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Where does L.A. get its water from?
by RITHWIK KALALE | Nov. 21, 2023
The city of Los Angeles, the second most populous in the country only behind New York City, gets most of its water from the northern part of the state and local groundwater sources.
The state of California is very diverse in terms of climate. It expands from the rain-heavy northern region to the dry and hot southern region, bordering Arizona, where Los Angeles is situated.
Owens Lake, located approximately 220 miles north of downtown Los Angeles, used to be a large water source for the region during prehistoric times, but dried out by the time most settlers began moving in. After the first aqueduct was constructed, the dried lake became highly dust-emittive.
Today, L.A. has a “three straws and a bathtub” model of water transportation, largely dependent on aqueducts built throughout the decades, according to David Pettijohn, director of water resources at the Los Angeles Department of Water and Power.
The first two “straws,” the Los Angeles and California Aqueducts, bring water in from the eastern and western Sierra Nevada mountain slopes, respectively. The Colorado River aqueduct is the third “straw” and the local groundwater supply is the “bathtub.”
Historically, the growth of the city has always led itself to new innovations in its water supply systems.
“Into the 1960s, it became apparent that the growth – not only of the city of Los Angeles but all of Southern California – was going to be more than those two aqueducts systems could provide,” said Pettijohn. “That gave rise to the State Water Project, which feeds cities from the Central Valley all the way down into Southern California.”
The California State Water Project has been used to deliver water to all major urban cities throughout the region, consisting of a network of aqueducts. The project has various contractors depending on the region of California it is in. For Los Angeles, it is handled by the Metropolitan Water District of Southern California, serving a population of over 19 million people.
Today, the city relies on both water from these aqueducts as well as local groundwater sources, but recent developments in climate change have affected water availability and quality in the drier parts of the state.
“Climate change has really kind of pushed us into a new normal,” said Pettijohn. “Not that long ago, we didn't have dramatic swings (from) wet to dry, like we're starting to see now.”
Changes in the amount of precipitation a region gets can affect both water availability and water quality. Other climate-related factors such as flooding, wildfires, reduced snowpack from the Sierra Nevada mountains and rising sea levels can all impact the city’s water supply.
“To accommodate all this you really need to diversify your water supply and your storage portfolio because if you're getting more water coming in wet years, you have to find ways to store that water above ground or below ground so that when the dry years come you'll be able to manage those dry years.”
Pettijohn said while the LADWP have taken these steps, constant maintenance and improvements between their systems along with the Southern California Metropolitan Water District systems are crucial.
“We need to make some improvements in integration between our system and theirs and we've been advocating for that.”
Although population growth was an issue in the past, Los Angeles County, the nation’s most populous county, now leads the U.S. in highest annual population decline— losing over 180,000 people in 2021 and nearly 91,000 in 2022 according to U.S. Census Bureau estimates.
Relying on continued population decline is not a strategy for managing the extreme impacts of climate change.
The LADWP provides incentives for people to be more efficient with their water consumption.
“We now offer $5 a square foot for people who want to retrofit their lawns with California Friendly Landscaping,” said Pettijohn. “That's a very lucrative incentive that can provide the lion's share of the cost to retrofit your landscape at home to a much more efficient landscape that will not only look beautiful, but save you money every month once you go through the process.”
Treating recycled water to replenish groundwater sources is another investment the city is currently making.
In July of this year, the state allocated $80 million to the Pure Water Southern California project, a large-scale, regional water recycling program to offset the supply effects of climate change.
The goal is for cleaned wastewater currently sent to the ocean to be purified and delivered through up to 60 miles of pipielines, straight to groundwater basins and water treatment plants.
“The emerging technologies that are becoming available in the area of recycled water can really provide a bright future for people in Southern California,” said Pettijohn. “We are going to face more swings due to climate change where we go from wet to dry. And in those dry years, we're going to need to be able to provide the city with water.”
Although desalinating seawater is another option, it is not currently a main priority for the city.
“Until we've exhausted all the less expensive options like conservation, groundwater recovery, recycled water and just purple pipe recycled water to irrigate landscapes, we probably are not going to be making investments of our customers’ money in seawater desalination, but we want to stay up on the technology to make sure that we are aware of what's going on,” said Pettijohn.
After the Fifth National Climate Assessment released this month, the Biden administration promised $100 million in funding for water infrastructure upgrades in order to advance drought resilience in the West.
The Department of Interior plans to allocate $50 million to improve water resource reliability in the western states. The other $50 million will go toward water conservation projects and hydroelectric upgrades.
In Los Angeles, the city is looking toward more sustainable options for water sources — APM Research Lab
Aqueducts constructed over the decades bring water into Los Angeles, from the Sierra Nevada Mountains and elsewhere around the state. The city continues to consider where it will get its water from in the future.
www.apmresearchlab.org
