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.

Growing human-induced climate change fingerprint in regional weekly fire extremes

Nature Portfolio (Springer Nature) | April 23rd, 2025

Growing impact of wildfire on western US water supply

National Academy of Sciences (NAS) | February 22nd, 2022

Streamflow often increases after fire, but the persistence of this effect and its importance to present and future regional water resources are unclear. This paper addres

Streamflow often increases after fire, but the persistence of this effect and its importance to present and future regional water resources are unclear. This paper addresses these knowledge gaps for the western United States (WUS), where annual forest fire area increased by more than 1,100% during 1984 to 2020. Among 72 forested basins across the WUS that burned between 1984 and 2019, the multibasin mean streamflow was significantly elevated by 0.19 SDs (P < 0.01) for an average of 6 water years postfire, compared to the range of results expected from climate alone. Significance is assessed by comparing prefire and postfire streamflow responses to climate and also to streamflow among 107 control basins that experienced little to no wildfire during the study period. The streamflow response scales with fire extent: among the 29 basins where >20% of forest area burned in a year, streamflow over the first 6 water years postfire increased by a multibasin average of 0.38 SDs, or 30%. Postfire streamflow increases were significant in all four seasons. Historical fire–climate relationships combined with climate model projections suggest that 2021 to 2050 will see repeated years when climate is more fire-conducive than in 2020, the year currently holding the modern record for WUS forest area burned. These findings center on relatively small, minimally managed basins, but our results suggest that burned areas will grow enough over the next 3 decades to enhance streamflow at regional scales. Wildfire is an emerging driver of runoff change that will increasingly alter climate impacts on water supplies and runoff-related risks.

Guadalupe River mercury concentrations and loads during the large rare January 2017 storm

San Francisco Estuary Institute (SFEI) | February 9th, 2018

The Guadalupe River watershed has a long history of urbanization and is the location of a historic mining district that produced 40 million kg of mercury (Hg) during ope

The Guadalupe River watershed has a long history of urbanization and is the location of a historic mining district that produced 40 million kg of mercury (Hg) during operation. The river system is listed as impaired and is a large pathway of Hg to San Francisco Bay. The TMDL calls for stakeholders to reduce load to an average of 9.4 kg per year over 20 years by removing H-laden wastes in the mining and urban areas and implementing other treatment practices. To demonstrate success, the stakeholders are documenting management efforts and have been conducting water sampling to show that average loads are decreasing or that Hg concentrations on suspended particles are trending towards the TMDL target of 0.2 mg/kg (dry wt., annual median). The Guadalupe River is capable of flows >10,000 cfs, and a flood flow of >6,000 cfs has a return interval of approximately 1:5 years yet most sampling has occurred at flows <4,000 cfs. Since most Hg is transported in the system during large storm events when Hg can be mobilized from the historic mining district, it is essential to measure the Hg load during these rare events. The main objective of this study was to sample and estimate loads during such a rare events.

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 for Developing Onsite Water Systems to Support Regional Water Resilience

Pacific Institute | January 26th, 2023

Across the United States, urban communities face growing water challenges, from water scarcity to flooding, pollution, aging water infrastructure, and more. These challen

Across the United States, urban communities face growing water challenges, from water scarcity to flooding, pollution, aging water infrastructure, and more. These challenges present risks, but also an opportunity to rethink how we manage water, including adopting circular approaches in new buildings that reduce their water footprint and improve urban water resilience. Onsite water systems, for example, collect, treat, and reuse water from onsite sources, including wastewater, rainwater, and stormwater, for non-potable water uses like toilet flushing, outdoor irrigation, and cooling. Onsite water systems have the potential to provide multiple benefits for a site, water and wastewater systems, ecosystems, and communities. They can, for example, help companies mitigate water- related risks, like water shortages that threaten to disrupt business operations, and support corporate water stewardship goals. For communities, onsite water systems can enhance water supply reliability, improve water quality, reduce localized flooding, and increase urban green space. The realization and magnitude of benefits will vary with the type of system, scale of adoption, and other context-specific factors. This guide helps site developers consider how onsite water systems can be planned, designed, and operated to provide multiple benefits, and contribute to planning and designing onsite water systems that advance water resilience, support equity, support the environment, and protect public health at the site, water system, and community scales. For each of these outcomes, the guide provides sample questions to consider, stakeholders to engage, resources to examine, and analyses to perform.

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 for Implementation of SB 610 and SB 221 to assist water suppliers, cities, and counties in integrating water and land use planning

California Department of Water Resources (DWR) | October 10th, 2003

Senate Bills 610 (Chapter 643, Statutes of 2001) and Senate Bill 221 (Chapter 642, Statutes of 2001) amended state law, effective January 1, 2002, to improve the link bet

Senate Bills 610 (Chapter 643, Statutes of 2001) and Senate Bill 221 (Chapter 642, Statutes of 2001) amended state law, effective January 1, 2002, to improve the link between information on water supply availability and certain land use decisions made by cities and counties. SB 610 and SB 221 are companion measures which seek to promote more collaborative planning between local water suppliers and cities and counties. Both statutes require detailed information regarding water availability to be provided to the city and county decision-makers prior to approval of specified large development projects. Both statutes also require this detailed information be included in the administrative record that serves as the evidentiary basis for an approval action by the city or county on such projects. Both measures recognize local control and decision making regarding the availability of water for projects and the approval of projects.  Under SB 610, water assessments must be furnished to local governments for inclusion in any environmental documentation for certain projects (as defined in Water Code 10912 [a]) subject to the California Environmental Quality Act. Under SB 221, approval by a city or county of certain residential subdivisions requires an affirmative written verification of sufficient water supply. If coordinated and comprehensive water supply planning is underway at the time that the SB 610-water assessment is prepared, compliance with SB 221 will be greatly facilitated. SB 221 is intended as a ‘fail safe’ mechanism to ensure that collaboration on finding the needed water supplies to serve a new large subdivision occurs when it should – before construction begins. Not every project that is subject to the requirements of SB 610 would also require the mandatory water verification of SB 221 (e.g. if there is no subdivision map approval). Conversely, not every project that is subject to the requirements of SB 221 would also require the environmental document to contain an SB 610 water supply assessment. Projects approved before January 1, 2002 were not subject to the requirements of SB 610 or SB 221; however, some projects may have been subject to the requirement to prepare a water supply assessment as set forth in Senate Bill 901 of 1995 (Chapter 881, Statues of 1995). A foundational document for compliance with both SB 610 and SB 221 is the Urban Water Management Plan (UWMP). Both of these statutes repeatedly identify the UWMP as a planning document that, if properly prepared, can be used by a water supplier to meet the standards set forth in both statutes. Thorough and complete UWMPs will allow water suppliers to use UWMPs as a foundation to fulfill the specific requirements of these two statutes. Cities, counties, water districts, property owners, and developers will all be able to utilize this document when planning for and proposing new projects.