Public workshop to explain staff report on Tulare Lake Subbasin ahead of SGMA probationary hearing

Courtesy of California Water Boards

Historic process underway to protect vital groundwater resources

The State Water Resources Control Board today will conduct an in-person workshop at the Hanford Civic Auditorium from 6-8:30 p.m. on a draft report recommending actions for the board at an upcoming hearing for the Tulare Lake Subbasin under the Sustainable Groundwater Management Act (SGMA). During the workshop, State Water Board staff will begin accepting public comments at 7 p.m.

Tulare Lake is the first groundwater basin to be scheduled for a probationary hearing, which is set for April 16, 2024. Its groundwater sustainability plan, submitted by the basin’s groundwater sustainability agencies to fulfill SGMA’s requirements, was deemed inadequate in March by the Department of Water Resources.

Passed by the state Legislature in 2014, SGMA established a new framework for how groundwater would be managed locally at the basin scale to achieve long-term sustainability and preserve California’s at-risk groundwater resources for future generations. The board’s role in this process is to intervene and manage groundwater resources where local sustainability agencies cannot ensure that a basin will be brought into sustainable use within the 20-year timeline required by the legislation.

The 176-page draft staff report provides background on the requirements of SGMA, details how human activity over the past century has impacted the hydrology of the Tulare Lake basin, and lists recommendations for board action. An 11-page Executive Summary is also available for the public to review. If the board votes to place the basin on probation, the agencies that submitted the original sustainability plan will have 12 months to revise their plan.

Address of the workshop: Hanford Civic Auditorium, 400 N Douty St., Hanford, CA 93230

Time: 6-8:30 p.m., with public comments accepted beginning at 7 p.m.

2023-11-08T15:43:49-08:00November 8th, 2023|

Notice of Tuesday, April 16, 2024 SGMA Probationary Hearing for the Tulare Lake Subbasin

At its April 16, 2024 meeting, the State Water Board will consider designating the Tulare Lake subbasin a probationary basin under the Sustainable Groundwater Management Act (SGMA). See the hearing notice for information on the hearing time and location and how to participate.

If the State Water Board designates the subbasin probationary, it will also identify deficiencies (issues) and potential actions people in basins could take to address the deficiencies. While the basin is in probation, many people who extract groundwater will need to report their extractions to the State Water Board and pay fees. The State Water Board may also require extractors to install and use meters or other methods to measure their extractions.

State Water Board staff have developed draft recommendations of actions for the State Water Board to consider. They invite your input on the Draft Staff Report no later than December 11, 2023, at 12:00 noon. View the Draft Staff Report online here; a shorter Executive Summary is also available in both English and Spanish. Staff will consider all comments received by December 11, 2023, at the noon deadline when developing the Final Staff Report.

See the hearing notice for:

  1. Instructions for how to comment on the Draft Staff Repor
  2. Information on two public staff workshops prior to the probationary hearing. At the workshops, staff will explain the Draft Staff Report and share more about how to participate in the State Water Board’s process. Staff will also accept verbal public comments on the Draft Staff Report at the workshops.

Questions? Contact the SGMA Program at or 916-322-6508.

More information about SGMA and the State Water Board’s role can be found here:

2023-10-13T14:24:19-07:00October 13th, 2023|

Westlands’ Westside Subbasin Groundwater Sustainability Plan Receives Green Light

Courtesy of Westlands Water District

Westlands Water District (District) received official notice from the California Department of Water Resources (DWR) that the Westside Subbasin Groundwater Sustainability Plan (Westside GSP) was approved. Submitted in conformity with the Sustainable Groundwater Management Act (SGMA), the Westside GSP’s approval is a significant step in ensuring a long-term water future in the heart of the San Joaquin Valley’s prime farmland.

In response to the Westside GSP approval, Allison Febbo, general manager of Westlands Water District, issued the following statement:

“DWR’s official stamp of approval reflects a great deal of time and dedication from Westlands’ staff and Board of Directors who worked diligently and collaboratively with DWR to develop a GSP that will serve as a roadmap for achieving the Westside Subbasin’s sustainability goals well before the 2040 deadline. With this milestone, we look forward to continuing the work we’ve already started by implementing groundwater projects that yield the best results for the communities we serve, including the District’s family-owned farms that reliably feed the world and support the San Joaquin Valley.”

