Groundwater in California has received a lot of attention lately, and for good reason: We use a lot of it. So much so, California has been identified as the heaviest groundwater user in the United States, with approximately 16% of the nation’s groundwater supplies being extracted from the state’s aquifers.
Groundwater is often described as a ‘hidden resource’; but because it cannot be directly seen, it is likely most Californians do not give much thought to the economic benefits that vast groundwater supply has added to the State, nor consider it’s value. But it is unlikely that California could have achieved its present status as the largest food and agricultural economy in the nation and eighth largest overall economy in the world without groundwater resources.
These economic benefits have not come without many costs: the diminished quantity and degraded quality of groundwater resources, the infrastructure damaged by land subsidence, the decline in ecosystem services provided by the interaction of groundwater and surface water, and the increased energy required to bring the groundwater to the surface.
Many of the state’s groundwater basins are being managed sustainably – meaning that withdrawals do not exceed the amount replenished by man or by nature; but some basins, especially those in major agricultural regions in the southern Central Valley and Central Coast, groundwater withdrawal exceeds the amount that is recharged, causing conditions of overdraft and threatening this vital resource.
Groundwater is a critical important part of California’s supply, accounting on average for 40% of total annual agricultural and urban water uses statewide in an average year, and up to 65% or more in drought years. About three-quarters of the state’s residents – about 30 million people – depend on groundwater for at least a portion of their water supply; for 6 million residents, it is their only supply.
The Department of Water Resources estimates that on average, 16.5 million acre-feet of groundwater is extracted per year, with 39% going towards agriculture, 41% supporting urban dwellers, and 18% being used for managed wetlands. The USGS estimated that in 2010, groundwater withdrawals in California were equal to about 13 billion gallons per day.
The state’s groundwater storage capacity is more than 10 times that of all its surface reservoirs, although not all that water is accessible or of acceptable quality. However, the state’s groundwater resources are not evenly distributed. Whether or not there is groundwater in a particular area depends on the geology of the underlying soils.
Some of the state’s largest cities, such as San Diego and San Francisco, have very little groundwater resources available, while others, such as Bakersfield, rely solely on groundwater to support their population. The Central Coast region is the most dependent on groundwater, with 80% of its supplies coming from groundwater aquifers.
DWR estimates that on average, 2 MAF is withdrawn from the state’s aquifers per year more than what is being recharged, and much more so during periods of drought. This is nothing new; scientists estimate that since California’s development in the late 1800s, the state’s groundwater reserves have been reduced by 125 MAF, or 4.5 times the capacity of Lake Mead. Most of this groundwater depletion has occurred in the San Joaquin Valley.
Based on estimates by DWR for the period between 2005 and 2010, with respect California’s total water supply, groundwater supplies contributed 39% of the supply to meet the agricultural uses, 41% of the supply to meet urban uses, and 18% of the supply to meet managed wetland uses. During that same time period, with respect to total annual groundwater extraction, about 76% of the groundwater extracted went to meet agricultural uses, 22% to meet urban uses, and 2% for managed wetlands uses.
Groundwater is held in geologic formations known as aquifers. An aquifer is astores water in the spaces and voids between the granules. California’s groundwater supplies come from two types of aquifers: fractured rock aquifers and alluvial aquifers.
Fractured-rock aquifers store groundwater in fractures or other void spaces within the rocks; these types of aquifers are typically found in the mountain and foothill areas of the coastal ranges and Sierra Nevada, as well as in the volcanics of the Modoc Plateau. Wells served by these fractured rock formations typically have much smaller yields than an alluvial groundwater basin with half of all hard rock wells yielding only enough for individual domestic supplies. In addition, the limited storage capacity of these fractured rock systems can mean that supplies can vary dramatically over the summer and during dry years. (For more on fractured-rock aquifers, click here.)
Alluvial aquifers are composed of sand, gravel, and other fine-grained sediments that store the water in the voids and spaces among the sediments. The Department of Water Resources has identified 515 alluvial groundwater basins across the state which cover 62,000 square miles or about 42% of the state’s area. These basins are highly variable in their water yields, geologic origins, physical and hydrogeological characteristics, production properties, and water quality.
The most prodigious of the state’s groundwater basins are found in the Central Valley where a structural trough forms an aquifer system extending from north of Red Bluff to south of Bakersfield, about 400 miles long and from 20 to 70 miles wide. The aquifer system is comprised primarily of sand, gravel, and clay deposits with most of the freshwater found at depths of less than 2,500 feet. The northern portion of the valley is drained by the Sacramento River, the middle portion is drained by the San Joaquin River, while drainage in the Tulare Lake basin is completely internal. Nearly three-quarters of the state’s groundwater use and 83% of the state’s agricultural groundwater use is extracted from the Central Valley aquifer system.
Coastal aquifers include a number of basins in the Bay Area, Central Coast, and Southern California regions; seawater intrusion is a common problem for coastal aquifers. Other alluvial aquifers include basins in the Eastern Sierra, and the Mojave and Colorado deserts.
Bulletin 118, California’s groundwater
The state’s groundwater basins are described in Bulletin 118, California’s Groundwater, which provides groundwater basin maps and descriptions for the state’s 515 alluvial groundwater basins. Information includes geology of the basin, groundwater quality and quantity, and current groundwater practices.
The bulletin also includes guidance and tools to assist local agencies in effectively managing groundwater, such as required and recommended components of effective groundwater management plans and a model ordinance that can be used by local governments, as well as a chapter that describes the roles of state and federal agencies in protecting groundwater quantity and quality.
Last published in 2003, the report is currently being updated, with an interim report due out in 2017 and the full report by 2020.
For more information …
- Basic concepts of groundwater hydrology, by Thomas Harter, UC Division of Agriculture and Natural Resources (6 pages)
Groundwater can be recharged in many ways: by precipitation, by water that leaks into aquifers from surface waters, by intentional recharge efforts, by irrigation water applied in excess of what crops use, or even inadvertently from leaky pipelines and canals.
There is a balance that occurs when the amount pumped out approximates the amount of recharge; however, if more water is pumped out than is recharged, the groundwater basin can become overdrafted.
Groundwater overdraft can have numerous impacts:
One of the first and most noticeable impacts of excessive groundwater pumping is the lowering of the water table. As the depth to water increases, the water must be lifted higher to reach the land surface, requiring more energy to drive the pump, increasing energy costs. At the same time, as water levels decline, the rate of water the well can yield may decline as well. If groundwater levels continue to decline, the well might have to be deepened, or even a new one drilled.
