The Big Water Supply Shift: Groundwater Key to Water Security in California's Changing Climate

Union of Concerned Scientists | November 1st, 2015

For more than a century, California has relied on its snowmelt-fed reservoirs, rivers, and streams for the majority of its water, but drought and climate chang

For more than a century, California has relied on its snowmelt-fed reservoirs, rivers, and streams for the majority of its water, but drought and climate change are depleting those traditional supplies. Snow is already melting as many as 30 days earlier than in the mid-twentieth century, meaning less water is available during the hotter months when water demand is highest. California is increasingly turning to groundwater to meet its water needs. Today, groundwater supplies up to 50 percent of California’s water, but California’s prolonged drought has led to the over-pumping of groundwater, overdrafting the Central Valley’s aquifers. Sustainable groundwater management will allow the state to adapt to climate change while increasing water reliability in the future.

The Cost of Regulating Active Landfills for Water Quality

California State Water Resources Control Board (SWRCB) | January 3rd, 2016

This report to the legislature was prepared pursuant to Chapter 718, Statutes of 2010 (SB 855, Committee on Budget and Fiscal Review), which requires the State Water Reso

This report to the legislature was prepared pursuant to Chapter 718, Statutes of 2010 (SB 855, Committee on Budget and Fiscal Review), which requires the State Water Resources Control Board (State Water Board) to submit to the budget committees in each house of the legislature a report on the costs of regulating water quality at active landfills. The State Water Board and Regional Water Quality Control Boards (Regional Boards, collectively, the Water Boards) analyzed the cost of resources required to implement State and Federal statutes, regulations, and policies at these facilities. This report provides an overview of the Water Boards’ Land Disposal Program, followed by a cost analysis. The Water Boards’ Land Disposal Program provides regulatory oversight to 439 active landfills and 235 other waste management facilities in the State. Active landfills are all landfills that still pose a threat to the environment, even if they have stopped accepting waste. Active landfills are classified as operating or non-operating, with non-operating landfills including proposed, closing, and closed landfills. There are an estimated 1600 legacy landfills that were not included in the cost analysis for this report. Legacy landfills are waste management units that were closed, abandoned, or inactive prior to the adoption of revised State Water Board regulations in November 1984. In response to the legislative requirements, the results of this analysis show the cost of regulating the 439 active landfills to be approximately $18.1 million. The Land Disposal Program also regulates other waste management facilities as an integral part of the program, and tracks these facilities along with active landfills. Based on this analysis, the cost of regulating the 235 other waste management facilities is approximately $7.6 million. In total, implementation of the Land Disposal Program would cost approximately $25.7 million (not including legacy landfills). In Fiscal Year 2011-2012, the total expenditures incurred by the Land Disposal Program were approximately $10.6 million. As this presents an approximately $15.2 million shortfall in funding, the program prioritizes work based on threat to water quality, complexity, and level of activity at the facility. Working within existing resource constraints, the Land Disposal Program is currently implementing a series of efficiency measures to improve program effectiveness. A discussion of these efforts concludes this report.

The Ecological Significance of the Submarine Discharge of Groundwater

Commonwealth Scientific and Industrial Research Organisation (CSIRO Publishing) | December 15th, 1980

Discharge of groundwater into the sea is widespread. Overlooking it may lead to serious misinterpretations of ecological data in studies of coastal pollution, of benthic

Discharge of groundwater into the sea is widespread. Overlooking it may lead to serious misinterpretations of ecological data in studies of coastal pollution, of benthic zonation and productivity, and of the flux of dissolved substances within and between bottom sediments and overlying water. Data are presented indicating that in the Perth region of Western Australia, submarine groundwater discharge delivers several times as much nitrate to coastal waters as does river runoff.

The Economic Impact on the Local Economy of Irrigated Agriculture in the Paso Robles Area and Potential Impacts of the Sustainable Groundwater Management Act

California Polytechnic State University, San Luis Obispo (CSU) | August 26th, 2020

The purpose of this study is to analyze the economic impact of the agricultural and wine industry within the Paso Robles Subbasin and AVA and San Luis Obispo County and t

The purpose of this study is to analyze the economic impact of the agricultural and wine industry within the Paso Robles Subbasin and AVA and San Luis Obispo County and to assess the economic impact of potential changes in the agricultural industry as a result of the Paso Robles Subbasin Groundwater Sustainability Plan that will reduce water allocations and/or increase the cost of water in the basin from 2020 – 2040 and beyond.

The Economic Value of Carryover Storage in California’s Water Supply System with Limited Hydrologic Foresight

University of California, Davis (UC Davis) | July 1st, 2021

The security and prosperity of California’s economy depend on a large, interconnected and highly engineered water supply system with vast surface and groundwater stora

The security and prosperity of California’s economy depend on a large, interconnected and highly engineered water supply system with vast surface and groundwater storage operated for over-year storage. Substantial public investment is needed to maintain and improve these systems with changing climate risks, increasing demands, and aging infrastructure. Hydro-economic optimization identifies promising opportunities for managing such systems, but scientific and engineering advances are needed to better incorporate hydrologic uncertainty and conjunctive management of streams and aquifers into such models. Over two decades of research the California Value Integrated Network (CALVIN) linear programming hydro-economic model has yielded insights for California’s inter-regional water system on many fronts, including climate change, groundwater sustainability, conjunctive management in southern California, water markets, and reservoir operations in Northern California. Yet there remains unrealized potential to improve the model’s formulation to better represent inter-annual hydrologic variability while concurrently developing reservoir control rules. To address this gap, this study implements linearized quadratic carryover storage value functions on 26 surface reservoirs and linear groundwater storage penalties on 32 groundwater reservoirs to optimize California’s inter-regional water system seasonal and inter-annual operations with limited seasonal foresight. A convex Pareto front tradeoff between total system cost and groundwater overdraft is developed through multi-objective evolutionary optimization of inter-annual carryover storage penalties. Resulting over-year storage valuations span a wide range of nearoptimal reservoir operations, suggesting substantial system flexibility and adaptability when managed in an integrated way. Generalized relationships between carryover capacity, carryover use, and the marginal value of carryover storage are drawn for the multi-reservoir system. When compared to carryover operations based on California’s current simulation model, CalSim-II, the performance of these near-optimal reservoir operations suggests room to improve currently prescribed reservoir control rules, especially in supporting more  sustainable conjunctive management with aquifers. Overall, this study demonstrates the practicability, feasibility, and utility for understanding large-scale integrated multi-reservoir conjunctive use systems using limited foresight with explicit carryover storage values.