2023-08-07T10:27:37-07:00August 7th, 2023|

Westlands Water District Shows Groundwater Recharge Success

By Elizabeth Jonasson

Today, Westlands Water District (District) released new data on the District’s groundwater recharge efforts. Since 2019, the District has been working with District landowners to establish on-farm recharge projects, with the goal of taking advantage of abundant water supply (when available) to improve groundwater levels in the lower and upper aquifers.


Sustainability is at the core of the District’s comprehensive water delivery system and groundwater recharge is a key strategy to both store and preserve water for future dry years or droughts and improve groundwater conditions in the subbasin. The District is committed to ensuring a sustainable water future by investing in recharge projects and encouraging landowners to explore and implement creative approaches that maximize water use efficiency and storage while improving climate resilience.


“We recognize the next drought is not if but when and it is critical we use extra water to prepare for future years when water may be sparse,” said Allison Febbo, General Manager, Westlands Water District. “The District’s groundwater recharge efforts will help ensure we meet our Groundwater Sustainability Plan objectives while allowing our farmers the opportunity to save water and plan next year’s crop.”


The District is currently offering three groundwater recharge programs to help landowners refill and replenish the aquifers in the District. Project types include percolation basins, flood irrigation, sublateral recharge, and dry well injection. The District is seeing strong enthusiasm and interest from landowners as new applications continue to be submitted.

With increased surface water supply this year, the District has been able to take advantage of the opportunity to prepare for the future. In May 2023 alone, recharge efforts resulted in 24,000 acre-feet (af) being stored. Water year to date, (March 1st through June 20th) the District has recharged approximately 60,000 af. The District is aiming to get to over 200,000 af of total recharge by the end of this water year (February 29,2024).

Additional recharge projects will be online in the coming months as the District has processed 273 applications for 61 Aquifer Storage and Recovery, 131 flood Managed Aquifer Recharge (MAR) projects, 77 percolation basins and 4 sublateral projects.

District recharge projects and in-lieu recharge (also known as foregone pumping) have had a positive impact on groundwater levels. In May 2023, groundwater elevation levels in the Lower Aquifer registered at –54 mean sea level, which is an increase of 40 feet compared to average groundwater elevation in the fall of 2022. Though these results have been encouraging, there is more work that needs to be done for a water-secure California.

“Strengthening water security in California isn’t something that can be done by just one water district, one water agency, or even one region,” Febbo added. “This is a statewide problem where we need to prioritize collaboration and develop multifaceted solutions to address California’s water crisis. That’s why we are committed to exploring and implementing creative approaches to maximize water use efficiency and storage and improve climate resilience.”

To learn more about the District’s recharge efforts see our groundwater recharge factsheet.

2023-06-20T15:31:10-07:00June 20th, 2023|

Westlands Water District Encourages Growers to Apply for Phase 2 of LandFlex Grant Funding

By Elizabeth Jonasson

Today, the California Department of Water Resources (DWR) grower application enrollment period for Phase 2 of the LandFlex Program (LandFlex) will officially reopen at 5 pm. Westlands Water District Groundwater Sustainability Agency (GSA) Westside Subbasin is one of 4 GSAs eligible for this second phase of funding. Growers will have access to approximately $10 million in grant funding and be incentivized to limit agricultural groundwater use near domestic wells.

“As the San Joaquin Valley continues to battle the impacts of the recent prolonged drought, we are grateful to provide farmers in Westlands access to grant funding through the LandFlex program,” said Allison Febbo, General Manager, Westlands Water District. “The District will continue to prioritize identifying resources like the LandFlex program so that our farmers can transition their land in the face of an uncertain water future.”