Groundwater overdraft can create new water quality problems or make existing groundwater pollution worse. As aquifer levels decline from chronic overdraft, natural and manmade pollutants can concentrate in the remaining groundwater, making it unsafe for irrigation or drinking without costly treatment. In some cases, wells must be shut down.
Groundwater quality can also be impacted as continued pumping may cause polluted groundwater or seawater to migrate or be drawn into areas that would otherwise not be impacted.
Seawater intrusion is the movement of saline water into freshwater aquifers. It occurs naturally to some degree in most coastal aquifers, due to the hydraulic connection between groundwater and seawater; however, seawater intrusion is most often is caused by groundwater pumping from coastal wells causing the groundwater level to drop, reducing water pressure, and slowing the saltwater to flow further inland.
In the 1950s, the post World War II population boom in Southern California led to groundwater overdraft and seawater intrusion. To combat the problem, a seawater barrier was constructed by positioning a series of injection wells between the ocean and the groundwater aquifer that inject water into the aquifer to ensure the water level near the ocean stays high enough to keep the seawater from seeping in.
Along the Central Coast, seawater intrusion remains an issue, with seawater intruding as far as five miles inland in the Salinas Valley, and three miles inland in the Pajaro Valley.
These subsidence impacts occur over a wide area, damaging roads, canals, buildings, and other infrastructure. In some aquifers, this subsidence is permanent, forever reducing the storage capacity of the aquifer.
Subsidence in the San Joaquin Valley has been called the single largest alteration of the land surface attributable to humankind with subsidence in some areas reaching nearly 30 feet. In the current drought, a NASA report measured land subsidence rates in some areas of the San Joaquin Valley at as much as 2 inches per month.
The San Joaquin Valley is not the only region in California to experience subsidence; subsidence has occurred in the Sacramento Valley, the Santa Clara Valley, the Antelope Valley and other southern desert groundwater basins. A recent report by the California Water Foundation found that land subsidence has cost billions of dollars in damage to canals, roads, bridges, building foundations, pipelines, and other infrastructure, as well as altering the capacity of flood bypasses and diminishing the effectiveness of levees.
For more information …
- San Joaquin Valley: The largest alteration of the earth’s surface, fact sheet from the USGS
- Land Subsidence and Groundwater Use in California, a report from the California Water Foundation
Traditionally, management of water resources has focused on surface water or groundwater as if they were separate entities. Surface water commonly is hydraulically connected to groundwater, but these interactions are difficult to observe, hard to measure, and therefore commonly have been ignored in water-management considerations and policies.
However, surface water and groundwater systems are connected in most landscapes. Surface waters can gain water from the inflow of groundwater through the streambed, lose water to groundwater by outflow through the streambed, or they can do both, depending upon the situation. It is groundwater that generally keeps streams flowing between precipitation events or after snowmelt.
For more information …
California depends on groundwater for a major portion of its annual water supply, and sustainable groundwater management is essential to a reliable and resilient water system. In recognition of this, Governor Brown signed a three-bill legislative package of laws collectively known as the Sustainable Groundwater Management Act (SGMA) in September of 2014 that set in motion a plan to sustainably manage the state’s groundwater basins.
The centerpiece of the legislation is recognition that groundwater management is best accomplished at the local level, and so SGMA requires the creation of groundwater sustainability agencies to develop and implement locally-developed groundwater sustainability plans, allowing 20 years to achieve sustainability.
The legislation defines ‘sustainable groundwater management’ as the ‘management and use of groundwater in a manner that can be maintained during the planning and implementation horizon without causing undesirable results’.
Undesirable results are defined in the legislation as:
- Chronic lowering of groundwater levels indicating a significant and unreasonable depletion of supply
- Significant and unreasonable reduction of groundwater storage
- Significant and unreasonable seawater intrusion
- Significant and unreasonable degraded water quality
- Significant and unreasonable land subsidence
- Surface water depletions that have significant and unreasonable adverse impacts on beneficial uses of surface water
The legislation does not alter any water rights: the legislation adds Water Code section 10720.5(b) that states that nothing in the legislation “determines or alters surface water rights or groundwater rights under common law or any provision of law that determines or grants surface water rights.”
There are some exclusions. Adjudicated groundwater basins are excluded from having to form GSAs and develop plans, but they are subject to reporting requirements. Agencies that have ongoing successful groundwater management programs that are managed to a sustainable yield can be exempted if they meet the requirements in the alternatives section of the Groundwater Sustainability Plan regulations.
For more information …
- For more information on implementation of the Sustainable Groundwater Management Act, click here.
- For the history of the passage of the legislation, go here: Desperate times call for sensible measures: The making of the Sustainable Groundwater Management Act, by Tina Cannon Leahy
The legislation defines roles for local agencies, the Department of Water Resources, and the State Water Resources Control Board.
The Sustainable Groundwater Management Act requires local groundwater pumpers to form Groundwater Sustainability Agencies and to develop Groundwater Sustainability Plans to manage their groundwater basins. All groundwater basins designated by the CASGEM program as high and medium priority must be managed by a groundwater sustainability plan by 2022, or by 2020 if the groundwater basin has been determined to be in conditions of critical overdraft. A GSA may adopt a single plan to cover an entire basin or a number of plans can be combined through a coordination agreement.
Groundwater Sustainability Plans must identify when and where groundwater conditions are causing undesirable results; the specific projects and actions that the GSA will undertake to prevent those impacts; and milestones to track plan progress. Plans must include measurable objectives, as well as describe how the GSAs will groundwater conditions in the basin.
In order to effectively implement the plans, SGMA provides new tools and authorities which were modeled on specific authorities that the Legislature historically has granted to specific groundwater management agencies, such as requiring registration of groundwater wells, measuring and limiting groundwater extractions, imposing fees for groundwater management, and enforcing the terms of a groundwater sustainability plan.
For more information …
The Sustainable Groundwater Management Act defined the new and expanded responsibilities for the Department of Water Resources, which include developing regulations to revise groundwater basin boundaries; adopting regulations for evaluating and implementing Groundwater Sustainability Plans (GSPs) and coordination agreements; identifying basins subject to critical conditions of overdraft; identifying water available for groundwater replenishment; and publishing best management practices for the sustainable management of groundwater. DWR is also tasked with evaluating groundwater sustainability plans for adequacy.
Since the legislation became effective, DWR has accomplished a number of tasks required of it and made significant progress on others. DWR had adopted the basin boundary regulation by the end of 2015 and identified basins subject to critical conditions of overdraft at the beginning of 2016; regulations to evaluate Groundwater Sustainability Plans, their implementation, and coordination agreements are under development and due by June 1, 2016.
