CA WATER COMMISSION: Advancing Flood-MAR: What are the possibilities?

Dr. Graham Fogg and DWR’s Jenny Marr discuss the efforts underway to assess the potential for Flood Managed Aquifer Recharge (or Flood MAR)

At the April meeting of the California Water Commission, the Commission continued examining the state’s role in conveyance projects by hearing from two experts on flood-managed aquifer recharge, or Flood MAR.  First, Dr. Graham Fogg, UC David professor emeritus of Hydrogeology, discussed scaling up Flood MAR and how that will likely present new conveyance needs.  Then, Jenny Marr, Supervising Engineer at the Department of Water Resources, outlined the state’s approach to flood Mar.

GRAHAM FOGG: Flood-MAR Perspective: American-Cosumnes Basin Experience

Dr. Graham Fogg’s presentation gave the big picture perspective on Flood MAR and highlighted a case study underway in the American-Cosumnes basin as part of a UC Water initiative since 2014.

He began by pointing out California is not alone in having groundwater problems.  Groundwater depletion is a global problem. Depleted aquifers are being increasingly written about all over the world. In some cases, it’s becoming an existential crisis in water security.

Why is that? Dr. Fogg noted that since we’ve been developing groundwater, which has only in the last 50-70 years at high amounts, we’ve concentrated mainly on pumping it.

Typically, we pump the groundwater and hope for the best,” he said.  “The alternative in terms of managing it, now we can pump groundwater, is that we can also do things that increase the groundwater storage; we can replenish the groundwater. So one way to look at it is we’ve worked a lot harder in the last 50 years or so in pumping groundwater than we have in replenishing it.”

Replenishing groundwater is becoming a worldwide trend, and California is at the forefront of it, working to improve groundwater recharge and conjunctive management of groundwater and surface water.  However, we’re just starting to get good at it, he said.

The snowpack historically, on average, is about 17 million acre-feet, total reservoir capacity in California is about 42 million acre-feet, and the total unused storage capacity in the aquifers in the San Joaquin Valley because of groundwater depletion is 140 million-acre feet.  So while flood MAR can apply broadly, the big opportunities for Flood MAR are in the Central Valley.  

So if we’re talking about water storage, and water storage is key to water security, the big element there is the groundwater storage and in particular the unused groundwater storage,” said Dr. Fogg.  “So one of the goals of initiatives such as Flood MAR is to look at how can we use that giant, relatively unused reservoir that’s being used more as a depletion reservoir than as a storage reservoir.  These numbers and a lot of the rationale behind them can be found in the UC Water-California Groundwater Resources Association publication, Recharge Roundtable Call to Action: Key steps for replenishing California’s groundwater.”

There are four significant storages for water in California: 

  • Snowpack: which is diminishing and melting sooner because of climate change
  • Mountain groundwater: There is groundwater in the mountains, but it isn’t managed much
  • Surface reservoirs
  • Alluvial groundwater basins, such as the massive groundwater system beneath Central Valley and other alluvial valleys.

In the past, we’ve mainly managed the surface reservoirs, but we haven’t really proactively managed most of the alluvial groundwater reservoirs.  SGMA is gradually changing that, but it’s a key challenge.

The two largest water storages are the surface reservoirs and groundwater basin. A key challenge is to get a lot better at managing them together. It’s like teamwork, and there hasn’t been a lot of teamwork between surface storage and groundwater storage in our management schemes, he said.

Just as a reminder, 97% of all liquid freshwater on earth is in groundwater, so groundwater is always the big reservoir,” said Dr. Fogg.  “The counterintuitive thing is we can only pump a fraction of that without causing bad things to happen – think of the six undesirable results in SGMA.  So you can store a lot of water proactively in groundwater, but management can be a little tricky. The technology to do it is there. It’s not expensive compared to surface storage and maintaining a dam, for example, but it can be involved.”

What is Flood MAR?

