What’s the Potential for Increased Groundwater Replenishment in California?

The Santa Ana River feeds adjacent groundwater recharge basins in Anaheim.
Florence Low / California Department of Water Resources

Panel at ACWA highlights state efforts to scale up Flood Managed Aquifer Recharge, survey on groundwater recharge in the Central Valley, and ACWA’s groundwater replenishment initiative

With implementation of the Sustainable Groundwater Management Act (SGMA) fully underway, the newly formed Groundwater Sustainability Agencies (GSAs) now turn their attention to developing Groundwater Sustainability Plans (GSPs) for their basins.  For basins that are critically overdrafted and many others, bringing groundwater basins under sustainable management while maintaining current acreage in production means finding a way to recharge their basins.

At the the recent ACWA conference, a panel of groundwater experts discussed the potential for increasing groundwater recharge across the state.

On the panel:

  • Kamyar Guivetchi, manager of Statewide Integrated Water Management from the Department of Resources;
  • Sarge Green, a member of the Research Network with the Public Policy Institute of California and the Water Policy Center;
  • Timothy Parker, Executive Director of the Groundwater Resources Association; and
  • Eric Averett, General Manager of the Rio Bravo Water Storage District and vice-chair of ACWA’s groundwater replenishment initiative.

KAMYAR GUIVETCHI: Scaling Up Flood~MAR: An Integrated Strategy of Flood, Groundwater & Ecosystem Management

Kamyar Guivetchi, manager of Statewide Integrated Water Management from the Department of Resources, began by pointing out that California water is a tale of two extremes, which, as a Mediterranean climate in and of itself is not unusual.  However in recent years, those extremes have become more consequential.   There was the five-year drought followed by the wettest year on record, and all indications are that with climate change and the diminishing snowpack, that those extreme events are going to become more frequent and deeper and more extreme.  This really requires that we rethink the way we manage California’s water resources, because snowpack has been and is still our largest surface reservoir, he said.

The concept of Flood Managed Aquifer Recharge, or Flood MAR, is somewhat straightforward: Use floodwaters to recharge groundwater while getting environmental and ecosystem benefits.  Kamyar called it a ‘moon shot,’ (meaning: an ambitious, ground-breaking project undertaken without any expectation of near-term profitability or benefit and also, perhaps, without a full investigation of potential risks and benefits.)

It will require some foundational, institutional, and changes in practice of managing our water,” he said.  “Traditionally we’ve managed our water supply and water resources in those outer circles, somewhat in silos, and now we have to find projects that are providing multiple benefits and lie more in the center circle and get as many of those overlaps of those different sectors as possible.”

SGMA has really enabled the state to become a strong partner in scaling up and advancing a Flood MAR strategy.  SGMA has now reconnected the water cycle in California both hydrologically and institutionally  for the first time after 200 some years of having surface water rights system, and now the state is poised to be able to make the types of changes in our water management that would enable more aggressive Flood MAR strategy implementation, he said.

The Department of Water Resources released the Water Available for Replenishment report in draft form in the spring for comments; the final report is due to be published in the upcoming weeks.  The report estimated that there was about 1.5 MAF per year available, but that amount is distributed quite differently in different regions of California (as shown in the pie chart).  Mr. Guivetchi noted that ironically, the areas that have the greatest challenge from a groundwater perspective are the areas where the water available for replenishment is the least.

The above hydrograph shows how DWR staff determined the estimates; Mr. Guivetchi explained that the bottom line is the minimum instream flows and the top line was determined by the maximum amount of current infrastructure and institutional arrangements that was available for getting surface water into groundwater basins.

He also pointed out that Flood MAR has the benefit of reducing flood risk.  As the the climate warms and the snowpack melts earlier, there will be higher and more flashy flows in the rivers which will increase flood risk, so Flood MAR can provide the benefit of reducing that risk.  In the 2017 update of the Central Valley Flood Protection Plan, this strategy is called out amongst a portfolio of actions, he noted.

Several years ago, the legislature directed DWR to undertake a system reoperation study to estimate how much more water could be made available if there were more conjunctive water management and the State Water Project and Central Valley Project operations were more consolidated.  In August, DWR completed the third phase of the system reoperation study.

