South Coast

Conserving California’s Coastal Habitats: A Legacy and a Future with Sea Level Rise

Nature Conservancy | May 15th, 2018

The California coast that we know today will not be the coast of the future. Sea level rise and other climate change impacts will have profound effects on o

The California coast that we know today will not be the coast of the future. Sea level rise and other climate change impacts will have profound effects on our coastline and its natural resources. California harbors high numbers of native, rare, and imperiled species in an array of unique coastal habitats. A majority of California’s coastline exists as natural habitat, over one-third of which has been preserved by a legacy of conservation efforts. Yet, this conservation legacy is at risk and we must act now to conserve the unique values of California’s coast—for both people and nature—into the future. To inform current and future adaptation decisions and conservation actions we conducted the first statewide, comprehensive assessment of the vulnerability of California’s coastal habitats, imperiled species, and conservation lands to sea level rise. Coastal habitats exist in narrow bands at the land-sea interface and are therefore extremely susceptible to inundation by sea level rise. However, some habitats may be able to adapt vertically and possibly move inland, assuming local topography and the built environment do not constrain this movement. We assessed the vulnerability of 40 habitats to sea level rise by quantifying the sensitivity and spatial extent of projected exposure of each habitat patch to intertidal and subtidal waters, relative to its ability to move inland in response to rising sea levels.

Considerations and Pathways for Potential State Oversight of Community Water Systems’ Wildfire Fighting Efforts in California

University of California, Los Angeles (UCLA) | March 3rd, 2026

Since the Los Angeles Fires of January 2025, dramatic shifts have occurred in perceptions, expectations, and understanding of water systems’ role in fighting wildfires

Since the Los Angeles Fires of January 2025, dramatic shifts have occurred in perceptions, expectations, and understanding of water systems’ role in fighting wildfires in California. As a consequence, policy attention has increased regarding the potential for enhanced statewide oversight to enhance wildfire-fighting capacity across community water systems. No state in the U.S. has previously pursued this path. Water systems face many obstacles to fighting wildfires that they have not been expected or supported to overcome. At the same time, as wildfires become more urban and increasingly encroach into the service territories of community water systems, the concept introduces interesting questions and potential innovations in design and implementation that may be good investments as part of long-term climate change adaptation.

Considerations for Management of the Mouth State of California’s Bar-built Estuaries

Southern California Wetlands Recovery Project | January 10th, 2019

Bar-built estuaries are the dominant estuary type in California, and many of these small estuaries are subject to closure with a sand barrier separating a lagoon

Bar-built estuaries are the dominant estuary type in California, and many of these small estuaries are subject to closure with a sand barrier separating a lagoon estuary from the ocean for days, months or even years. In the lagoon impounded behind the sand barrier, water levels may rise or fall depending on net water budget and water quality extremes may develop. These conditions and the obstruction of fish passage motivate managed breaching of the sand barrier in many systems statewide – an intervention that alleviates or preempts environmental problems, but which also can result in undesirable secondary impacts due to the acute effect of a single breach or the chronic effect of repeated breaching over years. Management decisions are based on an implicit trade-off between anticipated benefits and costs that depend on the values and priorities of stakeholders. This report was written to provide an overview of considerations for managed breaching in California. It presents a synthesis of processes and phenomena related to mouth closure and breaching in general and uses this to identify potential impacts of breaching, without intending any judgment of which impacts are more or less desirable. Three specific systems are reviewed in detail: Los Peñasquitos Lagoon in San Diego County, Scott Creek Estuary in San Mateo County and Russian River Estuary in Sonoma County. While there are fundamental similarities in the closure and breaching cycle across all bar-built estuaries statewide, there is also an immense diversity between these systems due to differences in size, in hydrology (wet north to dry south), and in development (rural, urban, agricultural, road/rail). The local community is likely to develop the best management strategy where there is significant effort and experience in local monitoring, science, and stakeholder consultation. However, where there is limited monitoring, science or consultation, the considerations outlined in this report provide preliminary guidance – and comparison with one of the study systems can provide more specific insight to the potential impacts of breaching management decisions. We synthesize current understanding related to how mouth state influences estuary functions and conditions, which in turn affect ecological services. While both natural and managed breaching affect many processes and phenomena in the estuary, breaching events and managed breaching regimes do not occur in isolation and many other factors affect the estuary functions and conditions, including freshwater inputs, the adjacent landscape, and stressors in the watershed. However, managed breaching is one of very few short-term management options and therefore a valuable adaptive management tool, specifically in systems that are already perturbed or impacted by human encroachment. Although emergency breaches may be required in rare occasions, our recommendation is to develop a breaching strategy for specific systems in which breaching has been used or in which it is likely to be used as a management tool. In this context, we recommend ways in which science can provide improved support for management decisions and identify a few systems in California in which there is already a well-developed, science-based management plan. Associated document: "Wetlands on the Edge: The Future of Southern California's Wetlands - Regional Strategy 2018"

