GSA SUMMIT: Setting Sustainable Management Criteria: It’s easy, isn’t it?

The details of how a groundwater sustainability plan will be implemented are defined by the setting of sustainable management criteria (or SMC). With several undesirable results to consider, a range of technical analyses to perform, data gaps yet to be filled, and potentially conflicting stakeholder interests, the process to establish sustainable management criteria is often involved and challenging.

At the Groundwater Resources Association’s 3rd annual GSA Summit, a panel reviewed how the process went for the groundwater sustainability plans that were submitted to the Department of Water Resources earlier this year, focusing on four of the six sustainable management criteria: water levels, water quality, land subsidence, and interconnected surface waters.

GROUNDWATER LEVELS: How low is too low?

Jim Blanke, a Senior Hydrologist with Woodard & Curran, began the presentations with a discussion of the challenges of setting the sustainable management criteria for groundwater levels.  And when setting minimum thresholds, how low is too low?

For groundwater levels, undesirable results are typically based on the users that are the first to experience significant and unreasonable impacts when establishing minimum thresholds for chronic lowering of groundwater levels.  There are three broad categories of stakeholders and uses that are considered: domestic well users, ag well users and wells for stock ponds can have shallow wells, and groundwater dependent ecosystems.

For this presentation, Mr. Blanke focused exclusively on domestic wells noting that minimum thresholds often do have to focus on domestic wells, which are often the shallowest wells in the basin or subbasin.  It is important to consider domestic wells, because a domestic well going dry has a major impact on the well users; it’s a health and safety issue, and often those homeowners have few resources to deepen the well and few or no alternatives to alternate water supplies, he said.

Challenges with data on domestic wells

Mr.Blanke noted that while there is plenty of data on municipal wells, finding data on domestic wells is much harder.  Ideally, a GSA needs to know where the wells are, how deep those wells are, and the pump settings so the GSA knows when the well will really go dry.  However, there are a lot of records on wells that were put in a long time ago; those wells may have been destroyed or are otherwise inactive. It’s almost an impossible task without a well survey, he said.

There are a few different data sources where they typically look for this data:

Department of Water Resources Well Completion Report Map application

The Department of Water Resources Well Completion Report Map application compiles all the well completion reports on a GIS-based interface on the internet.  The advantage is that the application is readily available and the data easy to retrieve. However, Mr. Blanke said it can be difficult to tie the wells to associated water level data, so if you’re trying to figure out how deep a well is, you also have to know how deep the water levels are so you can understand where to set that water level threshold so that it doesn’t impact the well.  He also noted that locations are often estimated and most importantly, the records can contain abandoned wells, so there is the possibility that wells may be listed but are abandoned or otherwise no longer in use.

To illustrate his point, he presented a map of downtown Sacramento which lists 11 domestic wells but is highly doubtful that those wells are still in use.  If you drill down into the data, those well records were from the 1950s.

They are very likely not to be in use anymore, and they are typically about 100 to 150 feet deep, so if we were trying to develop a minimum threshold in this area and we pulled up this data, we might say that we want to make sure we keep these wells in water, but is that reasonable since they are probably no longer in use,” he said.  “The question becomes then, how do you figure out that those wells are no longer in use?  That can be a real challenge; it can require trying to sift through these wells and figure out if there are permit records of abandonment and they may just no longer be in use, but there may not be records of that abandonment at all, even if you could track it down.”

Local permitting agency records

Another place to look for data is the local permitting agency, typically the county, to see what kind of data they have.  Mr. Blanke said that if you are lucky, they might have done a survey assessing local well conditions throughout the area or a portion of the area.

There are some additional considerations, he said.  Does the county or local permitting agency have better records than DWR?   Some counties might have adjusted to a digital system earlier or they may have a better method of matching the abandoned wells with the original permits so you might be able to sift through it and determine which wells are there and which wells aren’t there – at least for some of the wells.  How good are the records of well abandonment?  Is that even possible to try to get at which wells might no longer be there?

