Sources Of Supply Imported

Metropolitan imports water supplies to Southern California from two main sources: the Sacramento and San Joaquin Rivers through the State Water Project and the Colorado River via the Colorado River Aqueduct . Both river systems provide vital baseline supplies for the region and are the foundation of Metropolitan's multifaceted water resource portfolio. Metropolitan invests significant resources in both systems – expanding, repairing and upgrading facilities to ensure the region's water supplies are reliable.

About 30 percent of Southern California's water comes from the State Water Project, the largest state-built water and power system in the nation. The project runs from Lake Oroville in Northern California to Southern California, crossing the Sacramento-San Joaquin Delta along the way. The SWP serves a population of nearly 25 million Californians from the Bay Area to San Diego as well as providing irrigation for some of the nation's most productive farmland in the Central Valley. The State Water Project is operated and maintained by the California Department of Water Resources and includes 34 storage facilities, reservoirs and lakes; 20 pumping plants; 4 pumping-generating plants; 5 hydroelectric power plants; and about 700 miles of open canals and pipelines.

Metropolitan is the largest contractor on the State Water Project system, receiving about 50% of the SWP's supplies, roughly 1.2 million acre feet (MAF) in an average year.

Metropolitan's SWP allocation varies depending on water conditions in the Eastern Sierra Mountains and environmental conditions in the Sacramento-San Joaquin Delta, which can restrict water deliveries.

To meet regional demands and ensure reliable supplies for Southern California, Metropolitan has been working with state and federal agencies as well as other water contractors to address environmental conflicts and reduce threats to state water supplies in the Sacramento-San Joaquin Bay Delta. In addition, Metropolitan augments water supplies through collaborative water transfer and groundwater banking agreements with other agencies.

Update on Oroville Facilities

April 2019: First Use of Oroville Dam's Reconstructed Spillway

On April 2, California's Department of Water Resources began releasing flows from the Oroville Dam's main spillway for the first time since its reconstruction. DWR planned the releases at 8,300 cubic feet per second to provide room for flood storage within the reservoir in preparation for forecasted storms and growing snowpack.

DWR was anticipating increasing flows to the Feather River later in the week, and planning for further releases later this spring to continue managing snowmelt and lake elevations.

Oroville's main spillway was reconstructed after it suffered severe damage during the record wet start to the 2017 rain season and the subsequent use of an emergency spillway created erosion concerns that promoted an evacuation of communities downstream.

News release from DWR - https://water.ca.gov/News/News-Releases/2019/April/DWR-Uses-Oroville-Main-Spillway

Article from The Sacramento Bee - https://www.sacbee.com/news/local/article228619034.html

Lake Oroville and Oroville Dam in Butte County are part of the State Water Project and an important source of water for Southern California. The Metropolitan Water District of Southern California is the largest State Water Contractors, importing about 30 percent of the Southland's water supplies from Northern California via the state project.

Oroville's main spillway suffered severe damage in February 2017 when flood control releases from the lake eroded sections of a concrete channel. The subsequent use of an adjacent emergency spillway raised erosion concerns that prompted an evacuation of communities downstream. Recovery efforts included work on both the main flood control spillway and the emergency spillway to accommodate potential flows from winter storms.

DWR collaborates with regulatory agencies and a Board of Consultants on the Oroville Spillway design and construction project. Metropolitan has no direct role in the review or implementation of these projects. However, Metropolitan continues to work with DWR on operational issues and future activities at the Oroville facilities. Click here for more.

California Aqueduct

Water from the State Water Project is delivered through the California Aqueduct, a 444 mile-long canal beginning at the south Delta and ending at Lake Perris in Riverside County. It varies in width from 50 to 110 feet and 19 to 32 feet in depth.

Exchanges & Water Banking

Water transfers, water exchanges and groundwater banks (which store water in underground aquifers) are important water management tools that allow agencies to augment local supplies and utilize external distribution and storage systems. Metropolitan’s water portfolio includes a number of water transfer and groundwater banking agreements with state, federal, public and private water districts and individuals.

Transfers and exchange programs were developed to improve the reliability of State Water Project and Colorado River Aqueduct supplies during dry years.