Block grant funding through LandFlex will be made available to growers with a 3-year average Adjusted Gross Income of $2.5 million or less, for each enrolled acre up to 40 acres or 25% of their total acreage, whichever is greater. LandFlex funding must be used for the following actions:

  • Provide immediate drought relief by fallowing land for a 12-month period (note: recharge activities are allowed on fallowed land in lieu of cover crops)
  • Permanently retire any current and future groundwater overdraft on enrolled acreage
  • Land use transition of enrolled acreage (e.g., orchard or row crop removal and planting of cover crops)

To be considered for block grant funding through LandFlex, willing and eligible growers must apply through the Grower Application Portal at by the deadline:  June 28, 2023 at 5 pm.

A priority for scoring applications will be based on land proximity to domestic wells that have gone dry or are in jeopardy of going dry, within the Subsidence Prone Area or approved recharge projects. Overall process for growers submitting applications in Phase 2 and receiving grant awards:

  1. LandFlex Grower Portal opens June 14, 2023 at 5pm
  2. All grower applications will be submitted through
  3. DWR, Technical Assistance Providers and the GSAs will score applications and determine distribution of awards.

You can learn more about LandFlex by visiting: or

2023-06-15T08:09:46-07:00June 15th, 2023|

New Research Offers Clarity on Actual Water Use by Agriculture

Recent scientific work by the California Bountiful Foundation, the 501(c)(3) science and research arm of the California Farm Bureau, has found that California farmers and ranchers use only 15% of the total water the state receives.

These findings, now available on the California Bountiful Foundation website under Research and Studies, offers a data-based analysis of water use of California agriculture, the largest food producing sector in the U.S. The data contradicts stereotypes often repeated on the share of water used for agriculture.

 A policy brief and peer-reviewed scientific publications will follow to memorialize this work, said Dr. Amrith Gunasekara, director of science and research for the California Farm Bureau.

“We set out to understand how agriculture water is allocated, portrayed, and presented,” Dr. Gunasekara said. “What we found out is that commonly expressed beliefs over water use by farmers and ranchers are simply not supported by actual data on how much water California receives.”

The California Bountiful Foundation, in collaboration with the Governmental Affairs Division of the California Farm Bureau, has started to release policy briefs to educate policy makers and stakeholder groups.

“For an agricultural sector that leads the nation in food production and provides a diverse, nutritious, affordable and safe food supply, this data shows that California agriculture is highly efficient,” said California Farm Bureau President Jamie Johansson. “We are working hard to educate our policy makers to bring understanding to California’s critical agricultural food production.”

More information on policy briefs can be found here. A recent commentary in the Ag Alert newspaper on the agriculture water-use findings may be found here.

2023-06-06T09:49:18-07:00June 6th, 2023|

Friant Water Authority

Top News

  • Over the past week, the northeastern portion of the State and most of the Northern and Central Sierra received 0.25 to 1 inch of precipitation. The North and South Coasts and Southern Sierras received trace amounts to 0.25 inches of precipitation.
  • Through the weekend, temperatures are expected to be 5 to 10 degrees below normal along the coasts and near normal to 10 degrees above normal elsewhere in the State. As the week progresses, temperatures are expected to cool to near normal to 10 degrees below normal throughout most of the State. Next week, 0.5 to 1.5 inches of precipitation are expected in the Sierras from sporadic thunderstorms, trace amounts to 0.25 inches of precipitation are expected in the northeastern portion of the State, and trace amounts of precipitation is expected along the Central and South Coast.
  • DWR released the May 1st water supply forecast for water year 2023 on May 8th. The forecast indicates a Sacramento Valley Index of 9.4 (Wet) at the 50% exceedance level and a San Joaquin Valley Index of 6.5 (Wet) at the 75% exceedance level. The May 1st values are the official water year types for 2023. The April forecast showed a Sacramento Valley Index of 9.6 (Wet) and a San Joaquin Valley Index of 6.5 (Wet).
  • Keswick Reservoir releases decreased to 10,000 cfs on May 29th for storage management and are expected to remain at that level to help with fill management but will be adjusted as conditions allow.
  • Folsom Reservoir releases (below Nimbus) decreased to 13,000 cfs on May 31st for fill management and are expected to remain at 13,000 cfs unless adjustments are necessary to manage reservoir fill.
  • The Delta is currently controlled by Limited Real Time Demand/Available Facility Capacity.  The DWR Delta Ops Report indicates that the Delta is currently in an Excess condition (no restrictions).
  • The daily Delta outflow index is currently 68,900 cfs (7-day average).
  • As of February 1st, the D-1641 E/I ratio export cap is 35%, and the ratio is currently at 12% (14-day average).
  • Jones Pumping Plant remained a 5-unit operation of approximately 4,200 cfs.
  • Banks Pumping Plant pumping is at 4,500 cfs. There is no pumping for Cross Valley Canal Contractors.
  • The Federal share of San Luis decreased by 3 TAF to 956 TAF, which is considered full. CVO currently expects CVP San Luis drawdown to begin the week of June 5th.
  • The State share of San Luis decreased by 19 TAF in the last week to 1,059 TAF.
  • As demands begin to increase exports at Jones and Banks Pumping Plants are likely to be at or near capacity for most of the summer. With the volume of water expected in the Delta through the next few months, regulatory requirements are unlikely to restrict export operations.
  • The State Water Project (SWP) allocation for 2023 is 100% of requested supplies.
  • CVP SOD allocations remain at:
    • 100% for San Joaquin River Exchange Contractors and CVP Refuge supplies
    • 100% for Eastside Water Service Contractors
    • 100% of historic use for M&I Water Service and Repayment Contractors
    • 100% of contract maximum for Agricultural Service and Repayment Contractors (up from 80%)

