100% of the Districts water supply (treated and untreated) is purchased from San Diego County Water Authority, which purchases its water from the Metropolitan Water District of Southern California. The water is a blend of Colorado River water and California State Water Project water. The higher the amount of Colorado River water, the greater the hardness of the water. The District’s water purchase percentages may vary depending on the status of the Bargar Water Treatment Plant, which can supply up to 30% of the treated water when in service.

Untreated water (for agricultural use) is pumped to Lake Ramona (1,150 MSL) from an elevation of 781 MSL at Poway Pump Station near Espola Road. Approximately 3,500 acre feet (AF) a year is pumped into the lake and delivered to approximately 6,200 acres of agricultural lands in the Highland Valley area. Lake Ramona has a capacity of 12,200 AF. The lake was completed in 1988.

Treated water is pumped to Mt. Woodson (1,800 MSL) and West end (1,700 MSL) reservoirs from an elevation of 781 MSL at Poway Pump Station near Espola Road. Approximately 7,600 acre feet (AF) a year is pumped into the two reservoirs and delivered throughout Ramona. In 2003, the Poway Pump Station was enlarged from a capacity of 9 MGD to 19.6 MGD. This improved treated water reliability by adding a new 30-inch pipeline and increased the potential for meter connections from approximately 9,500 meters to approximately 19,000 meters.