The economic value of local water supplies in Los Angeles

Nature Portfolio (Springer Nature) | May 21st, 2018

Los Angeles imports water over long distances to supplement local supplies. Reduced reliability of the available imports is driving many local agencies to promote conserv

Los Angeles imports water over long distances to supplement local supplies. Reduced reliability of the available imports is driving many local agencies to promote conservation and enhance local water sources. These include stormwater capture, water reuse and groundwater. But financial considerations are often a significant impediment to project development, especially when comparing new and existing sources. Here we demonstrate a comprehensive approach for evaluating the economic implications of shifting to local water reliance in Los Angeles County. We show that local water supplies are economically competitive. Results from integrated hydroeconomic modelling of urban water in Los Angeles identify cost-effective water supply portfolios and conservation targets. Considering costs across the ‘full-cycles’ of urban water supply that span agency boundaries yields better comparisons of planning alternatives. Throughout the region, many water retailers could successfully mitigate effects of imported water cuts while still supporting drought-tolerant landscapes, but some would suffer due to over-reliance on imports. Updating economic assessment methods would support needed innovations to achieve local reliance in Los Angeles, including infrastructure investments, institutional reforms, many more drought-tolerant landscapes and reallocated groundwater rights.

The Effect of Declining Groundwater Levels on Supply Well Operations

University of California, Davis (UC Davis) | August 15th, 2016

This report explores the impact of droughts on domestic and irrigation well operations. Well completion reports and groundwater depth data obtained from the Department of

This report explores the impact of droughts on domestic and irrigation well operations. Well completion reports and groundwater depth data obtained from the Department of Water Resources were used in the analysis. The percentages of wells in which the top, middle or bottom of the screened interval became exposed above the pumping water level were calculated and implied maintenance or replacement costs were estimated. Increases in pumping costs from greater depths to groundwater were estimated as well. For our case study, we selected a 27 square mile area in Tulare County, where the California Department of Water Resources has determined that groundwater is in a state of critical overdraft and designated the basin as High Priority under the Sustainable Groundwater Management Act. Results indicate that for the 2015 drought, there was significant potential for incurring well maintenance and replacement costs as a result of drought conditions and water levels approaching critical points in the screened intervals. While the assumptions associated with the current method appear to result in overestimation of impacts, the current drought may have resulted in several million dollars in well maintenance and replacement costs. For irrigation wells that remained in operation, increased depths to groundwater would increase overall pumping costs. About $5.31 per acre ($1.7 per acre-foot) were estimated as increased pumping costs in the recent 2012-2015 drought. While these costs are not large on a per acre basis, they may be significant when incurred across large agricultural areas. This proof of concept analysis highlights the value of information on groundwater levels and well constructions for estimating impacts of droughts on long term groundwater pumping capacity and operation. This analysis can be extended for the entire Central Valley in an effort to quantify the impacts of drought and the importance of groundwater management.

The effects of artificial recharge on groundwater levels and water quality in the west hydrogeologic unit of the Warren Subbasin, San Bernardino County, California

U.S. Geological Survey (USGS) | November 4th, 2013

The Future of Agriculture in the San Joaquin Valley

Public Policy Institute of California (PPIC) | February 9th, 2023

The Future of Groundwater in California: Lessons in Sustainable Management from Across the West

Environmental Defense Fund (EDF) | January 31st, 2018

The 2014 Sustainable Groundwater Management Act (SGMA) created, for the first time and on an unprecedented scale, a mandate to change how groundwater is managed statewide

The 2014 Sustainable Groundwater Management Act (SGMA) created, for the first time and on an unprecedented scale, a mandate to change how groundwater is managed statewide in California. While enacting SGMA was a tremendous step forward, communities and water districts now face the considerable challenge of creating successful groundwater management programs. This report is aimed at helping California’s water managers, public water agencies, county commissioners, city planners, and others better understand the suite of tools and approaches that can be used to enhance the sustainable management of groundwater. Specifically, we consider four categories of management tools—regulatory, incentive-based, agency supply augmentation and protection, and education and outreach—to evaluate how these tools are being used to address water quantity, water quality, and surface water and groundwater interaction challenges. We present nine comprehensive case studies of groundwater management across the Western United States to highlight how these tools have been used to address those challenges. The case studies represent basins that have a range of water uses— agricultural, municipal, or mixed water use, as well as basins with diverse hydrologic, political and social settings. Effective groundwater management takes time and requires significant resources and commitment on the part of water managers and communities. Each groundwater management program presented in this report relies upon a variety of interdependent tools and actions to meet management goals. The case studies illustrate the importance of building trust, having sufficient data, using a portfolio of management approaches, assuring performance, and access to funding. Given the similarities between the goals of SGMA and those described in the case studies, these themes emerge as crucial to the successful implementation of California’s landmark groundwater legislation.