Current banking/transfer programs that provide supplies for delivery via the California Aqueduct include:

Semitropic Water Banking and Exchange Program, Wasco
Arvin-Edison Water Management Program, Arvin
San Bernardino Valley Municipal Water District Program, San Bernardino
Kern Delta Water District Water Management Program, Taft
Desert Water Agency/Coachella Valley Water District Advance Delivery Program, Coachella
Market Transfer Options, DWR Dry-Year Purchase Program and Sacramento Valley Transfer Agreements

The Colorado River Aqueduct has been the backbone of Southern California’s imported water supply for more than 70 years. Built and operated by Metropolitan, the 242-mile aqueduct delivers water from the Colorado River at Lake Havasu west of the California/Arizona border. Along with the State Water Project, the CRA is one of two imported drinking water sources for Southern California.

Originally conceived by William Mulholland and designed by Metropolitan’s first Chief Engineer Frank Weymouth, the CRA was the largest public works project in Southern California during the Great Depression. Financed by $220 million in voter-approved bonds, the project employed 30,000 people over an eight-year period, with as many as 10,000 workers at one time.

After a population boom following World War II, the CRA was expanded to its full design capacity of 1 billion gallons of water a day to meet growing demands. Today, the CRA is comprised of two reservoirs, five pumping stations, 63 miles of open canals, 92 miles of tunnels, 55 miles of concrete pipe and 28 miles of pressurized siphons, with a delivery capacity of over 1.2 million acre-feet a year.

Operation of the CRA is dictated by The Law of the Colorado River, beginning with the Colorado River Compact of 1922 which allocates use of water between the upper and lower Colorado River Basin states, and the subsequent Boulder Canyon Project Act of 1928, and California Seven Party Agreement of 1931 which allocate water among the lower basin states and within California, respectively. A treaty with Mexico in 1944 guaranteed supplies would be available south of the border as well.

The Sacramento-San Joaquin Delta is where California’s two largest rivers meet, an area where saltwater from the Pacific mingles with freshwater from the rivers.

The 738,000-acre Delta is a complex web of waterways, sloughs, canals and islands. It also is the linchpin in the State Water Project, the system that supplies drinking water to more than 25 million Californians and approximately 45 percent of the fruits and vegetables produced in the United States.

The Delta is home to 500,000 people and provides habitat for more than 300 species of wildlife, 29 of which are threatened or endangered. The fertile peat soil produces $700 million annually in agricultural crops. And the Delta’s ecosystem supports the commercial salmon industry of the entire west coast.

Delta Water Supplies

Water flowing through the Delta, supplies 30 percent of Southern California’s drinking water, 33 percent of the Bay Area’s, and up to 90 percent of the Central Valley’s drinking and irrigation water. Some communities are 100 percent dependent on the Delta for their water supplies.

Over the years, the Delta’s ecosystem has deteriorated, and its 1,100-mile levee system is increasingly vulnerable to failure caused by earthquakes, floods and other forces of nature. The decline of the Delta’s ecosystem has led to historic restrictions in water supply deliveries. The result is a pressing two-fold need: improve California’s water reliability and restore the Delta’s fragile ecosystem.

The Delta was once a vast marshland covered with tulles and teaming with wildlife. Settlers, lured at first by the gold rush of the mid 1800s, built levees to drain and reclaim the land.

Environmental Conflicts

Tidal wetlands are an important source of food and shelter for fish such as delta smelt that live year-round in the estuary. Adjacent floodplains such as the Yolo Bypass are feeding grounds for young salmon on their journey to the Pacific Ocean.

Today, about 95 percent of the original wetlands and original floodplains are no longer part of the Delta ecosystem due to levee construction and other human activities. Yet it remains California’s most important estuary and a vital environmental resource, home to more than 750 plant, bird, animal, and fish species.

Water Supply Risks

Today’s Delta region faces numerous threats that are projected to worsen. Absent intervention, California’s water supply system and the Delta ecosystem are at risk of collapse and are projected to worsen due to a variety of natural and man-made stressors.