Alerts for Friant Division

  • On May 31st, there were 1,102 cfs diversions to the Madera Canal, 3,660 cfs diversions to the Friant-Kern Canal, and 9,993 cfs of releases to the river.
  • Storage in Millerton was 232,991 AF on May 31st. Storage increased by about 14,700 AF compared to last week.
  • Restoration Flows at Gravelly Ford ramped down from 395 cfs to 175 cfs by the end of May. Reclamation is releasing Restoration Flows concurrently with flood flows. Total flows at Gravelly Ford on May 31st were 9,248 cfs which includes approximately 175 cfs of Restoration Flows. The ordered rate of Restoration Flows passing Sack Dam for May 31st was 160 cfs.
2023-06-02T11:52:35-07:00June 2nd, 2023|

Louder Voices, Bigger Investments Needed for California Water Security, Local Experts Say

By Alex Tavlian, San Joaquin Valley Sun

The California Water Alliance’s water forum tackled how best to fight for a stable, plentiful water supply for America’s breadbasket.

As the San Joaquin Valley yo-yos from drought to flooding, the region’s top water experts spent Thursday afternoon examining how to best approach the Valley’s long and short-term needs.

The viewpoints came amid the California Water Alliance’s third-annual water forum featuring the leaders of Friant Water Authority, Westlands Water District, farmer Cannon Michael, and Rep. John Duarte (R–Modesto).

Duarte hones in on twin crises: With the expected ‘Big Melt’ likely to increase flooding likelihoods across the San Joaquin Valley over the spring and summer, Duarte opened the forum by noting that he pressed the U.S. Army Corps of Engineers to expedite permitting for channel flow improvements by water agencies.

  • “I would encourage anyone who can to move ambitiously on this opportunity. There may be some Federal grants available, but the diesel is going to be cheaper than the biologists later,” Duarte said. “So get busy.”
  • The freshman Republican congressman stressed that bringing California’s water security conversation to its urban hubs in the Bay Area, and particularly Southern California, should center around its ability to relieve housing affordability through the creation of new, available 50-year water supplies.
  • He added that the dream list of water projects – from proposed new dams to raising pre-existing reservoirs – would run the state roughly $12 billion.
  • “I’m in favor of the Federal government and the state government paying for it. California had $31 billion in unemployment fraud during COVID. California’s paying $120 billion for a bullet train nobody’s going to ride. It’s currently flooded, it’s a bullet boat. [Gov. Gavin Newsom’s] gonna go from Woke Moses to Woke Noah this summer,” Duarte said.
  • “The money’s there. There’s a definite sentiment in at least part of Congress, and I think it’s spreading. I think there’s a lot of urban legislators that are Democrats that are starting to wake up and find out that our water scarcity in California is really hurting working families up and down the state. Without water abundance we will never have affordable housing for working families in California again.”

