In January of this year, the Kings and Tulare Lake Subbasin Groundwater Sustainability Agencies (GSAs) were notified by the Department of Water Resources (DWR) that their Groundwater Sustainability Plans (GSPs) were incomplete. DWR identified several deficiencies in the GSPs. Below is a summary of the responses to DWR’s identified deficiencies in the Kings and Tulare Lake Subbasin GSPs.


The Department of Water Resources centered their comments of the Kings Subbasin GSPs around the Sustainable Management Criteria. The deficiencies covered four main topics:  groundwater levels, land subsidence, interconnected surface water systems, and water quality.

Deficiency – Groundwater Levels: GSPs do not set Sustainable Management Criteria for chronic lowering of groundwater levels in a manner consistent with the requirements of SGMA and the regulations.

Response: Changes to the GSPs included adding language stating groundwater levels will decline in dry periods to a point that they will not likely recover during normal/wet periods and a significant and unreasonable number of shallow domestic wells will go dry. A Shallow Well Mitigation Program was added to the GSPs.

Deficiency – Subsidence: GSPs do not set Minimum Thresholds and Measurable Objectives for subsidence in a manner consistent with their undesirable result definition, SGMA requirements, and GSP regulations.

Response: Primary concern is loss of capacity in gravity flow water conveyance systems. Changes to the GSPs include focus on impacts on infrastructure on main irrigation canals based on canal capacity. It was noted that the Subbasin does not have good data on confined aquifer pumping.

Deficiency – Interconnected Water Systems: GSPs do not consistently identify interconnected surface water systems, or provide the location, quantity, and timing of depletions of those systems due to groundwater use. The GSPs do not define Sustainable Management Criteria for the depletions of interconnected surface water in the manner required by the regulations.

Response: Much of the language in the GSPs was revised to list this as a data gap. A plan was included to gather missing information and determine extent of interconnection, as well as estimate of possible groundwater pumping.

Deficiency – Water Quality: GSPs do not provide adequate information to support the selection of degraded water quality Sustainable Management Criteria.

Response: Language was revised to be more specific about the determination of undesirable results. Water quality data will be collected annually and compared against Minimum Threshold levels. If there is an exceedance, site-specific investigation will try to determine if GSA actions have contributed to groundwater quality degradation, and if so, management actions would be implemented.


The Department of Water Resources centered their comments of the Tulare Subbasin GSP around the Sustainable Management Criteria. The deficiencies covered three main topics: groundwater levels, land subsidence, and water quality.

Deficiency- Chronic Lowering of Groundwater Levels: The GSP does not address potential impacts of dewatering wells in the context of the undesirable result of significant and unreasonable depletion of supply associated with the chronic lowering of groundwater levels.

Response : The GSAs will implement a well registry of active wells locations and their construction information. The information will provide additional clarification on the amount of pumping in each aquifer zone. Each GSA will prepare a mitigation plan to address impacted wells following the general requirements of the Mitigation Plan Framework. The GSAs are seeking to coordinate these mitigation programs.

Deficiency- Chronic Lowering of Groundwater Levels: The GSP does not set Sustainable Management Criteria for chronic lowering of groundwater levels in a manner consistent with the requirements of SGMA and the regulations.

Response: The methodology used to calculate the Minimum Threshold (MT) has been updated. The revised approach for developing the Sustainable Management Criteria (SMC) is based on a regional analysis of aquifer and well completion depths. This method defines a mapping framework within which the groundwater level SMC is defined. The groundwater infrastructure used to access the groundwater beneficial uses has been statistically analyzed using DWR’s database of well completions in the Subbasin. The MTs were set to be protective of 90% of wells listed in the database.

Deficiency- Land Subsidence: The GSP does not define undesirable results or set sustainable management criteria for subsidence in the manner consistent with SGMA and the GSP Regulations.

Response: Addressed using a risk assessment approach by combining the key elements of subsidence. MTs were set for total subsidence to be protective of infrastructure with “early warning” monitoring based on differential subsidence. Areas where impacts are most likely occurring will be identified through the risk framework. Local-scale minimum thresholds are defined that relate to specific infrastructure tolerances. Additionally, a regional scale risk framework is defined to identify areas that are most prone to undesirable results.

Deficiency- Water Quality: The GSP does not identify sustainable management criteria for degraded water quality. The reliance on existing regulations and policies to define undesirable results that represent degraded water quality conditions occurring throughout the Subbasin for the purposes of SGMA does not satisfy the requirements of the GSP Regulations.

