South Coast

Seawater Intrusion in a Coastal California Aquifer

U.S. Geological Survey (USGS) | July 18th, 1996

Seawater intrusion in aquifers underlying the Oxnard Plain, Ventura County, California, was first observed in the early 1930's and became a serious problem in the mid-195

Seawater intrusion in aquifers underlying the Oxnard Plain, Ventura County, California, was first observed in the early 1930's and became a serious problem in the mid-1950's (California Department of Water Resources, 1965) (fig. 1). Historically, local agencies responsible for the management of ground water used a criterion of 100 milligrams per liter (mg/L) chloride to define the leading edge of the seawater front. It was assumed that all high-chloride water from wells behind the front originated from seawater that entered aquifers through outcrop areas in submarine canyons. Recent work (Izbicki, 1991; Stamos and others, 1992) showed that other sources of high-chloride water to wells are present and that the areal extent of seawater intrusion in the upper aquifer system is smaller than previously believed.

Second Report of Recharge Parties Pursuant to RWQCB Resolution No. R8-2008-0019 Cooperative Agreement to Protect Water Quality and Encourage the Conjunctive Uses of Imported Water in the Santa Ana River Basin, Yucaipa and San Timoteo Management Zones

San Bernardino Valley Municipal Water District | July 18th, 2012

The importation of water (i.e., State Water Project (SWP) water, Colorado River water, and imported groundwater) to groundwater basins within the Santa Ana River Region

The importation of water (i.e., State Water Project (SWP) water, Colorado River water, and imported groundwater) to groundwater basins within the Santa Ana River Region is necessary to meet increasing demand. However, long-term conjunctive use of water within the Region could affect groundwater quality. As such, the California Regional Water Quality Control Board Santa Ana Region (RWQCB) is requiring that groundwater quality be managed to meet the water quality objectives for total dissolved solids (TDS) and nitrogen (i.e., Salinity Objectives) regulated in the 1995 Water Quality Control Plan for the Santa Ana River Basin (Basin Plan). On January 22, 2004, the RWQCB adopted Resolution No. R8-2004-0001, incorporating an updated TDS and nitrogen management plan that includes revised groundwater subbasin boundaries; revised TDS and nitrate-nitrogen water quality objectives for groundwater; revised TDS and nitrogen waste load allocations; and revised reach designations, TDS and nitrogen objectives and beneficial uses for specific surface waters. On May 19, 2006, the RWQCB considered a resolution and order that would have adopted general waste discharge requirements for the recharge of imported water to the Santa Ana River Basin. Based on input from stakeholders, it was decided by the RWQCB that the feasibility of a cooperative program should be investigated that would achieve the objectives of and obviate the adoption of the draft resolution and order under consideration. On January 18, 2008, the RWQCB adopted Resolution No. R8-2008-0019 authorizing a “Cooperative Agreement to Protect Water Quality and Encourage the Conjunctive Use of Imported Water in the Santa Ana River Basin.” The purpose of the cooperative agreement is to allow the participating parties to “…monitor and improve water quality objectives within the Santa Ana River Region in a manner that is consistent with the needs of the inhabitants of the Region for a reliable supply of water.” (Cooperative Agreement, 2008). The following Parties have entered into this cooperative agreement: California Regional Water Quality Control Board, Santa Ana Region, City of Corona, City of Riverside, City of San Bernardino Municipal Water Department, Eastern Municipal Water District, Elsinore Valley Municipal Water District, Orange County Water District, San Bernardino Valley Municipal Water District (Valley District), San Gorgonio Pass Water Agency, and Western Municipal Water District of Riverside County (Western).  

Senate Bill No. 1157

State of California | September 28th, 2022

Senate Bill No. 389, Chapter 486, An act to amend Section 1051 of the Water Code, relating to water

State of California Office of Legislative Counsel | October 8th, 2023

Click here for analysis by Legal Planet.

Click here for analysis by Legal Planet.

