Successful Groundwater Sustainability Planning

Dudek hydrogeologist Jill Weinberger discusses groundwater sustainability planning and lessons learned

California’s Sustainable Groundwater Management Act (SGMA) requires all groundwater basins designated as medium or high priority to develop a Groundwater Sustainability Plan (GSP) to achieve sustainable management by 2040-2042.   In this webinar, Jill Weinberger, a hydrogeologist with Dudek, gives a high-level overview of the groundwater sustainability planning process and shares some of the lessons learned from the work she and Dudek have been involved with in various groundwater basins in California.


Ms. Weinberger began by saying that every 100 years or so, California gets around to regulating water in some form.  Back in 1914, surface water regulations were passed when the state looked quite different than it does today.  A few years after that, Article 10 Section 2 of the California Constitution was added which required that the water resources of the State be put to beneficial use to the fullest extent possible and that the waste or unreasonable use or unreasonable method of use of water be prevented, although the definition of what is reasonable has changed over time, she noted.

In 1960, Governor Pat Brown set in motion the construction of the State Water Project which further changed the look of water in the state.  Over the past 100 years or so, the state of California has undergone tremendous population growth as well as economic growth in the form of agricultural uses of water in the state.  That growth has been driven in no small part by the wet periods that occurred in the 20th century which also happened to be the wettest period in 7000 years of tree ring records, Ms. Weinberger said.

The drought the state experienced from 2011 to 2017 was the worst drought in the historical record of precipitation from 1885, and as a result, there was a decline in groundwater levels throughout the state.   This alarmed Governor Brown and the legislature so a package of three bills was passed which became known as the Sustainable Groundwater Management Act; it was signed by the Governor and became effective January 1, 2015.

The legislation required that Groundwater Sustainability Agencies be formed for all basins designated as high or medium priority groundwater basins by DWR.  Those Groundwater Sustainability Agencies are required to prepare Groundwater Sustainability Plans which have to achieve sustainability within 20 years of being adopted: 2040 for critically overdrafted basins and 2042 for all other basins.  Low and very low priority basins are not required to prepare a GSP at this time.

The deadline for Groundwater Sustainability Plans is coming up fast – just a year and a half plans for critically overdrafted basins, Ms. Weinberger pointed out, although she noted a lot of work has been done on these plans already.

When the Governor signed these bills, he said that an essential tenet was the recognition that groundwater management in California is best accomplished locally, which is great and it’s true; it gives local agencies a lot of discretion, which is very important,” Ms. Weinberger said.  “It also means that local agencies are left to figure out how to actually implement these bills and this legislation.  So learning from those who have gone before us is going to be the key to getting this done.”


Ms. Weinberger noted that Dudek have been consulting several agencies in the Central Coast, East Bay, San Diego County, and Ventura County throughout the SGMA process, so she will be giving an update on what’s required as well as a few case studies.  “We’ve gone a long way towards learning some of the lessons and understanding how to start putting this legislation into practice in writing these plans,” she said.

The Borrego Valley in San Diego County is a basin that is geographically isolated, on the edge of the desert, and has no actual connection to state water or other external sources of water.  The basin is in critical overdraft with groundwater elevations declining over 100 feet since the 1950s.

In order to actually reach sustainability, there are some projections currently that the water usage in the basin has to be cut by 70% – that’s not to 70%, that’s by 70%,” she said.  “What have we been doing with this basin?  Here at Dudek, we helped them in the beginning going through a basin boundary modification … It’s really a critical step when it comes to actually managing these basins because getting those boundaries right and understanding what is in your jurisdiction and not what is in your jurisdiction is really critical.  It avoids fighting in the long run, although those fights may get pushed to the forefront.  However, in this particular case, there was no issue with basin boundary modification.”

Ms. Weinberger noted that another thing they have learned through their work in the Borrego Valley is the importance of stakeholder outreach.

In preparing the Groundwater Sustainability Plan, the first few chapters provide the technical analysis and framework that will determine sustainability; it includes creating a hydrogeologic conceptual model of the basin and documenting the historical conditions.

It’s all the basin engineering and hydrogeology work, such as collecting the data, synthesizing it, managing the data, characterizing the hydrogeology, developing the water budget, and doing groundwater modeling,” she said.  “Although it is not absolutely required, it is strongly recommended that there be a groundwater model that the plan is built around and simultaneously, characterizing the uncertainty.  The idea of characterizing uncertainty is at the heart of creating an adaptive plan.”

Ms. Weinberger noted that Department of Water Resources does not expect that the plans will be aware of every groundwater condition in the basin when they are submitted – they can’t be, she said.  “This is new legislation and people have not had the opportunity to collect data in some cases.  Some basins have been doing it forever; others have not.  It’s a veritable mishmash when it comes to data collection.”

