Status and Understanding of Groundwater Quality in the South Coast Interior Groundwater Basins, 2008: California GAMA Priority Basin Project

U.S. Geological Survey (USGS) | May 14th, 2014

Groundwater quality in the approximately 653-square-mile (1,691-square-kilometer) South Coast Interior Basins (SCI) study unit was investigated as part of the Priority Ba

Groundwater quality in the approximately 653-square-mile (1,691-square-kilometer) South Coast Interior Basins (SCI) study unit was investigated as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The South Coast Interior Basins study unit contains eight priority groundwater basins grouped into three study areas, Livermore, Gilroy, and Cuyama, in the Southern Coast Ranges hydrogeologic province. The GAMA Priority Basin Project is being conducted by the California State Water Resources Control Board in collaboration with the U.S. Geological Survey (USGS) and the Lawrence Livermore National Laboratory. The GAMA South Coast Interior Basins study was designed to provide a spatially unbiased assessment of untreated (raw) groundwater quality within the primary aquifer system, as well as a statistically consistent basis for comparing water quality between basins. The assessment was based on water-quality and ancillary data collected by the USGS from 50 wells in 2008 and on water-quality data from the California Department of Public Health (CDPH) database. The primary aquifer system was defined by the depth intervals of the wells listed in the CDPH database for the SCI study unit. The quality of groundwater in the primary aquifer system may be different from that in the shallower or deeper water-bearing zones; shallow groundwater may be more vulnerable to surficial contamination. The first component of this study, the status of the current quality of the groundwater resource, was assessed by using data from samples analyzed for volatile organic compounds (VOCs), pesticides, and naturally occurring inorganic constituents, such as trace elements and minor ions. This status assessment is intended to characterize the quality of groundwater resources within the primary aquifer system of the SCI study unit, not the treated drinking water delivered to consumers by water purveyors. Relative-concentrations (sample concentration divided by the health- or aesthetic-based benchmark concentration) were used for evaluating groundwater quality for those constituents that have Federal or California regulatory or non-regulatory benchmarks for drinking-water quality. A relative-concentration greater than 1.0 indicates a concentration greater than a benchmark, and a relative-concentration less than or equal to 1.0 indicates a concentration equal to or less than a benchmark. Relative-concentrations of organic constituents and special-interest constituents were classified as “high” (relative-concentration greater than 1.0), “moderate” (relative-concentration greater than 0.1 and less than or equal to 1.0), or “low” (relative-concentration less than or equal to 0.1). Relative-concentrations of inorganic constituents were classified as “high” (relative-concentration greater than 1.0), “moderate” (relative-concentration greater than 0.5 and less than or equal to 1.0), or “low” (relative-concentration less than or equal to 0.5). Aquifer-scale proportion was used as the primary metric in the status assessment for evaluating regional-scale groundwater quality. High aquifer-scale proportion is defined as the percentage of the area of the primary aquifer system with a relative-concentration greater than 1.0 for a particular constituent or class of constituents; percentage is based on an areal rather than a volumetric basis. Moderate and low aquifer-scale proportions were defined as the areal percentage of the primary aquifer system with moderate and low relative-concentrations, respectively. Two statistical approaches—grid-based and spatially weighted—were used to evaluate aquifer-scale proportions for individual constituents and classes of constituents. Grid-based and spatially weighted estimates were comparable in the SCI study unit (within 90-percent confidence intervals). Inorganic constituents (one or more) with health-based benchmarks were detected at high relative-concentrations in 29 percent of the primary aquifer system, at moderate relative-concentrations in 37 percent, and at low relative-concentrations in 34 percent. High aquifer-scale proportions of inorganic constituents primarily reflected high aquifer-scale proportions of nitrate (14 percent), boron (8.6 percent), molybdenum (8.6 percent), and arsenic (5.7 percent). In contrast, the relative-concentrations of organic constituents (one or more) were high in 1.6 percent, moderate in 2.0 percent, and low or not detected in 96 percent of the primary aquifer system. Of the 207 organic and special-interest constituents analyzed for, 15 constituents were detected. Perchlorate was found at moderate relative-concentrations in 34 percent of the aquifer. Two organic constituents were frequently detected (in greater than 10 percent of samples): the trihalomethane chloroform and the herbicide simazine. The second component of this study, the understanding assessment, identified natural and human factors that may have affected groundwater quality by evaluating land use, physical characteristics of the wells, and geochemical conditions of the aquifer. This evaluation was done by using statistical tests of correlations between these potential explanatory factors and water-quality data. Concentrations of arsenic, molybdenum, and manganese were generally greater in anoxic and pre-modern groundwater than other groundwater. In contrast, concentrations of nitrate and perchlorate were significantly higher in oxic and modern groundwater. Concentrations of simazine were greater in modern than pre-modern groundwater. Chloroform detections were positively correlated with greater urban land use. Boron concentrations and chloroform detections were higher in the Livermore study area than in the other study areas of the SCI; total dissolved solids and sulfate concentrations were greater in the Cuyama study area.