If the data just simply isn’t available, Mr. Blanke suggested what could be done to avoid having the analysis weighed too greatly by wells that are no longer there.  “You can consider a cutoff date for older wells, so maybe those wells that were drilled 30, 40, 50, 60 years ago, which are no longer likely to be there, depending on how long lived wells are in your basin and how likely you feel they are to still be in use and what the useful life of those wells are.  The cutoff date can serve as a surrogate for abandoned wells.”

One final thing to consider with well depth data is that often total depth data are more available than screen data.  “Obviously you may have water above the total depth of the well, that doesn’t mean that the pump can get to it, so you have to recognize the implications of that,” he said.  “You want to try to have water levels some level above the bottom of the well or are you going to recognize that there are wells, that if you are at that water level, the pump won’t be able to reach or produce water?

Policy-level questions

Mr. Blanke noted that this brings up some policy level questions, such as, do you protect all wells, which gets into one of the core components of SGMA which is, what is significant and unreasonable?  If you don’t protect all wells, do you mitigate?  If you mitigate, how do you do that?  Do you set up a program to deepen wells?  Are those private wells close to municipal purveyors where you can extend water service to those wells?  Might that be combined with a sewer program to solve water quality issues?

It’s important to think about the options.  “Those mitigation programs can be challenging to put together because you have to know how many wells you’re going to mitigate so you can figure out how much it’s going to cost,” he said.  “That can be hard to do, which kind of circles back around again to the fact that we have a hard time figuring out where all these wells are.”

It’s also important to consider if the wells are actually accessing other sources of water.  “In some areas, we’ve seen some very shallow wells that went dry during the drought and they went dry when the irrigation district’s canal stopped flowing water, so that well was obviously not capturing water from the regional water system but instead it was really basically taking water out of that canal,” he said.  “There are special cases everywhere and every basin has its own special cases and you have to be careful that you’re not developing minimum thresholds to adhere to these special cases but that you’re really looking at a more regional condition for your minimum threshold development.”

He also advised that there can be simple errors and issues in your dataset.  “No dataset is without errors, so if you try to be protective of every single well and you get one total depth measurement or one screen depth measurement in there incorrectly, it can throw off your whole analysis and it may not be something that you’re doing it – it may be in the source dataset,” he said, noting that a lot of well completion reports are handwritten.  “There are a lot of challenges associated with transcribing those and moving those data into a digital format, and so there are a lot of opportunities for errors to be introduced that you have to be aware of.”

Mr. Blanke pointed out that SGMA is not taking away any protections. “It’s not that when you set the minimum thresholds that you’re saying you’re definitely going to take water down that low; it is trying to set that significant and unreasonable threshold at a level where it’s appropriate for the state to step in.”

Further considerations for setting minimum thresholds

Mr. Blanke said you can consider using statistical analysis to identify outliers.

He also noted that there may be county well standards, so if there are wells that are shallower than the minimum field depth for the county, the GSA could decide if they want to set a level to be protective of those wells.  “Maybe that’s something that we would allow to go dry because they are either installed at depths that aren’t consistent with the current regs or maybe they weren’t installed consistent with those current guidelines because they are older wells,” he said.

Another thing is to consider comparing historical lows for groundwater levels.  “If groundwater levels in the recent past have been lower than that well, can you assume that well was abandoned or deepened and you just don’t have records of that?  Maybe you can set the threshold at the historical low rather than at the bottom of that well or at the top of the screen.”

In conclusion …

Mr. Blanke reminded everyone that setting the minimum thresholds for groundwater levels is an important topic with real impacts on people.  “It’s a substantial health and safety concern and a financial concern for people to be able to have access to water for their residence,” he said.  “In developing minimum thresholds, you need to focus on what is significant and unreasonable.  Can you and should you protect every well?