- For more from the Department of Water Resources on their role in implementing SGMA, click here.
- For more on the roles of DWR and the State Water Board, go here: DWR and State Water Board discuss their roles in implementing the Sustainable Groundwater Management Act at public meeting in Sacramento
While the Sustainable Groundwater Management Act is centered on the concept that local governance is the key to successful groundwater management,
in cases where the local and regional agencies are unable or unwilling to sustainably manage the groundwater basin, the legislation also authorizes the State Water Resources Control Board to step in to protect groundwater resources in cases. State intervention only occurs when local efforts are not successful, and remain in place until local efforts are able to sustainably manage groundwater resources.
The legislation allows for intervention by the State Water Board instances where no local agency is willing to serve as a groundwater sustainability agency; the groundwater sustainability agency does not complete a groundwater sustainability plan by the mandated deadline (2020 or 2022); the groundwater sustainability plan is deemed inadequate by DWR and remains so after efforts to cure the deficiencies; or the groundwater sustainability plan is being implemented and simply does not work. In these cases, the State Water Board is authorized to create an interim plan that will remain in place until the GSA is able to reassume responsibility. Of course, all that State Water Board love doesn’t come for free: the legislation authorizes the State Water Board to establish fees to recover costs incurred in connection with the intervention.
The earliest the State Water Board can implement the State Intervention is 2017, when local agencies in high- and medium-priority basins must form GSAs. If local agencies fail to form a GSA by July 1, 2017 local groundwater users must begin reporting groundwater use to the State Water Board.
- For more on the timelines that trigger State Water Board intervention, click here.
- For more from the State Water Board on their role in implementing the Sustainable Groundwater Management Act, click here.
- For more on the roles of DWR and the State Water Board, go here: DWR and State Water Board discuss their roles in implementing the Sustainable Groundwater Management Act at public meeting in Sacramento
Information on the state’s groundwater levels is available through the California Statewide Groundwater Elevation Program, or CASGEM.
CASGEM is the state’s long-term program to collect and track groundwater elevations statewide. The program is a collaborative effort between the Department of Water Resources and the local agencies (called Monitoring Entities) who are responsible for collecting and reporting the data; the Department’s role is to coordinate, maintain, and make the data available in a publicly-accessible database. The intent of the CASGEM program is to establish a permanent, locally-managed program of regular and systematic monitoring in all of California’s alluvial groundwater basins.
The data compiled from the CASGEM program is made available to the public through on online system. The system uses reports, search tools, and GIS to allow users to view a wide-range of data, such as find information on the Monitoring Entities; search and view groundwater elevation data and monitoring well information, and download summary reports, well information, groundwater data, hydrographs and maps.
For more information …
As part of the legislation that established the CASGEM program, the Department of Water Resources was required to assess and prioritize the state’s groundwater basins to help evaluate and determine the need for additional groundwater level monitoring. The legislation specified eight criteria to be considered: the overlying population; projected population growth; number of public supply wells; total number of wells; overlying irrigated acreage; reliance on groundwater as the primary source of water; and impacts on the groundwater; including overdraft, subsidence, saline intrusion, and other water quality degradation; as well as any other information determined to be relevant by the Department.
In June of 2014, the final basin prioritization was completed. Out of California’s 515 groundwater basins and subbasins, 127 were categorized as High and Medium priority. These basins account for 96% of California’s annual groundwater pumping and supply 88% of the population which resides over groundwater basins. The remaining 388 basins are Low and Very Low priority and comprise 75% of the groundwater basins in the State. The basin prioritization will be used to align the Department’s limited resources.
The final basin prioritization is available by interactive map, summary tables, and reports. Individual basin summary sheets provide the ranking values for the eight components and the basin’s total ranking score.
At the end of 2015, only 7 of the 127 high and medium priority basins were either partially or fully unmonitored, making them non-compliant with the CASGEM program. Although CASGEM is a voluntary program, non-participation could result in ineligibility for a State water grant or loan. The list of High and Medium priority groundwater basins that are not in compliance with the program is provided to state water grant programs, with grant eligibility being determined by the respective grant program.
For more information …
Provisions in the Sustainable Groundwater Management Act directed the Department of Water Resources to identify groundwater basins and subbasins in conditions of critical overdraft, defined by SGMA as a condition ‘when continuation of present water management practices would result in significant adverse overdraft-related environmental, social, or economic impacts.’ Those adverse impacts can include seawater intrusion, land subsidence, groundwater depletion, and/or chronic lowering of groundwater levels.
In January of 2016, the Department of Water Resources released the final list of groundwter basins designated in critical overdaft. SGMA requires that all groundwater basins designated as high or medium priority and considered critically overdrafted must be managed by groundwater sustainability plan by January 31, 2020; that deadline for all other high and medium priority basins is January 31, 2022. For more information, click here.
Besides CASGEM, there are other sources for groundwater level information:
Water Data Library: Access to data and hydrographs for nearly 20000 wells in groundwater basins throughout California from Department of Water Resources.
USGS Groundwater Data for California: The USGS monitors an estimated 1,909 wells for groundwater level information, mostly located within the South Lahontan and Central Coast hydrologic regions.
Groundwater Protection Program (California Department of Pesticide Regulation): DPR’s Ground Water Protection Program evaluates and samples for pesticides to determine if they may contaminate ground water, identifies areas sensitive to pesticide contamination and develops mitigation measures to prevent that movement.
Other Groundwater Topics
Conjunctive management refers to the planned use and management of both surface and groundwater resources to maximize the availability and reliability of water supplies in a region. With the right infrastructure in place, water districts and agencies can manage surface water and groundwater as a single source, using one to balance the other when surface water or groundwater levels are low, thus reducing diversions and groundwater pumping while enhancing supplies.
Conjunctive management involves the efficient use of both surface and groundwater resources through the managed operation of a groundwater basin and a surface water storage system where water is stored in the groundwater basin to be used later by intentionally recharging the basin when excess water supply is available. There are many methods an agency can use, such as in-lieu recharge programs, natural infiltration, managed infiltration such as spreading basins, or by direct injection.
Conjunctive management in California is nothing new; many agencies have implemented conjunctive management programs for decades to meet demands when surface water is cutback, to replenish declining groundwater levels, and to help control subsidence. Conjunctive management programs can range from the Semitropic Water Storage District at 2.1 MAF to the small 2289 AF program run by the Compton Water Department.
For more information …
- Conjunctive water management: What is it? Why consider it? What are the challenges?