Consumption Change Detection for Urban Planning: Monitoring and Segmenting Water Customers During Drought

American Geophysical Union (AGU) | March 11th, 2020

Demand management is a powerful way for water utilities to address the challenges of population growth and climate change. Although active conservation efforts have been

Demand management is a powerful way for water utilities to address the challenges of population growth and climate change. Although active conservation efforts have been studied extensively, recent evidence suggests households respond to many external events beyond a utility's control, including political responses to extreme climatic episodes and corresponding mass media coverage. Despite their importance, these external factors are difficult to analyze in a controlled setting, and few tools exist to evaluate their influence on customers. Here, we present a consumption change detection (CCD) method that offers new insights into how climate‐related mass media and policy events affect conservation by pinpointing the timing and magnitude of customer‐level water use shifts. We use CCD to monitor and segment the responses of residential water customers to policy and media events in Costa Mesa, California, during the severe 2012–2016 drought. Our results show consumption reductions among 75% of customers. Of these, 80% reduced water use before mandatory restrictions were imposed, coincident with intensifying state policy responses and spikes in media coverage that affected all customer types during 2014. Analysis of standardized drought consumption trajectories indicates that 16% of conserving customers increased consumption in 2015–2016. Conservation and rebound were both more likely among affluent and educated customers, suggesting that CCD can identify engaged and informed water savers who make suitable targets for water‐efficient retrofit incentive schemes. This study demonstrates CCD's potential as a novel demand analysis tool in an interconnected world where external social, political, and climatic stressors can exert an important influence on customer behavior.

Contributions of Climate Change and ENSO Variability to Future Precipitation Extremes Over California

American Geophysical Union (AGU) | June 14th, 2023

Counties Wresting Control: Local Responses to California's Statewide Water Market

University of Denver Water Law Review (UDWLR) | January 1st, 2003

Critical Review: Regulatory Incentives and Impediments for onsite Graywater Reuse in the United States

Water Environment Research | July 11th, 2013

Graywater is a potential water source for reducing water demand. Accordingly, a review was undertaken of graywater reuse regulations and guidelines within the 50 United

Graywater is a potential water source for reducing water demand. Accordingly, a review was undertaken of graywater reuse regulations and guidelines within the 50 United States. Major issues considered included acceptability for graywater segregation as a separate wastewater stream, allowable graywater storage, onsite treatment requirements, and permitted graywater use applications. Existing regulations and plumbing codes in the different states suggest that there are impediments to overcome but also potential incentives for graywater reuse. It is encouraging that regulations in 29 states promote safe graywater reuse, but there are also inconsistencies between plumbing codes and other regulations within and among the 50 states. Impediments to graywater reuse include disallowances of graywater segregation or collection, and restriction of graywater reuse to mostly subsurface irrigation with limited indoor use permission. Ease on restrictions and guidelines to promote development of low-cost and proven treatment technologies are needed to promote graywater reuse.

