South Coast

Synoptic conditions associated with cool season post-fire debris flows in the Transverse Ranges of southern California

Natural Hazards (Springer) | April 22nd, 2017

The Transverse Ranges of southern California often experience fire followed by flood. This sequence sometimes causes post-fire debris flows (PFDFs) that threaten life a

The Transverse Ranges of southern California often experience fire followed by flood. This sequence sometimes causes post-fire debris flows (PFDFs) that threaten life and property situated on alluvial fans. The combination of steep topography, highly erodible rock and soil, and wildfire, coupled with intense rainfall, can initiate PFDFs even in cases of relatively small storm rainfall totals. This study identifies common atmospheric conditions during which damaging PFDFs occur in the Transverse Ranges during the cool season, defined here as November–March. A compilation of 93 PFDF events during 1980–2014 triggered by 19 precipitation events is compared against previous studies of the events, reanalysis, precipitation, and radar data to estimate PFDF trigger times. Each event was analyzed to determine common atmospheric features and their range of values present at and preceding the trigger time. Results show atmospheric rivers are a dominant feature, observed in 13 of the 19 events. Other common features include low-level winds orthogonal to the Transverse Ranges and other conditions favorable for orographic forcing, a strong upper level jet south of the region, and moist-neutral static stability. Several events included closed low-pressure systems or narrow cold frontal rain bands. These findings can help forecasters identify more precisely the synoptic-scale atmospheric conditions required to produce PFDF-triggering rainfall and thus reduce uncertainty when issuing warnings.

Synthesis Report: Integrating probability and targeted survey designs in regional stream condition assessments with examples from southern coastal California

California State Water Resources Control Board (SWRCB) | June 30th, 2010

Ambient water quality monitoring programs have traditionally relied on the use of targeted monitoring designs (in which sampling locations are assigned non-randomly) to a

Ambient water quality monitoring programs have traditionally relied on the use of targeted monitoring designs (in which sampling locations are assigned non-randomly) to assess the condition of aquatic resources. As probability-based surveys (in which site locations are assigned randomly) have become more widely adopted, there has been a growing desire to combine data from targeted sites with data from probability sites when making overall assessments of resource condition. We evaluated the potential for combining datasets and present an approach to combining data from the two types of surveys. We compiled biological, chemical and habitat data from 63 probability sites and 133 targeted monitoring sites in southern coastal California and compared the distribution of analyte values collected under the two designs. This analysis clearly demonstrates that both targeted and probabilistic sampling designs are necessary for effective non-point source water quality monitoring programs. Probability designs are the only survey type capable of giving an objective overview of the range of conditions present in the resource of interest. By contrast, targeted designs often are needed to fill in critical data gaps and answer site-specific questions. We conclude that the most effective way to ‘integrate’ probability and targeted surveys is to use probability surveys to produce an unbiased regional framework for interpreting targeted results and to supplement this framework as needed with sites targeted to fill data gaps.

Systems Analysis and Optimization of Local Water Supplies in Los Angeles

American Society of Civil Engineers (ASCE) | September 1st, 2017

Los Angeles, which relies on large infrastructure systems that import water over hundreds of miles, faces a future of reduced imports. Within Los Angeles and its hund

Los Angeles, which relies on large infrastructure systems that import water over hundreds of miles, faces a future of reduced imports. Within Los Angeles and its hundreds of water agencies, the capacity to adapt to future changes is influenced by laws, institutions, and hydrogeology. This paper presents a systems analysis of urban water management in metropolitan Los Angeles County to assess opportunities for increasing local water reliance. A network flow model was developed to investigate management tradeoffs across engineered, social, and environmental systems. With an aggressive regional demand target, increased stormwater capture (300%), and prioritized water reuse from existing facilities, imported water supplies can be cut by 30% while maintaining landscapes, economic productivity, and groundwater resources. Further reducing imports (by 40–50%) is possible through actions to promote additional reuse, recharge, conservation, and groundwater access. Reducing imported water without significant conservation results in likely groundwater overdraft. Fragmented networks of agencies in Los Angeles create an uneven landscape of vulnerability to water shortages. The paper discusses model applications, research needs, and policy implications of results for dry-climate cities.