- Conjunctive management and groundwater storage, from chapter 9 of the California Water Plan
California has long relied on surface reservoirs to manage the state’s fluctuating water supply as evidenced by the over 1300 reservoirs both large and small that dot the landscape – from Redding in the north to San Diego in the south. However, environmental impacts, evaporation, and other concerns associated with reservoirs and the dams that create them have caused a shift towards groundwater banking as a water storage and management strategy for California.
The Central Valley, especially the southern portion of Kern County, is home to numerous groundwater banking operations which played a critical role during the dry years of 2007 to 2009, recovering over two-million acre-feet of banked supplies to their customers. However, groundwater banking is not just for the wide-open spaces of the Central Valley; when properly managed, the same techniques can be applied to groundwater basins in urban areas, providing a reliable local source of water.
Groundwater banking essentially uses the empty space in aquifers for storage purposes, storing water during wet periods that is later recovered for use during droughts. There are two basic methods for putting water into storage:
- direct recharge: adding surface water supplies either by using recharge ponds to percolate water into the aquifer or by injection wells to place the water directly there, or
- in-lieu agreements: surface supplies are provided to groundwater users to be used in lieu of groundwater pumping, and the amount of water that otherwise would have been pumped becomes the banked water.
The groundwater that is stored is then later recovered from the aquifer when needed through recovery wells.
Groundwater storage has several advantages over surface reservoirs as well as a few potential disadvantages. Groundwater banking projects can often store as much as a surface reservoir but cost much less to construct, and they can have a much smaller environmental impact than a reservoir. Another significant advantage is that once the water is recharged into the water bank, evaporation no longer occurs whereas evaporation losses in a reservoir can be several feet per year. Groundwater storage is flexible enough to respond to seasonal and inter-annual variability and will be an increasingly important tool for managing the state’s water resources in the face of climate change.
Among the disadvantages, groundwater banking projects have limited recharge capacity; when floodwaters are high, the limited infiltration rate can preclude them from fully capturing the all high flows. Energy costs for recovering water are a factor, and typically exceed energy costs for reservoirs. Pumping from the aquifer is limited by the pumping capacity of the banking facility and not well-suited to demands that can fluctuate significantly during the year.
The vast groundwater basin underlying the Central Valley is California’s largest reservoir and an important resource for the productive agriculture industry that farms the land above it.
A 2009 study by the USGS found that over the last four decades, the Central Valley has lost around 60 million acre-feet of water due to overpumping. This has had numerous negative effects such as localized subsidence and increased well-drilling as well as higher groundwater pumping costs.
However, the drawdown in the aquifer does present an opportunity to utilize the dewatered portions for groundwater banking, and agricultural water districts have found ways to take advantage of the resource, particularly in the southern portion of the Central Valley.
In Kern County, virtually all the water districts are involved in groundwater banking to some degree. Some are groups that have joined together to develop a project to improve their own water supply reliability while other projects are partnerships between Kern County Water districts and out-of-county entities who bank their excess water surface water in Kern County and then withdraw it in times of need.
One of the largest of the groundwater banks operating in Kern County is the Kern Water Bank (KWB), which serves Kern County farmers as well as the residents of Bakersfield.
Although it’s one of the smallest in terms of acreage, only occupying approximately 20,000 acres or about 30 square square miles, it’s geology makes it particularly conducive to groundwater banking: The water bank is located on a huge fan-shaped wedge of sand and gravel that forms where the Kern River exits out of the Sierras and spreads out into the grasslands of the southern San Joaquin Valley. Sediments here extend as much as 14,000 feet deep and as a result, the Kern Water Bank can add 460,000 acre-feet per year to its basin and recover up to 240,000 acre-feet per year with the capacity to store over 1 million acre-feet of water.
Jon Parker, general manager for the Kern Water Bank, gave discussed the water bank’s operations in depth to the Assembly Select Committee for Regional Approaches to Addressing the State’s Water Crisis in March of 2013 in an oversight hearing titled “The Science of Storing Water.”
There are six participants in the Kern Water Bank; they include water storage districts, an improvement district, and a mutual water company.
Mr. Parker then began with a brief history of the Kern Water Bank. In the early 1980s, the Department of Water Resources (DWR) purchased 20,000 acres of land in Kern County to implement a groundwater banking project after conducting a feasibility study. However, DWR encountered many legal, institutional, and political roadblocks to implementing the project including concerns about the State Water Project’s ability to pump Delta water for recharge, questions about the ability to meet water quality standards for pump-in to the California Aqueduct, and an inability of DWR and Kern County Water Authority to reach agreement on measures to comply with Water Code Section 11258.
“There were priority questions on who would be able to use the facility and would Kern River water be excluded from the facility so there were problems there,” said Mr. Parker. “There were endangered species issues, both in the Delta and on the lands themselves, and there were water quality questions, such as arsenic and other constituents in the water that would those prevent us from recovering the water. In 1993 DWR halted all design efforts and developed a revised workplan that provided just minimal activities on the bank.”
In 1994, provisions in the Monterey Agreement included a transfer of the property over to designated State Water Project agricultural contractors in exchange for permanent retirement of 45,000 acre-feet of their Table A contract amount. The provision transferred the state’s ownership of the Kern County property to Kern County Water Agency, and then to the Kern Water Banking Authority for local agency development and use as a groundwater bank.
The newly formed Kern Water Banking Authority still had to overcome the roadblocks that had derailed the earlier project. There were three sets of stakeholders to be considered: other users of the basin’s groundwater, the wildlife protection agencies (the Department of Fish and Wildlife and the US Fish and Wildlife Service), and the downstream users of the conveyance facilities that would receive water blended with recovered water from the water bank.
“In 1995 , Kern Water Bank MOU was signed, and that was a critical agreement with local adjoining entities to overcome those institutional issues,” said Mr. Parker. “In 1997, a Habitat Conservation Plan was approved that was a critical agreement to get over issues with endangered species on the land and that has worked extremely well. In 2001, the aqueduct pump in policy was developed, and this was a critical agreement with downstream stakeholders to be able to recover our water. Part of that also included extensive sampling and modeling to demonstrate the program’s effect on downstream stakeholders.”
For a successful groundwater banking program, there must be a suitable aquifer with the right hydrogeologic attributes. The Kern River Alluvial Fan is particularly suited to groundwater banking with the upper 1,000 feet of the aquifer consisting of 50 to 70% or more of sand and no laterally extensive confining or perching layers present. Mr. Parker ran down the numbers: “Specific yield is about 18%, hydraulic connectivity is about 60 feet a day – those are really good numbers. Groundwater quality is generally excellent – average concentrations for arsenic are 3 parts per billion, nitrates are 8 parts per million, and TDS is about 290 parts per million.”
