13.3 1979
Total 79,566 100.0  
One acre foot is 325,851 gallons, enough water to cover one acre, about the size of a football field, to a depth of one foot.
*Enlarged in 1924 and 1941
**Enlarged in 1982

Sonoma County Sources


Over 25% of MMWD’s water is imported from the Sonoma County Water Agency. SCWA water originates from rainfall that flows into Lake Sonoma and Lake Mendocino, and is released to the Russian River. The Russian River water is filtered naturally through 80 feet of sand beds adjacent to the River. The Russian River water blends nicely with the District’s reservoir water within the District’s distribution system.
Photo of Russian River