What we basically concluded is that our system is pretty well optimized,” said Mr. Guivetchi.  “There’s not a lot more that can be had from the system.  We looked at operating the CVP and the SWP as one project, and found that we might be able to get 100,000-150,000 AF more yield per year, with the footnote when we talked with the operators of the system, they said, actually informally they have been doing the types of things explored in the system reoperation study, so some of those benefits have already been occurring.”

ACWA then conducted a storage integration study using much of the same analytical framework DWR used in the system reoperation study and then added additional groundwater and surface water storage.  “They estimate that with more conjunctive water management, maybe we could add another 3.5 MAF per year of additional flexibility and water reliability in the system.  This will help feed into the implementation of Prop 1 water storage investment program, because many of the facilities that the ACWA investigation added to the system are ones that have been proposed in the dozen or so applications to the Water Commission.  The Water Commission is now in the process of evaluating those applications.”

Mr. Guivetchi noted that when the legislation for Prop 1 was developed, SGMA had not been implemented, and so groundwater recharge in and of itself is not called out as a public benefit.  “Therefore projects that are solely developed to do groundwater recharge would not be eligible for money from the Prop 1 storage program,” he said.  “I really want to hit home on the term, public benefit, because that’s really what will open the door on getting public funding for projects that will add to groundwater storage and replenishment.”

One of the things that I’ve understood in conversations with water board staff is that the act of recharge for the water board in terms of water rights is storage,” he said.  “In the water rights system, recharge is a storage activity and not a use activity, which is what happens when you extract the water.  I think we’ve been wrapping ourselves around the axle when we say that recharge should be a beneficial use when in fact I think if we say recharge should be considered a public benefit and maybe a non-consumptive beneficial use, we could make more headway in working with the water board.”

Flood MAR is inherently an integrated water management strategy because it requires the flood management community, the groundwater management community, and the ecosystem management community to work across traditional or historical boundaries; Mr. Guivetchi noted that you would have to go out of your way to do Flood MAR and not have multiple benefits.

In this context, Flood MAR is a companion to what is called stormwater management in the urban settings; Flood MAR in this context is water that would be floodwaters that are applied to agricultural and working lands for the purpose of recharging groundwater and providing terrestrial ecosystem benefits, he said.

Mr. Guivetchi then presented the graphic from the Water Available for Replenishment Report, explaining that the flows that Flood MAR is considering on the hydrograph are those above the existing green line.  The goal is to explore the potential to capture some of the high winter flows and sink it into the ground in a way that is not damaging to agricultural production, he said.

Mr. Guivetchi acknowledged he is often asked about the possible negative impacts to fish and flows for fish.  “With climate change, we’re actually seeing a shift in our high flows to earlier in the winter, and less flows in the late spring and early summer, so this hydrograph is actually going to have higher peaks in the winter time and lower flows in the summertime,” he said.  “Even if we just took the difference between what has historically been the winter peak and what climate change is going to confront us with and sunk that into the ground, that would reduce flood risk and would help replenish groundwater without having a significant depletion of fish flows.”

A Flood MAR strategy can provide many benefits, including making sure that agricultural lands and production are not sacrificed as part of the SGMA water budget balancing.  “Without Flood MAR, more focus is going to have to be put on water conservation and at some point land retirement when you’ve exhausted alternative water supplies and water conservation,” he said.  “With Flood MAR, we’re adding a new alternative supply that will help GSAs balance their water budgets more effectively.  Flood MAR is also inherently a climate adaptation strategy because with the changes in the hydrograph that climate change will bring, Flood MAR actually helps us manage that proactively.”

However, there are many aspects, both institutional and physical, that will need to be addressed to really scale up this strategy, he noted.

A number of studies have been done over the past 15 years that most people aren’t aware of, Mr. Guivetchi said.  In 2002, the Corps of Engineers in Davis, did a study that found that by just reoperating the reservoir rule curves, almost 800,000 AF in Sacramento Valley and the San Joaquin Valley could be made available for groundwater recharge.  The University of California in Santa Cruz since 2006 has been doing a pilot project with farmers with a net metering program where they pay farmers for recharging high winter flows, and in some cases, the farmers are making more money than the cost of their groundwater extraction, he noted.  The Central Valley Flood Protection Plan has an entire attachment or appendix on this very topic to show how it could help flood risk reduction.

