State water planners are preparing for a hotter and drier climate in the coming years.
Completed in 1967, with a storage capacity of about 2 million acre feet, the San Luis Reservoir is the fifth largest in California. Work is already underway to add an additional 130,000 acre feet of capacity. Toms Auzins Shutterstock/standard
As a California native and longtime resident of the Central Coast, I’ve been traveling between the coast and the Sierra my entire life. As a kid in the sixties, when my dad drove me and my brothers to Yosemite, we’d take Highway 152 up over the Diablo Range through Pacheco Pass, drop down to the valley and back up into the Gold Country foothills on the other side of Merced, and then head up into the mountains.
Back then, Highway 152 was two lanes. The massive Casa de Fruta roadside attraction was at that time a glorified farm stand, and the San Luis Reservoir had yet to be built. We passed by a number of times as it was under construction before being completed in 1967.
I have a dim memory of my dad taking us to an opening ceremony and getting a tour of the B.F Sisk Dam back then, but I wasn’t paying attention. On those trips my mind was always laser focused on getting to the A&W in Merced for a root beer, burger and fries, and the passing scenery was of vague interest.
Which is a pity, because I was missing the construction of the largest, most complex water supply system in the world.
And lately, our state water supply has been in the news.
What We’re Seeing
As climate change induces the aridification of the state, California is planning for a hotter and drier future.
Water for drinking and irrigation, across the majority of the state, is provided by a vast infrastructure of pipelines, canals and reservoirs in the combined California Department of Water Resources (DWR) operated State Water Project (SWP) and the federal Central Valley Project (CVP).
In both of those agencies,system managers measure water use in acre feet, which is the volume of water one foot deep on a square acre, or 325,851 gallons. California consumes between 60-90 million acre feet of water per year from the state water system and from the feds’ CVP. Climate change is projected to reduce supply by up to 10 percent, or 6-9 million acre feet, by 2040.
The state of California has a four-step plan to cover the shortfall in the SWP:
New storage:
The building of additional storage is already underway at the San Luis Reservoir itself, where the dam is being raised and strengthened to store an additional 130,000 acre feet of water.
The Sites Project in Glenn and Colusa Counties, the first new large reservoir project in California in 50 years, recently cleared a legal hurdle and will proceed, with a goal to add 1.8 million acre feet of storage to the SWP system by 2030.
Meanwhile, plans to fast track repairs and maintenance necessary to increase storage in existing dams are frustrated by the huge deficit in California's 2024 budget.
New supply:
The controversial Delta Conveyance Project to construct a pipeline 140 feet underground to convey water 45 miles from the Sacramento River to the SWP storage and distribution system continues to lurch forward. On May 16 2024, DWR released a financial analysis of the project touting $33 billion in benefits (and an upwardly revised cost of $20 billion).
With 840 miles of coastline, California has for years considered desalinization a tantalizing prospect as a future water supply. This, too, is controversial, and so the state is encouraging research and implementation of new projects. The process is already in use in Santa Barbara, Carlsbad/San Diego, and Fort Bragg, and a new plant is being constructed in Monterey despite having faced fierce local opposition. Desalinization is also sometimes used to process brackish groundwater, as is the case of the Cities of Antioch, Camarillo, Santa Monica and Torrance.
In December 2023, California approved rules for the recycling of treated sewage to potable water, and the Metropolitan Water District in Los Angeles County is already building the Pure Water Southern California plant to process and deliver up to 150 million gallons of drinking water per day.
Orange County is home to the Groundwater Replenishment System (GWRS), the largest wastewater recycling plant in the world, in operation since 2008. In April 2023, GWRS announced a milestone in processing 100 percent of the county’s wastewater for recharging the groundwater basin that provides drinking water for 2.5 million people.
New conservation efforts:
Overall, SWP and CVP system water is allocated to three areas of use: 10 percent for drinking water, 40 percent for agriculture, and 50 percent for environmental use. That means, in theory anyway, half of the surface water in the state is meant to stay in rivers, streams and lakes for fish and other habitat, and to preserve wetland and river health.
Tension exists between the oftentimes competing interests among users, especially the large allocation for environmental use. Faced with cuts to water allocation in drought years, an almond farmer in the San Joaquin Valley has little sympathy for the plight of the Delta smelt. (Or for the Sacramento-San Joaquin Delta itself, one of the the largest estuaries on the West Coast, which supplies the state with two-thirds of its water and faces deep ecological challenges.)
Agriculture uses 80 percent of water not allocated to environmental uses, much of it devoted to water-intensive crops. In a study released in March 2024, researchers from UC Santa Barbara and NASA report that California agriculture could reduce water consumption by a whopping 93 percent, (but only by converting to economically unsustainable crops such as grains and hay).
Updated state water conservation goals faced substantial pushback from local water agencies, so the deadline to meet mandated reductions in urban water use were pushed back and the original goal of a savings of 500,000 acre feet of water was reduced.
New rules and enforcement:
While efforts are underway to meet the water needs of the future, the water usage of the past has made an indelible impression on the state through the overdrawing of groundwater in the Tulare Lake Subbasin and the San Joaquin Valley. This has resuted in the dramatic subsidence of the ground—in some areas, the surface of the earth is sinking at an astonishing rate of one foot per year.
That the ground underfoot is literally sinking would argue for legislative action, and efforts are underway to “modernize” water rights and increase state regulatory authority. The recent passage of State Senate Bill 389 gives the State Water Resources Control Board more power to investigate and enforce water usage. On April 16, 2024, regulators used the new oversight powers to place agricultural water users in the Tulare Lake Subbasin on probation due to over pumping of groundwater. Because whiskey is for drinkin' and water's for fightin' over, the Kings County Farm Bureau is raising money to take the matter to the courts.
Less dramatic but of equal importance, modernization efforts also include digitizing the estimated seven million pieces of paper, some over a century old, which collectively memorialize and formalize water rights in the state.
Making progress:
Adapting an already huge and complex statewide infrastructure to future needs and reforming the legal underpinnings of water rights and usage while also working to restore an environment impacted by past mistakes present a daunting challenge.
Fortunately, California has a plan.
