Groundwater-Quality Data in the Santa Cruz, San Gabriel, and Peninsular Ranges Hard Rock Aquifers Study Unit, 2011–2012: Results from the California GAMA Program

U.S. Geological Survey (USGS) | December 11th, 2014

Groundwater quality in the 2,400-square-mile Santa Cruz, San Gabriel, and Peninsular Ranges Hard Rock Aquifers (Hard Rock) study unit was investigated by the U.S. Geologi

Groundwater quality in the 2,400-square-mile Santa Cruz, San Gabriel, and Peninsular Ranges Hard Rock Aquifers (Hard Rock) study unit was investigated by the U.S. Geological Survey (USGS) from March 2011 through March 2012, as part of the California State Water Resources Control Board (SWRCB) Groundwater Ambient Monitoring and Assessment (GAMA) Program’s Priority Basin Project (PBP). The GAMA-PBP was developed in response to the California Groundwater Quality Monitoring Act of 2001 and is being conducted in collaboration with the SWRCB and Lawrence Livermore National Laboratory (LLNL). The Hard Rock study unit was the 35th study unit to be sampled as part of the GAMA-PBP. In the Hard Rock study unit, groundwater samples were collected from 112 wells and springs in 3 study areas (the Santa Cruz, the San Gabriel, and the Peninsular Ranges) in San Mateo, Santa Clara, Santa Cruz, San Benito, Los Angeles, Orange, Riverside, San Bernardino, and San Diego Counties. Eighty-three wells and 11 springs were selected by using a spatially distributed, randomized grid-based method to provide statistical representation of the study unit (grid wells), and 15 wells and 3 springs were selected to aid in evaluation of water-quality issues (understanding wells). The groundwater samples were analyzed for field water-quality indicators; organic constituents; one constituent of special interest (perchlorate); naturally occurring inorganic constituents; and radioactive constituents. Naturally occurring isotopes and dissolved noble gases were also measured to help identify the sources and ages of the sampled groundwater. In total, 209 constituents and water-quality indicators were measured.

Groundwater: The Water-Budget Myth

National Academy of Sciences (NAS) | June 1st, 1982

Water-resource scientists are concerned that some basic principles are being overlooked by water managers. Rather than discuss the scope of groundwater hydrolog

Water-resource scientists are concerned that some basic principles are being overlooked by water managers. Rather than discuss the scope of groundwater hydrology, we have chosen to focus on a common misconception to illustrate the point. Perhaps the most common misconception in groundwater hydrology is that a water budget of an area determines the magnitude of possible groundwater development. Several well-known hydrologists have addressed this misconception and attempted to dispel it. Somehow, though, it persists and continues to color decisions by the water-management community. The laws governing the development of groundwater in Nevada as well as several other states are based on the idea that pumping within a groundwater basin shall not exceed the recharge. It is the intent of this paper to re-examine the issue.

Groundwater/Aquifer Remediation (Resource Management Strategy)

California Department of Water Resources (DWR) | July 29th, 2016

Portions of aquifers in many groundwater basins in California have degraded water quality that does not support beneficial use of groundwater. In some areas, groundwater

Portions of aquifers in many groundwater basins in California have degraded water quality that does not support beneficial use of groundwater. In some areas, groundwater quality is degraded by constituents that occur naturally (e.g., arsenic). In many urban and rural areas, groundwater quality degradation has resulted from a wide range of human (anthropogenic) activities. Groundwater remediation is necessary to improve the quality of degraded groundwater for beneficial use. Drinking water supply is the beneficial use that typically requires remediation when groundwater quality is degraded. Contaminants in groundwater can come from a many sources, naturally occurring and anthropogenic. Examples of naturally occurring contaminants include heavy metals and radioactive constituents, as well as high concentrations of various salts from specific geologic formations or conditions. Climate change that results in altered precipitation, snowfall patterns, and rising sea levels may exacerbate salt water intrusion and flooding of low-lying infrastructure and urban facilities. These phenomena will add new challenges to protection of groundwater from contamination. In addition, groundwater can be contaminated by anthropogenic sources with organic, inorganic, and radioactive constituents from point and non-point sources. These anthropogenic sources include industrial sites, mining operations, leaking fuel tanks and pipelines, manufactured gas plants, landfills, impoundments, dairies, septic systems, and urban and agricultural activities. The contaminant having the most widespread and adverse impact on drinking water wells is arsenic, followed by nitrates, naturally occurring radioactivity, industrial/commercial solvents, and pesticides. Groundwater remediation removes constituents, hereafter called contaminants, which affect beneficial use of groundwater. Groundwater remediation systems can employ passive or active methods to remove contaminants. Passive groundwater remediation allows contaminants to degrade biologically or chemically or disperse in situ over time. Active groundwater remediation involves either treating contaminated groundwater while it is still in the aquifer (in situ) or extracting contaminated groundwater from the aquifer and treating it outside of the aquifer (ex situ). Active in situ methods generally involve injecting chemicals into the contaminant plume to obtain a chemical or biological removal of the contaminant. Ex situ methods for treating contaminated groundwater can involve physical, chemical, and/or biological processes.