Access to supplies and regional recovery infrastructure is critical, said Mr. Parker. Conveyance facilities are needed for delivering water to and from a groundwater banking project and the ability to access surplus flows for recharge is necessary. “We have access to water from the State Water Project via the California Aqueduct which accesses the snowpack in Northern California; we have the Friant-Kern Canal which accesses snowpack from the Central Sierra, and we have the Kern River which accesses the southern Sierra, so we have facilities that access snowpack throughout the state going right past the water bank. That’s a tremendous benefit.”
Delivery of recovered water to water banking participants is accomplished either by direct deliveries via the California Aqueduct or by exchange deliveries. These exchanges can occur either by an upstream participant taking water from the California Aqueduct and the Kern Water Bank returns a like amount into the aqueduct downstream or by an agreement that allows the water bank to use San Luis Reservoir to regulate supplies. “A banking program recovers water slower than it can take it in,” said Mr. Parker. “It’s not like a reservoir where you can dump it out rapidly, so you have to have facilities where you can re-regulate that water to maximize the benefit from a groundwater bank.”
The quality of the groundwater is also important, said Mr. Parker. Although the banking programs may not deliver water directly to the stakeholders (and the Kern Water Bank does not deliver water to entities south of Kern County), since the recovered water is returned to the California Aqueduct, downstream stakeholders receive a blend of aqueduct water and recovered water. “If we’re going to provide water to one of our upstream participants such as Semitropic Water Storage District, they take water out of the aqueduct north of the bank, and we put a like amount of water back in the Aqueduct downstream – not necessarily at the same time, but matching it on an AF by AF basis – and what happens is the blend goes south. And so if we were to put in poor quality water … the folks down south would have a problem with that.”
“You’re not delivering the water to them; they are getting the chemistry of your water downstream,” Mr. Parker explained. Downstream stakeholders may rely on the water to blend and reduce a constituent present in other supplies, “so you really need to match aqueduct background quality on a constituent by constituent basis or mitigate for it,” he said, noting that the Pump-in Guidelines were developed by DWR and the downstream stakeholders in 2001 and have worked very well.
The water bank includes 70 shallow recharge ponds that cover 11 square miles. “Our average recharge rate is 1/3 of a foot a day … we can recharge about 60,000 AF a month,” said Mr. Parker, noting that recharge does decline over time. “In 2005-2006, we recharged for 2 years straight and that number dropped to about 30,000 AF a month; we also had groundwater showing up as surface water in low parts of the water bank.”
Maximum annual recharge capacity is about 500,000 acre-feet and the storage capacity is about 1.5 million acre-feet. “You don’t have a set limit with groundwater storage, but that’s more than a lot of the surface reservoirs throughout the state,” said Mr. Parker. “The Kern County Water Agency has estimated there is about 10 million AF of available storage in the Kern groundwater basin.”
“We have 84 wells with an average depth about 750 feet,” said Mr. Parker. “The annual recovery capacity is about 240,000 AF at the beginning of a recovery program, so that is about half of our recharge capacity which is why you need the facilities to reregulate your supply.”
The water bank operates under a Habitat Conservation Plan/Natural Community Conservation Plan that was executed in 1997. The HCP provides for the management of water bank lands with the stated dual purposes of accomplishing both water banking and environmental objectives. “For example, rather than having well-groomed ponds that have levees on a four sides, the levees are just on downslope areas, and the upslope areas just feather out in a natural topography so it makes for a very natural setting.”
He noted that a statewide-recognized ornithologist did some studies, with one of his bird counts finding over 35,000 water birds. “He considers the water bank one of the top five freshwater wetlands in the state so it really is environmentally a beneficial program.”
Of the 20,000 acres, only 236 acres have been permanently disturbed for water banking facilities, and water bank activities have helped to reestablish willows, cottonwoods, sedges, and other wetland vegetation and habitat that existed historically throughout much of the southwestern San Joaquin Valley. This upland habitat supports a wide range of species including large populations of raptors, burrowing owls, tri-colored blackbirds, kangaroo rats, rabbits, badgers and coyotes.
Mr. Parker then presented a graph that shows the water bank’s recharge and recovery since the bank was formed in 1995. About 65% of the water banked has come from State Water Project supplies; the Kern River has supplied 21% and the Friant-Kern Canal has supplied 14%. “The total recharge over that period of time has been about 2 MAF and our total recovery has been about 1 MAF, so current storage is about 1 MAF in the bank,” he said.
Participants in the water bank have spent about $40 million on infrastructure, with about 90% of the water banks capital costs being funded by the participants. The water bank’s annual expenses are funded through recharge and recovery expenses that are paid by the user. “For recharge, they are about $9.50 to $16 an acre-foot, and on the recovery side they are $70 to $90 an acre-foot,” said Mr. Parker. “The recovery is more expensive because you need energy to recover the water.”
The MOU sets a percentage of loss due to evapotranspiration at 6% of the gross amount of water recharged to provide assurance that the banking operations will not recover more water than actually recharged, so 94% of the water put into the water bank can be pumped out, he said.
For more information:
- Click here to visit the Kern Water Bank Authority website.
- Click here for more information on the Kern Water Bank: includes an essay on how the water bank works and a copy of the MOU that created the bank, from Jon Parker’s testimony to the Little Hoover Commission in 2010.
- Click here for Improving Water Management through Groundwater Banking:Kern County and the Rosedale-Rio Bravo Water Storage District, from the Pacific Institute.
- Click here for more on the geology of the Kern Alluvial Fan.
- Click here for the 2009 USGS study of the Central Valley groundwater basin.’
- Kern Water Bank is not without controversy: The issues are more focused on ownership, not so much operation. This article details the issues surrounding the Kern Water Bank: DWR must reopen environmental review on the Kern Water Bank. The transfer of the property was protested by C-WIN and the Center for Biological Diversity. Explore the issue further at this page from C-WIN: The Kern Water Bank; the Kern Water Bank responds here: Kern Water Bank: Myth and Reality.
The Water Replenishment District of Southern California (WRD) manages two of the most utilized groundwater basins in Southern California, the West Coast Basin and the Central Basin. The two basins extend 420 square miles throughout southern Los Angeles County and are one of the region’s most reliable sources of water.
In a legislative oversight hearing before the Assembly Select Committee for Regional Approaches to Addressing the State’s Water Crisis in March of 2013, chief hydrologist Ted Johnson gave a presentation on the district’s operations.
“Our agency was formed under the Water Replenishment District Act of 1955, AB 2908, that was signed by then-Governor Goodwin Knight,” began Ted Johnson. “To my knowledge, we are the only water replenishment district formed under this act … which defines a special district to put water into the ground. Not necessarily to take it out and serve it for drinking water, but to put it under ground and store the water.”