Serum concentrations of PFASs and exposure-related behaviors in African American and non-Hispanic white women

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

Per- and polyfluoroalkyl substances (PFASs) are used in a wide range of consumer products for their water- and grease-resistant properties, but few studies have e

Per- and polyfluoroalkyl substances (PFASs) are used in a wide range of consumer products for their water- and grease-resistant properties, but few studies have explored this exposure route. We used multiple regression to investigate associations between six self-reported behaviors hypothesized to influence PFAS exposure and serum concentrations of six PFAS chemicals in 178 middle-aged women enrolled in the Child Health and Development Studies, about half of whom are African American. Blood samples were collected in 2010–2013, and participants were interviewed about behavior in 2015–2016. Results showed that African American women had lower levels of perfluorooctanoic acid (PFOA) and perfluorohexanesulfonic acid (PFHxS) compared with non-Hispanic white women. In African Americans, but not others, frequent consumption of prepared food in coated cardboard containers was associated with higher levels of four PFASs. Flossing with Oral-B Glide, having stain-resistant carpet or furniture, and living in a city served by a PFAS-contaminated water supply were also associated with higher levels of some PFASs. Product testing using particle-induced γ-ray emission (PIGE) spectroscopy confirmed that Oral-B Glide and competitor flosses contained detectable fluorine. Despite the delay between blood collection and interview, these results strengthen the evidence for exposure to PFASs from food packaging and implicate exposure from polytetrafluoroethylene (PTFE)-based dental floss for the first time.

SGMA’s First Groundwater Market: An Early Case Study from Fox Canyon

Nature Conservancy | May 1st, 2019

In 2014, amid California’s most recent drought, the state passed the Sustainable Groundwater Management Act (SGMA). This new law regulates groundwater at scale for th

In 2014, amid California’s most recent drought, the state passed the Sustainable Groundwater Management Act (SGMA). This new law regulates groundwater at scale for the first time, requiring the state’s largest source of stored water to be managed for long-term resilience. SGMA delegates the responsibility of achieving sustainable groundwater management by 2040 to local Groundwater Sustainability Agencies (GSAs). GSAs must achieve sustainability for their groundwater basins by developing and implementing Groundwater Sustainability Plans (GSPs). Balancing groundwater basins to achieve sustainability will require increasing water supply to the basin and/or decreasing water demand. The Fox Canyon Groundwater Management Agency (FCGMA), in western Ventura County, is the first GSA to pursue a groundwater market as a tool to decrease water demand when implementing its GSP. This white paper outlines FCGMA’s experience—the steps taken and lessons learned—in developing the first groundwater market to emerge under SGMA. It is a combined effort of The Nature Conservancy (TNC), California Lutheran University’s (CLU’s) Center for Economic Research and Forecasting (CERF) and FCGMA, with the support of local growers and the Farm Bureau of Ventura County (Farm Bureau). This document is meant to serve as a resource for GSAs and other public agencies, organizations, practitioners and stakeholders involved in water resource management and contemplating the creation of groundwater markets to meet SGMA’s sustainability mandate. This report focuses on the design and testing of the Fox Canyon groundwater market; a companion report will likely follow to evaluate the performance and share additional lessons learned once the market has launched.

Sharpening of cold-season storms over the western United States

Nature Portfolio (Springer Nature) | January 19th, 2023

Winter storms are responsible for billion-dollar economic losses in the western United States. Because storm structures are not well resolved by global climate models, it

Winter storms are responsible for billion-dollar economic losses in the western United States. Because storm structures are not well resolved by global climate models, it is not well established how single events and their structures change with warming. Here we use regional storm-resolving simulations to investigate climate change impact on western US winter storms. Under a high-emissions scenario, precipitation volume from the top 20% of winter storms is projected to increase by up to 40% across the region by mid-century. The average increase in precipitation volume (31%) is contributed by 22% from increasing area coverage and 19% from increasing storm intensity, while a robust storm sharpening with larger increase in storm centre precipitation compared with increase in storm area reduces precipitation volume by 10%. Ignoring storm sharpening could result in overestimation of the changes in design storms currently used in infrastructure planning in the region.