RMC and the Water Foundation did a study in 2008/2009 where they found that in the Merced, Chowchilla, Fresno, and Kings Rivers, you could get as much as 130,000 AF per year through a Flood MAR approach and it would be cost effective, he continued.  More recently, Sustainable Conservation and EarthGEO have put together a gaming tool to help farmers and GSAs actually determine how much winter flows they could safely put on their various crops for the purposes of groundwater recharge.

DWR has taken the remaining money for the system reoperation study and is going to produce a white paper and a plan of study to advance or scale up Flood MAR.  There is a discussion draft of a white paper that was distributed in November which was released to motivate discussion and get public comments.  DWR is developing a research and development plan of study which they will release in draft form to engender a discussion and gather input to identify what studies have been done and what new pilot projects can be done to get the information needed to safely and rationally scale up this new strategy.

Having an R&D plan and implementing it is going to require resources, so my hope is by engaging a large community in the development of that study plan, we can jointly go and look for multiple pots of money to get those studies and pilot projects done,” concluded Mr. Guivetchi.

SARGE GREEN:  Recharging Groundwater in the San Joaquin Valley: Preliminary Findings from a Survey of Water Managers

Sarge Green, a member of the Research Network with the Public Policy Institute of California and the Water Policy Center, then discussed the results of a recent survey  conducted by the PPIC that asked water managers in the San Joaquin Valley about their groundwater recharge efforts during the very wet year last year, what barriers they encountered, and what is needed going forward in order to accomplish more groundwater recharge in the future.

Mr. Green began with the basics: The San Joaquin Valley is the largest critically overdrafted contiguous area in the state with the exception of portions of Stanislaus County; groundwater withdrawals exceed recharge by over 2 MAF per year.  The San Joaquin Valley has had numerous problems associated with groundwater overdraft, such as dry wells and land subsidence.  Now, with the Sustainable Groundwater Management Act, groundwater must be managed more sustainably.

The balance is either we’re going to have to figure out how to recharge more or we’re going to have to pump less or some combination of the two, so we wanted to find out what it is that we could do and what are some of the barriers,” he said.

The survey included questions about recharge tools, how much recharge was accomplished, and what were the barriers encountered.  Survey respondents included both agricultural and urban water districts that were actively involved in groundwater recharge.  Researchers subsequently held focus group sessions with some of the respondents to discuss the findings.

The survey found that agricultural districts utilized a wide range of methods such as flooding open land, flooding fallowed land, flooding cropland, in lieu groundwater recharge, unlined canals, injections wells, and recharge basins.  Urban districts predominantly utilized recharge basins, in lieu recharge, and unlined canals.  Although recharge basins have been a preferred alternative in the past, other methods are gaining traction, he noted.

The survey also asked if the survey respondents performed recharge for others, or if conversely, if they had recharge done off-site by others (such as a groundwater bank).  The analysis was that most of the recharge that is done off-site by others is mostly in the southern San Joaquin Valley in Kern County, which is probably not surprising given the successful groundwater banking programs in the area, he said.

The good news was that we had 75% of the districts that did report say that they were very involved in active recharge projects, and 75% of those gave some idea of the volumes that they were able to get into the ground this year,” said Mr. Green.  “This year, we found that the total onsite recharge was about 1.4 MAF, and off-site recharge was about 500,000 AF.  So we really had a good year.  Now you put that in context with the 2 MAF that we’ve been overextracting every year, we’ve just caught up for two years.  We took care of this year’s water, and one of the prior year’s, so we’re still behind the eight ball.”

Most of the recharge occurs in the San Joaquin Valley in Kern County, with significant recharge also occurring in Eastern Fresno and Tulare Counties.  Mr. Green noted that the other areas aren’t all that active as they don’t necessary have the recharge areas nor the water, and amount of the recharge is absolutely connected to the surface water supply.