The Water Replenishment District is a public agency with five board members elected by the public to four year terms. “We operate under Division 18 of the California Water Code, and our mission is to put water back into the aquifers that other entities are pumping out at a more rapid pace than can be refilled naturally, so we provide artificial replenishment water to fill up and make up the deficit,” he said. The WRD is also involved in groundwater monitoring, safe drinking water programs, and combating seawater intrusion throughout Southern Los Angeles County.
The Water Replenishment District has 43 cities within its boundaries and serves 4 million people – over 10% of the state’s population, he said. “In our service area, about 60% of the water is imported, either from the Colorado River or through the Bay-Delta in Northern California, but 40% is still groundwater from local wells,” said Mr. Johnson.
The groundwater basins contain multiple aquifers in layers of sand anywhere from 50 feet to hundreds of feet thick which are separated by layers of clay. “The water wells that go down and tap every good aquifer they can find and they might go down over 2000 feet deep,” said Mr. Johnson. “Below those aquifers are the bedrock, so that defines the extent of our groundwater basins, and our job is to try and pour water into these things and fill them back up as those 43 cities are pumping out water from their wells.”
There are over 400 active wells pumping from the groundwater basins. “From Los Angeles to Downey to Long Beach and Lakewood, and over on the Westside with the city of Torrance and Manhattan Beach, they all have wells that are pumping out groundwater,” said Mr. Johnson. “We have a Geographic Information System or GIS that helps us map where all of those wells are located. Each one of those wells, they have to pay us a fee as they pump out groundwater, and we use that money to buy water and put it back into the ground, so it is the users of the groundwater that are paying for us to replace the groundwater and that’s a good system. If you don’t pump any groundwater, you don’t have to pay us. If you pump a lot of groundwater, you have to pay us a lot so we can put the water back into the ground.”
Prior to the formation of the District in 1959, over-pumping caused many water wells to go dry and allowed sea water intrusion to contaminate coastal groundwater. “Groundwater pumping as development occurred was quicker than Mother Nature could replace the water,” said Mr. Johnson. “The hydrographs show water levels going to a high and just plunging down uncontrolled; we saw 160 feet of draw down in the water table, which is about 8 feet per year and wells were going dry.”
The water table dropped so low it went below sea level. “When you’re next to the ocean and your water table is below sea level, that just allows the ocean to pour in underground, and contaminate the fresh water with salt water, and so we had a real problem with seawater intrusion which was wrecking our groundwater supply,” he said.
If left unchecked, it would have been a disaster for the Los Angeles region to lose such a valuable water resource, he said, but three things occurred to fix the problem. First, wells were installed along the coast to combat seawater intrusion. “Hundreds of wells along the coast exist today that are constantly pumping fresh water into the ground to stop the ocean from coming in,” said Mr. Johnson.
Second, the Water Replenishment District was formed in 1959. “We were enacted to make up the difference between Mother Nature’s water and what the shortage was,” said Mr. Johnson. “Our mission is to buy supplemental water whenever we can find it and as cheaply as we can find it and stick it underground. So we do modeling and contour maps and analysis to see how much water we need to buy and put into the ground every year. That is our main job.”
Lastly, in the 1960s, the two groundwater basins were adjudicated to control the amount of pumping. “That got rid of the wild cat anybody could pump whatever they want kind of pumping, and instead, put a limit and told each entity, each city, how much they could pump,” said Mr. Johnson. “And they are held to that today, but it’s still more pumping than Mother Nature gives us and that’s why our job is to put water back into the ground in storage.”
Afterwards, with the sea water barriers, the groundwater recharge and the controlled pumping, water levels have returned to healthy levels now, saving the groundwater resource, said Mr. Johnson. “In fact, we’ve put in over 7 MAF into storage since that time which could provide enough groundwater for 28 years of pumping, so it is the groundwater storage programs that really has allowed continued use of these groundwater basins and will so in the future.”
The easiest way to put water into the ground is to let gravity do its work. “You pour water on the ground and it soaks in, but you can only do that in certain areas so it has to be geologically suitable,” he said. “You have to have sandy soil and you have to have thorough geological investigations to see if you can even have this water go down.”
The Rio Hondo and San Gabriel Spreading Grounds, located in the cities of Montebello and Pico Rivera, are situated over a geologic uplift in the Central Basin that allows surface water to percolate into the aquifers below ground. The spreading grounds collect local stormwater runoff, important water and highly treated recycled water for recharging the aquifer.
Injection wells are another way to get water into the ground. The seawater barrier wells along the coast are an example of this; fresh water is pumped down hundreds of feet to keep the sea water from intruding, he said.
In-lieu programs that pay groundwater pumpers to use surface water from Metropolitan instead: “When water is plentiful for Metropolitan and water is cheap, we’d rather have them take the Met water than take the groundwater, so that’s another way to put water into storage.”
WRD’s general manager is a professional engineer and of the 31 staff, half of them hold engineering or science degrees, said Mr. Johnson. WRD conducts groundwater monitoring, modeling and planning to monitor the health of the basin as well as prepare for future conditions. “You have to know a lot about the technical details of putting the water in, the specific capacity, the hydraulic permeability and all of these other issues, so it’s important to have a lot of good science behind groundwater storage,” he said.
There is a long list of things that we look at as hydrogeolists, he said. “You need to know where your aquifers are, how big they are, how deep they are, where are the best places to put water into the ground, and what damage might happen if you put it in at the wrong place. You might have a Superfund site nearby and you don’t want to put your good, freshwater in with superfund water and contaminate your water, so you have to be very careful where you put in your water for storage.”
The district uses multiple tools to monitor conditions in the groundwater basin. “We have a very extensive groundwater monitoring program that we have put in with over 300 monitoring wells all throughout the basin,” he said. “Monitoring wells are our eyes into the underground so we have to drill wells, find out where the water is, test its quality, take the aquifer test to know what the permeabilities are, and after that we can figure out where the water is going to go.”
The district also uses extensive computer models, geophysical logs, and geographic information systems, as well as GeoTracker data from the State Water Board which identifies contaminated sites, and the CASGGEM system for monitoring short and long term groundwater levels throughout the basin.
“For the future, we’ve identified over 450,000 acre-feet of space just kind of sitting there; it’s like an empty safe deposit box that we want to fill up with water and we’re looking for ways to do that,” he said. “If we can tap into that 450,000 acre-feet, we could drought-proof the region and have a long term water supply.”