Seismic

There are several faults running through the San Francisco Bay Area region that could affect the Delta. According to the U.S. Geological Survey, there is a 66 percent chance of a magnitude 6.5 earthquake hitting the Bay-Delta region by 2032. Such an earthquake could cause the levees that surround the Delta islands to collapse, flooding up to 30 Delta islands. Salt water from San Francisco Bay could migrate eastward, rendering the Delta as an undrinkable source of water supply for up to three years until extensive repairs are completed. The statewide economic costs of such an event could exceed $40 billion.

Sea-level Rise

The official state guidelines call for planning efforts in the Delta to assume a 16-inch rise in sea level by 2050 and 55 inches by 2100. Rising sea levels will not only put greater pressure on the Delta’s dirt levees, but will cause seawater to intrude further inland impacting water quality.

Subsidence

When levee construction beginning in the 1850s transformed the Delta from marshland to farmland, it exposed the peat soils, which began to oxidize, compact and blow away. This process of subsidence continues. What were once islands are now more like bowls, constantly depending on levees. The total volume of soil lost, or the void currently below sea level, is in excess of 3.5 million acre-feet or almost 8,000 Rose Bowl stadiums. As the subsidence continues, the water pressure on the levees becomes greater.

Fishery Declines

While numerous scientific panels have attributed the decline in the Delta’s health to numerous causes, enforcement efforts to date have focused almost exclusively on curtailing public water supplies from Delta facilities. Export agencies experienced cutbacks to pumping dating back to 1991 due to Endangered Species Act requirements. During the last two decades export pumping to the State Water Project and Central Valley Project has been reduced by more than 2 million acre feet.

Non-native Species

More than 95 percent of the biomass in the Delta is non-native. Striped bass, Black bass, Asian clams and many other invaders, large and small, are either eating the native populations or the foods on which they rely.

In this highly-altered environment, the introduced species are over-running the native species and are a key factor in reducing populations of some endangered species.

Public water agencies like Metropolitan are promoting a more comprehensive approach to restoring the Delta as a way to restoring reliable water supplies long-term.

Delta Conveyance

About 30 percent of the water that flows out of taps in Southern California comes from Northern California via the Sacramento-San Joaquin Delta. The state is heading an effort to modernize the water system in order to maintain supply reliability and provide environmental benefits. Metropolitan made an historic decision to invest in a twin tunnel project in 2018. Governor Newsom's project vision takes a one-tunnel approach.

Learn more about Delta Conveyance.

Delta Islands

Delta Islands Web Site

Fact Sheet

Executed Purchase and Sale Agreement

Notices of Exemption:
   Contra Costa County
   San Joaquin County
   Solano County
Public Comment Letters

Bay-Delta Live

Bay-Delta Live is an online data hub used by resource managers, scientists, conservationists, policy makers, academics, local community interests, and other stakeholders. The goal of the project is to expand open and transparent sharing of information to better understand the complex and dynamic ecosystem of the Sacramento-San Joaquin Bay Delta. Bay-Delta Live provides information from multiple sources using enhanced visual interfaces. This site is supported by state and federal water, wildlife and natural resources organizations, science workgroups, The Metropolitan Water District of Southern California, State and Federal Water Contractors Water Agency and others.

Drought Contingency Plan

In December 2017, the Department of Water Resources’ Reclamation Commissioner Brenda Burman called on the seven Colorado River Basin States and water entitlement holders in the Lower Colorado Basin to continue developing Drought Contingency Plans in response to ongoing historic drought conditions in the Basin and reduce the likelihood of Colorado River reservoirs – particularly Lake Powell and Lake Mead – further declining to critical elevations.

All seven Colorado River Basin States diligently worked on a set of draft DCP greements that would implement Drought Contingency Plans in the Upper and Lower Basins. The agreements would include an Upper Colorado River Basin Drought Contingency Plan and a Lower Colorado River Basin Drought Contingency Plan. Read the Final Review Draft of the Upper and Lower Basin DCPs.

This would provide flexibility to meet local water demands. By agreeing to moderate voluntary cutbacks under the DCP, the Lower Basin states can significantly reduce the chance of severe shortages if lake levels were to reach certain critical points in coming years.