Supporting sustainable groundwater management

California Agriculture (UCANR) | March 13th, 2018

Implementation of the 2014 Sustainable Groundwater Management Act is on schedule. The first phase, completed in 2017, created a new layer of local government —

Implementation of the 2014 Sustainable Groundwater Management Act is on schedule. The first phase, completed in 2017, created a new layer of local government — groundwater sustainability agencies. Now, these new agencies must prepare groundwater sustainability plans. These plans will lay out a basic reckoning for every overdrafted basin: without additional water to replace groundwater pumping or to recharge aquifers, there will be less available to produce food, supply homes and businesses, and ensure there is enough water for the environment.

Sustainability Outlook Indicator Descriptions and Methodology

California Department of Water Resources (DWR) | December 13th, 2018

The Sustainability Outlook describes how, through the lens of four societal values — public health and safety, healthy economy, ecosystem vitality, and opportunities fo

The Sustainability Outlook describes how, through the lens of four societal values — public health and safety, healthy economy, ecosystem vitality, and opportunities for enriching experiences — it will help identify desired water management outcomes and indicators. Those outcomes and indicators can be used to gauge the status of, and progress toward, sustainability. Because sustainability is not something achieved once and forever, the Sustainability Outlook and the representative indicators are intended to be adaptive and help water resource managers address changing circumstances and incorporate lessons learned.  This document details the process to date for developing the sustainability indicators and includes descriptions of the initial indicators. Indicators are presented according to societal value, corresponding intended outcome, and classification (“Basic” with potential statewide application or “Watershed” level application, “Advanced” for future development, or “Archived” with no additional development identified at this time). Each intended outcome has several indicators, and in some cases, indicators may apply to multiple outcomes.  This version of the document (December 2018) is being released concurrently with the public review draft of Update 2018. It is considered an in-progress review draft because indicator assessments are ongoing, and the contents are subject to change as indicators are more fully developed, combined, or otherwise modified. As part of Update 2018, future versions of this paper will reflect the status of indicator development and stakeholder input. 

Sustainable Groundwater Management

U.S. Geological Survey (USGS) | February 1st, 2016

According to the [Sustainable Groundwater Management] act, local agencies must develop and implement groundwater-sustainability plans for managing and using groundwater w

According to the [Sustainable Groundwater Management] act, local agencies must develop and implement groundwater-sustainability plans for managing and using groundwater without causing “undesirable results” related to the following: • Groundwater-level declines. • Groundwater-storage reductions. • Seawater intrusion. • Water-quality degradation. • Land subsidence. • Interconnected surface-water depletions. The U.S. Geological Survey (USGS) uses data collection, modeling tools, and scientific analysis to help water managers plan for and assess hydrologic issues that can cause “undesirable results” associated with groundwater use. This information helps managers understand trends and investigate and predict effects of different groundwater management strategies.  

Sustainable Groundwater Management Act (with 2015 amendments)

State of California | January 5th, 2016

Sustainable Groundwater Management Act [And Related Statutory Provisions from SB1168 (Pavley), AB1739 (Dickinson), and SB1319 (Pavley) as Chaptered]

Sustainable Groundwater Management Act [And Related Statutory Provisions from SB1168 (Pavley), AB1739 (Dickinson), and SB1319 (Pavley) as Chaptered]

Sustainable Groundwater Management Act 2019 Basin Prioritization Process and Results

California Department of Water Resources (DWR) | April 1st, 2019

Sustainable Groundwater Management Act Governance Strategies Summary Report

California State University, Fresno (CSUF) | September 15th, 2021

A three-bill legislative package, referred to as the Sustainable Groundwater Management Act (SGMA), created a fundamental change in the governance of California’s groun