The district used to rely on imported water from the Delta, but not so in recent years. “Metropolitan doesn’t have the surplus that they used to and the costs are going through the roof, so we’re having to develop our own sources of water to replace the Met water we used to use,” he said. “We use any source available. We use a lot of recycled water from the wastewater plants. We use local stormwater by building rubber dams and capturing that water. We treat Superfund water and make it pure and then put it back into the ground … so there’s a lot of other water you can use for groundwater storage.”
“If we were to buy imported water today, it is about $700 an acre-foot – and that’s just for untreated raw river water from the Delta,” said Mr. Parker. “The recycled water from the sewage treatment plant next door is $40 an acre-foot, and it’s just as clean, it’s just as good, so we love that recycled water from those wastewater treatment plants,” noting that the district follows the health department’s regulations for putting recycled water into the ground.
The Water Replenishment District has a program called WIN, or Water Independence Now, the purpose of which is to completely eliminate dependence on imported water by developing local sources. “By using more recycled water and more storm water, we’ll be able to put storage water in there without using imported water,” he said. “That will help save the Bay Delta because we won’t need the Bay Delta water anymore which will free it up for other uses.”
There are both technical and non-technical challenges for the Water Replenishment District. “The technical challenges are all about the science – you need to have open space, you need to have the geology, you need to have the hydrogeology, you need to have the water quality, and that’s very important to study,” he said. “In urban Los Angeles, we don’t have 11 square miles of open land to put water into the ground so we have to be more creative with injection wells and other opportunities.”
The non-technical challenges can be even more challenging, he said. “There are a lot of litigation actions – we’ve been ten years in litigation on groundwater storage issues. We like to unfortunately joke that the courts are getting more action than our aquifers.” He noted that last year, SB 1386 by Senator Lowenthal passed that helped settle a long-term legal dispute. “It defined who gets to do groundwater storage, so it put to bed the competitiveness and the litigation of multiple agencies fighting over who would control storage.”
So in conclusion, “The Water Replenishment District has demonstrated as others have that groundwater storage works and it works well, and it can save groundwater basins; it’s a proven method, there’s nothing magic about it and it’s a benefit,” said Mr. Johnson. “But you have to do it with caution and you have to know what you’re doing. Increasing recycled water and stormwater is a benefit to Bay-Delta water and will help save the Delta for other uses if our local groundwater agencies can use our own water and be self-sustainable. Proper science is needed to fully understand the ramifications of what you’re doing, and we feel a lot of those challenges can be overcome with a lot of education and discussion and help from friends as needed.”
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At the Assembly Select Committee for Regional Approaches to Addressing the State’s Water Crisis in March of 2013, Roy Herndon, Chief Hydrogeologist from Orange County Water District spoke about the successes and challenges of storing water in their District, noting that while they do some similarities to the neighboring Water Replenishment District, there are some differences as well.
The boundaries of the Orange County Water District cover only the north half of the county, not the entire county. “We have about 2.4 million people that live in our water district, so that is the most populated part of Orange County; the area gets about 70% of its supply of water from the groundwater basin,” he said. The groundwater basin can hold between 10 million and 40 million acre-feet of water, of which about 1.5 million acre-feet is usable.
However, in the southern part of the county, less than 5% of total supply comes from groundwater because there are few groundwater basins in that area, “so it really is the geology that makes the difference between the northern half of the Orange County and the southern half of Orange County.”
The agency was formed by the legislature in 1933 with the mission to manage the groundwater basin under Orange County that now serves water to more than 20 cities and water agencies which in turn serve more than 2.3 million Orange County residents. “That is our purpose in life,” said Mr. Herndon. “We are not a retail agency. We manage the aquifer, we replenish it, we have recharge facilities, and we have seawater barriers.”
The district has a 10 member board of directors of which seven are publicly elected and three are appointed, he said. “We get our revenue from charging an assessment on the amount of water that is pumped from the production wells much like the Water Replenishment District. Our major source of revenue is from water users.”
The District has a number of programs to protect water quality. “We are cleaning up some groundwater contamination plumes that have been abandoned and a number of other projects that we’re working on to protect and keep this groundwater basin sustainable,” he said.
There are over 200 production wells that draw water from the basin. “These are large capacity city wells owned by cities such as Anaheim, Santa Ana, and Orange,” said Mr. Herndon. “They are the ones that own the wells; they pump the groundwater and they sell it to the residents and the businesses in their cities. They are essentially our customers. Our job is to manage the basin so they can rely on it for up to 70% of their water supply.”
When the Orange County Water District was first formed in 1933, 86% of its customers were agricultural. “We have very few farmers at this point. It’s almost all urbanized; there is very little farming left in the basin to speak of,” he said. “In some respects, I think that makes things easier for us.”
Water enters the groundwater basin via settling or percolation ponds in the cities of Anaheim and Orange and along the Santa Ana River. “We take water and we percolate it through the river bed, and we also divert water from the river into old gravel pits and that water percolates into the aquifer,” he said.
The groundwater basin has three major aquifer systems; a shallow, a middle and a deep zone. “The middle zone is where most of the wells pump water from; they are typically about 1000 to 1200 feet deep,” he explained. “Our recharge water comes in from the inland areas through the river and the percolation basins and spreads out vertically into the different aquifers, and replaces the water that’s pumped out on an annual basis. We also inject quite a bit of water for sea water intrusion; similar to Water Replenishment District, we use quite a bit of recycled water to do that.”
Mr. Herndon then presented a time series graph showing the amount of available storage in the groundwater basin dating back to 1969. “This illustrates how we empty and fill the basin just like a reservoir,” he said. “This underground reservoir has taken us through four different drought periods. We draw the basin down in a drought, and when we have some wet periods and we have available surface water, we refill the basin, just like you would any other reservoir. We know that if we manage it properly, we can take it down, draw it down, but we need to bring it back up.”
Mr. Herndon said that 500,000 acre-feet has been established as the bottom end of the range. “We have established an operating range for our basin through trial and error and understanding our basin. Sea water intrusion is a major issue for us. If we go below 500,000 acre-feet, we can’t control sea water intrusion.”
The District primarily recharges the basin with water from the Santa Ana River and, to a lesser extent, with imported water purchased from the Metropolitan Water District of Southern California. The District currently holds rights to all Santa Ana River flows that reach Prado Dam: “We get our recharge water from the Santa Ana River through storm flows which happen during about 2 or 3 months out of the year, although not this year, I’m afraid, as it’s been a very dry year for us,” said Mr. Herndon. “And base flows, which are essentially upstream discharges of treated sewage effluent coming down the Santa Ana River. We divert that water and percolate it where it’s then filtered and it’s very good drinking water quality when its pumped out of the production wells.”