Understanding where those data gaps are and understanding how that will affect your determination of the sustainable yield is going to be important, because this is not just a plan that sits on the shelf that never gets read again,” she said.  “It’s meant to be an adaptive management plan, and in fact, 5-year updates are required.  So if you understand what your data gaps are, you identify them in this section, you can then also been to begin to identify how to narrow those data gaps and to narrow down certain things going forward so that you have a better handle on your sustainable yield in the next five years, and then the five years after that.”


Another lesson learned is that the old adage of geologists – that the past is the key to the present – simply is not actually true when it comes to sustainable groundwater management and developing a water budget, Ms. Weinberger pointed out. It’s not true because of climate change, the length of future drought cycles, and the extremes of high and low precipitation.  “It’s also not true because SGMA and groundwater sustainability plans do not actually have a requirement that you manage based on the historical water budget,” she said.  “In fact, they don’t have a requirement that you manage based on the water budget at all, and instead, with these plans now, the management is based on sustainable management criteria.”

It’s easy to get hung up on the minutia of the past water budget, and the past water budget is important for building the groundwater model and for understanding the hydrogeology of where the water is going and where the water is coming from in the basin, Ms. Weinberger acknowledged.  “But spending too much energy on your water budget and understanding the past isn’t going to help you move forward in this process,” she said.  “In this particular case, that old geologic adage doesn’t hold true, because instead of managing based on a historical water budget or based on the historical data, these agencies are left to determine what sustainable management looks like in their basin.  They’re allowed to determine that by coming out with a set of sustainable management criteria.”


Once the technical framework is complete, the harder work begins.  It’s important to understand the data gaps so those data gaps can be adaptively managed, she said.  The picture of the basin on the slide shows a theoretical basin on the coast with a river flowing by that has a number of wells.

One of the tasks that will be left to the agencies in the groundwater sustainability plans is to identify which of those wells are going to be monitoring wells and what triggers will happen if water levels in those wells or concentrations in those wells hit certain thresholds,” she said.

DWR has a vision that in the plot to the left that if you’ve selected a few of these wells, the ones here that are circled in green on that lower left plot, those are fine.  Water levels are going up with time, and by 2040 they are higher than they were in 2015, so those don’t have any problem.”

The ones that are circled in orange on the other hand, actually dipped below what has been determined in this particular theoretical basin to be the minimum threshold for that basin, and that’s okay, too, according to DWR, because by the time you get to 2040, which is that time in which the basin has to be sustainable, you are no longer below your minimum threshold.”

The minimum threshold is a level or indicator that is left for the Groundwater Sustainability Agency left to define, and sustainability is when there aren’t any significant and unreasonable impacts to those indicators.   The sustainability indicators are specifically defined by the legislation as no ‘significant and unreasonable impacts’ to groundwater levels, groundwater storage reductions, land subsidence, interconnected surface-water depletions, seawater intrusion, or water quality degradation.

Once you start coming up with words like significant and unreasonable, you’re no longer solely in the realm of a technical decision,” said Ms. Weinberger.

The other thing to keep in mind is the minimum threshold is the regulatory threshold,” said Ms. Weinberger.  “For instance, if the water levels start falling below that minimum threshold and they do it at too many wells across the basin (which is a number to be determined by the agency), then the basin is no longer being managed sustainably.”


In preparing a GSP, the agency has to define a sustainability goal in their plan which is similar to a mission statement.  “What is it that we would like the basin to look like, how would we like it to be managed, what are the water levels or concentrations or the healthy ecosystem we would like to see in that system?” she said.  “It’s not a target number.”

Associated with the sustainability goal or mission statement are the measurable objectives.  On the slide to the right, the water levels are depicted by the blue line; the 2015 SGMA benchmark date is shown by the blue line.  “Through time, you have the basin define the measurable objectives as being somewhere above that 2020 time period,” said Ms. Weinberger.  “In this particular graph, it looks like it’s actually about at the 2015 benchmark, so that would be the ideal operational scenario for that basin, acknowledging that there is some flexibility in between the ideal level of that measurable objective level and the minimum threshold.  That is what DWR has defined as the margin of operational flexibility.”

Looking at this plot, it becomes really clear why adaptive management and why identifying data gaps is important,” she said.  “Because if you have errors associated with what you think that groundwater level is going to be and you narrow those through time, then you’ll actually be able to truly understand what your operational flexibility is and what the minimum thresholds are.”

