The District is primarily dependent on surface water imported by the Metropolitan Water District of Southern California (MWD) from the Colorado River and Northern California. From these distant sources there are two major conveyance systems that bring water to District customers, the 242-mile long Colorado River Aqueduct and the State Water Project’s (SWP) 444-mile long California Aqueduct. The Colorado River Aqueduct begins its journey at Lake Havasu on the California-Arizona border and ends at Lake Mathews near Riverside. Water from Northern California originates in the Sacramento-San Joaquin Delta and is transported to Silverwood Lake in Hesperia. Raw water from these two sources is then treated at two filtration plants.
To ensure a reliable supply of water for southern California in times of drought, Diamond Valley Lake, located near Hemet in southwest Riverside County, stores water received from both aqueducts. Measuring 4-1/2 miles long and 2 miles wide, the lake holds enough water to meet the area’s emergency and drought needs for six months.
MWD owns and operates the Weymouth Water Treatment Plant located in the city of La Verne. The District, through its designated wholesale agency Three Valleys Municipal Water District (TVMWD), purchases a blend of the treated Colorado River and SWP water from the Weymouth plant. When surplus water is available, the District is also able to purchase water treated by TVMWD at its Miramar Water Treatment Plant located in the city of Claremont. TVMWD purchases raw SWP water from MWD and treats and sells it to retail water purveyors.
|Weymouth Treatment Plant
District’s primary water supplier
|Miramar Treatment Plant
Additional District water supplier
Average Annual Water Supply
Weymouth Treatment Plant: 20,685 Acre-Feet
Miramar Treatment Plant: 2,978 Acre-Feet
TOTAL Annual Water Supply (on average): 23,663 Acre-Feet
* An acre-foot is equal to about 326,000 gallons of water, or the amount that 2 families use in one year.