“A lot of that base flow water is essentially upstream effluent from treatment plants and the upstream agencies are doing more and more to capture that water and use it for themselves, instead of dumping it in the river for us so we’re having to make changes and accommodate that or handle that,” he said. “Imported water has historically been a good source of recharge water during times of surplus; however, as Ted mentioned, that imported water is now declining. With the Bay Delta and the endangered species issues, we’ve seen our imported supply for recharge drastically drop, so how we’re compensating for that is by recycling more water in a very highly treated process and that is how we’re making up for the loss of imported water.”
The District has 1100 acres of infiltration basins, which is a little less than 2 square miles. “We put a lot of water in the ground in a very small area so we have some very high percolation rates that we’re able to sustain in our spreading basins,” he said. “We and the sanitation district partnered to build a $480 million water recycling project that we call the Groundwater Replenishment System,” noting that the system recharges about 20 to 25 percent of all the water that is pumped out of the basin or about 70,000 acre-feet. “That’s been a big project that is cost-effective compared to imported water.”
Sea water barriers inject about 30,000 acre-feet per year through injection wells, and the District has a stormwater storage agreement with the Army Corps of Engineers to hold water behind a dam upstream and release it more slowly so we can get that water into the groundwater basin, he said.
“We couldn’t do it if we didn’t have cooperation from our pumpers,” he said. “The agencies report all their pumping so we know how much is being pumped out of the basin and we know how much we’re putting in so at any given time, so we know how much water is being stored in our basin.”
There are over 500 monitoring wells throughout our basin so it is well understood and well characterized. “Similar to Water Replenishment District, we have a highly skilled and dedicated staff,” he said. “We have a long term need for that kind of skill set and we hire people to handle and understand this.”
The economic benefit of using groundwater instead of imported water is significant, Mr. Herndon pointed out. “For the City of Anaheim, to buy an acre-foot of treated, drinkable water, either from the Colorado River or Northern California, it is $900 an acre-foot,” he said. “Our groundwater, after they pump it out and deliver it into their system, is $430 an acre-foot, so it is less than half the cost. When you multiply that by the amount of pumping in the basin – 300,000 acre-feet per year, there is a $141 million economic benefit by using the groundwater basin versus imported water, and that’s an annual savings to the producers.”
Of the $430 an acre-foot, the District charges currently $266 an acre-foot; “That’s our charge to manage the groundwater basin and put water back in the ground, so the rest of the cost is the energy to lift it out of the ground and to send that water into the producers retail system.”
“It pays for itself, and that’s why we were able to build that $480 million recycled water project because it offsets $900 an acre-foot imported water,” he said. “We built that project and it’s approximately $700 an acre-foot fully loaded cost, so it is cost effective to do recycling in our area versus import.”
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Content coming soon.
California’s Groundwater Update 2013, special update to the California Water Plan, from the Department of Water Resources (2015) Bulletin 118: California’s groundwater, from the Department of Water Resources (2003) Land subsidence in the Central Valley, NASA/JPL (2015) Land subsidence from groundwater use in California (summary report), from the California Water Foundation (2014) (full report here) Water availability and land subsidence in the Central Valley, California, from the USGS (2015) Regional land subsidence studies, from the USGS Designing Effective Groundwater Sustainability Agencies: Criteria for Evaluation of Local Governance Options, from UC Berkeley School of Law (2016) Know Your Options: A guide to forming Groundwater Sustainability Agencies, from the California Water Foundation (2015) Measuring What Matters: Setting Measurable Objectives to Achieve Sustainable Groundwater Management in California, from the Union of Concerned Scientists (2015) An evaluation of adjudicated basins, from UC Santa Cruz and the State Water Board (2016) Collaborating for Success: Stakeholder Engagement for Sustainable Groundwater Management Act Implementation, from the Union of Concerned Scientists (2015) California’s Sustainable Groundwater Management Act: Recommendations for preventing and resolving groundwater conflicts, from Stanford’s Water in the West Program (2015) The 2014 Sustainable Groundwater Management Act: A handbook to understanding and implementing the law, from the Water Education Foundation (2015) Groundwater Sustainability Program Draft Strategic Plan, from the Department of Water Resources (2015) Addressing nitrate in California’s drinking water, from UC Davis and the State Water Board (2012) Communities that rely on a contaminated groundwater source for drinking water, report to the legislature from the State Water Board Geology of the Northern Sacramento Valley, by DWR (2014) Central Coast Groundwater: Seawater Intrusion and Other Issues, from the California Water Foundation (2014) Transitioning to sustainability: Modeling groundwater sustainability in the Kings-Tulare Lake region, from the California Water Foundation (2015)
California’s Groundwater Update 2013, special update to the California Water Plan, from the Department of Water Resources (2015)
Bulletin 118: California’s groundwater, from the Department of Water Resources (2003)
Land subsidence in the Central Valley, NASA/JPL (2015)
Land subsidence from groundwater use in California (summary report), from the California Water Foundation (2014) (full report here)
Water availability and land subsidence in the Central Valley, California, from the USGS (2015)
Regional land subsidence studies, from the USGS
Designing Effective Groundwater Sustainability Agencies: Criteria for Evaluation of Local Governance Options, from UC Berkeley School of Law (2016)
Know Your Options: A guide to forming Groundwater Sustainability Agencies, from the California Water Foundation (2015)
Measuring What Matters: Setting Measurable Objectives to Achieve Sustainable Groundwater Management in California, from the Union of Concerned Scientists (2015)
An evaluation of adjudicated basins, from UC Santa Cruz and the State Water Board (2016)
Collaborating for Success: Stakeholder Engagement for Sustainable Groundwater Management Act Implementation, from the Union of Concerned Scientists (2015)
California’s Sustainable Groundwater Management Act: Recommendations for preventing and resolving groundwater conflicts, from Stanford’s Water in the West Program (2015)
The 2014 Sustainable Groundwater Management Act: A handbook to understanding and implementing the law, from the Water Education Foundation (2015)
Groundwater Sustainability Program Draft Strategic Plan, from the Department of Water Resources (2015)
Addressing nitrate in California’s drinking water, from UC Davis and the State Water Board (2012)
Communities that rely on a contaminated groundwater source for drinking water, report to the legislature from the State Water Board
Geology of the Northern Sacramento Valley, by DWR (2014)
Central Coast Groundwater: Seawater Intrusion and Other Issues, from the California Water Foundation (2014)
Transitioning to sustainability: Modeling groundwater sustainability in the Kings-Tulare Lake region, from the California Water Foundation (2015)