Our Water Supply

MNWD, like most south Orange County water providers, does not have the benefit of access to local supplies of water, so the majority of the District’s water is imported from the Colorado River and the Sacramento-San Joaquin Delta. MNWD supplements these sources by treating and delivering recycled water for irrigation purposes, which diversifies our supply and adds greater reliability during times of drought and other emergencies.

Even if Mother Nature provides the state enough water to meet everyone’s needs, court rulings, environmental regulations, a shortage of water reservoirs, and an outdated delivery system limit our ability to capture water and move it from where it falls in the north to where it’s needed in the south. That means MNWD customers must always be as efficient as possible to protect our region’s limited water resources.

Primary Supply Sources
Approximately 78 percent of MNWD’s water is purchased through the Municipal Water District of Orange County from the Metropolitan Water District of Southern California, a regional water wholesaler that delivers water from Northern California and the Colorado River.

State Water Project
The State Water Project, also known as the California Aqueduct, transports water 600 miles from Northern California to the Central Valley and the southern portion of the state. It is owned and operated by the State of California and is the longest aqueduct system in the world, featuring 23 dams and reservoirs, 22 pumping plants that lift water to heights of 3,500 feet, and six power plants. The aqueduct is comprised of 473 miles of canals, 175 miles of pipeline and 20 miles of tunnels.

Colorado River Project
The Colorado River Aqueduct brings water 242 miles from the Colorado River through deserts and over mountain ranges to its terminal reservoir, Lake Mathews, in Riverside County. The aqueduct system includes five pumping plants that lift the water 1,617 feet.

Recycled Water
MNWD produces approximately 25 percent of our supply by capturing water that normally would run out to sea, treating it, and re-using it for irrigation and other non-potable, or non-drinking, uses. Every gallon of recycled water we use saves a gallon of drinking water. In total, we save 2.7 billion gallons of water each year through recycling.

Emergency Storage
MNWD has taken steps to increase our emergency water supply capacity from a 10-day to a 31-day supply, to allow the District to continue providing customers water in both planned and unplanned service interruptions. To achieve this three-fold increase in emergency storage, the District is partnering with other South County water agencies to construct a number of water supply reliability improvement projects. These include the Upper Chiquita Reservoir in Rancho Santa Margarita, which will store up to 266 million gallons of emergency water, and the Baker Treatment Plant in Irvine, which will allow south Orange County to treat its own water when regional treatment plants shut down. MNWD is also working with other water districts in the area to build interconnections, so alternative means of delivering water will be possible. These interconnections could make it possible in emergencies to gain access to alternative groundwater sources in north Orange County, which normally aren’t available to MNWD.

Water Supply Updates