Saltwater Intrusion in Los Angeles Area Coastal Aquifers— the Marine Connection

U.S. Geological Survey (USGS) | August 14th, 2002

Saltwater from the Pacific Ocean is seeping into some Los Angeles Basin coastal aquifers and replacing freshwater. Without treatment, this ground water does not conform t

Saltwater from the Pacific Ocean is seeping into some Los Angeles Basin coastal aquifers and replacing freshwater. Without treatment, this ground water does not conform to drinking-water or agricultural standards. This problem is significant because much of the water used by the nearly 10 million residents of Los Angeles County comes from ground-water sources. Although not all coastal aquifers in the region are at risk, the existing resources are vital and must be protected to maintain adequate supplies of potable water. In the 1950’s, construction began on the first of three “barriers” in an attempt to halt saltwater intrusion. Each barrier consists of a series of injection wells that essentially form a subsurface wall of freshwater designed to keep saltwater from penetrating further into aquifers. The barriers are only partly effective; saltwater continues to infiltrate in some areas. New studies show that the ground-water geohydrology of the coastal aquifers is more complex than previously imagined. U.S. Geological Survey (USGS) scientists, working in cooperation with the Water Replenishment District of Southern California and the Los Angeles County Department of Public Works, are expanding efforts to understand the geologic processes and fluid pathways that control saltwater intrusion.

San Andreas Fault Stress Change Due To Groundwater Withdrawal in California's Central Valley, 1860-2010

American Geophysical Union (AGU) | December 28th, 2021

We investigate the spatial and temporal effects of groundwater removal in California's Central Valley on ground surface deformation and on stress changes on the nearby ce

We investigate the spatial and temporal effects of groundwater removal in California's Central Valley on ground surface deformation and on stress changes on the nearby central San Andreas fault (CSAF). In particular, we focus on two outstanding questions: (a) What are the spatial distributions of Coulomb failure stress (ΔCFS) on the CSAF? (b) What are the effects of viscoelasticity on uplift and ΔCSF over time? We focus on the well studied 2006–2010 drought, estimating the change in groundwater storage and the resulting uplift and stress change through a numerical model for the Earth. Viscoelastic effects are examined through an estimate of historical groundwater change from 1860-1961 and a hydrological model from 1961-2003 added to the 2006–2010 drought estimates. Here we find that lower crust or upper mantle viscosity variations enhance uplift and stress changes and that CSAF stress changes may accumulate with time, especially with droughts and groundwater consumption.

San Antonio Creek Valley Groundwater Basin Groundwater Sustainability Plan

San Antonio Basin Groundwater Sustainability Agency | December 16th, 2021

The Sustainable Groundwater Management Act (SGMA), effective as of January of 2015, created a new statewide framework for managing California’s groundwater at the loca

The Sustainable Groundwater Management Act (SGMA), effective as of January of 2015, created a new statewide framework for managing California’s groundwater at the local level through the formation of Groundwater Sustainability Agencies (GSAs). SGMA requires the development and implementation of a Groundwater Sustainability Plan (GSP) for each groundwater basin in the state that has been designated as high or medium priority. A GSP presents strategies for maintaining or bringing a groundwater basin into a sustainable condition within the next 20 years. SGMA exempts de minimus pumpers (e.g., individual domestic well owners who extract up to 2 acre-feet per year [AFY]) from most of the SGMA requirements and does not require metering. The San Antonio Basin Groundwater Sustainability Agency (SABGSA) was formed in 2017 for the purpose of sustainably managing groundwater and developing this GSP for the San Antonio Creek Valley Groundwater Basin (Basin). The SABGSA member agencies are the San Antonio Basin Water District and Los Alamos Community Services District. The Basin occupies approximately 123 square miles in western Santa Barbara County (see Figure ES-1). It is bounded on the north by the Casmalia Hills and Solomon Hills, on the east by the San Rafael Mountains and a watershed divide separating the adjoining Santa Ynez River Valley groundwater basin, on the south by the Purisima Hills and Burton Mesa, and the west by the approximate western boundary of Barka Slough. This GSP describes the physical setting of the Basin; quantifies historical, present, and future water budgets; develops quantifiable management objectives that account for the interests of the Basin’s beneficial groundwater uses and users and identifies a group of projects and management actions that will allow the Basin to achieve sustainability within 20 years of plan adoption. This document also includes the list of references and technical studies, documentation of the stakeholder engagement process undertaken in the development of this plan, and several supporting appendices. Due to size, the file has been divided. Part 1, Part 2, Part 3, Part 4, Part 5, Part 6