Another point is to develop the measurable objectives and the interim milestones together with the stakeholders so you can focus on both the desired state of the basin and trying to get to that desired state of the basin at the same time that you develop your minimum thresholds so that when you do have your stakeholder outreach, people understand where you trying to go and what you’re trying to avoid, so you can balance that message,” he advised.

Consider additional nonregulatory thresholds if needed.  “In some basins, we have established a threshold between the measurable threshold and the minimum threshold that’s kind of local guidance for how low we want to go as opposed to the minimum threshold which is really where the state steps in.  And the final thing is to consider mitigation options if that’s something works for your region.”

Question: What is the purpose of the minimum threshold?  What’s the difference between the measurable objective and the minimum threshold?

The minimum threshold is what the stakeholders are trying to avoid,” Jim Blanke said.  “It signifies significant and unreasonable results for the area … If you go past that, then you risk state intervention and that’s what we’re all trying to avoid.  The measurable objective is more of a desired state of the basin so that’s going to be a higher groundwater level where we all want to be and where we’re all targeting.  So we set that measurable objective high enough so that in the event of droughts and other not known but certainly foreseeable climactic conditions, we can decline to a level where we can avoid that minimum threshold and not have those often undesirable results.”

WATER QUALITY: How does SGMA interact with other established water quality programs?

Teresa (Tess) Dunham is a partner at Kahn Soares & Conway.  She has worked for over 20 years with agriculture, publicly owned treatment works, and stormwater agencies on water quality issues.  Ms. Dunham is one of the chief architects of the Central Valley Salt and Nitrate Management Plan, which is designed to deal with the problem of salt and nitrate in Central Valley groundwater basins.

Ms. Dunham began by acknowledged that the water quality component is challenging in general because there is already a long-time regulatory program with respect to water quality in California under the Porter-Cologne Act, so with the water quality component of the Sustainable Groundwater Management Act, there remains a lot of questions on how the two interact with each other.  And now there is a new program, CV-SALTS, which also relates to groundwater quality in the Central Valley.

Setting minimum thresholds

The regulations for Groundwater Sustainability Plans require setting minimum thresholds for degradation of water quality and considering state and federal water quality standards in the basin plans.  Ms. Dunham said that in the GSPs she has reviewed, the GSAs seem to understand that and have considered them in some way or another.  For this presentation, she selected the Kaweah basin, which has three different GSAs with three different GSPs and is also a Priority 1 basin under the CV-SALTS program; she wanted to look at the three GSPs to determine how they differ and how they are alike.

She presented the slide on the upper right that shows the water quality standards and the minimum threshold from the different GSPs, noting that they have all recognized the primary Maximum Contaminant Levels for perchlorate, arsenic, DBCP, and 1,2,3-TCP.

She pointed out that there are two different standards or threshold levels for hexavalent chromium.  The 20 μg/L standard is what is currently in place.  The 10 μg/L is what the State Water Board has been working to adopt as the Maximum Contaminant Level; they did adopt it but it was challenged and turned back to the State Water Board.  Ms. Dunham anticipates they will readopt that standard once they conduct the required economic analysis.

With respect to PCE, some GSAs pulled out a threshold level from OEHA.  Different standards were set for TDS and chloride which is more related to the agricultural protection rather than municipal drinking water protection; the municipal standard is 1000 mg/L; for agriculture, some GSAs used 450 mg/L.

The GSAs have different ways of determining what is an undesirable result. For two of the GSAs, an exceedance of a threshold triggers an evaluation to determine if GSA projects caused the exceedance; an undesirable result occurs when 1/3 of the subbasin monitoring sites exhibit exceedance.  The third GSA defines an undesirable result if GSA projects or management actions cause concentrations of constituents to increase beyond baseline conditions & significantly impact beneficial uses and users.

They all are based upon the baseline condition of when the GSP is basically adopted and not looking at any potential legacy impacts that may already exist,” she noted.

CV-SALTS and GSPs: How do they match up?

