Implementing the Sustainable Groundwater Management Act

Salinas Valley groundwater sliderboxDr. Thomas Harter gives an overview of the Sustainable Groundwater Management Act, the key components of a Groundwater Sustainability Plan,and how to address uncertainty

In the fall of 2014, Governor Brown signed the Sustainable Groundwater Management Act, bringing groundwater management under regulation for the first time.  The central principle of the legislation is that groundwater is best managed at the local level, and so the legislation requires the formation of Groundwater Sustainability Agencies by June 30 of 2017, and the development of Groundwater Sustainability Plans by the year 2020 or 2022.

In this presentation from the UC Division of Ag and Natural Resources’ Insights: Drought and Water series, Dr. Thomas Harter, a Professor in Cooperative Extension Specialist in the Hydrology Program of the Department of Land, Air, and Water Resources at UC Davis,  reviews how drought and overpumping has impacted groundwater, gives an overview of the Sustainable Groundwater Management Act (or SGMA), and then discusses some of the management concepts for implementation of the legislation.


He began with a review of the impacts of groundwater pumping.  California has had a number of droughts over the last several decades; there was the 1977 drought, the drought of the late 80s and early 90s; and a drought in the early 2000s, in the late 2000s, and then the drought the state has been experiencing since 2011.

Predictably in all of those droughts, groundwater levels in many places go down because groundwater is not replenished at a normal rate and its being extracted at rates that far exceed the rate of replenishment.  In some place, the annual drop in water levels may be 10 – 15 feet; in other places, often not far away, that annual drop in water levels from spring to spring may be as much as 40 feet per year,” he said.  “In many areas of California, because of the rapid sequence of droughts that we have seen over the last 15 years, we’re now at water levels that are far lower than we have ever recorded in the history of this state.”

Harter SGMA PPT_Page_06Dr. Harter presented a map of the state showing the change in the groundwater levels in wells across the state from the beginning of 2011 and the spring of 2016.  “You can see that in most wells throughout the state that are being monitored by the Department of Water Resources, we have seen far more than 10 feet, often more than 50, and in many cases even more than 100 feet of drop in water levels,” he said.  “The middle of the 20th century was the last big period in which groundwater resources were tremendously stressed because California didn’t have some of its very large surface water projects like the Central Valley Project and the State Water Project.  Since then and compared to that time, water levels that we have seen over the last three years are significantly lower in parts of the southern Central Valley by more than 50 – 100 feet lower than in those relatively dire times of groundwater extraction in the 1940s, 50s, and 60s.

Harter SGMA PPT_Page_08Now this last winter, the winter of 2015-16, was somewhat wetter, but it was barely an average winter in Northern California and it was a dry winter in Southern California, and that’s very much reflected in the change in water levels just within the last year.  Despite the rain in Central and Northern California, many wells have continued to drop in water levels due to the large pumping that happened in the summer of 2015 which was not recovered over this last winter.  Especially in Southern California and the southern part of the Central Valley, we have seen continued decrease in water levels.”

Harter SGMA PPT_Page_09That decrease in water levels has run many wells dry – mostly shallower, domestic wells, but irrigation wells as well.  People have had to drill new wells, deepen their wells, or drop their pumps; they also had to pump the deeper water with a much higher lift.  The overall cost of that has been estimated to be about a half a billion dollars per year in 2014 and in 2015.  “In each of those years, we have seen a record number of wells being drilled in many counties throughout the state, both in the valleys and in the mountains; this has impacted the agricultural economy at a scale of a couple of billion dollars per year.“

Harter SGMA PPT_Page_11There has also been increased seawater intrusion in groundwater basins that are near the ocean.  Seawater intrusion occurs because groundwater levels fall below the sea water level, which allows seawater to intrude into aquifers by gravity, he said.  “In the Salinas Valley for example, we see sea water intrusion now going almost 8 miles to the doorstep of the city of Salinas,” Dr. Harter noted.

There has also been a recurrence of subsidence, much like what occurred in the 1950s and 60s which was the last time there were rapid changes in groundwater levels.  That subsidence has impacted many Central Valley and Southern California basins.  “In 2014, there were places in the Central Valley that have seen subsidence rates on the order of 8 to 12 inches within less than 8 months, both in the southern part of the Central Valley, but also in the Sacramento Valley, northwest of Sacramento,” he said.