San Antonio Water Company v. Foothill Irrigation Company, et al

Superior Court of California, County of San Bernardino | July 25th, 1958

From "An Evaluation of California's Adjudicated Groundwater Basins" by Langridge et al: "The Cucamonga Basin is a small groundwater basin located in San Bernardino Co

From "An Evaluation of California's Adjudicated Groundwater Basins" by Langridge et al: "The Cucamonga Basin is a small groundwater basin located in San Bernardino County. In the 1950s, approximately 25 parties, mostly small local water companies and several individual water users, filed an action to adjudicate the rights to the basin’s groundwater and certain surface waters tributary to the basin. The subsequent adjudication resulted in a 1958 Decree that contains some provisions for the metering and recording of water production, inspection of records, prohibitions against new water production, and potential reductions in water production. The court did not appoint an official Watermaster for the basin, and annual reports are not required. Since adjudication, water use in the basin has shifted from primarily agricultural use to primarily municipal use. Today there are three main water agencies — Cucamonga Valley Water District, San Antonio Water Company, and West End Consolidated Water Company — that hold nearly all of the adjudicated rights in the basin and jointly manage the basin pursuant to the 1958 Decree. Studies differ regarding the condition of the basin. A 2007 Metropolitan Water District review indicates that water levels in key wells have decreased about 120 feet and that the basin is experiencing long-term decline. Basin managers point to production data that also shows water production in the basin can trend below the total allocated rights production data."

San Fernando Groundwater Basin Remediation Program

Los Angeles Department of Water & Power (LADWP) | January 1st, 2018

San Francisco Bay Hydrologic Region Groundwater Update

California Department of Water Resources (DWR) | April 1st, 2015

The primary goal of the San Francisco Bay Hydrologic Region (San Francisco Bay region) groundwater update is to expand information about region-specific groundwater condi

The primary goal of the San Francisco Bay Hydrologic Region (San Francisco Bay region) groundwater update is to expand information about region-specific groundwater conditions for California Water Plan Update 2013 and to guide more informed groundwater management actions and policies. A second goal is to steadily improve the quality of groundwater information in future California Water Plan (CWP) updates to a level that will enable regional water management groups (RWMGs) to accurately evaluate their groundwater resources and implement management strategies that can meet local and regional water resource objectives within the context of broader statewide objectives. The final goal is to identify data gaps and groundwater management challenges that will guide prioritizing of future data collection and funding opportunities relevant to the region. This regional groundwater update is not intended to provide a comprehensive and detailed examination of local groundwater conditions, or be a substitute for local studies and analysis. Nonetheless, where information is readily available, this update does report some aspects of the regional groundwater conditions in greater detail.

San Gabriel Valley Groundwater Basin Salt And Nutrient Management Plan

Publisher not available | May 31st, 2016

San Gabriel Valley Superfund Sites Progress Updates

U.S. Environmental Protection Agency (EPA) | May 31st, 2021

San Gorgonio Pass Subbasin Groundwater Sustainability Plan

San Gorgonio Pass Groundwater Sustainability Agency | January 28th, 2022

San Joaquin Basin Flood-MAR Watershed Studies Study Design Report

California Department of Water Resources (DWR) | December 3rd, 2025

Click here to be taken to the California Department of Water Resources Watershed Studies home page

Click here to be taken to the California Department of Water Resources Watershed Studies home page