Flood MAR is a management strategy for using high magnitude flows from rainfall or snowmelt for managed aquifer recharge on agricultural lands.  The concept is that there will be more high-magnitude flood flows from atmospheric rivers in the future and that water cannot be stored, for the most part, in the reservoirs in winter; it has to be passed on through.  So the idea is to route the water downstream and onto agricultural fields to recharge it in winter.  The water can also be routed to spreading basins, such as in Orange County or the Kern Water Bank.

Key considerations are the environmental needs and river flow requirements.  Dr. Fogg noted there is ongoing work at UC Davis and other places to determine how much water is needed in the state’s rivers and streams to sustain environmental flows and ecosystems.

Flood MAR is voluntary, multisector, scalable, and multifaceted; that all sounds great, but it’s also part of the challenge, he said. 

Surface storage is a lot more expensive, but it’s simple,” he said.  “You build the dam, the politicians cut the ribbon, get their photoshoot, and then there’s money to maintain and distribute water and so on. But in terms of creating the resource, you’re done. With Flood MAR, you have to mobilize 1000s of people. So that voluntary part is great. But to get it to work on the scale that would create a big dent statewide, you need to mobilize and incentivize thousands of people.”

Flood MAR is a different strategy. It’s essential to understand all the things that need to be considered, such as the ecosystem, flood control, water quality, water rights, water supply reliability, and getting access to the land to put the water on.

Case study: American-Cosumnes basin

Dr. Fogg then briefly discussed a case study of the American-Cosumnes basin funded by UC Water and the Agricultural and Natural Resources Division of the University of California.

I’m going to show you that the Flood MAR potential is very high,” he said.  “Before you go and invest in some complicated thing, you need to have some idea of what’s the potential payoff. And that’s what I try and provide with this work. What’s the potential payoff of this is.  It is high. However, this is a basin that is not limited by conveyance. So this is a good example of a case where, if you have the conveyance, of what potentially one could do.   The other thing about this basin is there’s a lot of water compared to the Southern San Joaquin Valley. So, this is also an example of how much water could put in storage when you have the water to store.”

The main mechanisms for Flood Mar are recharging or irrigation on ag lands; winter recharge ponds sited strategically based on the soils, the geology of the aquifer system and the depths of the water table; and floodplain inundation.

People don’t often think of it, but Dr. Fogg said when the Yolo Bypass floods, it’s a prime example of floodplain Flood MAR.  It recharges groundwater to the benefit of Yolo County and, to some extent, Sacramento County.

The key ingredients for success

Knowledge of the amount of water hydrologically and legally available for recharge in the various basins

Knowledge of the best sites for recharge; access to sites:  Dr. Fogg noted that it isn’t necessarily limiting if you don’t know what the best sites are.  “When California switched to irrigation in the Central Valley, the groundwater recharge increased by at least a factor of three, maybe a factor of 10. What does that mean? Well, irrigation over broad areas of the landscape increases recharge.  So if you have the water to recharge, it is good to know where best to put it. But there’s typically going to be places where you can put it that will achieve benefits.”

Adequate conveyance

Incentivization of recharge projects: “You have to mobilize thousands of people, not just a handful of entities. And by people, I mean individual landowners agencies, GSAs and irrigation districts, and so on.”

Operating the groundwater ‘reservoirs’ in concert with surface reservoirs: “This is something that civilization is just starting to come to grips with. Typically they’ve been managed separately; they need to be managed in concert. There are big benefits to be gained from that.”

Making the groundwater ‘reservoirs’ sufficiently transparent to enable effective management of both water quantity and quality: “Making the groundwater reservoir sufficiently transparent to enable effective management of both water quantity and quality. That’s something that’s happening increasingly. But I think in the coming years, you’ll see some very encouraging developments in that direction.”

The study area is shown on the map.  The American River and the Cosumnes River are combined because those rivers are interconnected to the groundwater basin.  A key feature is the Folsom South Canal, an underused conveyance structure with a capacity of 3500 cubic feet per second, or 7000 acre-feet per year.

He noted that in many watersheds in California, there isn’t the conveyance infrastructure to support Flood Mar yet; in other basins, there is existing conveyance that needs to be updated or that subsidence has caused the conveyance structure to move less water.  Investments are needed to correct these problems, Dr. Fogg said.