Falling groundwater levels are also impacting ecosystems, including in the mountains where springs and seeps have ceased to exist, as well as the ecosystems on the valley floors of the various groundwater basins across California, he said.

This overreliance on groundwater to make up for the lack of surface water in these dry years has caused a number of impacts.  “These impacts exist, not because we’re out of groundwater, but because the groundwater levels are lowering,” he said.

So partly in response to the drought, and partly in response to a longer term development in policies over the last 20 years, in 2014 the State Legislature passed the Sustainable Groundwater Management Act.


The Sustainable Groundwater Management Act is based on two principles,” explained Dr. Harter.  “The first principle is that groundwater resources be managed sustainably for long term reliability and for multiple economic, social, and environmental benefits.  The second principle is that management of groundwater is best achieved locally.”

Sustainability is defined in the Act as having no significant and unreasonable undesirable results,” he explained.  “The undesirable results specifically defined in the Act are chronic lowering of groundwater levels, a reduction in groundwater storage, sea water intrusion, degradation in water quality, land subsidence, and surface water depletion and impacts on groundwater dependent ecosystems.  These six undesirable results are those that we have to manage towards avoiding in the next 20 years.”

Harter SGMA PPT_Page_21The implementation of the Sustainable Groundwater Management Act is envisioned as a multi-pronged approach.  “There will be much public engagement in many of the decisions that have to be made in managing our local groundwater resources.  We will have local agencies involved in groundwater management, and we will have state agencies overseeing and supporting these local efforts.”

The first step is that groundwater sustainability agencies will have to be formed in all groundwater basins that have been ranked by the Department of Water Resources as medium and high priority basins by June 2017.  “Medium and high priority is mostly defined not whether or not there are critical conditions in a groundwater basin, but rather defined by the usage of groundwater and the importance of groundwater to overlying land uses, as well as the availability of groundwater resources in these particular basins.”

Dr. Harter presented a map of the state’s groundwater basins, noting that each of the basins shown in orange and yellow falls into the category of medium and high priority basins and will have to be governed by one or several groundwater sustainability agencies.  Those basins which have been designated as critically overdrafted will have to have groundwater sustainability plans and management practices in place two years sooner than the other basins.

The Sustainable Groundwater Management Act exempts adjudicated basins and agencies that are functionally equivalent to groundwater sustainability agencies from the groundwater sustainability planning, although they still have to submit material that is essentially equivalent to a groundwater sustainability plan, Dr. Harter said.

Groundwater sustainability agencies can be any local public agency – cities, counties, irrigation and water management districts, special act districts, and other public agencies that have a responsibility for water supply or water management or land use management.  In some areas, there will be new special act districts specifically created to do sustainable groundwater management.

The formation of these groundwater sustainability agencies will have far reaching decision power moving forward in terms of managing local groundwater resources, and so there has to be a lot of engagement with local stakeholders,” he said.  “What we are seeing is an active dialog in many areas where stakeholders communicate among themselves, and there is a lot of communication among local agencies, key stakeholders and landowners who are getting involved in the planning of GSAs.”

There can be one groundwater sustainability agency per groundwater basin, or there can be many per groundwater basin.  It might be that each GSA has a groundwater sustainability plan, or that many groundwater sustainability agencies overlying one basin may choose to have one groundwater sustainability plan.  “There’s a lot of discussion of how to coordinate these groundwater sustainability agencies across the groundwater basin and how to coordinate their planning efforts.”

There are efforts underway to collect information to find out what do we actually know about our basins and what information is already available,” Dr. Harter continued.  “There is much interest in understanding what it is these agencies do and what the groundwater sustainability planning process going to look like.  People are looking over their fence and looking elsewhere to see what’s happening, and much of this process is done very transparently, very open and very publicly.  You don’t have much time.  By June, 2017, all of these agencies have to be officially formed and have their declaration submitted to the Department of Water Resources.”

Harter SGMA PPT_Page_28In many areas, the agencies will be able to rely on existing ground work, some of it extensive, on groundwater management.  “We have groundwater management plans dating back to the early 1990s and having been created throughout the 2000s in many places in California shown here on this map,” he said.  “Once these groundwater sustainability agencies are formed, they have five years, or in the case of critically overdrafted basins, they will have three years to develop a groundwater sustainability plan.”