He then presented a chart showing average volume by method used (above, right), stating that recharge basins stored the most water and the off-site by others was mostly the Kern County area.   Other methods, such as open space, fallowed land, crop land, in lieu, and unlined canals do not have any direct data available.  More data is needed for these other methods, he said.

Infrastructure issues were the most significant barriers to recharge this year, he said.  “The number one problem in all the surveys was capacity to sink the water in, but capacity was really the conveyance.  While the basins are always expensive to build, we don’t have enough conveyance  both system conveyance and district conveyance.”

The system conveyance issues included the Friant-Kern Canal and the California Aqueduct; the Friant-Kern Canal could not deliver enough floodwaters because of the subsidence area down in southern Tulare County, and similarly, the California Aqueduct lost capacity in the Kettleman City area.  There were also district-level conveyance issues so more investment is needed to better connect the supply of floodwaters to recharge areas, he said.

There were other problems that were somewhat dependent on whether it was ag or urban.  “With ag, the second largest problem was farm-related, and that split out into two things: lack of an irrigation system that could deliver volumes of water and concerns about the cropland or crop impacts.  Flooding certain crops will kill them, so more research is needed on the impacts of flooding croplands.”

Other problems cited were funding barriers and regulatory barriers.  Mr. Green acknowledged that funding is always a challenge, but they were somewhat surprised that regulatory barriers didn’t score higher.  He attributed it to the extremely wet year where there was plenty of water and everyone worked hard to get into the ground, but in normal water years, he suspects that regulatory barriers will present more of a problem.

Managers also emphasized capacity improvements as top priorities for action.  “Once again, capacity came up as number one,” he said.  “We’ve got to figure out how to move the water around, whether it’s in the flood management process, whether it’s wet year water, whether it’s normal year water – if we’re going to meet the intent of SGMA, we’ve got to figure out the capacity issues and work on them.”

Regulatory barriers were rated higher with water managers, but Mr. Green said the big surprise was how often planning was cited.  “Planning was a big issue,” he said.  “We don’t have enough coordinated planning yet to be able to do some of these things, so there’s going to have to be a meeting of the minds to figure out how to collectively work better together.

Mr. Green then gave his takeaways.  “Many districts in the San Joaquin Valley can recharge, but they are the districts with the biggest water supplies,” he said.  The smaller districts that don’t have much water, also don’t have much opportunity to recharge.  Interest is expanding and we want to expand recharge wherever we can, and so we’re going to have to work on figuring out the capacity, funding, and regulatory issues, and dive deeper into them and get them cleaned up.  At least in a wet year, capacity constraints were larger than the regulatory issues.”

SGMA is a game changer,” he continued.  “We’re going to have to be better at accounting for recharge, so whether it’s in lieu, whether it’s canals, basins, farmland, whatever it is, we’re going to have to do a better job.  Water has entered big data.  We’re going to have to have better data platforms to be able to deal with the large amount of information, because this isn’t the only program that’s bringing data into the water management picture.”

SGMA will encourage joint programs and opportunities for some districts who have good water supplies but cannot recharge for themselves to partner up on the off-site process,” he said.  “There could be a lot more of that if we do it right, so it gets back to some of the regulatory issues might be one of those challenges, and as well as capacity.  Having moved water that’s already gone downhill and getting back to a recharge area that may be upslope, so it’s both capacity and regulatory, but always money.”

TIMOTHY PARKER: Call to action to recharge depleted aquifers

Timothy Parker, Executive Director of the Groundwater Resources Association, began by stating that the mission of the Groundwater Resources Association of California is that they are dedicated to resource management that protects and improves groundwater supply and quality through education and technical leadership.  He noted that his work for the Groundwater Resources Association is a passion and a volunteer position; he is also a groundwater management consultant.

Many of us are on the same page in terms of realizing that we need to do more for recharge,” he said.  “My main message is that we can do more, we need to do more, and we will do more.”

Groundwater faces a quadruple threat: increase in demand, less surface water available, land use changes, and rainfall intensity which translates to less groundwater recharge.  “We’ve been very good at pulling it out of the ground,” he said.  “We just need to crank down and find out how we can do more in terms of putting it back into the ground.”