Reservoir reoperation 

When I talk to stakeholders in the watershed, one of the things I ask them is, if you could have another Folsom Lake in the watershed without the high cost and environmental damages, would you want it?,” said Dr. Fogg.  “And the answer is yes, of course, we would want it.   There is about a million acre-feet of storage in the groundwater basin between the American and Cosumnes Rivers because of depletion. There hasn’t been dramatic groundwater depletion in this basin, but there has been enough depletion that you could have the equivalent of another Folsom Lake by better utilizing the groundwater reservoir. So we sought to explore how much water could you really get in the ground, given the limitations of the reservoir and the Delta outflow requirements.”

Folsom reservoir operations were remodeled to first maximize total water storage and next to maximize hydropower.  They found that an additional half-million acre-feet of water could be available for recharge; however, groundwater operations could realistically use about half of that.

So in terms of water available for recharge, what we found is there’s a lot of water that could be made available for recharge without violating the Delta outflow requirements in the American River,” said Dr. Fogg.

Recharging groundwater

To understand where to store the water, it’s essential first to understand what the subsurface is like in the Central Valley and many of the state’s other alluvial basins. 

The typical conception of it is shown on the slide, which is a great textbook figure, but the subsurface is nothing like that,” said Dr. Fogg.  “In the subsurface, you see that brown layer in the diagram – that’s called an aquitard. It’s clay or a low permeability bed.  In the subsurface in the Central Valley, most of it is that.  It is an aquifer. There are sand and gravel networks with these fine-grained materials that operate as a very productive aquifer. So it is an aquifer but is not like what people think.”

The slide shows the geologic heterogeneity of the subsurface.  The colors represent different sediment types in the subsurface: the red is gravel, the yellow is sand, and the green and the blue are sediments with silt and clay in them, for which the technical term that geologists use is mud (that’s not a joke, noted Dr. Fogg).  The depiction on the slide is based on about 1100 drillers’ logs in the area and modeling of the three-dimensional anatomy of the system.

If you look at the cross-section, the aquifer portion, shown in red and yellow, makes up the minority,” said Dr. Fogg.  “Internally, most of those gravels and sands are interconnected, so you can get this tremendous aquifer network that functions quite nicely for producing groundwater.”

There’s going to be places where you can recharge much more easily than others,” he continued.  “You can recharge anywhere here. But what we find is that if we recharge on the red zones, in particular, we can get 60 times the recharge rate.”

It’s important to exploit the geologic features for maximizing recharge rates and volumes.  These specific features are predictable in terms of their existence, but where they are located on the landscape is still somewhat uncertain.  However, there’s a lot of work underway to improve the knowledge of the subsurface anatomy of Central Valley, such as the airborne electromagnetic surveys, which will be very helpful for defining the subsurface and places to recharge.

Groundwater reoperation

The study considered how much recharge could be accomplished utilizing farmlands and the geologic features of the basin.   The slide shows land use in the study area, with the different crops shown in various colors. 

When you incentivize recharge, farmers who would do it will regard it as a risk, and the level of risk to them is dependent on the crop value,” said Dr. Fogg.  “So we used crop value to apportion the risk and, in turn, calculated and optimized how much water could be realistically allocated to those different crop types to engage in recharge.  This was all superimposed on a groundwater model.  The C2V-SIM, DWR’s Central Valley groundwater model, was used to model then the recharge, both on these agricultural lands and geologically strategic locations.” 

Study results

So what were the findings?  ” The results of the study found that the average water available for recharge is about half a million acre-feet; for perspective, the state’s annual water deficit is on the order of one to 2 million acre-feet,” said Dr. Fogg.

The modeling analyzed the 20 years from 1984 to 2003 and considered the question, if the reservoir was reoperated using farm recharge and managed aquifer recharge in strategic locations, how much more recharge could be accomplished?  The study found that 50% of the water available for recharge was used, totaling 5.4 million acre-feet recharged over 20 years.  3.7 million acre-feet was stored; Dr. Fogg noted that not all the water recharged will stay in the basin.  There were increases in streamflow of .87 million acre-feet and flow to other basins of .89 million acre-feet.