The Central Valley Salinity Alternatives for Long-Term Sustainability initiative (CV-SALTS) is a collaborative effort that began in 2006 to develop a comprehensive plan to address salinity, including nitrates, throughout the region in a comprehensive, consistent, and sustainable manner.  The Salt and Nitrate Control Program was approved by the State Water Resources Control Board on October 16, 2019 and the Office of Administrative Law (OAL) on January 15, 2020.   Approval by the U.S. Environmental Protection Agency for specific subsections of the Basin Plan Amendments that fall under federal jurisdiction is still pending. However, the remaining portions of the program became effective on January 17, 2020 after OAL’s Notice of Decision with the Central Valley Water Board began sending out Notices to Comply for the Salt and Nitrate Control Program in late May 2020.

The differences between CV-SALTS and GSPs

Ms. Dunham described the primary difference between CV-SALTS and GSPs is that CV-SALTS is looking at what is going into the ground and the GSPs are looking at what comes out and depending upon how much is coming out, what is that potential impact.

The map on the left shows the critically overdrafted groundwater basins and the map on the right shows the nitrate-based priority basins within CV-SALTS.  Clearly, there’s an overlay, she pointed out.

CV-SALTS management zones differ from groundwater basins in several ways.  A management zone is a regulatory construct in the basin plan and is not necessarily determined by geologic or political boundaries (such as county lines).   A CV-SALTS management zone is not set in statute but is instead a defined area for a discrete regulatory compliance unit for meeting the basin plan requirements that have been adopted into the basin plan and now are in effect.

A CV-SALTS management zone is a discharger cooperative,” Ms. Dunham said.  “It is dischargers coming together somewhat voluntarily and somewhat with incentive to work together to develop a management plan for dealing with nitrate in groundwater.  It is also looking to make sure we have safe drinking water for those that are within the management zone if their wells are impacted by nitrate.”

There are significant differences in authority.  The management zone again is a regulatory construct whereas the groundwater sustainability agency is state law.

Management zones will basically be contractual arrangements with the regulatory overlay from the regional board,” she said.  “The sustainability agencies have far more power and authority then a management zone does under a contractual relationship, but the regional water board continues to have a big hammer when it comes to implementation of management zones in that if you’re not implementing your management zone which will become a permit requirement, then you are out of compliance and potentially subject to enforcement action by the regional water quality control board.”

Ms. Dunham noted that the notices to comply for the nitrate priority basins were issued in May, and so the preliminary management zone proposals will be due in early to mid-March of 2021.  Folks are now working collectively in the priority one areas to start putting together proposals and early action plans to address the nitrate drinking water issues.

Commonalities between CV-SALTS and GSPs

Both CV-SALTS and GSPs are looking at nitrate in drinking water.  The difference is that CV-SALTS management zones will likely be required to do more, even if it’s not a direct impact caused by a current discharge, whereas the GSPs only have responsibility if they can tie the impact of the implementation of the GSP to the cause of the water quality undesirable result.

Management zones have responsibility regardless of whether their discharge has ever contributed in the past,” she said.  “We are basically taking on responsibility for things that have happened previously, but it’s all long-term planning, we’re all looking to protect drinking water resources, and most importantly, it all involves multiple stakeholders who have an interest in drinking water and water quality issues within the Central Valley and beyond.”

We all want to protect Central Valley groundwater resources, we’re trying to balance agricultural and drinking water needs, and we want to establish long-term plans,” concluded Ms. Dunham.

Questions and Answers

Question: Is there a hierarchy of beneficial water uses where drinking water is higher above all others?

Not under Porter-Cologne,” said Tess Dunham.  “However, the most sensitive beneficial use will drive the applicable water quality objective.  For example, I think TDS is a good example in that the applicable water quality objective or the interpretation for salinity is typically more sensitive to agriculture than it is to municipal drinking water uses because the municipal use is the secondary MCL which ranges between for electrical conductivity, from I think 900 up to 1600, whereas for agriculture, depending on the crop, it could be far more sensitive.  Putting that on the other side, obviously, agriculture wants nitrate, it can have a lot of nitrate in water, whereas the municipal beneficial use, the more sensitive would be the 10 milligrams per liter as nitrogen.”