In order to do Managed Aquifer Recharge, you need source water and a water right; conveyance and infrastructure such as reservoirs, dams, aqueducts, canals, ditches, and pipes; and a way to get the water into the ground, such as spreading grounds, low impact development facilities, or other appropriate site-specific methods of recharge.  In lieu recharge, or substituting surface water for groundwater should also be considered.  A legal and regulatory framework that facilitates recharge while protecting water rights is also needed.

In terms of the science, there needs to be adequate infiltration rate; you need to understand if there are subsurface materials that might impede the water; and you need to about the hydrologic properties, such as the vertical interconnection and mapping of the soil and geology.

For shallow, you can start with trenching, something really cost-effective, and do some infiltrometer testing to understand the soils,” Mr. Parker said.  “Going deeper you get into more holes and more expense, but again you can do instrumentation and test to understand the geomechanics and the physical properties of the soils.   Then do pilot testing, so then once you’ve done the little tests, you need to go out and really do some large scale testing, whether that’s wells or impoundments.”

The Santa Clara Valley Water District was among the first who started doing recharge back in the 1920s-30s after experiencing land subsidence and inundation in the San Francisco Bay Area; they recharge around 200,000 acre-feet per year.  The MAR facilities with the Water Replenishment District and LA Department of Public Works, combined with Orange County, have about 300 seawater intrusion barrier wells; these wells function effectively as managed aquifer recharge along the coast; facilities include spreading grounds and associated facilities and they recharging about 150,000 acre-feet a year.

The Orange County Water District has the groundwater replenishment system, which is currently at 100 MGD and they are expanding to 130 MGD; they are recharging on the order of 200-250,000 acre-feet per year in their facilities.

The increased interest in groundwater recharge is a result of enduring the five driest years on record, followed by the second wettest year on record, climate change, Cal Water Fix, and politics, with SGMA being a big driver, Mr. Parker said.

The Groundwater Resources Association and UC Water recently held a roundtable, where it was suggested that overdraft could even be higher than first thought, on the order of 5 to 10 MAF a year over the last ten years; and overdraft can only be reduced by reducing discharge or increasing recharge, he said.  There were estimates that 2.6 to 2.8 MAF of floodwaters a year could be available, so conveyance and reservoir reoperation is needed to help move that water around.

One of the challenges in the Central Valley is that the aquifer systems are semi-confined with clay and silt layers that impede recharge, so knowing the underlying geology in the basin is important, he said.  He explained that during the late Pliestocene, a lot of ice that melted very quickly, and seawater was about 300 feet lower, so the baseline of erosion was much stronger and when the ice melted, it incised a number of channels.

These channels are good areas to recharge and that provide regional benefits; he presented some graphics (above) showing the known incisions in the King’s River system and the Modesto formation.

There are emerging technologies to help determine the underlying geology in a basin.  In the Indian Wells Valley, they are using Danish technology called aerial electromagnetics, which uses a big coil flown around by helicopter to do data collection.  There are currently three basins utilizing the technology and it looks like the DWR will be developing a best management practice for how to apply this more widely in the state.

It was $150,000 to fly 800 miles to do the data collection and another $150,000 to do the evaluation and get a revised conceptual model, but it can tell us a lot more about the subsurface and where the best recharge areas are and where there are structures to be concerned about and just get a better understanding of the geology,” Mr. Parker said.

Another challenge is the legal uncertainty for diversion, storage, and recovery, as other speakers have noted.  Mr. Parker also said that recharging the groundwater basins on the scale we need to is not going to be done by a small number of big projects, but rather it’s going to have to be a lot of projects, small and big.  “It’s a shift in thinking,” he said.  “We need to maximize recharge in the future to balance our water budgets in these basins that are out of balance.”

