Water

Even in wet years, wells are still dry. Why replenishing California’s groundwater is painfully slow

After abundant rain and moderate snowfall this year in the northern half of the state, California’s largest reservoirs are holding more than 120% of their historical average. But underground, the state’s supply of water for drinking and irrigating crops remains depleted.

Even after multiple wet winters, and despite a state law that’s supposed to protect and restore the state’s precious groundwater, thousands of wells — mostly in rural, low-income communities in the San Joaquin Valley — have gone dry because of over-pumping by growers.

So why hasn’t the recent bounty of rain and snow replenished the state’s underground supplies?

Governor Gavin Newsom’s March 10 Executive Order makes it easier to capture water from storms to recharge groundwater supplies and replenish depleted groundwater basins while helping to reduce flood risk. Don Cameron, a groundwater recharge pioneer, describes how these projects work, and why they are especially important during years of intense storms like this year.

“Long-term groundwater storage remains in a deficit from years of pumping more than what has been replenished,” according to the state’s 2024 semi-annual update on groundwater conditions.

Gov. Gavin Newsom has long vowed to enhance groundwater replenishment. In his 2020 Water Resilience Portfolio, the governor said he would “explore ways to further streamline groundwater recharge.” Then, in his 2022 Water Supply Strategy, he promised to increase average recharge by half a million acre-feet a year. (An acre-foot of water is enough to submerge one acre of land a foot deep.)

The effort has had some success. In 2023, San Joaquin Valley farmers sank 7.6 million acre-feet of water into the ground, compared to 6.5 million in 2017, another wet year, according to the Public Policy Institute of California.

However, “it’s safe to say that very little, if any, recharge happened in 2020 to 2022 as these were some of the driest years on record in many parts of the state,” said Caitlin Peterson, a research fellow at the institute.

The Los Angeles region’s water table is dropping, with only sluggish recovery after 2023’s heavy rains, according to a Stanford University study published early this month. “Only about 25% of the groundwater lost since 2006 was restored,” the study says. “Wet winters do not compensate for the substantial depletion during dry years.”

Even the extraordinary wet year of 2023 had missed opportunities.

That year, the state issued permits to landowners allowing more than 600,000 acre-feet of water to be diverted from the Sacramento and San Joaquin river basins for recharging groundwater during floods. But because some landowners received their permits too late in the rainy season and they  were required to install costly fish screens to protect salmon, the program only resulted in about 20,000 acre-feet of recharge, according to the Department of Water Resources.

“We haven’t reached our full potential in California for groundwater recharge,” said Helen Dahlke, a UC Davis professor of integrated hydrologic sciences. “We’re still tinkering around with small numbers.”

Farmers taking action to capture groundwater

Since he began farming more than 40 years ago, Don Cameron has watched the groundwater beneath his ranch near Fresno drop a half-foot to a foot every year. In total, the water table has dropped at least 30 feet.

So he decided to take action to replenish his aquifer. He has been flooding his fields and orchards since 2011 to let that water trickle underground.

Cameron has installed several miles of canals, along with headgates and pump systems, to bring more water to his Terranova Ranch from the Kings River during floods. He used earth excavated from the canals to enclose several active farmfields, forming 350 acres of recharge basins.

Though he was assisted with a $5 million state grant, he spent about $13 million total, he said. He finished in 2020, in the midst of the last drought.

“Then we waited for a flood,” he said.

It came in 2023, and that wet winter his recharge system helped draw the water table up 15 feet.

He would like to see managed recharge projects like his own replicated statewide.

“We know that groundwater recharge works and increases aquifer resilience,” he said. “If we had better infrastructure to do it, we could really put a lot more water underground.”

But not all landowners will invest in these projects. That’s because the water that sinks below one person’s farm becomes available for others to pump. Without a detailed accounting and crediting system, farmers don’t necessarily get back what they invest.

“When someone recharges, they’re mainly benefitting their neighbors,” said Graham Fogg, a UC Davis professor emeritus of hydrogeology. “The recharge is local, but the benefits are regional.”

Cameron, for all his investments, knows this.

“The water I put in the ground does not have my name on it,” he said.

“We know that groundwater recharge works and increases aquifer resilience. If we had better infrastructure to do it, we could really put a lot more water underground.”

Don Cameron, San Joaquin Valley grower

To address this problem, some irrigation agencies have developed accounting systems that credit farmers who help sink water into a region’s basin.

On the Central Coast, for example, the Pajaro Valley Water Management Agency uses “recharge net metering” that provides rebates to landowners based on how much water passes through their metered percolation system.

In the Tulare Irrigation District, groundwater managers similarly credit farmers who use their land for recharge, so that they are entitled to most of that water later.

California invests millions in replenishing groundwater 

As a pattern of wetter wet periods and drier droughts develops in the West, California water managers, anticipating a 10% decline in water supply by the 2040s, are increasingly concerned with capturing water when it’s available.

The governor waived environmental restrictions in 2023 with a series of executive orders aimed at facilitating groundwater recharge. Early that summer, the governor and Legislature codified some of these regulatory easements into a new law.

Since 2018, the Department of Water Resources has directed more than $121 million to at least 69 recharge projects.