Question: What’s the potential for those that are implementing SGMA and those that are implementing the irrigated lands regulatory policy and CV-SALTS to coordinate and join forces?  Are there coordination agreements for nitrate management zones and shouldn’t some of that work get factored into GSPs somehow?

My vision and that of many others is that hopefully, we will have this organic coming together with respect to the two and that we will see agreements between the nitrate management zones and implementation of GSPs,” said Ms. Dunham.  “In particular, a management zone needs to put together an implementation plan as to how they are going to address nitrate over the long term.  I can’t imagine that looking at nitrate in the Central Valley and how we resolve it in the long term to try and make drinking water standards in basins that currently exceed them how recharge isn’t part of that implementation.  There’s what we can do on the source control side on the surface of the land, but at some point, there also has to be projects to change the water quality within the basin as it currently exists.  One of those mechanisms would be recharge, and when we have GSPs are looking to do the same thing from a sustainability quantity side, it seems to me that there is this synergy between the two, and we should be looking to see how we can do it together.”

Another big issue is the monitoring,” she continued.  “The irrigated lands and the management zones are going to continue to do groundwater monitoring and trend monitoring and long-term surveillance and monitoring programs, and SGMA is doing the same thing, so how do we combine to have an efficient and efficient monitoring program throughout the valley without duplicating monitoring? And to use the resources most efficiently which in large part is coming from the same set of fee payers as far as the irrigated lands programs have the farmers paying for it, and SGMA it’s the landowners which are the farmers, so we’re all tapping into the same economic base.”

LAND SUBSIDENCE:  Proper accounting in the water budget

Mike Basial is a principal hydrologist currently at AECOM with 25 years of experience working in hydrogeology and groundwater modeling.  He has prepared a GSP for an area affected by subsidence as well as reviewed some GSPs for clients who were concerned about subsidence, so he shared his perspective on what sees as a problem in accounting for land subsidence in the water budget.

Subsidence and the water budget

Mr. Basial began with subsidence and the water budget reminding all that with subsidence, the task is to avoid significant and unreasonable land subsidence that substantially interferes with surface land uses, which frequently in California has to do with irrigation infrastructure.

He recalled how near the beginning of his career, a very wise hydrogeologist named Fritz Carlson repeatedly made the point, ‘it’s always the water budget’, and he noted over the last 25 years, that has pretty much always been true.

It is also true in subsidence issues,” he said.  “When subsidence is occurring, the pore space is collapsing and the water becomes available for extraction, and not accounting for that in your historical water budgeting can cause sort of a characteristic problem.  I think that multiple GSPs can do a better job of acknowledging that it is part of the water budget and do some quantification and some mitigation.”

He then gave what he acknowledged was an extremely simplified example with some rather egregious simplifying assumptions just for illustration.

In terms of coming up with the historical water budget, if we knew the truth of what was really going on, some of what turns into pumped groundwater is reflected in declining water levels and elastic storage, some of it is pore spaces collapsing and reducing the thickness of the actual aquifer, some of it can be return flows from irrigation, and some of your inflow may be subsurface inflow coming from upgradient.  But what frequently seems to happen in GSPs is that in the conceptual water budget, they are seeing declining water levels, they are seeing subsurface inflow, but they are not seeing subsidence.”

For this example, I am showing all of the water that actually came from subsidence into the return flows category, even though in real life, if this is being done, it’s probably getting smeared across multiple things,” said Mr. Basial.  “So the area shown in the yellow color represents the water that actually came from subsidence but conceptual water budget assigned to return flows.”