The Oxnard, Pleasant Valley, and Las Posas Valley basins in Ventura County comprise three of four basins that are managed by the Fox Canyon Groundwater Management Agency.  Two of the basins are in critical overdraft and have to put their plans together and submit by 2020.   The Fox Canyon Groundwater Management Agency was formed in 1982 in response to long-term overdraft and seawater intrusion and was one of several agencies that were named in the Sustainable Groundwater Management Act as a Groundwater Sustainability Agency for the basins they oversee.

In this particular area, agriculture is a large economic generator, so getting what that sustainable yield is and limiting the economic impacts to agriculture are really critical for these basins,” said Ms. Weinberger.


Dudek has been working to prepare the Groundwater Sustainability Plans for Fox Canyon Groundwater Management Agency.  They have been compiling and analyzing technical information and working on turning those into the sustainable management criteria as well as meeting with stakeholders and working with the agency and technical advisory groups in writing the plan.

Ms. Weinberger said that one thing that has come out of their work with the Fox Canyon Groundwater Management Agency is how important it is to educate.  “Many of you are aware that these GSAs are new entities,” she said.  “In this case, Fox Canyon was not, but in most cases these are new entities and they are bringing together multiple agencies and municipalities that all have traditionally separate jurisdictions.  On top of that, we have these agencies managing basins that may face required reductions in groundwater use or changes in groundwater use, and once we start talking about water, things can get a little tense.  So maintaining communication is really important throughout this process.”

The legislation really focuses on stakeholder engagement which essentially says a GSA must develop a stakeholder contact and participation list to understand who the stakeholders are and what they need to get out of the process, she said.  She also noted that a stakeholder engagement plan is required to be developed and included in the GSP.

Along with that, you have to talk about what stakeholder engagement activities have happened,” she said.  “For example, if you prepare preliminary drafts or release drafts for public review, that really gives stakeholders a chance to understand how this process is working and where these decisions are headed and it gives them a chance to weigh in as the process occurs.  This is going to be important when DWR reviews these plans, so it shows you’ve given them the opportunity to weigh in and you’re reviewing and responding to stakeholder feedback.”

Communication is also important between the agencies working on developing the plan.  “If you have multiple different jurisdictional entities coming together, they have to communicate well with each other in order for these plans to work,” she said.  “They have to build trust, and that’s going to take awhile.  These agencies also have to communicate when they are managing other basins.  You’ll have to coordinate between basins, and so you have to develop lines of communication with your neighbor and build trust there, and that can take awhile.”

If an agency decides to rely on a technical advisory group or committee or panel, Ms. Weinberger said it’s also important there be clear communication with that group, both from a standpoint of what the agency wants from the group, and what the group thinks its mandate is.  “I strongly encourage any agencies out there to be very clear in their mandates to the principal advisory groups that they form because those groups can be immensely helpful and really help move the process forward,” she said.  “At the same time, if the technical advisory group is on a different page from the agency as to what the timeframe is, what the schedule is, or what the work is that needs to be done, then that group can dig in its heels and substantially slow the process down.  That mandate and that understanding of what the goal is needs to be spelled out quite clearly so everyone is on the same page moving forward.”


Once the sustainability criteria have been determined, the stakeholders have been engaged, the technical work completed, and the sustainable yield calculated, the last component of these plans is really to figure out how the basins can achieve sustainability.  It also means continuing with stakeholder outreach and engagement as people have different ideas for what is going to be sustainable, but it’s also important to understand what projects are available and what measures are available out there to potentially increase your sustainable yield of the basin moving forward, she said.

The Groundwater Sustainability Plans will include an analysis of projects, programs, and policies that will impact the sustainable yield; it can be at a conceptual level such as design feasibility studies or a cost benefit analysis; looking at capital and O&M costs for a cost benefit analysis; that’s one of the last steps, but it is a critical step in putting the plan together, she said.

After plan preparation is complete, the process is not over; there will be ongoing updates, filling in the data gaps, and looking at additional data collection and analysis and how that is targeted to areas where more information is needed.  It might include developing additional models, ground-truthing data such as groundwater dependent ecosystems, and considering the relationship between groundwater elevation and concentrations of specific constituents of concern.

All of that needs to be spelled out in the plan and targeted so you can start to fill in the data gaps to really understand how these basins work and what the sustainable yield is,” said Ms. Weinberger.  “Part of the ongoing activities will be developing projects and getting them approved.  Depending on the sustainable yield, there may be some projects developed in order to sustain the economic activities in the basin.”

Ms. Weinberger pointed out that while the actual groundwater sustainability plan themselves are exempt from CEQA, any project that comes out of the plan does have to go through CEQA.

Last but not least, it’s going to be important to continue coordinating with other planning documents,” she said.  “The overall general plan and other land use plans for these basins need to mesh with the GSP.  That is part of this process, and that continued link will be improved moving forward.”

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