Harter SGMA PPT_Page_30The groundwater sustainability plan is everything that needs to be done to reach the ultimate goal of sustainable groundwater management which is to maintain sustainability on these six undesirable results,” he said.  “In its final regulations on what needs to be in these groundwater sustainability plans, the Department of Water Resources coined the term, ‘sustainability indicators’.  The sustainability indicators will be essentially the speedometers; much of the management under the Sustainable Groundwater Management Act will be towards making sure that these indicators are in essentially good status.”

Harter SGMA PPT_Page_31Dr. Harter then presented an analogy.  “What needs to happen is much like health management,” he said.  “On the left side in the slide, you see a health management system, and on the right, you see the equivalent of groundwater management.  Ideally we have sustainability groundwater management; we do that through adaptive supply management and adaptive demand management, we do that through stakeholder engagement; and just like we maintain our personal health through nutrition and exercise, through engagement and some monitoring assessment, some of that monitoring may just be done intuitively.”

In monitoring our health, we have triggers to tell us whether or not something is wrong with our health, and similarly, there need to be triggers in sustainable groundwater management to tell the groundwater manager and the public whether or not we are getting to a place where we don’t want to be,” he continued.  “Once we get into that place, we take some extraordinary measures – maybe putting in projects that increase the groundwater supply, putting in conservation projects, or putting in projects to do demand reduction.  Maybe it requires additional monitoring, much like when I’m falling ill with fever, I will measure my temperature twice daily rather than never at all.”

Harter SGMA PPT_Page_32Being critically ill is something that we want to absolutely avoid.  That’s what we’re managing towards is avoiding of getting to that place of being critically ill,” he said.  “Similarly in sustainable groundwater management, we want to avoid getting into a place where we have major undesirable impacts.  When that happens, the Act’s Chapter 11 falls in place, where the state essentially takes over management and may implement very drastic measures to make sure that these undesirable impacts are discontinued or even reversed.”

Harter SGMA PPT_Page_33The principle of having some indicators that help us manage sustainability, and along with those indicators is a status that we would like to achieve – the measurable objectives, and having thresholds that allow us to trigger management actions and clearly identifying those minimum thresholds above which we want to stay – that’s a key part of the groundwater sustainability plan,” he said.  “Having those in place for all six sustainability indicators and monitoring those sustainability indicators on a regular and sufficient basis so we know that we’re within our measurable objective range, we know when we reach triggers and can do certain management actions to avoid falling below these triggers, and avoid hitting the minimum threshold.”

Besides the governance issues, the groundwater sustainability plans govern the data collection, the monitoring, the modeling, and the assessment of the groundwater basins; they identify and spell out what supply management actions may be taken at which point, what kind of groundwater management actions may be taken at which point related to certain triggers, and how local stakeholders are being engaged within the groundwater sustainability plan, he said.

Dr. Harter then gave an example using seawater intrusion.  “How do we manage seawater intrusion?  An action to avoid seawater intrusion may be to have injection wells that create a seawater barrier near the coast, something that’s frequently done in southern California.  These are examples from the Orange County Water District that has built injection wells near the coast to build up the water table and avoid seawater intrusion.”

Other basins have begun to better collect local runoff and put in local surface water storage, or put local groundwater storage in place to recover their water levels and avoid seawater intrusion, he said.

There are groundwater banks in the state, particularly in the southern San Joaquin Valley and Southern California that have space in their aquifers to store groundwater, and they can bank groundwater for an agency that may be 100 or 200 miles away and store that groundwater for use during drought, he said.  “These water banks often operate either by flooding recharge basins or by using injection wells with water that is of sufficient quality is directly injected into the aquifer and then later recovered from that same well.”

Orange County Water District has an entire portfolio of actions that includes bringing in imported water through the State Water Project, managing stormwater flows, and managing local storage projects, as well as the groundwater replenishment system, which takes wastewater, cleans it, and treats it to very high water quality standard before the wastewater is used for recharging into the groundwater basin.

Orange County Water District, in order to do that, has set itself a measurable objective,” he said.  “Their measurable objective is certain levels of groundwater storage, and they operate that groundwater storage between an upper bar and a lower bar, with the lower bar being their minimum threshold and the upper bar being the measurable objective.  Their actions will depend on where they are in the cycle.  The closer they get to these lower places in their groundwater storage hydrograph, the more actions they take to avoid further overdraft.”

Other regions may be managing towards environmental flows in surface streams where they are trying to avoid groundwater pumping depleting surface water flows, he said.