The Groundwater Resources Association is working with UC Water and with a number of different organizations.  The actions they are working on are:

  1. Quantity, timing and location of water available for recharge
  2. Technical challenges to capturing, releasing and moving water to recharge locations
  3. Recharge location suitability and quantity
  4. Legal and regulatory framework for allocating, recharging and recovering MAR water
  5. Incentives to facilitate many, many MAR projects and actions short-term
  6. Adequate recharge quantification – Mr. Parker noted that you need to do the science so you really understand how much water and you can account for it
  7. Potential water quality impacts from MAR – He said that groundwater can be impacted if you don’t do it right; for example, if there are areas with arsenic in the materials and you add oxygenated water to it, it can release arsenic.
  8. Expansion of conjunctive use and in lieu to increase recharge

Mr. Parker then concluded with what they have learned so far.  “We know we have to be smart to invest in the best opportunities, and some locations may be better for regional benefits,” he said.  “We need a lot of projects in the Central Valley and especially the San Joaquin Valley so how do we incentivize to do as much as we can.  We need the legal and regulatory framework for permitting that’s flexible and floodwater opportunity recognition and process, and then funding and finance … there’s SB 5 that’s headed to the ballot in the spring of 2018 and there’s another water bond that’s an initiative, that’s on the order of $9 billion for water that will hopefully end up on the ballot in the fall.

Agriculture and water industry are resilient,” he said.  “We can do this and lead to the future.  One of the things we are considering is whether or not we should set the statewide goal for recharge, much like the conservation.

ERIC AVERETT: The potential for increased groundwater replenishment

Eric Averett is the General Manager of the Rio Bravo Water Storage District and vice-chair of ACWA’s groundwater replenishment initiative.  He began by displaying a visual from Indiana Jones, the Temple of Doom, and said he felt it’s a good description of how most GSAs feel about developing projects and having to decide whether demand reduction or supply augmentation is the route they are going to take.

In this particular scene, he walks out to the bridge and finds challenges in both front and behind, and I think that’s true of the GSAs as they develop their GSPs,” he said.  “Today we’ve heard about a number of studies that have been done that identify a wide range of water supplies.  I’m in the Tulare Basin, and DWR WAFR report came out estimated about 30,000 AF of water supplies available for recharge in our basin; that’s about 7% of our annual overdraft, so that’s really not helpful.”

Then the ACWA study determined there could be 400,000 AF and the PPIC study said that there’s potentially even more than that, he said.  “How many of you, after hearing these numbers, have the ability to walk away and go to your GSP planning groups and say, I know what we’re going to do for supply augmentation?” he said.  “Probably not, because these studies don’t get into the local context; they identify opportunities.  The ACWA initiative is intended to take some of that information and stand on the shoulders of it, and then working with local and regional stakeholders to identify potential projects and opportunities that maybe you can pull into your GSP planning effort.”

The initiative is focused primarily on the Central Valley because that’s where the it’s needed most.  Mr. Averett noted that the amount of overdraft to amount of supply was inversely proportional between the amount of the supply in the Sacramento Valley and the amount of overdraft in the Central Valley, and so he views it as a unique opportunity to partner with those that are in the Sacramento Valley to develop working relationships that are mutually beneficial.

The goals of the initiative are to:

  • Identify the potential absorptive capacity, including direct and in-lieu recharge, within key geographic regions (central valley etc.) for purposes of maximizing deliveries of high-flow water supplies for groundwater replenishment.
  • Identify and document conceptual or emerging projects and programs, and the estimated quantities of water available and timeframe for significant groundwater replenishment in the south San Joaquin Valley.
  • Identify promising state and federal funding programs and actions in support of local and regional SGMA GSP efforts, with a focus on increasing groundwater replenishment, at a basin and sub basin scale to deliver sustainable groundwater management.

Mr. Averett said that one of his local water managers has lamented that he does not understand why they have dry recharge basins and somebody’s losing water in the system.  “So the idea of this initiative is to bring those diverse interests together and cross the supply boundary that sometimes we exist in, whether it’s a local supply, a federal supply, or a state supply, so we need to start thinking globally and the goal of the initiative is to allow us to do that,” he said.

The ACWA initiative will also look at potential funding programs, consider existing and potentially new water banks, and utilize modeling and tools if and when necessary.  The ultimate work product will be a report with implementation recommendations, working with local stakeholders to develop these project concepts and technical memos if and where needed, he said.

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