Managing Our Water Supply

Photo: Carlsbad Desalination Plant

Concerned About the Future?

Don’t be. Yes, drought and climate change are impacting our traditional water resources, but three strategies will see us through and the future is already under construction.

Strategy 1: Supply Diversification

A diverse portfolio of local and imported water resources from different states and suppliers insulates the San Diego Region against water shortages caused by drought, regulatory issues in the Delta, or facility issues.

Supply Diversification


  • Metropolitan Water District of So Cal 95%
  • Local Surface Water 5%


  • Metropolitan Water District of So Cal 49%
  • Imperial Irrigation District 16%
  • Water Conservation 14%
  • All American and Coachella Canal Lining 13%
  • Recycled Water 4%
  • Groundwater 3%
  • Local Surface Water 1%


  • Metropolitan Water District of So Cal 30%
  • Imperial Irrigation District 24%
  • Water Conservation 13%
  • All American and Coachella Canal Lining 10%
  • Seawater Desalination 7%
  • Recycled Water 6%
  • Local Surface Water 6%
  • Groundwater 4%

Strategy 2: Advanced Water Treatment

Advanced water treatment technology adds three steps to the water recycling process — micro-filtration, reverse osmosis and disinfection with ultraviolet light and hydrogen peroxide — to produce purified water that exceeds all state and federal drinking water standards.  Variations on the process allow water suppliers to purify water from the Pacific Ocean, brackish groundwater, municipal wastewater and rainwater running down streets after a storm, and utilize these water resources when traditional resources cannot meet demand.

Advanced Water Treatment

Orange County

The Groundwater Replenishment System (GWRS) transforms Orange County’s wastewater into high quality drinking water for nearly 600,000 homes. The GWRS went online in 2008 and is a joint project of the Orange County Water District and Orange County Sanitation District.


City of San Diego

The City of San Diego’s Water Purification Demonstration Project operated from 2009 to 2013 with no lapses in water quality and proved the feasibility of adding purified water to a reservoir rather than an aquifer. The city’s goal is to produce 83 million gallons per day, one third of San Diego’s future water supply, by 2035.

Pure Water San Diego

Helix Water District

Padre Dam Municipal Water District is planning the East County Advanced Water Purification to provide a drought-resilient water supply for east county. Helix Water District, the City of El Cajon and the County of San Diego are potential partners in the project.

East County Advanced Water Purification Program Planning Study

Strategy 3: Improved Land Use and Development

How and where we build has a profound effect on California’s future water supply. Designing better homes and buildings reduces the amount of water we need, and designing better residential and public landscapes reduces the amount of water running down city streets after a storm – the primary source of water pollution in rivers and streams. Two examples show where we are headed.

San Francisco PUC

The San Francisco Public Utility Commission’s headquarters, completed in 2012, uses 65 percent less water than comparable buildings by treating wastewater from toilets onsite, using engineered wetlands next to the sidewalks, and capturing rainwater and stormwater. After completing the building, PUC staff created a program to show developers how to do it.

Managing Growth and Development

City of Los Angeles

The City of Los Angeles’ Department of Water and Power completed a Stormwater Capture Master Plan in 2015 that outlines how to transform Los Angeles into a watershed that naturally replenishes the groundwater supply under the city. How? By breaking up concrete and asphalt and creating greenbelts and basins where stormwater can infiltrate into the soil.

Capturing Stormwater

Helix’s Water Supply in 2014

  • Colorado River 90%
  • State Water Project 10%
  • Lake Cuyamaca 0%

Colorado River


243,000 square miles

Water Demand

Nearly 40 million people and 5.5 million acres of agriculture

Water Supply

A series of agreements and court decisions collectively known as the Law of the River allocate the Colorado River’s annual flows among states and water suppliers.

Law of the River


Drought conditions in the Colorado River Basin that began 16 years ago have reduced the river’s annual flow and the water levels in Lake Mead and Lake Powell. A 2012 study by the U.S. Bureau of Reclamation, which manages the Colorado River, projects a future gap between supply and demand.

Colorado River Basin Water Supply and Demand Study

Our Supply Chain

San Diego County Water Authority

The Legislature formed the San Diego County Water Authority in 1944 to administer the San Diego region’s Colorado River water rights. The region’s 24 retail water suppliers, including Helix, are member agencies of the Water Authority, which has spent over $3 billion since 1992 to diversify the region’s water resources, increase local water storage and increase water conservation.

SDCWA Water Supply

SDCWA Infrastructure

SDCWA Budget

U.S. Bureau of Reclamation

The Bureau of Reclamation is the largest wholesale water supplier in the U.S., producing 10 trillion gallons of water and 40 billion kilowatt hours of energy each year in 17 western states. The Bureau manages the Colorado River: the water rights of contractors, dams and water storage, habitat and recreation.

USBR Lower Colorado River Operations

USBR Infrastructure and Budget

Metropolitan Water District

Metropolitan Water District of Southern California was formed by the Legislature in 1928 to construct and operate the 242 mile Colorado River Aqueduct, which pumps water out of the Colorado River at Lake Havasu and delivers it to Lake Matthews near Riverside.

MWD’s Imported Water Supply

MWD Infrastructure & Budget

Imperial Irrigation District

Imperial Irrigation District, which has senior rights to Colorado River water for agriculture in the Imperial Valley, entered into a water transfer agreement with the San Diego County Water Authority in 2003 to provide up to 200,000 acre feet of water annually to the San Diego region for up to 75 years.

IID Water Transfer Agreement

IID Fact Sheet

IID Budget

State Water Project


The upper Feather River watershed is 3,200 square miles

Water Demand

25 million people and 750,000 acres of agriculture

Water Supply

The State Water Project delivers Feather River water to the Bay Area, Central Coast and Southern California.

State Water Project

Fly Over the State Water Project


A smaller winter snowpack in the Sierra, river water that is too warm for salmon, and rising sea levels inundating the Delta with saltwater are all potential effects of climate change.

California Climate Adaptation Strategy for Water

Our Supply Chain

State of California

California’s Department of Water Resources manages and operates the State Water Project: the dams and reservoirs that provide water storage, and the aqueducts that convey water throughout the state.

State Water Project

San Diego County Water Authority

The Water Authority collects water from Metropolitan’s system and delivers it to the San Diego region through its own aqueducts.

San Diego Aqueduct

Metropolitan Water District of S.C.

Metropolitan is one of 29 State Water Project Contractors, water suppliers that purchase water from the State Water Project.

State Water Project Contractors

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