A three-bill legislative package, referred to as the Sustainable Groundwater Management Act (SGMA), created a fundamental change in the governance of California’s groundwater. SGMA requires, with some exceptions, the formation of groundwater sustainability agencies (GSAs) for identified groundwater subbasins. Signed into law in 2014 by Governor Jerry Brown, it set forth a long-term, statewide framework to protect groundwater resources. This report outlines the initial implementation of these new laws by the GSAs in 21 critically overdrafted groundwater subbasins2. Based on a review of multiple statutes, regulations, early research, official government documents and interviews with individuals involved in the process, the authors explain how these first GSAs were created and the organizational and governance challenges they navigated. Once formed, the GSAs were charged with the development and implementation of groundwater sustainability plans (GSPs). The purpose of a GSP is to avoid the undesirable results of groundwater depletion and mitigate overdraft within 20 years. A review of the formation process for this set of GSAs was particularly instructive as they were required to meet a set of SGMA requirements two years earlier than the remaining legislatively identified basins. Presented in an approach that moves from the general to the specific, this report documents the historic process of how 125 GSAs began to implement SGMA. In addition, this report provides important baseline information to help researchers, regulators, policy makers and GSAs themselves, in the development and evaluation of governance and future governance strategies, statutes and regulatory actions. The report is organized into two major topics. 1. Governance structure choices available to GSAs and the GSA formation process set forth in SGMA, including: Specific examples of GSA governance choices. How governance choices were influenced by the preparation and financing of GSPs. 2. Summary findings and observations from interviews of policymakers, technical experts, and thought leaders on their perception of the GSA governance decision-making process and the improvements they believe would benefit SGMA outcomes.The interviewees’ insights reflect the experience they gained during the formation of the critically overdrafted basins GSAs. They identified key elements they felt would be helpful when forming future GSAs, most notably: Providing simplified groundwater science education information for managers, leaders, and groundwaters users. Implementing agency leadership training so the organizational structures and efforts of GSAs can be fully responsive to constituents. Heightening attention relative to some of the beneficial uses of groundwater that were not adequately addressed by GSPs, such as small domestic wells and environmental needs. These experts also observed that implementation of SGMA is an iterative process and that time will be needed to develop, implement, measure, and improve the results of groundwater management strategies. A variety of additional sources of information are offered throughout this report. In addition, Appendix A includes searchable links and information on GSAs, GSPs and other governance elements found in DWR’s (Department of Water Resources) SGMA Portal.

Sustainable Groundwater Management Program Groundwater Sustainability Plan Assessment Staff Report – Big Valley Basin (No. 5-004)

California Department of Water Resources (DWR) | October 26th, 2023

Sustainable Groundwater Management: What We Can Learn from California’s Central Valley Streams

Nature Conservancy | June 13th, 2014

Groundwater is intimately connected to surface water, which has profound implications for sustainable water resource management. California has historically overlooked th

Groundwater is intimately connected to surface water, which has profound implications for sustainable water resource management. California has historically overlooked this important interaction and as a consequence, decisions about groundwater extractions have generally failed to address the resulting impacts to surface flows and aquatic ecosystems such as rivers, wetlands and springs. This has contributed to a loss of approximately 95 percent of the historical wetlands and river habitat in California’s Central Valley. With the passage of the Sustainable Groundwater Management Act (SGMA), groundwater sustainability agencies across the state will soon be required to manage groundwater resources to avoid causing undesirable results to groundwater levels and interconnected groundwater and surface water. These groundwater levels and areas of interconnection support groundwater- dependent ecosystems2 (GDEs). Therefore, an important first step in sustainable groundwater management is to understand how groundwater pumping impacts surface water, including streams, and GDEs.

Sustainable Water Management Strategy for Specialty Crop Expansion in the Sacramento Valley

Sacramento Area Council of Governments (SACOG) | June 26th, 2018

The Sacramento Area Council of Governments (SACOG) is an association of local governments in the six-county Sacramento Region of El Dorado, Placer, Sacramento, Sutter, Yo

The Sacramento Area Council of Governments (SACOG) is an association of local governments in the six-county Sacramento Region of El Dorado, Placer, Sacramento, Sutter, Yolo, and Yuba counties (excluding the Tahoe Basin in Placer and El Dorado counties) and the 22 cities therein. SACOG provides planning and funding for the region and serves as a forum for the study and resolution of regional issues. SACOG prepares the region’s long range plan which considers both transportation and land use. Through the lens of rural planning, SACOG has actively engaged in a Rural-Urban Connections Strategy (RUCS) Program that has studied ways to enhance rural economies and natural assets. The RUCS Program includes a scenario analysis modeling tool that links a parcel-level crop map with environmental and economic factors, including a comprehensive profile of per acre operational cost and return metrics for each crop. The study described in this report looks at how new agricultural crops and markets coupled with improved irrigation techniques will support new specialty crop acreage in the SACOG area. While new and improved irrigation techniques can result in better crop yields and decreased water demands, increases in irrigation efficiency also result in reduced groundwater recharge from irrigation return flows. SACOG received grant funding from the California Department of Food and Agriculture (CDFA) to evaluate the feasibility of recharging groundwater on agricultural lands within the SACOG portion of the Sacramento Valley to benefit specialty crop production. The primary goal of the project is to bring together a broad range of different factors impacting groundwater recharge and infiltration and to identify areas across the region that are most suited for strategic flooding of specialty crop fields; in other words, areas that will most efficiently and effectively facilitate recharge, while minimizing cost to the specialty crop producer. Ultimately, this feasibility information will be incorporated into SACOG’s RUCS model to evaluate the potential benefits of recharging groundwater on agricultural land for the benefit of specialty crops.