Regarding the water available for recharge, Dr. Fogg said he was initially skeptical, but MBK, the engineering firm that works at Folsom reservoir, has confirmed the numbers are realistic.

So I think the numbers look big,” he said.  “Do I think we’ll ever achieve that in the basin? I don’t know. Probably not anytime soon. But I think it’s important to recognize that if we really worked at it and wanted to store a lot more water in these basins, we could. These numbers rival the entire state’s water deficit. And it’s just one watershed. So even if we achieve 10% of these numbers, but we did it in multiple watersheds, that could be a big deal.”

There are some caveats, he said.  One is that this basin already has good conveyance, but not all basins do. There’s credible knowledge that the water is hydrologically available for recharge; however, whether the water is legally available is still uncertain.

As far as I can tell, the Bureau is interested in increasing its releases from Folsom reservoir to support recharge,” he said.  “And as long as the Delta outflow requirements in the American River are not violated, it’s my understanding that there’s still strong potential for securing that amount of water to accomplish recharge.”

He also noted there is a lot of water in this basin; the Merced Flood MAR study that the Department of Water Resources is working on has similar numbers.  But he pointed out that as you go further south in the San Joaquin Valley, it’s drier; the watersheds have less water that can be claimed or secured in those basins.  So the further south, which is also where most of the recharge is needed, the water availability is less.

So if you were to accomplish these kinds of results in watersheds further south in the San Joaquin Valley, such as the Kings or the lower San Joaquin, you would likely have to move water through the Delta in winter,” he said.  “That’s where the Delta becomes a critical issue to figure out here. Can you do that? How much can you do it?  And if you can’t do that, you can still do a lot with Flood MAR, but its role in helping to balance state’s water budget would be less.”

He pointed out that the existence of the Folsom South canal is the basis for the benefit, and the emphasis in the study was on operating the surface reservoirs and the groundwater reservoirs together.

The study is ongoing

The work in the American-Cosumnes basin continues today.  The Sacramento Area Flood Control Agency (SAFCA) is now pushing for Flood MAR.  SAFCA has been interested in the study results and how it potentially matches with their objectives, one of which is to retrofit their rim spill reservoirs in the upper watershed to allow more water to be released in the winter to maintain more flood storage in those reservoirs.  Since the water can’t be stored in Folsom, they are pushing for groundwater recharge in the basin as a means of storing the increased winter outflows that would have normally been stored in the snowpack.  This includes pumping water out of Folsom South Canal when it is available and recharging via dry wells.

To be honest, the best recharge locations that are west of there in Sacramento County, the county is already planning to allow subdivisions to be built there,” said Dr. Fogg.  “When you talk to them about how these locations are like the Yosemite Valley of recharge locations in terms of special-ness, their response is that they’ve been planning for 30 years to develop those lands.  But there’s beginning to be talk of perhaps building with green belts and recharging along those green belts as a multi-use approach to that.”

In summary …

Increasing groundwater storage addresses several problems, including:

  • Greater total water stored in watershed; greater water security; less overdraft
  • Groundwater storage is cheaper than building and maintaining a dam
  • Mitigation of effects of overdraft on disadvantaged communities (shallow wells)
  • Mitigation of effects of overdraft on groundwater-dependent ecosystems as more full groundwater systems supports groundwater-dependent ecosystems
  • Potential stabilization of declining groundwater quality from non-point sources
  • Stabilization of declining groundwater quality due to intra-basin salt concentration and redistribution from rocks to the water

Flood MAR has tremendous unrealized potential. Is it a panacea? No. Is it easy to implement? No. It requires mobilizing multiple players, and that’s the challenge,” said Dr. Fogg.  “DWR and Jenny Marr have worked hard to try and create cooperative networks of people that will start moving in the same direction.”

I think it really needs some kind of economic incentivization to get multiple users and stakeholders to move in the same direction.  People who recharge should be paid by how much they recharge. People should also, in an ideal world, pay by how much groundwater they pump. If groundwater pumpers are paying by how much they’ve pumped and being paid back if they recharge, we start to get an economic incentivization framework along the lines of how we do net metering solar metering for domestic home solar. Andy Fisher and Mike Kiparsky of UC Water have a really nice study on groundwater recharge, net metering for the Pajaro Valley.”