The plan was signed on May 2019. Read the General Manager's statement regarding this historical event.

The Metropolitan Water District has been a leader in this ongoing collaboration and is committeed to working cooperatively within California and beyond to ensure the plan's success.

Water Supplies

California is one of seven western states that rely on water from the Colorado River or its tributaries. For years, California used more than its basic apportionment of 4.4 million acre-feet of water a year, primarily by relying on surplus supplies and water apportioned to but unused by Arizona and Nevada.

In the late 1990s, as Arizona and Nevada began to fully use their apportioned supplies, and federal authorities, along with other Colorado River Basin states, challenged California to develop a comprehensive plan to reduce its reliance on surplus Colorado River supplies and ultimately live within its basic apportionment.

In response, California developed the draft California Colorado River Water Use Plan to gradually reduce the state’s use to its apportionment of 4.4 million acre-feet by 2017. The plan described key terms which were included in the 2003 Quantification Settlement Agreement, and the 2003 Colorado River Water Delivery Agreement which established water budgets for Imperial Irrigation District and Coachella Valley Water District to help facilitate water transfers from farms to cities.

Exchanges & Water Banking

The projects and programs Metropolitan has developed to restore reliability of Colorado River supplies cover a wide range of topics. In addition to transfers, exchanges and groundwater banking, Metropolitan has developed specialized conservation programs whereby Metropolitan invests in conservation programs outside its service area and receives the water that is conserved. The conservation programs vary and include canal lining, land fallowing, crop rotation and irrigation improvements, among other options. In addition, Metropolitan has collaborated with other parties in the Colorado River basin to bank water in surface reservoirs. Known as “Intentionally-Created Surplus" these surface water banking programs have allowed Metropolitan to take advantage of existing surface reservoirs to store conserved supplies for later use.

Water transfers, exchanges and water banks are important water management tools that allow agencies to augment local supplies and utilize external distribution and storage systems. Metropolitan’s water portfolio includes a number of water transfer and banking agreements with state, federal, public and private water districts and individuals.

Current banking/transfer programs that deliver supplies via the Colorado River Aqueduct include:

Imperial Irrigation District Conservation Program
Palo Verde Irrigation District Land Following and Crop Rotation Program
Quantification Settlement Agreement Transfers

Additional projects funded jointly with Southern Nevada and Central Arizona:

Warren Brock Reservoir
Yuma Desalting Plant
Mexico Water Treaty Pilot Conservation Project (Minute 319)

Planning for Long-term CRA Supplies

Metropolitan’s principal goal in investing in these supply programs is to provide a full Colorado River aqueduct to meet Southern California’s water needs in dry years. Ultimately, however, climate change and legal disputes could make meeting that goal more challenging in the future. To provide reliable supplies in the future, Metropolitan is coordinating with other basin states to implement recommendations of the Colorado River Basin Study and working to preserve the Quantification Settlement Agreement for the Colorado River.

Colorado River Basin Study
Released by the Bureau of Reclamation and the Colorado River Basin states in December 2012, the Colorado River Basin Study evaluates water supply and demand in the Colorado River Basin over the next 50 years, and identifies options and strategies to meet the demand gap. Options identified in the study include:

Increases in urban and agricultural water-use efficiency
Agricultural-to-urban water transfers
Brackish water desalination
Weather modification through cloud seeding
Removal of non-native species
Seawater desalination

While some of the options can be developed quickly, others could take decades to realize. Metropolitan is working with the Colorado River Basin states and the federal government to evaluate which options are the most promising and to implement them.

Delta Water Supplies

Water flowing through the Delta, supplies 30 percent of Southern California’s drinking water, 33 percent of the Bay Area’s, and up to 90 percent of the Central Valley’s drinking and irrigation water. Some communities are 100 percent dependent on the Delta for their water supplies.

Over the years, the Delta’s ecosystem has deteriorated, and its 1,100-mile levee system is increasingly vulnerable to failure caused by earthquakes, floods and other forces of nature. The decline of the Delta’s ecosystem has led to historic restrictions in water supply deliveries. The result is a pressing two-fold need: improve California’s water reliability and restore the Delta’s fragile ecosystem.

