Flush with rain, California plans to replenish drought-depleted groundwater with floodwaters

With torrential rains flooding California, state water regulators have approved a plan to divert floodwaters from the San Joaquin River to replenish groundwater that has been depleted by heavy agricultural pumping for three years of record drought.

The State Water Resources Control Board has approved a request from the United States Bureau of Reclamation to take more than 600,000 acre-feet from the river and send much of that water to areas where it can spill, s infiltrate into the ground and percolate down to the river. aquifer below the San Joaquin Valley.

The amount of water to be diverted under the plan is greater than the City of Los Angeles’ annual supply. Some of the water will also be directed to wildlife refuges along the San Joaquin River starting next week, officials said.

The plan aims to address potential flood risks, capitalize on California’s near-record snowfall, and capture some of the high flows from recent extreme storms to store water underground.

“We are taking steps to maximize groundwater recharge in a way the State of California has never truly done before,” said Erik Ekdahl, deputy director of the State Water Board’s water rights division. . “This is a huge opportunity to help recharge these depleted aquifers.”

State officials said their order allows the Bureau of Reclamation to manage flood flows from Friant Dam and change the points where water is diverted along the San Joaquin River.

Where water sinks into the ground and replenishes the aquifer, it could help cope with falling water levels that have left families with dry wells in rural areas of the Central Valley. Stabilizing water levels could also help alleviate the widespread problem of ground collapse caused by over-pumping, which has caused costly damage to canals and other infrastructure.

Governor Gavin Newsom said after the driest three years in state history, “California is taking decisive action to capture and store water for the return of dry conditions.”

Newsom has sought to prioritize stormwater capture and groundwater recharge as central components of his administration’s strategy to adapt to more intense water extremes with climate change. On Friday, the governor’s office announced that it had signed an executive order authorizing the abstraction of water from the latest series of storms.

The Bureau of Reclamation manages the Central Valley Project’s dams, reservoirs, and canals and sends water to contractors, including major agricultural irrigation districts and other agencies. The state ordinance allows the federal government to provide floodwater from the Mendota Pool, a small reservoir on the San Joaquin River, to be used to replenish groundwater.

Water that would otherwise have flowed into the San Joaquin River will be available for irrigation districts and other agencies to divert to replenish groundwater for more than four months. Under temporary contracts with the federal government, they will be able to send water through canals to areas with permeable soils allowing groundwater recharge.

Some floodwaters will also flow into wildlife refuges, including the San Luis National Wildlife Refuge, Mendota Wildlife Area and Los Banos Wildlife Area.

The State Water Board said in its order that the changes capture “high flows that would otherwise go unused,” easing pressures on flood control infrastructure and helping to address chronically declining groundwater levels.

Environmental groups including the Natural Resources Defense Council and the Bay Institute opposed the plan, saying in a letter that water diversions would allow lower flows in the San Joaquin River than expected under a settlement of 2006, and would likely be harmful to Chinook Salmon.

“While the order will not completely dry up the San Joaquin River, it will divert most of the water that was supposed to flow into the river under the court-approved settlement agreement, primarily for the benefit of businesses. agribusinesses in the Westlands Water District,” said Doug Obegi, senior counsel for the Natural Resources Defense Council. “Again, agribusinesses win while the environment gets less than its fair share of water.”

Amanda Fencl, senior climate scientist for the non-profit Union of Concerned Scientists, said the plan raises questions about who will benefit the most, especially as many water contracts in the region are held. by agricultural irrigation districts.

“It is essential to recharge the aquifers, especially when there is an influx of rain,” Fencl said. “But it remains an open question for me as to whether other water users like households on domestic wells and community water systems will benefit.”

State officials disagreed with the objections raised by environmental groups, saying the water diversions will not harm the environment and the flows left in the river will meet requirements.

“There will still be a lot of water coming down the San Joaquin,” Ekdahl said. “The amount of water that will be redirected here is still relatively small compared to the amount of water that will flow through the system.”

The Newsom administration and federal government drew criticism from environmental groups for another move last month, when they asked the State Water Board to temporarily waive water quality rules in the Sacramento River Delta. -San Joaquin with the aim of storing more water in the reservoirs. The board ended the waiver on Thursday, saying recent rains and snow made it no longer necessary.

Newsom set a goal last year as part of its water supply plan to increase average annual groundwater recharge by about 500,000 acre-feet. The State Water Board said that since December it has approved the diversion of about 790,000 acre-feet of water for groundwater replenishment as well as supplying wildlife refuges.

Most of the water pumped from wells in the Central Valley feeds farms that produce a wide variety of crops, from almonds to tangerines.

Scientists found in a recent study that groundwater depletion in the valley has accelerated in recent years. They estimated that groundwater losses since 2003 totaled about 36 million acre-feet, or about 1.3 times the total water storage capacity of Lake Mead, the nation’s largest reservoir.

As state officials increasingly prioritize aquifer recharge, they pointed out that there is vast storage space available underground and that groundwater replenishment is one of the most easiest and most economical way to take advantage of wet years.

Local water agencies have begun planning recharge projects as they begin to implement plans to curb excessive pumping, as required by the 2014 Sustainable Groundwater Management Act. State.

Water managers have also increasingly focused on finding ways to facilitate the process of permitting the use of stormwater to recharge aquifers and strategically investing in infrastructure to deliver stormwater. water to areas where permeable soils provide fast pathways to groundwater.

The State Water Board said the federal government’s request alone paved the way for large-scale recharge without the need to approve many small permits.

The water used to replenish the aquifer will help local agencies meet their goals to curb overpumping under the Groundwater Act, said Thomas Harter, professor of water resources at UC Davis.

Harter said 600,000 acre-feet is “a big part, and it’s certainly a big stepping stone to future wet years and to meeting those goals.” He said water stored underground may allow possible reductions in well water use to be somewhat less severe than reductions would otherwise have to be.

“To the extent that we can increase supply, and we can only do that by capturing these large flood flows and storing them, that’s our main card in this game,” Harter said. “It won’t remove the need to reduce demand, but it will reduce the need to do so.”

Ann Willis, California regional manager for American Rivers Group, said she thinks the newly approved plan is a good approach to recharging severely depleted groundwater.

“It speeds up the regulatory process to take advantage of those higher streams when they’re available,” Willis said. “It’s a positive thing that we’re doing this, and I think we’re going to learn a lot from it.”

She said the minimum river flow required under the permit appears too low to sustain a healthy San Joaquin River, but flow gauges have recorded increased flows above that level.

“I think right now we have plenty of water to do both – both recharge and environmental flows,” Willis said. “But that’s not always true. And we have to be mindful of one of those goals that we prioritize when there’s not enough water for everyone.

While the state takes advantage of storms to store water underground, efforts to replenish depleted groundwater supplies will take time, said Karla Nemeth, director of the California Department of Water Resources. She said state officials are working with local agencies to expand those efforts and improve the permitting process for more charging projects.

“We hope that during these next series of storms, we can identify these projects and activate these charging systems,” Nemeth said. “We know drought conditions will return to California, and those are really the times we need to capture, so we can be resilient in the event of future dry conditions.”

Times writer Hayley Smith contributed to this report.

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