Reality check needed: Michael, a member of a litany of water organizations and chairman of the San Luis-Delta Mendota Water Authority, pressed for an all-of-the-above approach to the state’s water fluctuations, acknowledging the need for groundwater recharge while boosting above ground water storage.

  • “It makes me nervous a little bit that some of the NGO community is highlighting groundwater recharge as strongly as they are. Not that I don’t think it’s valuable. But in some ways, it’s kind of a head fake. It’s this shiny object that’s going to solve these problems. It’s going to solve some problems, but [the Water Blueprint for the San Joaquin Valley] has done a great job of pointing out the deficit in the Valley of water and the only way out of that is from above ground storage.
  • Michael singled out Shasta Dam as the poster child for the tug of war.
  • “There’s this opposition to raising Shasta, which is just insane. It was designed to be bigger and it’s a key component of our system. That reservoir has essentially been hijacked,” Michael said. “That reservoir will never be drawn down below 1 million acre-feet any more. We saw that last year when the Settlement contractors, who were supposed to get 75 or 100 percent of their supply got 18 percent At the same time, there was 1 million acre-feet more of water in Shasta than in 1977.”

Embracing recharge: Freshly-minted Westlands Water District executive director Allison Febbo noted that the nation’s largest agricultural water district is focused on tackling water scarcity by leaning into efficiencies while rapidly embracing in groundwater recharge, a top priority of the district.

  • “What we need to do is be able to recharge and really squirrel away the water when we have this abundance of water that we’re seeing right now we need to be able to take that and save it for the future,” Febbo said.
  • “Westlands has gone from zero recharge to right now over 1600 acre feet a day of recharge, and we’re hoping to get to over 65,000 acre feet of recharge in the next month or two, possibly more.”
  • Febbo added that a collaborative approach was the route to strengthen water security in the Valley.
  • “This isn’t something that can be done by just one water district or one water agency or even one region, this is really a statewide solution where we need to be collaborating with each other, partnering with each other, and moving away from this ‘If I win, you lose’ or ‘If you win, I lose’ mentality,” she said. “We need to be collaborating together and finding multifaceted solutions for these problems.”

A call-to-action: Jason Phillips, the chief of the Friant Water Authority, laid bare the deficiencies in securing increased water supplies for central California, calling on farmers to utilize their voices for targeted investments.

  • “I would say that we need to understand something very clearly: we have failed miserably for 40-plus years at generating new water supplies and constructing anything. We’ve gotten nothing done for new storage. So, we need to be very careful when we say ‘We need to build new storage.’ We’ve been saying that for 40 years,” Phillips said.
  • “We failed with CALFED, which was a President Clinton and Governor Gray Davis joint proposal to build five new reservoirs, none of which happened. That was 23 years ago,” the Friant chief said. “[2014’s] Prop. 1 was a failure. It passed, but it has not been building any new storage.”
  • “When we talk about what we should be focusing on, the only people who should be focusing on storage is Congressman Duarte and others who can write into law that you are going to go get it done. Because the environmental community and the current people that run this government, they have our number. Checkmate it every time. They will make sure we don’t build it, no matter how smart or how good we think we’re going to get it done.”
  • “We need to get more sophisticated at how we can go and actually start building water supply. The most important infrastructure that we need is infrastructure of advocates and advocacy to be able to use our existing project facilities. The reason we failed for the last 40 years and depressing as it might sound we might fail for the next 40 is because we’re not able to sit up here and articulate quickly enough – because it’s so complicated in California – why we’ve lost so much water.”
  • “In 2008 and 2009 there was a biological opinion that was forced upon us by government employees – not Congress – that cost us more water than five Temperance Flat Reservoirs would have produced like that. Gone.”
  • Phillips turned the table on professional advocates, lawyers, and lobbyists working on behalf of water agencies and grower groups who have insufficiently fought onerous water cutbacks.
  • “Most of [the 2008/2009 biological opinions], you were all paying someone who agreed to it. That was our advocacy. You were paying somebody to agree to give up water on an order of magnitude that far exceeds any storage projects we’ve built,” Phillips said.
  • “The hardest thing is that the government employees using the Endangered Species Act and other laws to take our operation of existing projects and constantly tweak it to send more water out to the ocean – and it’s not instead of what they were sending, it’s always on top of that.
  • “We will have choices to make: do we want to advocate against that? Or do we want all of who you’re paying for to go sit at the table with the government to agree to give up more of our water?”