The Delta was once a vast marshland covered with tulles and teaming with wildlife. Settlers, lured at first by the gold rush of the mid 1800s, built levees to drain and reclaim the land.

Environmental Conflicts

Tidal wetlands are an important source of food and shelter for fish such as delta smelt that live year-round in the estuary. Adjacent floodplains such as the Yolo Bypass are feeding grounds for young salmon on their journey to the Pacific Ocean.

Today, about 95 percent of the original wetlands and original floodplains are no longer part of the Delta ecosystem due to levee construction and other human activities. Yet it remains California’s most important estuary and a vital environmental resource, home to more than 750 plant, bird, animal, and fish species.

Water Supply Risks

Today’s Delta region faces numerous threats that are projected to worsen. Absent intervention, California’s water supply system and the Delta ecosystem are at risk of collapse and are projected to worsen due to a variety of natural and man-made stressors.

Seismic

There are several faults running through the San Francisco Bay Area region that could affect the Delta. According to the U.S. Geological Survey, there is a 66 percent chance of a magnitude 6.5 earthquake hitting the Bay-Delta region by 2032. Such an earthquake could cause the levees that surround the Delta islands to collapse, flooding up to 30 Delta islands. Salt water from San Francisco Bay could migrate eastward, rendering the Delta as an undrinkable source of water supply for up to three years until extensive repairs are completed. The statewide economic costs of such an event could exceed $40 billion.

Sea-level Rise

The official state guidelines call for planning efforts in the Delta to assume a 16-inch rise in sea level by 2050 and 55 inches by 2100. Rising sea levels will not only put greater pressure on the Delta’s dirt levees, but will cause seawater to intrude further inland impacting water quality.

Subsidence

When levee construction beginning in the 1850s transformed the Delta from marshland to farmland, it exposed the peat soils, which began to oxidize, compact and blow away. This process of subsidence continues. What were once islands are now more like bowls, constantly depending on levees. The total volume of soil lost, or the void currently below sea level, is in excess of 3.5 million acre-feet or almost 8,000 Rose Bowl stadiums. As the subsidence continues, the water pressure on the levees becomes greater.

Fishery Declines

While numerous scientific panels have attributed the decline in the Delta’s health to numerous causes, enforcement efforts to date have focused almost exclusively on curtailing public water supplies from Delta facilities. Export agencies experienced cutbacks to pumping dating back to 1991 due to Endangered Species Act requirements. During the last two decades export pumping to the State Water Project and Central Valley Project has been reduced by more than 2 million acre feet.

Non-native Species

More than 95 percent of the biomass in the Delta is non-native. Striped bass, Black bass, Asian clams and many other invaders, large and small, are either eating the native populations or the foods on which they rely.

In this highly-altered environment, the introduced species are over-running the native species and are a key factor in reducing populations of some endangered species.

Public water agencies like Metropolitan are promoting a more comprehensive approach to restoring the Delta as a way to restoring reliable water supplies long-term.

Delta Conveyance

About 30 percent of the water that flows out of taps in Southern California comes from Northern California via the Sacramento-San Joaquin Delta. The state is heading an effort to modernize the water system in order to maintain supply reliability and provide environmental benefits. Metropolitan made an historic decision to invest in a twin tunnel project in 2018. Governor Newsom's project vision takes a one-tunnel approach.

Learn more about Delta Conveyance.

Delta Islands

Delta Islands Web Site

Fact Sheet

Executed Purchase and Sale Agreement

Notices of Exemption:
   Contra Costa County
   San Joaquin County
   Solano County
Public Comment Letters

Bay-Delta Live

Bay-Delta Live is an online data hub used by resource managers, scientists, conservationists, policy makers, academics, local community interests, and other stakeholders. The goal of the project is to expand open and transparent sharing of information to better understand the complex and dynamic ecosystem of the Sacramento-San Joaquin Bay Delta. Bay-Delta Live provides information from multiple sources using enhanced visual interfaces. This site is supported by state and federal water, wildlife and natural resources organizations, science workgroups, The Metropolitan Water District of Southern California, State and Federal Water Contractors Water Agency and others.