The state does not have a mechanism for tracking the amount of floodwater that water managers and landowners are diverting to groundwater recharge projects. But the looming threat of groundwater regulations has propelled a new race to grab more water in the wet years to prepare for the dry years.
Innovative new collaborations are showing both promise and the regulatory hurdles ahead in scaling up efforts to tap into this natural water supply storage.
In 2021 researchers at the Public Policy Institute of California (PPIC) developed a dataset of specific groundwater banking projects as part of a policy report on groundwater trading to support the implementation of the Sustainable Groundwater Management Act.
Kern County was one of the first to get banking projects in California and accounted for most of the growth in stored volume from the early 1990s to mid-2000s, according to PPIC. The Kern Water Bank stores around 90% of the county’s total groundwater supply. The 32-square-mile property has the capacity to store 1.5 million acre-feet of water, nearly as much as Lake Berryessa in Napa County, with some additional expansion since 2019.
The county severely depleted its groundwater banks during the 2012-16 drought, but the wet years of 2017 and 2019 led to a record total amount stored. Urban and agricultural interests contribute about the same amount of water to banks, though agricultural clients tend to tap the water more in dry years.
The Semitropic Water Storage District is one of the member agencies for the joint powers authority that governs the Kern Water Bank and manages its own set of groundwater banking projects as well.
“We're pretty much all ready to go to start recharge once water becomes available,” Semitropic Director Jason Gianquinto told Agri-Pulse.
While the new precipitation is promising, he cautioned that it is still early in the water year. The Department of Water Resources has yet to revise the State Water Project (SWP) allocation from the 5% initial amount set in December and has not made floodwater available for the project, since Shasta and Oroville reservoirs have enough capacity to store more of that runoff. State restrictions on Delta pumping have also led to reduced Delta exports to SWP contractors.
According to Gianquinto, the district has “a tremendous capability to recharge water” but the limiting factors have been access to the water and the SWP’s peak flow of 1,500 cubic feet-per-second (CFS) through the California Aqueduct.
Beyond the larger water banks, groundwater sustainability agencies are proposing 340 new groundwater recharge projects—a testament to the immense amount of work put into groundwater sustainability plans (GSPs) since the passage of SGMA in 2014 and how that has coalesced regional collaborations, according to Andrew Ayres, a research fellow at the PPIC Water Policy Center. Yet a review of GSPs by Ayres and his colleagues in 2020 found that the anticipated volumes for unclaimed floodwater “do not appear realistic” and that “there are serious capacity constraints to getting this water underground.”
“Those plans are all very heavy on recharge as a solution to groundwater overdraft problems,” Ayres told Agri-Pulse. “Some of those plans contain conflicting visions about how much water is available for new recharge off of these river systems and who's going to have access to it.”
Yet he saluted the work of local water agencies in establishing new projects, such as a creative new partnership between the East Bay Municipal Utilities District (MUD) and San Joaquin County. The Bay Area public utilities district already pipes its drinking water 90 miles from the Mokelumne River, across the San Joaquin Valley and over the county’s critically overdrafted groundwater basin.
“We identified over two decades ago that there's an opportunity here,” said Mike Tognolini, director of water and natural resources at East Bay MUD. “There are years when there's plenty of water and then there are years where there's not enough for us.”
Storing the extra flows in the county’s aquifer would help to restore the basin and balance the district’s water needs during droughts. But it took “a long, long time” to deal with the technical issues and institutional challenges, build trust and develop a program that local interests would support. Under the program, the district would provide water to a grower in lieu of pumping water for irrigation and the district would get credit for half the water in the basin.
After completing the permitting process, the district has nearly finished building the pipeline connections and has launched a pilot project with a single well, starting with less than 100 acre-feet in the ground. Tognolini hopes the wet winter will provide an opportunity to deposit more water in the basin later.
Like many recharge projects, permitting was a considerable challenge. Along with standard questions over water rights and availability, the district had to obtain a groundwater exporting permit from San Joaquin County, since local ordinances sought to protect that vital resource from water grabs.
“Over time, we've been able to overcome that by building trust and creating a program that really is controlled locally,” said Tognolini. “We have an account. We put water in, we pull water out, but they control all the knobs and dials, they control the valves.”
It was an important lesson for an urban agency coming to a rural county that is at the center of some of California’s fiercest water battles.
Other agencies striving to get banking projects online remain mired in the permitting process. Joe Hopkins, a principal engineer at the Provost & Pritchard Consulting Group, has guided the Aliso Water District Groundwater Sustainability Agency through the tumultuous process of gathering a permit to secure floodwater from the Chowchilla Bypass, which bisects the district. The project would eventually divert about 10,000 acre-feet to store underground.
Growers have long pumped water from the bypass for recharge during flood flows. With SGMA, however, the state interjected and said the water belongs to the state and districts now need a statement of diversion, according to Hopkins. So the GSA began securing 180-day permits in 2018, hoping wet weather would eventually deliver floodwater. Obtaining a permanent water right, however, has not been as simple as they initially thought, particularly since the GSA is not a landowner and has a higher regulatory threshold to meet.