Paul Gosselin, the department’s director of sustainable water management, said the efforts are working. Newsom’s 2023 orders allowed farmers to divert more than 400,000 acre-feet of water for recharge that otherwise would have flowed directly to the ocean, he said.

Between 2023 and 2024, Westlands Water District recharged almost 400,000 acre-feet. The Tulare Irrigation District recharged about 200,000 acre-feet — “a record-breaking year for us,” said General Manager Aaron Fukuda.

Sarah Woolf, a San Joaquin Valley farmer and president of the agricultural consulting firm Water Wise, said the governor’s order in 2023 to capture more water underground was a sign that “we’ve done nothing to support recharge” since the state’s groundwater law passed in 2014. Woolf said there has been “still no real resolution from the state board on this recharge issue.”

A more recent order issued by Newsom in January directed state officials to remove or minimize barriers “that would hinder efforts to maximize diversions to storage of excess flows.”

While Newsom’s executive orders appeased farmers, they reduced Delta river flows, potentially harming endangered salmon, sturgeon and smelt. 

“This outflow of freshwater might seem like excess water to some but it’s not excess to the environment, and it’s absolutely critical to this ecosystem that is on the brink of collapse,” said Ashley Overhouse, water policy advisor with Defenders of Wildlife.

Thousands of dried-up wells

Recent groundwater gains have not undone the decades of unregulated groundwater pumping, especially in disadvantaged communities in the San Joaquin Valley.

So much groundwater there has been pumped to irrigate orchards that the Earth has collapsed, subsiding almost 30 feet near Mendota last century, for example, as the water table has dropped. In the past two decades, subsidence has accelerated, with much of the valley floor plunging at a geologic freefall pace of a foot per year.

Even in 2023, groundwater managers in the San Joaquin Valley reported drawing 5.4 million acre-feet from the ground, mostly offsetting the total amount that was recharged.

Consequently, thousands of residents reliant on groundwater have reported drinking water wells drying out, especially in 2014-2015 and 2021-2022, all years of extreme drought.

State officials received about 700 reports of dry wells over the past two years, and a state database shows that more than 200 wells — many in the San Joaquin Valley — stand at all-time low levels. Eight dry household wells were reported in the San Joaquin Valley in the last 30 days alone.

During wetter periods, the number of dry wells reported tends to slow down. However, activists in the region say there has been little to no recovery of dewatered wells, forcing communities to find solutions.

“A lot of people have been relying on bottled and hauled water, and they’ve also committed a lot of money to digging deeper wells,” said Tien Tran, policy manager with the Community Water Center, an advocacy group that works in the San Joaquin Valley and Central Coast, another region with depleted groundwater.

The world’s most rapidly declining groundwater

Spain, Iran, China and Chile are among the world’s hot spots for the most rapidly dropping groundwater levels in the 21st century, according to a new analysis of 1,700 aquifers in 40 countries. Six California basins rank in the top 100 for the biggest rate of decline. About 12% of the aquifers studied showed losses of more than 20 inches a year.

Median annual change in groundwater basin levels (meters):

In downtown San Jose, groundwater overdraft has led to 13 feet of permanent subsidence, according to Cindy Kao, the Santa Clara Valley Water District’s imported water manager.

“Our county’s demands began outstripping our local groundwater supplies more than 100 years ago,” Kao said at a state water board hearing on Feb. 18.

Like other water supply advocates who spoke that day, Kao supported Newsom’s proposed $20 billion Delta tunnel as a means for boosting deliveries of Delta water that is deposited into the local aquifer.

Wade Crowfoot, secretary of the California Natural Resources Agency, said water from the tunnel would “recharge groundwater basins in the Central Valley, which is critically important for water supply and implementation of the Sustainable Groundwater Management Act.”

“Our county’s demands began outstripping our local groundwater supplies more than 100 years ago.”

Cindy Kao, Santa Clara Valley Water District

In the Sonoma Valley, a region heavily pumped by wells to irrigate vineyards, groundwater supplies have trended downward.

Marcus Trotta, principal hydrologist with the Sonoma County Water Agency, said ample rainfall in the last two years muted this effect. “But there’s still been a long-term decline, mostly in the deeper aquifer system,” he said.

The valley’s deeper aquifers are separated from the surface by mostly impermeable clay deposits, Trotta said. This can make recharge of depleted basins almost hopelessly slow.

Room to recharge

As for space to store more water, there is plenty. An estimated 140 million acre-feet of groundwater storage space lies vacant beneath the Sacramento and San Joaquin valleys — three times the volume of all the state’s surface reservoirs combined.

Fogg, who helped produce that figure, said it was calculated by subtracting the current groundwater in storage from the estimated volume before California’s modern development.

One of the biggest bottlenecks to making use of this space is the capacity of conveyance systems.

“We have plenty of farmland for recharge, but the infrastructure to get the water to these places is still evolving,” Fogg said.

Agricultural production in California has steadily grown for many decades, now routinely exceeding $50 billion in gross annual sales. Thirsty nut crops have been so widely planted that prices have crashed from oversupply, and the Central Valley is carpeted with irrigated farms.

Ultimately, ensuring there is adequate groundwater for farms and communities means growers will have to permanently fallow large areas of cropland. Otherwise, Gosselin said groundwater recharge will never keep pace with agricultural demand.

“Farmers are not going to be able to recharge their way out of groundwater depletion,” he said.

 

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