Reservoir 1


  • Years Constructed: 1988 – 1990
  • Dedicated May 1990
  • Capacity: 10 million gallons
  • Pump Station Capacity: 9,500 gpm
  • Depth: 45.2 ft.
  • Width: 131.6 f t.
  • Length: 265 f t.
  • Area of Reservoir Site: 40,000 square feet

History of Reservoir 1

Reservoir 1 has been in operation since the spring of 1990. It is a 10-million gallon rectangular reservoir made from steel reinforced concrete and constructed partially below ground. The design of the Reservoir incorporates a number of unique structural features for earthquake safety. The exterior is architecturally designed to resemble a commercial building, such as a warehouse.

Mesa Water reservoir 1 construction


Reservoirs "float" on the water system, meaning the flow into the reservoir is set at average water usage. During times of the day when system usage is low, Reservoir 1 is filled. During periods of above- average or peak use, the reservoir is emptying. Reservoirs help equalize the demand on supply facilities. Mesa Water's wells produce water from the groundwater basin. System pressure fills the reservoirs. The ability to store more well water allows Mesa Water to maximize the use of a local, higher quality, less expensive source. The reservoir may also be filled with imported water. In addition to daily use, the reservoir provides emergency water storage. During an emergency, the water demand may exceed the capability of local wells and available import sources. Continuous local storage helps safeguard adequate supplies for such an event.

Long-range Planning

In 1986, the District introduced a Master Plan to meet the long-term growing needs of its customers. The plan defined ways to improve water delivery systems, create additional local storage facilities, and develop new sources of water. The plan was updated in 1990 with a focus to "drought-proof" the service area by developing additional local groundwater supplies and reducing reliance on imported water. Mesa Water is fortunate to have access to such a reliable, affordable source of water. 2015 brings an updated Master Plan to the District.

Mesa Water reservoir 1 construction

Source of Water

Mesa Water’s primary source of water is groundwater, pumped from Orange County’s natural groundwater basin via seven wells. The groundwater basin stretches 350-square miles from the Orange County line at Seal Beach and Long Beach, along the coast, down to the 55 freeway and east to Yorba Linda. Backup for Mesa Water’s well water is imported water, which comes from Updated January 2015 Northern California and the Colorado River. It flows through aqueducts to Metropolitan’s Robert B. Diemer Filtration Plant in Yorba Linda. Imported water is more costly than groundwater because of transportation and treatment costs.

Groundwater Basin

Groundwater in Orange County occurs in horizontal layers of water-bearing sand, gravel or broken rock and not in underground lakes or streams. These formations, called aquifers, are separated by layers of non-water bearing materials, and make up the groundwater basin. Orange County Water District (OCWD) manages the local groundwater basin and utilizes advanced techniques to recharge the basin. The Santa Ana River and the OCWD Groundwater Replenishment System (GWRS) are the main contributors to the groundwater supply. The Santa Ana River reaches the aquifers through the soil as rainfall, or percolates through the gravel of streambeds or unlined ditches. Water is also placed in the ground through man-made percolation ponds or injection wells.

Mesa Water reservoir 1

Service Area

Mesa Water provides water service to more than 108,000 customers in an 18-square-mile area, including the city of Costa Mesa, parts of Newport Beach and unincorporated Orange County, including the John Wayne Airport.