Shoreline retreat and beach nourishment are projected to increase in Southern California

Nature Portfolio (Springer Nature) | May 22nd, 2024

Sandy beaches in Southern California are experiencing rising coastal erosion due to changes in precipitation patterns and urban growth. As a result, beach nourishment is

Sandy beaches in Southern California are experiencing rising coastal erosion due to changes in precipitation patterns and urban growth. As a result, beach nourishment is necessary for mitigation. In our study, we forecast the rates of shoreline retreat and the required volumes of sand nourishment to mitigate it for the coming decades. We employ photogrammetric multi-decadal shoreline positioning and Digital Shoreline Analysis System methods to measure and predict the coastal evolution of the Gulf of Santa Catalina in Southern California. This region is hypothesized to be globally representative of other semi-arid sandy coasts facing similar hydroclimatic and anthropogenic challenges. Our findings indicate that Southern California’s shoreline retreat rates for sandy beaches will increase from the present average value of ~−1.45 to −2.12 meters per year in 2050 and to −3.18 meters per year in 2100. Consequently, the annual volume of sand required for beach nourishment could triple by 2050, increasing from the present-day amount of ~1223 to ~3669 cubic meters per year per kilometer. However, the associated cost for this nourishment will grow five times, exacerbating several coastal communities’ economic and logistical pressures. Similar trends are emerging globally, with semi-arid developing nations already grappling with coastal hazards and may struggle to manage the escalating costs of curbing beach nourishment.

Shoreline Seasonality of California's Beaches

American Geophysical Union (AGU) | January 30th, 2025

We report on remote sensing techniques developed to characterize seasonal shoreline cycles from satellite-derived shoreline measurements. These techniques are applied to

We report on remote sensing techniques developed to characterize seasonal shoreline cycles from satellite-derived shoreline measurements. These techniques are applied to 22-yr of shoreline measurements for over 777 km of beach along California's 1,700-km coast, for which the general understanding is that shorelines exhibit winter-narrow and summer-recovery seasonality. We find that approximately 90% of beach transects exhibit significant and recurring seasonal cycles in the shoreline position. Seasonal shoreline excursions are twice as large in northern and central California (17.5–32.2 m) than southern California (7.3–15.9 m; interquartile ranges). Clustering analyses were effective at characterizing the temporal patterns of the seasonality, revealing that ∼459 km of beach (59%) exhibit winter-narrow conditions, whereas ∼189 km (24%) and ∼50 km (6.4%) exhibit spring-narrow and summer-narrow conditions, respectively. These spring- and summer-narrow conditions are most common in southern California, where they represent over half of the total length of beach shoreline. Multivariate analyses reveal that wave climate and geomorphic setting are significantly related to the magnitude and timing of shoreline seasonal cycles. Combinations of these variables explain 44% of the seasonality variance of the complete data set and 85% of the variance for a subset of 93 long (>1 km) continuous beaches. We conclude that diversity in waves and geomorphic setting along California cause a broad range of seasonal patterns in the shoreline. Combined, this indicates that the overly generalized “winter-narrow/summer-recovery” conventions for California beaches are not expressed universally and that shoreline seasonality is far more diverse than these simple canonical rules.

Shrinking lakes, air pollution, and human health: Evidence from California's Salton Sea

Science of the Total Environment (Elsevier) | January 7th, 2020

Due to increased water withdrawals and ongoing climate change, many inland lakes around the world are shrinking and dry lake beds can be significant sources of particulat

Due to increased water withdrawals and ongoing climate change, many inland lakes around the world are shrinking and dry lake beds can be significant sources of particulate matter air pollution. Using a natural experiment provided by the shrinking Salton Sea in California, this paper shows that each one-foot drop in lake elevation is associated with a 0.28 μg/m3 (2.6%) increase in PM2.5 concentrations. IV model results then show that Salton Sea-induced changes in PM2.5 over 1998–2014 led to increases in respiratory mortality of 1.4/yr.–15.6/yr. in the counties surrounding the lake, generating $13.2–$147.3 million in annual health costs.