Up to 270,000 acre-feet in the American-Cosumnes groundwater reservoir was achieved in this study per year. That’s just one basin. So that’s big. There’s significantly less potential for this in southern Central Valley without moving water south of the Delta and conveyance improvements.”

There’s considerable potential with Flood MAR, but Dr. Fogg added a sobering caveat:  “There are water rights issues to be dealt with.  As far as I can tell, in the American basin for the kinds of waters that would be divertable, from my conversations with SAFCA and others, it does not appear that water rights or securing the permits to divert that water for recharge would be a limiter in that basin.  In other basins, I can imagine that might be a completely different story. I think the State Board should be commended for being proactive on trying to accommodate these needs for granting temporary water rights for recharge.”

JENNY MARR: DWR’s efforts to advance Flood MAR

Next, Jenny Marr, Supervising Engineer at the Department of Water Resources, outlined the state’s approach to flood Mar, discussing pilot projects and funding needs and alignment with other state programs.

DWR’s 2018 Flood MAR white paper stated, ‘Flood-MAR’s potential and value for California is achieved by integrating Flood-MAR with other regional recharge efforts; changing management of California’s water system to better integrate surface water and groundwater; upgrading conveyance, storage, and operations; and considering Flood-MAR’s opportunities as related to water transport and transfers are some of the system integration considerations.’

So the significant statewide potential for Flood Mar is at a system scale,” said Ms. Marr. 

The graphic on the slide is from the white paper and provides some high-level considerations for implementing Flood MAR.  She noted that conveyance is an important consideration, as there is no Flood MAR without getting water to where the recharge will happen. 

Ms. Marr agreed with the previous presenters that governance and coordination is probably the biggest hurdle – landowner willingness and those landowners being compensated and incentivized to participate in MAR programs. What are the needs and opportunities? How do we develop multi-benefit partnerships and agreements? How do we coordinate operations? How do we work through the legal and regulatory framework?

From an engineering standpoint, Flood Mar is doable, but it’s the complexity of the collaboration that it takes that provides a significant hurdle,” said Ms. Marr.

The slide lists some of the potential public benefits of Flood Mar, with those in yellow being the public benefits defined in Prop 1 for the Water Storage Investment Program.

We think there are additional public benefits that a Flood MAR program can provide, such as aquifer replenishment, working lands, preservation and stewardship, and climate change adaptation,” she said.  “Historically, water supply is considered a private benefit. But I think in the context of the human right to water, you could include water supply for basic needs in that public benefit category as well.”

DWR’s Flood MAR program

The Department’s Flood MAR program has three areas in which they need to make progress for Flood MAR to be successful: watershed studies, pilot projects and studies, and guidance and outreach. These activities are interrelated as they provide information and support efforts in other areas.

Watershed studies

The Department is conducting watershed-scale analytical studies to assess climate change vulnerabilities and evaluate potential flood MAR projects for adaptation and greater water resilience, as well as pilot projects at various spatial scales to demonstrate the public and private benefits of Flood MAR. The Department also aims to provide guidance and technical assistance and conduct outreach to landowners, local and regional agencies, non-governmental organizations, and Tribes to advance Flood MAR implementation.

The Merced Flood MAR study is a watershed-scale analysis that integrates technical tools for evaluating hydrology, hydraulics, surface and groundwater management with ecosystem tools that can help identify water supply benefits, flood risk reduction benefits, and ecosystem benefits. 

We’ve adopted some innovative climate change vulnerability and adaptation strategies,” said Ms. Marr.  “We hope that this Merced study provides a model moving forward for looking at integrated watershed planning and management.

The Merced Flood MAR study analysis has three levels:

Level one considers what the Flood MAR opportunities are using existing infrastructure operating under existing operational constraints.

Level two evaluates what more can be achieved using existing infrastructure but modifying operations.  This includes things like Forecast-Informed Reservoir Operations and prioritizing recharge based on different desired outcomes.