Guidance Document for Groundwater Sustainability Plan Stakeholder Communicaton and Engagement, June 2017 (Draft)

California Department of Water Resources (DWR) | June 1st, 2017

The objectve of this guidance document is to provide Groundwater Sustainability Agencies (GSAs) information to aid with stakeholder communication and engage

The objectve of this guidance document is to provide Groundwater Sustainability Agencies (GSAs) information to aid with stakeholder communication and engagement for Groundwater Sustainability Plan (GSP) preparation and to provide examples and existing resources related to public engagement and effective communication for Sustainable Groundwater Management Act (SGMA) implementation. Limitation and use of this guidance information This guidance document is not intended to prescribe specifc outreach and communications methods for GSAs or local agencies to follow, but to provide resources and various examples for consideration. This guidance document also summarizes the public notfcation requirements that GSAs must adhere to in order to comply with SGMA and the GSP regulations. Other than what is required by statute or regulation, GSAs have discretion on how they communicate and engage with the beneficial uses and users of groundwater within a basin.

Guidance Document for the Sustainable Management of Groundwater Engagement with Tribal Governments June 2017 (Draft)

California Department of Water Resources (DWR) | June 1st, 2017

The objective of this guidance document is to convey information, as provided by California’s Tribal governments, by which local agencies can engage Tribal gove

The objective of this guidance document is to convey information, as provided by California’s Tribal governments, by which local agencies can engage Tribal governments as part of an effort to identify interested persons, and consider the interests of beneficial users of groundwater; including those users on Tribal lands not subject to the Sustainable Groundwater Management Act (SGMA). This guidance document can also be used to help local agencies engage with a Tribal government in the planning, financing, and management of a Groundwater Sustainability Agency (GSA), or help with the development and implementation of a Groundwater Sustainability Plan (GSP) pursuant to SGMA.

Guidance for Climate Change Data Use During Groundwater Sustainability Plan Development

California Department of Water Resources (DWR) | April 12th, 2018

This Guidance Document was developed to help Groundwater Sustainability Agencies (GSAs) incorporate California Department of Water Resources (DWR)-provided climate change

This Guidance Document was developed to help Groundwater Sustainability Agencies (GSAs) incorporate California Department of Water Resources (DWR)-provided climate change and related data into their Groundwater Sustainability Plans (GSPs). The purpose of this Guidance Document is as follows: • Provide relevant data and tools for GSAs to incorporate climate change into their GSPs. • Provide an analysis approach using the provided data and tools that incorporates the best available science and best available information to date. This Guidance Document focuses on the use of DWR-provided climate change data and provides documentation about the following: • Climate change data development approach • Climate change data development methods and processes • Applications for using the provided climate change data • Climate change data assumptions and limitations This Guidance Document provides a process for using DWR-provided climate change data for computing projected water budgets and serves as a companion document to the water budget best management practices (BMPs)2 and the modeling BMP3. For Sustainable Groundwater Management Act (SGMA) implementation purposes, the use of climate change data can help with the following: • Developing projected water budgets • Long-term planning of groundwater basin sustainability • Assessing projects and management actions by performing sensitivity analyses of projected conditions • Adaptive Management