With the implementation of SGMA, now the water budget has to be predicted into the future.  “So we had our estimates of return flows and subsurface inflow and because we’re doing good management of groundwater, we’re not going to have declining water levels any more,” he said.  “We’ve reduced pumping, brought in surface water supplies, and we have done all the things we need to.  Except what’s actually happening is that because in our conceptual water budget, we didn’t recognize the fact that some of that water came from subsidence over the years, and now in the future, the actual water available for pumping of groundwater is [the darker blue on the far right bar] and you’re going to have declining water levels into the future because part of your water budget isn’t there.  If you have declining water levels, you might also be risking further subsidence.  I don’t think that this is a universal conceptual error but it’s not unusual in the GSPs I’ve looked at so far.”

Put yourself in the stakeholder’s shoes

Mr. Basial said it’s important to put yourself in the stakeholder’s shoes.  Ask stakeholders for help and listen, communicate, listen, communicate, and figure out what the pressure points are with your subsidence stakeholders or for any other of the sustainable management criteria.  Consider what the cumulative impacts are and close the loopholes.

The public draft is not the best time for stakeholders to learn about what your sustainable management criteria are going to be for the first time,” he advised.  “This should have been an ongoing discussion.  By the time you’re writing it, everybody should kind of know what it’s going to be and what it means.”

It’s also important to consider the cumulative impacts of land subsidence.  “You’re a GSP author and you’ve picked some small number – this is a number that is not necessarily seen in any GSP, I made it up,” he said.  “A tenth of a foot here seems pretty small, little bit more than inch.  And the way you’re managing the basin, you’re not even going to have that so it’s really not a big deal.   Basically you set this SMC to be relatively easy to achieve and just set it and forget it.  So you don’t need to think about it much into the future because you’re going to arrest declining water levels and subsidence will just take care of itself that way.”

The problem is that this relatively small increment per year multiplied by 20 years of SGMA implementation is now not so small; it’s a couple of feet.  “The real problem from the stakeholders side is that is the GSPs thought they were just setting and forgetting something that was going to be easy, but over on the other side, it looks like ‘you said that you could get 2 feet of subsidence here and cause serious damage, and you’re not going to even review it.  You didn’t even set anything up that says this is bad.  To you, this is fine, but you’re saying that in 20 years, you’re ok with ruining my stuff.’ That might be the only thing they can hear in your GSP until you work to correct that.”

So who your local subsidence stakeholders are is going to matter to what kind of information you need to seek, he said.  He recommended Appendix A of the California Aqueduct Subsidence Report.

It has some information about how looking at the decrease of subsidence into the future as water levels stabilize, and assuming a constant linear rate for forever might be terrifying to a stakeholder,” Mr. Basial.

Question: How does water come from subsidence?  You pump a well, you get water coming up out of the well, and some of that is from subsidence.  How does that work?

Essentially the groundwater is helping to hold up the ground and by removing it, you’re removing support as it helps support clay minerals and sand grains and other materials,” said Mr. Blanke.  “So when you remove the water and remove that structural type support, the aquifer collapses a bit and the pore space effectively goes away.  The aquifer gets shorter, the land drops, and when the rains come, that space is not available anymore for the water to go into.  You have shrunk your aquifer by overextracting water and making the aquifer a little bit thinner.  So the quantities of water that come out of that are sometimes surprising.”

The basin I wrote the GSP for has a MODFLOW model that incorporated the subsidence package and long-term it’s in the 5 to 10% range of the basin water budget,” Mr. Blanke continued.  “In particular years when subsidence is really accelerating, it can be like as much as a third of the water budget in a particular year if you’ve pumped really hard and collapsed the aquifer significantly.  If you think about the math, it ends up being relatively simple. If you drop the land surface a foot, you have more or less generated a foot of water over that entire area and it’s unfortunately short term water, you’re not getting that water again because you’ve made the aquifer smaller.  So if it’s a 100,000 acre GSA and you let the land subside by a foot, that’s 100,000 acre-feet that’s real water.”