Level three expands on level two by evaluating additional or new infrastructure, expanded infrastructure, and recharge capacity.  This will include things such as conveyance considerations, removing bottlenecks, and restoring floodplains.

Currently, the Department is working on level one and getting into level two, so they don’t have all of the findings yet.  The slide lists some of the early conveyance considerations.

From our level one analysis, we noticed that there is significant benefit in just strategically moving floodwaters to unlined distribution systems,” said Ms. Marr.  “A lot of districts do this already as part of their flood operations. But this is only really in high-flow events, and not everybody does it.  But we really see that we can take advantage of strategically pulling water off the system, putting it into unlined canals, and seeing significant flood risk reduction and recharge benefits at the district scale.  Currently, Yolo County has been doing this under a temporary permit, just moving floodwaters into their online distribution system. And they’ve seen significant benefits in their district. And so we’re replicating the same types of benefits in the Merced basin.”

Conveyance availability is a significant consideration.  Flood MAR would divert water in the wintertime, which is typically when conveyance canals are empty and maintenance is planned. So making sure that conveyance is available and there aren’t conflicting maintenance activities for Flood Mar is an important consideration. She noted that even with the pilot projects, they find that districts are interested in doing a pilot project, but there are significant maintenance activities planned, and the canal capacity isn’t available.

Pilot projects

One of the Department’s pilot programs is working with The Nature Conservancy on multi-benefit recharge.  This program evaluates and demonstrates managed aquifer recharge opportunities that deliver habitat for migratory shorebirds, groundwater recharge, and flood risk reduction. This program builds on the Nature Conservancy’s Bird Returns program that creates temporary habitat for migratory shorebirds. It also builds on a Colusa pilot project, which looked at taking the Birds Returns program and adding groundwater recharge and monitoring of recharge benefits of the program.

Now we want to add on that flood risk reduction potential because when we did the first pass analysis of opportunities in the Sacramento Valley alone, it was hundreds of thousands of acres that could be enrolled in some type of Bird Returns program,” said Ms. Marr.  “With that type of acreage, we think there could be some significant flood risk reduction benefits in the system.”

For this program, they have conducted a geospatial analysis for the Sacramento and San Joaquin basins to identify potential locations for this type of multi-benefit recharge.  They have developed a habitat needs calendar and are now looking at how habitat needs and crop/land suitability align.  They also hope to provide guidance for GSAs and landowners on how to enroll in a multi-benefit recharge program.

The nice thing about this program is temporary habitat windows are about 30 days, and you don’t have to do it every year,” she said.  “There’s a lot of flexibility of how the program can be rolled out.”

Ms. Marr also noted that the Department is working with GSAs right now to identify some pilot sites for this year and next year to put a handful of demonstration projects on the ground.  One of their considerations for these multi-benefit recharge projects is that there be existing conveyance within a quarter-mile of the proposed site. 

That’s the coverage you see in the map on the slide. So anything that’s filled in is within a quarter-mile of an existing man-made or natural conveyance,” she said.  “I thought this was good for illustrating for the work that you are doing that there are a lot of holes throughout the valley where there is no conveyance. So there’s a lot of conveyance limitations within the Sacramento and in San Joaquin valleys.”

The Department is also currently scoping other pilot projects, including farm demonstration projects in the Sacramento and San Joaquin Valley, a floodplain recharge and a demonstration project along the San Joaquin River in partnership with River Partners, and a district-scale implementation project in the San Joaquin Valley that will build on the Merced study.

Guidance and outreach

There have been many outreach activities of the program since its inception in 2017, including public forums, listening sessions, convening a Research Advisory Committee, monthly Lunch-MAR webinars, and convening the Flood-MAR network.

The Flood MAR research Advisory Committee had 13 topic-specific subcommittees, one of which was conveyance infrastructure and hydraulics subcommittee. Some of the feedback received from that effort includes:

In many areas of the state, lack of sufficient conveyance facilities is a constraint, and many critically overdrafted basins do not have sufficient infrastructure for managed aquifer recharge.

Capacity constraints can limit the conveyance of water to a groundwater recharge location.