Guide to Compliance with California’s Sustainable Groundwater Management Act: How to avoid the “undesirable result” of “significant and unreasonable adverse impacts on beneficial uses of surface waters"

Stanford University | September 4th, 2018

In enacting the Sustainable Groundwater Management Act (SGMA) the California Legislature, for the first time ever, expressly linked the two historically distinct legal r

In enacting the Sustainable Groundwater Management Act (SGMA) the California Legislature, for the first time ever, expressly linked the two historically distinct legal regimes governing water in the state that previously had been entirely separate: one governing surface water use and the other groundwater use. SGMA requires Groundwater Sustainability Agencies (GSAs) and their Groundwater Sustainability Plans (GSPs or Plans) to consider and address the groundwater-surface water interaction, and specifically the impacts of groundwater pumping on surface water beneficial uses. SGMA defines sustainable groundwater management as the avoidance of six “undesirable results” identified in the law. The purpose of this guide is to help GSAs and other stakeholders understand and comply with the requirement of SGMA that groundwater withdrawals must not cause “significant and unreasonable adverse impacts on beneficial uses of the surface water,” known as “undesirable result no. 6.” This guide is based on the principle that existing legal frameworks (laws, regulations, court decisions, etc.) provide the clearest and most pertinent guidance on what constitutes undesirable result no. 6. This guide addresses only the explicit legal aspects of this statutory mandate. It does not address technical and scientific aspects of SGMA compliance and offers no advice on the steps GSAs must take to get an adequate technical understanding of the groundwater-surface water connections under their purview. GSAs may look to other sources for guidance on that front. In addition, “Navigating Groundwater-Surface Water Interactions under the Sustainable Groundwater Management Act,” authored by experts at the University of California Berkeley provides a helpful overview of the steps involved in implementing SGMA provisions relating to groundwater-surface water interactions.  

Guidebook to studies of land subsidence due to ground-water withdrawal

United Nations Educational, Scientific and Cultural Organization (UNESCO) | July 1st, 1984

Guideline levels for PFOA and PFOS in drinking water: the role of scientific uncertainty, risk assessment decisions, and social factors

Journal of Exposure Science & Environmental Epidemiology (Springer) | January 8th, 2019

Communities across the U.S. are discovering drinking water contaminated by perfluoroalkyl and polyfluoroalkyl substances (PFAS) and determining appropriate actions. Ther

Communities across the U.S. are discovering drinking water contaminated by perfluoroalkyl and polyfluoroalkyl substances (PFAS) and determining appropriate actions. There are currently no federal PFAS drinking water standards despite widespread drinking water contamination, ubiquitous population-level exposure, and toxicological and epidemiological evidence of adverse health effects. Absent federal PFAS standards, multiple U.S. states have developed their own healthbased water guideline levels to guide decisions about contaminated site cleanup and drinking water surveillance and treatment. We examined perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) water guideline levels developed by the U.S. Environmental Protection Agency (EPA) and state agencies to protect people drinking the water, and summarized how and why these levels differ. We referenced documents and tables released in June 2018 by the Interstate Technology and Regulatory Council (ITRC) to identify states that have drinking water and groundwater guideline levels for PFOA and/or PFOS that differ from EPA’s health advisories (HAs). We also gathered assessment documents from state websites and contacted state environmental and health agencies to identify and confirm current guidelines. Seven states have developed their own water guideline levels for PFOA and/or PFOS ranging from 13 to 1000 ng/L, compared to EPA’s HA of 70 ng/L for both compounds individually or combined. We find that the development of PFAS guideline levels via exposure and hazard assessment decisions is influenced by multiple scientific, technical, and social factors, including managing scientific uncertainty, technical decisions and capacity, and social, political, and economic influences from involved stakeholders. Assessments by multiple states and academic scientists suggest that EPA’s HA is not sufficiently protective. The ability of states to develop their own guideline levels and standards provides diverse risk assessment approaches as models for other state and federal regulators, while a sufficiently protective, scientifically sound, and enforceable federal standard would provide more consistent protection.

Health of Native Riparian Vegetation and its Relation to Hydrologic Conditions along the Mojave River, Southern California

U.S. Geological Survey (USGS) | July 15th, 1999