“Getting the water right in place was one thing,” said Hopkins. “Complying with all the terms and conditions that come along with it was another thing. And that's what we've been struggling with.”
Every water right application the GSA submits garners a protest during the objection review period, with some more overreaching than they should be, Hopkins said.
“There's an abundance of floodwater here that’s a threat to health and human safety,” he said. “And we can't take it because we haven't gone through the studies to define what are the minimum bypass flows that need to exist and what species are we trying to protect.”
The GSA is dedicating a $10 million investment for the infrastructure, knowing floodwater may be available only once every four to seven years.
The agency secured another temporary permit in late December and floodwater became available on Jan. 3, when 5,000 cfs of water was rushing down the bypass. Districts were fighting to keep the water in the banks and prevent blowouts and seepages. But the GSA had not resolved all the issues with CDFW. It was waiting on a 14-day survey to monitor for the endangered San Joaquin kit fox and was in the process of installing a specialized screen to prevent endangered fish from being drawn into the pipe.
“By the time we satisfy all the terms and conditions, floodwater is going to have been running for at least a month before we're able to take advantage of it,” said Hopkins.
The call for flood releases tends to come quick with such storms. Hopkins was watching the reports with Millerton Lake and one day they started releasing flows at 4,000 cfs down the San Joaquin River, with the “flip of a switch.” On a more granular basis, growers along the system facing the threat of damage to their property installed temporary pumps to flood fields or charge their irrigation systems.
“There's an urgency to it,” he said. “It'll be another potentially four years before we see another [flood opportunity]. And in that time, the jaws of SGMA are closing. We have thresholds we need to hit.”
If the state sees only five flood years during the 20-year SGMA horizon, then 20% of the excess flows for recharge is already lost, he lamented.
To Daniel Mountjoy, the solution lies with the landowners at the granular scale. As the director of resource stewardship at the environmental group Sustainable Conservation, Mountjoy has worked for more than a decade to expand on-farm recharge projects. He took an approach modeled by Don Cameron, a pioneer of the practice and the president of the State Board of Food and Agriculture, and promoted it to more farmers and irrigation districts, finding strong support as well from groups like the Almond Board of California.
“If we wait for large infrastructure projects, it's going to cause stress on the whole farming industry,” said Mountjoy. “There, in fact, is an immediate solution that many farmers can practice using their own lands to capture water.”
It presents a separate realm of water quality issues and research needs related to fertilizers, pesticides and naturally occurring contaminants and has raised legal questions over water rights. Farmers have shared frustrations with Mountjoy that they can technically divert water onto floodplains but SGMA regulations state they do not have a right to pump that water up later for irrigation. But Mountjoy said the recharge still leads to multiple benefits, like raising the groundwater table, reducing pumping costs, improving environmental conditions and reviving drinking wells.
When infrastructure and permitting hurdles stand in the way of larger recharge programs, farmers can see immediate gains from on-farm projects. Sustainable Conservation has collaborated with DWR to study the opportunities for flood-managed recharge in the Merced watershed.
Using existing water rights, canals and other infrastructure, recharge could offset the groundwater overdraft by about 30%. And if reservoir managers release more water ahead of storms before flood conditions arise, about 40% of the overdraft could be addressed. Enlarging canals at critical locations and expanding floodplains in minor ways could bump it to 62%.
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When reservoir water is not available during storms, local streams, which are “flashier,” respond more quickly to rain events and become a critical resource.
“There's some big potential here that would be an alternative to restricting pumping and the economic harm and community impact that would have,” said Mountjoy, adding that it would also benefit rural drinking water supplies while protecting riparian ecosystems that have suffered during the drought.
The North San Joaquin Water Conservation District has demonstrated the recharge opportunities by partnering with a 13-acre vineyard. In December, the winegrape grower pulled the equivalent of 15 vertical feet of water from the Mokelumne River to percolate into the vineyard’s soil, and by the time the New Year’s Eve storm arrived, the ground was already too saturated to take more.
Further south, the Turlock Irrigation District typically lets their irrigation canal water flow into the river at the end of the season. This year the district instead dumped that water onto two almond orchards and used the canal as a flood capture system for local streams, protecting communities in the process. Mountjoy now showcases the project to get other farmers on board.
Following the wet winters of 2017 and 2019, the Madera Irrigation District flooded about 300 fields for recharge and just opened up the offer again to their growers. The Tulare Irrigation District hopes to sign up about 11 growers.
Factoring in grants from the USDA Natural Resources Conservation Service, irrigation districts and GSAs, Mountjoy estimates growers can end up with as much as a 75% subsidy for the costs. And some GSAs are considering pumping credits for farmers who invest in recharge.
During the drought, Mountjoy carried these success stories across the valley, hosting workshops and demonstration projects, while helping farmers and districts iron out the paperwork and navigate the permitting process—all to prepare for the wet years amid the dry ones.
“The presence of floodwater is a reminder to us all that we have to be prepared for these kinds of years,” he said. “If you are, you can capture a lot of water. There's a lot of potential.”
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