Briana Seapy is with the Department of Fish and Wildlife and was formerly the statewide SGMA coordinator for the Department.  She began with the common caveat that she is speaking on her own behalf and not on behalf of the Department of Fish and Wildlife.

The key starting point is to understand what the regulations are asking for when it comes to depletion of interconnected surface waters.  The fundamental building block is the identification and characterization of interconnected surface waters.  The regulations require identifying the systems that are interconnected as well as the quantity and timing of surface water depletion; then with that information, groundwater plans are supposed to derive their sustainable management criteria.

The groundwater regulations define interconnected surface waters are those that are hydraulically connected at any point by a continuous saturated zone in the underlying aquifer, so those can be both gaining streams where the aquifer is contributing to the surface flow, as well as losing streams where the streamflow is percolating into the aquifer but there is still a continuous saturated zone between the two,” said Ms. Seapy.  “The challenge comes in figuring out where those systems are in your basin, what times of the year, and what they look like.”

Really getting the first one right is critical to having long-term success,” she said.  “I’m going to walk through both of these components and the successes and challenges that we saw in the first round of plans.”

STEP 1: Identify and characterize interconnected surface waters

In the first round of plans, the biggest challenge was data.  Ms. Seapy acknowledged that understanding the connectivity between groundwater, shallow groundwater, and surface water is not something folks have spent a lot of time trying to understand, so the lack of data made it really hard to perform the analyses that were being asked for, including figuring out the timing and volume and location of surface water depletions.

There were many cases where numerical models were used where they were somewhat generalizing the volumes of surface flow contributions to aquifers for the purpose of water budgets and other components of the plan,” she said.  “They were looking at the larger river systems and not necessarily the smaller creeks where there was definitely an absence of data.  In those cases, the generalized model outcomes aren’t always groundtruthed with really specific empirical data from shallow groundwater monitoring paired with surface water gauges.  We don’t have this wealth of isotopic studies or temperature studies to help us understand the nuance of how surface water and groundwater speak to each other.  A lot of times, this data deficit leads to a bit of a dismissal of surface waters, or a simplified analysis without a specific plan for revisiting what interconnectivity looks like between surface water and groundwater with additional data.

Ms. Seapy pointed out there were also some successes.  Some plans didn’t just dismiss interconnected surface waters but instead committed to improving their shallow groundwater monitoring network by adding in new monitoring locations that are proximate to rivers in order to really understand hydraulic gradients close to those rivers, and to better get a sense of how shallow groundwater and surface water are interacting over time.

I think that commitment to improve data collection will also help the modeling efforts as they go along,” she said.  “One has plans to work hard to get a foundational paired numerical model in place and additional data over time that will refine the output to make them more relevant and better at informing the subsequent management decisions that need to be made around surface water depletions.”

She also acknowledged hybrid successes where there were clear plans for iterative data collection and analysis going forward, even though there wasn’t a lot of data to begin with to identify and characterize those surface waters.

STEP 2: Develop sustainable management criteria.

The next step is to figure out how to manage surface water depletions based on the information that you do have.

This is no small task,” Ms. Seapy said.  “Some of the key challenges we saw in this step was first of all, establishing the metric one would use for judging surface water depletions.  In many cases, even though the recommended metric is the volume or rate of depletion, the absence of data didn’t allow for that, so most plans differed to the practical groundwater elevation proxy approach for judging surface water depletions.  Sometimes that relationship between groundwater elevations and surface water depletions was pretty tenuous, but when using a kind of more coarse model, there were a few options for folks developing those plans.”

Another key challenge was 2015 as the baseline year for these analyses especially in terms of determining undesirable results, as 2015 was several years into a historic drought and not necessarily representative of normal conditions or even conditions that one would aspire to for avoiding significant and unreasonable outcomes, she said.