New or modified conveyance facilities, and modified operation of existing facilities, are required to maximize managed aquifer recharge statewide. The maintenance and restoration of existing and construction of new infrastructure to facilitate Flood-MAR needs to be evaluated.

Also, two of the priorities that came out of the conveyance subcommittee was the need to build a standardized GIS conveyance database of conveyance networks that could be used for Flood MAR projects and to research sediment transport impacts on conveyance networks that are used for Flood MAR operations for both built and natural conveyance systems. 

Flood MAR alignment with other state efforts

Water Resilience Portfolio: Flood MAR as a resource management strategy is very much integrated and touches many of the Water Resilience Portfolio actions, particularly the ones listed on the slide. 

Flood MAR is an integrating and aligning opportunity for all these actions to support water resilience,” said Ms. Marr.  “Within DWR and many of our external partners, we’re currently planning across these actions, and Flood Mar is an important part of these conversations.”

Central Valley Flood Protection Plan:   We need to better integrate flood and groundwater management, and most watersheds only have “floodwaters” legally available.

Most groundwater sustainability plans are looking to augment supply, not reduce demand, and so we’re looking to those floodwaters,” she said.  “There are opportunities to use ag lands for temporary flood storage or habitat. There are also conversations around repurposing ag land under SGMA implementation and bringing floodplain restoration into that conversation. So there’s a lot of opportunities to marry flood and groundwater management.”

The 2022 CVFPP Central Valley flood protection plan update will also highlight available results from the Merced study, looking specifically at how Flood MAR strategies can provide flood risk reduction and other benefits such as ecosystem enhancement.

In support of the Commission’s conveyance analysis, I’d recommend looking at the CVFPP and its supporting documents as a potential source of information as you develop your conveyance recommendations,” said Ms. Marr.  “The Central Valley flood planners have evaluated all the State Plan of Flood Control channels, including rivers and bypasses, for campaigns for conveyance capacity deficiencies. And so this information could help prioritize conveyance needs for flood risk reduction benefits.”

The Flood MAR program is also planning to use floodplain restoration opportunities and potential inundation analysis from the CVFPP conservation strategy to estimate floodplain recharge potential, which will be important for evaluating recharge benefits from floodplains.

Forecast-Informed Reservoir Operations:  Where forecast informed reservoir operations could be implemented, more efficient reservoir operations can improve flood response capabilities while at the same time potentially allowing water agencies to either retain more water in reservoir storage in dry years or better time reservoir releases to downstream groundwater storage projects to increase the amount of total water stored. 

It’s FIRO-MAR,” said Ms. Marr.  “This is a part of our level two and level three analysis in our Merced study. But we’d also like to work with the Central Valley flood planners to identify more opportunities for FIRO-MAR in the future at other reservoir sites. And we’ve also started talking with the Scripps Institute about bringing all these pieces together and forecasting and reservoir operations and conjunctively managing surface and groundwater storage.

Sustainable Groundwater Management Act: The Flood MAR program regularly coordinates with the Sustainable Groundwater Management Office within DWR on pilot project objectives and locations to align our technical assistance activities.  They have discussed how to align pilot projects for Flood MAR with the airborne electromagnetic surveys planned for this year and next year to make sure they are getting good aquifer characterization information for the pilot project locations.

In summary …

Ms. Marr noted there are some questions that they hope will be answered with the watershed studies:

  • Do conveyance facilities exist where they’re needed?
  • Is conveyance large enough to optimize Flood MAR operations?
  • When is conveyance capacity available?
  • Who owns the facility for what purpose?
  • Are they willing to partner with others for multiple benefits using the same facilities? 

Ms. Marr closed by noting they are convening a Flood MAR network, and all those interested in progressing Flood MAR projects and working with the network are invited to join.  The Flood Mar network is a diverse group of stakeholders looking to collectively expand flood MAR understanding and implementation.

Just last week, one of our network members said the state cannot meet our water resilience goals without Flood MAR,” she said.  “And to wrap up the conversation, conveyance, moving water to recharge locations when it’s available is critical to maximizing flood MAR’s potential.”

 

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