Response: The SMCs for each constituent of concern (COC) were developed using the most stringent water quality goal. Ongoing evaluation will be based on utilizing statistical analysis for establishing concentration limits and trend analysis to evaluate COCs annually. Under this approach, an undesirable result for degraded water quality may be triggered and protective efforts will be implemented if the statistical assessment conducted each year indicates an upward trend of one or more COCs.

Both Subbasins submitted their revised GSPs to the Department of Water Resources prior to the July 27 deadline. As August 1st, the public can comment on the updated Kings and Tulare Lake Subbasin GSPs on DWR’s SGMA Portal. The public comment period will last for 60 days and close on September 30.

What is Groundwater?

Right under your feet, millions of gallons of water exist between rocks, sand, and gravel. Those permeable bodies of rock and sediment that are saturated with water are called aquifers.  Much of the water in the world exists below the surface- in fact, there is twenty to thirty times more water in the ground than there is in all the earth’s rivers and lakes. During dry years like this one, groundwater fills up bodies of surface water and serves as a “critical buffer against the impacts of drought and climate change.” In some communities, it is the only source of drinking water. Groundwater also provides water for agricultural operations. But that’s not all.

Did you know?

💧 97% of all liquid freshwater on earth is groundwater. (Meaning- most freshwater that is not frozen in glaciers and is available to humans is groundwater.)

💧 Groundwater provides almost 40% of California’s total water supply, with that percentage increasing to 46% or more in dry years.

💧 CA’s Department of Water Resources estimates that the state’s 515 groundwater basins have a storage capacity of between 850 million and 1.3 billion acre-feet. This is an incredible amount when compared to the less than 50 million acre-feet that can be stored in all of CA’s major reservoirs.

Groundwater is essential to every facet of life in our state and region and has immense potential to increase our resilient water supply.


Sustaining Groundwater Supplies with Better Management

In the Central Valley this essential resource was being pumped from the ground faster than it could be replenished. Results of this include lower groundwater levels, which in some areas can cause the ground elevation to lower. This is called subsidence, which can cause damage to surface structures such as roads, building foundations, aqueducts, bridges, pipelines, and flood control structures.

When groundwater is not managed sustainably, water quality can also be impacted. Water quality can degrade due to over pumping, limiting its use for irrigation or drinking without expensive treatment.

Sustainable management of groundwater is needed to address these issues, in addition to avoiding the costs of energy expenses required to pump groundwater from greater depths, the expense of fixing damages caused by land subsidence, and subsequent indirect impacts such as higher food prices.

With these costs in consideration, it is evident that groundwater must be managed sustainability for the well-being of our Central Valley communities, agricultural operations, and economy.


Solutions at the Local Level

GSA map of the Kings and Tulare Lake Subbasins. Click image to find your GSA.


In 2014, California Governor, Jerry Brown passed the Sustainable Groundwater Management Act. This piece of legislation is commonly known as SGMA. SGMA requires local governments and water agencies to bring groundwater basins into balanced levels of pumping and recharge by 2040.

This led to the creation of Groundwater Sustainability Agencies (GSAs), which are agencies that manage groundwater at the local level.

GSAs designed Groundwater Sustainability Plans, (GSPs), documents that outline the agencies’ detailed plans for achieving sustainability. GSAs work with local landowners and communities on implementing their GSPs. (We love our acronyms in the water industry!)


Measuring Groundwater Sustainability

Under SGMA, sustainability is measured using “sustainability indicators” which include: groundwater storage, groundwater levels, interconnected surface water, water quality, and land subsidence. The sixth indicator, seawater intrusion, is not applicable to the Central Valley GSAs. Learn more about each sustainability indicator through the following graphics:



Securing Groundwater for Future Generations

Meeting each of these measurable objectives and achieving sustainability in the Central Valley is not a job for one group, agency, or industry. Groundwater sustainability requires the collaborative efforts of landowners, farmers, residents, policy makers, advocacy groups, engineers, water providers, and more!

You are part of the solution. Connect with your local GSA, advocate for policies that promote groundwater sustainability, innovate recharge projects, and stay in touch with organizations like KRCD to receive regular updates on Central Valley groundwater.

As Leonardo Da Vinci said, “water is the driving force of all nature.” Together, we can ensure this powerful resource is available for generations to come.


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