Understanding the influence of groundwater pumping on surface water depletions was another challenge.  “Surface water is subject to climatic variations and surface water diversion increases, so understanding the influence of pumping alone which is the management lever that GSAs have, is going to be challenging to do in these modeling exercises.  Then extrapolating that out and setting management criteria that are directly relatable to what the GSAs can and can’t do in terms of exercising their management, so basically setting sustainable management criteria that are achievable based on the GSAs authorities also proved to be a challenge.”

Ms. Seapy likened interconnected surface water as an egg hanging precariously as to whether or not it’s on the table or off the table for a lot of basins.  “What we don’t recommend is taking sparse data and using that limited understanding to just knock it off the table as if it’s not really a problem,” she said.  “Where we saw success, even in the light of lack of data, was where plans were intentional about collecting data and keeping that interconnected surface water egg on the table and then setting indicators and triggers in their plan for revisiting improved data and improved modeling outputs over time to better hone in on what groundwater pumping was doing to their surface water and how as a management agency they could establish responses, management criteria that would evolve over time and be iterative.”

Interconnected surface water is important for fish and wildlife species, so if you figure out the interconnected surface waters, it will inform your analysis of groundwater-dependent ecosystems, especially aquatic and riparian ecosystems, she said.

If you spend time getting that piece of the puzzle correct, I think groundwater-dependent ecosystem piece will follow in suit, and the monitoring for interconnectivity will tease out and help GSAs understand how their management will affect fish and wildlife,” Ms. Seapy said.

Her final message to the 2022 GSPs is to commit to concerted data collection, monitoring, and iterative analysis before dismissing interconnected surface waters.

Be prepared to allow the plan to evolve and adjust management criteria as more information is gathered over next 5 to 15 years,” she advised.  “Be specific in your plans to allow for that evolution and to improve subsequent iterations as we gather more information on surface water groundwater connectivity.”


Question: What guidance is there for identifying species in a basin that might be at risk in a groundwater-dependent ecosystem or in interconnected surface water?

The Nature Conservancy has put out a resource called the critical species look book that characterizes listed species in California or a subset of them and their relationship to groundwater, if it’s known, in a pretty concise fashion” said Ms. Seapy.  “In terms of species-specific resources, I’m not aware of other ones, but the Department put out a fish and wildlife considerations document for groundwater planning that’s available on the Department’s website.  The Groundwater Resource Hub that TNC has is a great compilation of literature and other documents that would be helpful.”


Question: Let’s say you have different sustainable management criteria, measurable objectives, and the minimum thresholds and one management area or one GSP is using one value and you get to the boundary between them, and then there’s another value in the next area over, and they are significantly different.  How do you think some of those issues are going to get worked out as we move forward on our SGMA adventure over the next 20+ years?

I strongly suspect that the state is probably in the process of finding that coordination across basins really isn’t handled as well as it needs to be,” said Mike Basial, noting that is not based on any conversations with DWR but what he expects to happen from looking at GSPs from adjacent basins.  “This is one of the things where I am not excusing myself from that working on a GSP also.  We’re all doing it for the first time, and it’s difficult, and what would be really great if the state could say, ok that was a practice run, now we’re doing it for real, because now we know all these things.”

A lot of times there are real differences in how one side of the boundary sees the issue compared to the other side,” said Mike Blanke.  “Especially when it comes to subsidence, there are several areas of the state where one side of the boundary line is seeing the subsidence but a lot of the cause of that subsidence may be coming from the other side, so there’s a natural reason why these stakeholders in these basins would develop different thresholds.  A lot of that does come down to the state trying to figure out how they align that, but in the meantime, as all those pieces play out, I think you do see recognition on the other side of the line that there are some actions that need to be taken.”

I think you’re starting to see more flexibility in trying to do those actions as long as they are not too extensive, but trying to take some actions to resolve some of those issues and more flexibility with that than there is there is flexibility in changing that minimum threshold to a point that might threaten state intervention, because there’s a real hesitancy to putting that threshold at a level that will push them into state intervention.”

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