Rethinking the Calif. equation: Ryan Jacobsen, the Fresno County Farm Bureau boss, noted that the state needed a reality check to its once-simple water equation of 50-40-10, meaning 50 percent of water went to environment, 40 percent of water went to agriculture, and 10 percent to municipal and industrial water users.

  • “That’s no longer true. Today, those numbers are 80.5 percent of the water in the state of California goes toward environmental purposes now. Of that, 50 percent of that is uncaptured in the environment, 30.5 percent is captured and stored for the environment. Fifteen percent of the total supply is now going toward agriculture, and 4.5 percent is the urban share,” Jacobsen said, citing a new study from the California Farm Bureau Federation.
2023-05-11T15:10:38-07:00May 11th, 2023|

Westlands Water District Celebrates 100% Water Allocation from the Central Valley Project

Today, the Bureau of Reclamation (Reclamation) announced an increase in water allocations for the Central Valley Project (CVP). Last month, Reclamation increased the CVP allocation to 80% for contractors like Westlands Water District (Westlands) following an initial allocation of 35% of the water entitled to under contract. Today’s announcement brings the total up to 100% for the first time since 2017.  


In response to the announcement, Jose Gutierrez, Westlands’ interim general manager, issued the following statement: 


“We are exceedingly grateful to Reclamation, and its dedicated and hard-working staff, for the increased water allocation. Following two years of 0% allocations, this announcement will provide much needed water to support the District’s communities, family-owned farms, and hard-working families in the San Joaquin Valley. This water supply will assist growers in Westlands with putting the land to work to grow the food that feeds the world.” 


Mr. Gutierrez noted further: 


“At the same time, we must recognize the need to continue preparing for the next drought and future dry years.  For that reason, Westlands  is investing in a sustainable water future for our farmers.  Westlands is exploring and implementing creative approaches to maximize water use efficiency, recharge and storage and improve climate resilience.”  


Seizing the opportunity that this year’s hydrology has presented, Westlands has supported its landowners’ efforts to use available water to recharge the Westside Subbasin.  To date, District landowners have the capability of recharging up to 3,300 acre feet of water per day. And, groundwater recharge is expected to increase over the coming weeks as both more projects become operational and water becomes available.  


This year demonstrates the need to continue the investment in California’s water infrastructure and to refine environmental regulations, so that California is able to capture, transport, and store as much water as possible during wet periods to avoid drastic cuts during dry periods.  As climate continues to change, we must remain steadfast in investing in a more predictable and reliable water supply system for our environment, residents, farms and communities. 

2023-04-24T09:58:15-07:00April 24th, 2023|

Study offers insights on reducing nitrate contamination from groundwater recharge

By Mike Hsu

With California enduring record-breaking rain and snow and Gov. Gavin Newsom recently easing restrictions on groundwater recharge, interest in “managed aquifer recharge” has never been higher. This process – by which floodwater is routed to sites such as farm fields so that it percolates into the aquifer – holds great promise as a tool to replenish depleted groundwater stores across the state.

But one concern, in the agricultural context, is how recharge might push nitrates from fertilizer into the groundwater supply. Consumption of well water contaminated with nitrates has been linked to increased risk of cancers, birth defects and other health impacts.

“Many growers want to provide farmland to help recharge groundwater, but they don’t want to contribute to nitrate contamination of the groundwater, and they need to know how on-farm recharge practices might affect their crops,” said Matthew Fidelibus, a University of California Cooperative Extension specialist in the UC Davis Department of Viticulture and Enology.

