Climate change threatens to reduce the amount of water California can deliver over the next 20 years and could reduce the supply available from the State Water Project by 23%, according to new projections released Wednesday by Gov. Gavin Newsom.
An analysis by the California Department of Water Resources examined various climate change scenarios and estimated that by 2043, the large network of reservoirs and canals that supply more than half the state’s population could decline between 13% and 23%.
These losses in the State Water Project’s water delivery capacity, if not addressed, could cause large shortages for many states, including Southern California.
“The SWP was designed for a 20th century climate,” said John Yarbrough, the project’s deputy director. “You need ongoing investment to get it in a place that can be used hydrologically in the future.”
State officials are analyzing how rising temperatures could affect existing water infrastructure without adaptation measures. They said the expected losses in system capacity show the need to invest in projects intended to boost supplies, such as the state plan to build new Reservoir Sites and water tunnels under the Sacramento-San Joaquin River Delta.
In addition to serving 27 million people, the National Water Project provides approximately 750,000 hectares of agricultural land.
According to the report, current infrastructure will be able to produce less water in the coming years as rising temperatures lead to more intense droughts, reduced snowpack, more extreme storms, and more precipitation falling as rain rather than snow. . Changes in runoff times will also create challenges. And rising sea levels will likely disrupt water managers’ efforts to manage salinity levels and meet water quality standards in the delta.
These estimates are included in reports published by the state every two years. The last update in 2021 reflects a 9% decrease in water supply in the State Water Project due to climate change. The latest projections include a more detailed analysis of various climate scenarios.
Newsom and other state officials have for years called for upgrades to the state’s water infrastructure to adapt to warming driven by the burning of fossil fuels and rising levels of greenhouse gases.
In 2022, Newsom presented a plan that calls for California to conserve about 10% of the state’s water supply by 2040.
The State Water Project transports water over more than 700 miles through a series of reservoirs, aqueducts, pipelines and pumping plants from Northern California to Southern California.
The current infrastructure, built in the 1960s, includes massive pumps that draw water from the delta and send it flowing into the California Aqueduct. Water exports from the delta have decreased since 2008, partly due to changes in regulatory and protection requirements for endangered fish species.
State officials say there is uncertainty about future regulatory requirements and climate conditions, but the analysis points to a possible reduction in water supplies. A more severe scenario would result in an average loss of 496,000 acre feet of water per year, enough to supply more than 1.7 million homes.
Karla Nemeth, director of the Department of Water Resources, said that the analysis “underlines the need to modernize and upgrade the aging infrastructure to be able to take the water supply during the rains.”
In a letter providing the report, Nemeth said the latest review “does not clearly indicate a significant reduction” in the project’s delivery capacity if no action is taken.
“Immediate action is essential to address the impacts of a warming climate,” he wrote.
State officials have sought to advance plans for a 45-mile water tunnel, which will create another route to draw water from the Sacramento River to the aqueducts of the State Water Project.
In May, the Newsom administration announced that the cost of building the proposed tunnel would be $20.1 billion, and a state analysis concluded the project’s benefits would outweigh the costs.
Opponents of the proposed Delta Conveyance Project have argued that the country’s analysis is flawed and underestimates the costs while overestimating the benefits.
Environmental groups, Indigenous tribes, fishing organizations and local agencies have filed lawsuits to block the project.
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