Dam effects on bedload transport on the upper Santa Ana River, California, and implications for native fish habitat

River Research and Applications (Wiley) | May 23rd, 2019

Dams disrupt the flow of water and sediment and thus have the potential to affect the downstream geomorphic characteristics of a river. Though there are some well‐known

Dams disrupt the flow of water and sediment and thus have the potential to affect the downstream geomorphic characteristics of a river. Though there are some well‐known and common geomorphic responses to dams, such as bed armouring, the response downstream from any particular dam is dependent on local conditions. Herein, we investigate the response of the upper Santa Ana River in southern California, USA, to the construction of a large dam at the transition from mountains to valley, using calculations of bedload transport capacity on the mainstem below the dam and for major tributaries. Approximate sediment budgets were constructed for downstream reaches to estimate deposition and erosion rates for sand, gravel, and cobble particle sizes. Our results indicate that the classical response of bed armouring and erosion is likely limited to a short reach immediately below the dam. Farther downstream, though transport capacity is reduced by flow regulation by the dam, the channel reaches are likely to remain depositional but with reduced deposition rates. Persistent deposition, as opposed to erosion, is the result of the replenishment of flow and sediment supply by large downstream tributaries. In addition, the calculations indicate that the composition of the bed is unlikely to change substantially in downstream reaches. A Monte Carlo approach was employed to estimate the uncertainty in the sediment budget predictions. The impacts of the dam on the geomorphic character of the river downstream could have implications for native fish that rely on coarse substrate that supports their food base.

Dams within Jurisdiction of the State of California

California Department of Water Resources (DWR) | October 31st, 2023

Data from Exploratory Sampling of Groundwater in Selected Oil and Gas Areas of Coastal Los Angeles County and Kern and Kings Counties in Southern San Joaquin Valley, 2014–15

U.S. Geological Survey (USGS) | December 9th, 2016

Exploratory sampling of groundwater in coastal Los Angeles County and Kern and Kings Counties of the southern San Joaquin Valley was done by the U.S. Geological Survey fr

Exploratory sampling of groundwater in coastal Los Angeles County and Kern and Kings Counties of the southern San Joaquin Valley was done by the U.S. Geological Survey from September 2014 through January 2015 as part of the California State Water Resources Control Board’s Water Quality in Areas of Oil and Gas Production Regional Groundwater Monitoring Program. The Regional Groundwater Monitoring Program was established in response to the California Senate Bill 4 of 2013 mandating that the California State Water Resources Control Board design and implement a groundwater-monitoring program to assess potential effects of well-stimulation treatments on groundwater resources in California. The U.S. Geological Survey is in cooperation with the California State Water Resources Control Board to collaboratively implement the Regional Groundwater Monitoring Program through the California Oil, Gas, and Groundwater Project. Many researchers have documented the utility of different suites of chemical tracers for evaluating the effects of oil and gas development on groundwater quality. The purpose of this exploratory sampling effort was to determine whether tracers reported in the literature could be used effectively in California. This reconnaissance effort was not designed to assess the effects of oil and gas on groundwater quality in the sampled areas. A suite of water-quality indicators and geochemical tracers were sampled at groundwater sites in selected areas that have extensive oil and gas development. Groundwater samples were collected from a total of 51 wells, including 37 monitoring wells at 17 multiple-well monitoring sites in coastal Los Angeles County and 5 monitoring wells and 9 water-production wells in southern San Joaquin Valley, primarily in Kern and Kings Counties. Groundwater samples were analyzed for field water-quality indicators; organic constituents, including volatile and semi-volatile organic compounds and dissolved organic carbon indicators; naturally present inorganic constituents, including trace elements, nutrients, major and minor ions, and iron species; naturally present stable and radioactive isotopes; dissolved noble gases; dissolved standard and hydrocarbon gases, ?13C of methane, ethane, and ?2H of methane. In total, 249 constituents and water-quality indicators were measured. Four types of quality-control samples (blanks, replicates, matrix spikes, and surrogates spiked in environmental and blank samples) were collected at approximately 10 percent of the wells. The quality-control data were used to determine whether the groundwater-sample data were of sufficient quality for the measured analytes to be used as potential indicators of oil and gas effects. The data from the 51 groundwater samples and from the quality-control samples are presented in this report.