A recently published study by UC scientists sheds new light on how nitrates move through an agricultural recharge site and how growers might reduce potential leaching. Researchers analyzed data from two grapevine vineyards at Kearney Agricultural Research and Extension Center in Fresno County – one flooded for two weeks, and other for four.

Understanding initial nitrate levels crucial

A key factor in mitigating contamination is understanding how much nitrate is in the soil at the outset, said study author Helen Dahlke, a UC Davis hydrologist and leader of UC Agriculture and Natural Resources’ strategic initiative on water. In areas with little precipitation and cropping systems that require greater amounts of synthetic fertilizer, the accumulation of residual nitrate – resulting from nitrogen in the fertilizer not taken up by the plants – can be quite high.

“The percentage of nitrates in some soils can really increase over the years, particularly if you have many dry years in a row where you don’t have access to irrigation water or natural precipitation flushing some of those nitrates out of the soil,” Dahlke said.

While intense rains in recent weeks have helped dilute nitrate concentrations naturally, farmers looking to participate in recharge during the dry years ahead should consider flooding their fields with greater volumes of water.

“If you’re doing this for the first time – on-farm recharge in the winter – check your residual soil nitrate levels because if they’re very high, you should apply a lot of water in order to make sure that the residual nitrate is diluted down,” said Dahlke, who also added that growers should check their soil properties for suitability of recharge projects.

She recommended using, as a “good first approximation,” the online Soil Agricultural Groundwater Banking Index map, a project led by Toby O’Geen, a UC Cooperative Extension soil resource specialist.

Researchers looking at other ways to reduce nitrates

Even before flooding the fields for recharge, there are several practices that can lower initial nitrate levels and risk of leaching. Cover crops such as alfalfa and triticale, for example, can help take up residual nitrates that accumulate from fertilizing a main crop over time.

Dahlke and Fidelibus – a co-author of the San Joaquin Valley vineyard study – both pointed to pre-flooding irrigation that encourages denitrification, a process in which soil microbes transform nitrates into gaseous forms of nitrogen.

“Those denitrifying microbes need to be stimulated to do the work,” said Dahlke. “What we have found is that if you do a little bit of irrigation before you start the flooding, increasing the soil moisture can get those microbes started and they can take out more nitrate from the soil.”

The timing and quantity of fertilizer applications are also major factors in reducing leaching. Although more growers are following high-frequency, low-concentration practices to maximize uptake by crops, Dahlke said there needs to be more emphasis on incorporating nitrogen transformation processes – such as denitrification – in the nutrient management guidelines that farmers follow.

“Implementing thoughtful nutrient management plans will play a particularly important role in participating farms,” Fidelibus added.

A more holistic view of groundwater recharge

In short, choices made during the growing season can affect those in the winter recharge season – and vice versa. For example, applying compost or other organic amendments to soil can give microbes the “fuel” they need for sustained denitrification.

“What we have found is that our denitrifying bacteria often run out of steam because they don’t have enough carbon to do the work,” Dahlke said. “Like us, microbes need energy to do the work, and for microbes this energy comes from soil carbon.”

Then, adding moisture via recharge to that field with high organic content can stimulate mineralization and nitrification, processes in which microbes transform the organic nitrogen into ammonium – and subsequently nitrates – that the plants can then take up. Those naturally occurring nitrates would thus reduce the need for the grower to apply synthetic fertilizer.

“The winter on-farm recharge experiments have shown that altering the moisture regime in the winter has consequences for the nitrogen budget in the summer growing season,” Dahlke explained. “Theoretically, what we need to be doing is better integrating both seasons by keeping an eye on the soil-nitrogen balance across the whole year so that we can ensure, at the end of the growing season, the residual nitrate in the soil is minimized.”

The study, published in the journal Science of The Total Environment, was part of the post-doctoral work of former UC Davis researcher Elad Levintal. In addition to Fidelibus and Dahlke, other authors are Laibin Huang, Cristina Prieto García, Adolfo Coyotl, William Horwath and Jorge Rodrigues, all in the Department of Land, Air and Water Resources at UC Davis.

2023-03-23T08:08:07-07:00March 23rd, 2023|
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