Harter SGMA PPT_Page_44Under the original groundwater management planning efforts that we’ve had in 1990s and the 2000s, some of these measures have already been taken; in particular, we’ve seen much groundwater characterization, some public agency involvement, basin management objectives being identified, and monitoring programs being put in place, but it’s really the Sustainable Groundwater Management Act is really an enforcement mandate,” Dr. Harter said.  “Now it’s no longer just a plan to plan, but it’s a plan to action, and it’s a plan to action within a very well defined time framework.  It empowers local agencies to do demand management, to integrate their groundwater management with surface water management, and to integrate their groundwater management with water quality management and also with land use planning.”

Harter SGMA PPT_Page_45Groundwater sustainability agencies have the discretion or authority to conduct studies, to do monitoring and assessment, and to register and monitor wells; they can set well spacing to control the groundwater demand, they can require extraction reporting, and even regulate extractions,” he said.  “They will most likely initially trend towards primarily focusing on groundwater supply management, increasing recharge, and implementing capital projects that help with increasing recharge.  These projects have costs associated with them, some of which will be covered through state help, some of which will have to be covered through assessing local fees.”

Because of these actions, and because of the broader implications and the cost of these actions, stakeholder engagement is a critical part of groundwater sustainability planning, and the state agencies that oversee the implementation of local groundwater sustainability plans will be looking for this stakeholder process being spelled out in a groundwater sustainability plan.


Harter SGMA PPT_Page_47Dr. Harter then lastly turned to the issue of uncertainty.  “We have these sustainability indicators, and we will have defined monitoring programs that specifically tie monitoring data to these sustainability indicators.  Certain levels of the monitoring data will have to be achieved to be in good status with respect to sustainability indicators.  Those data will inform the local agencies on whether or not they have to do more management actions; these actions will then hopefully have the desired impact on the sustainability indicator.

The state has developed a groundwater sustainability planning regulation that is primarily concerned with making sure that local agencies property monitor, identify measurable thresholds and measurable objectives, the data collected is reported to DWR, and that it is transparent and being collected properly.

Harter SGMA PPT_Page_49The purpose of the regulation is essentially that there is a solid framework in place that moves this groundwater management forward,” he said.  “But a lot of the decisions will be done locally and a lot of the decisions will be done as we learn more about our groundwater basins, so adaptive management is going to be a very essential part of moving forward on this.  We will not know right away every action that may be taken over the next 20 years.  Much of it will be also integrated with other regional water management actions.”

The monitoring program will be designed to provide maximum certainty with respect to understanding the status of the sustainability indicators, and we have the technology to do that rather well.  While some may be done on a statewide basis through remote sensing or through statewide programs implemented by the Department of Water Resources, much of it will be done at the local level through things such as water level measurements, water quality measurements, and through measurements of streamflow, he said.

Harter SGMA PPT_Page_50There is some uncertainty about how certain management actions may or may not impact groundwater levels and other sustainability indicators, and the risk of implementing a project and not having a result resides entirely with the groundwater sustainability agency,” he said.  “The agency will be very invested in minimizing that risk by understanding as much as they can about their local basins and investing what needs to be invested in monitoring and assessing the potential success and the potential risk of any project that will need to be implemented.  So risk management is really a burden on the side of the local groundwater sustainability agency.

The monitoring, the modeling, and the processing of the data is at the core of all of these actions as that is the part that will be reported up to the state and will become the measure by which local efforts are going to be evaluated to see whether or not they are successful,” he said.  “If local measures are successful and everything is good, they will be approved by the DWR, but the implementation after the plan has been installed will be regularly reviewed and approved.  If problems arise, local agencies will work with the DWR to correct problems, and if they are not able to correct those problems, then there will be intervention by the State Water Resources Control Board, which has then the authority to step in and take over groundwater extraction and also place the cost for taking over onto local landowners.”


Harter SGMA PPT_Page_53Ultimately, the idea of the SGMA is to be demonstrably in sustainable management operation by 2040, or no later than 2040, and that will be an effort that will require that the groundwater pumping will need to be matched by an equal amount of recharge.  There will be a joint effort focused on local implementation by the groundwater sustainability agencies and their stakeholders in conjunction with technical assistance, regulatory requirements, and also financial support from the Department of Water Resources and with the State Water Board being the enforcing agency.”

Dr. Harter then concluded with a list of online resources:

Contact Dr. Thomas Harter at

For more information …

For more information on groundwater …

California’s groundwater


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