Talbert Seawater Intrusion Barrier Operations & Maintenance Manual

Orange County Water District (OCWD) | March 15th, 2023

OCWD’s Talbert Seawater Barrier (Talbert Barrier, Barrier) has been in operation since 1976. Since 1976 the Barrier has undergone many changes including new well design

OCWD’s Talbert Seawater Barrier (Talbert Barrier, Barrier) has been in operation since 1976. Since 1976 the Barrier has undergone many changes including new well designs and improved injection water quality. Since 2008, the Talbert Barrier has been injecting advanced treated wastewater from OCWD’s GWRS treatment plant. This manual will examine in detail the various types of injection wells, their operational procedures and the procedures followed to monitor the quality of the injection water and evaluate injection well performance. Due to size, this document has been divided. Part 1, Part 2

Taming wildfires in the context of climate change: The case of the United States

Organisation for Economic Co-operation and Development (OECD) | January 22nd, 2024

Shifts in climate cycles (e.g., Pacific Decadal Oscillation, El Niño-Southern Oscillation), combined with ongoing changes in drought, temperature and snowmelt, together,

Shifts in climate cycles (e.g., Pacific Decadal Oscillation, El Niño-Southern Oscillation), combined with ongoing changes in drought, temperature and snowmelt, together, have contributed to the overall warmer, drier conditions that fuel extreme wildfires (Environmental Protection Agency, 2022[4]; Kitzberger et al., 2007[10]; Westerling, 2016[11]). The period with the largest increase in area burned coincides with many of the warmest years on record nationwide (Environmental Protection Agency, 2022[4]). Such changes are especially visible in the western United States, where the peak extent of area burned now occurs about one month earlier than just two decades ago. Other factors including longer dry seasons and drier soils and vegetation are increasingly creating the conditions for catastrophic wildfires (Environmental Protection Agency, 2022[4]; US Global Change Research Program, 2018[9]). Wildfires are also further spreading into areas historically unaccustomed to fire, including high elevation areas in the west of the country (Figure 1.2) (OECD, 2023[2]; Alizadeh et al., 2021[12]), which may be less prepared for wildfires and potentially harmed by its impacts.

Targeting Public Trust Suits

Social Science Research Network (SSRN) | February 22nd, 2021

The California public trust doctrine empowers private individuals and interest groups to protect the public trust and to enforce state laws that protect the public trust.

The California public trust doctrine empowers private individuals and interest groups to protect the public trust and to enforce state laws that protect the public trust. California has long led the development of the doctrine in the United States, becoming the first state to allow citizen suits to protect the public trust in 1971. A number of other states have followed California’s lead, resulting in a significant expansion in environmental standing. This broadened standing seems to be settled law. In contrast, two California Court of Appeal decisions create some uncertainty about appropriate defendants in public trust lawsuits. These decisions counsel some caution as private parties pick their targets for public trust litigation.

Temescal Basin Groundwater Sustainability Plan

Temescal Basin Groundwater Sustainability Agency | January 27th, 2022

Wishing to provide a framework for cooperative groundwater management and SGMA compliance, the City of Corona (Corona), City of Norco (Norco), and the Home Gardens Coun

Wishing to provide a framework for cooperative groundwater management and SGMA compliance, the City of Corona (Corona), City of Norco (Norco), and the Home Gardens County Water District (HGCWD) executed a Memorandum of Understanding (MOU) in March 2017 establishing the Temescal Basin Groundwater Sustainability Agency (Temescal GSA). In August 2017, the Temescal GSA became the GSA for the Basin by submitting a formation notice to DWR. While Corona is leading this effort, the GSP will be developed jointly among the three agencies, with coordinated implementation toward sustainable management. Due to size, the file has been divided into four parts. Part 1, Part 2, Part 3, Part 4

Temporal changes in the vertical distribution of flow and chloride in deep wells

National Groundwater Association (NGWA) | July 4th, 2005

The combination of flowmeter and depth‐dependent water‐quality data was used to evaluate the quantity and source of high‐chloride water yielded from different depth

The combination of flowmeter and depth‐dependent water‐quality data was used to evaluate the quantity and source of high‐chloride water yielded from different depths to eight production wells in the Pleasant Valley area of southern California. The wells were screened from 117 to 437 m below land surface, and in most cases, flow from the aquifer into the wells was not uniformly distributed throughout the well screen. Wells having as little as 6 m of screen in the overlying upper aquifer system yielded as much as 50% of their water from the upper system during drought periods, while the deeper parts of the well screens yielded 15% or less of the total yield of the wells. Mixing of water within wells during pumping degraded higher‐quality water with poorer‐quality water from deeper depths, and in some cases with poorer‐quality water from the overlying upper aquifer system. Changes in the mixture of water within a well, resulting from changes in the distribution of flow into the well, changed the quality of water from the surface discharge of wells over time. The combination of flowmeter and depth‐dependent water quality data yielded information about sources of high‐chloride water to wells that was not available on the basis of samples collected from nearby observation wells. Changing well design to eliminate small quantities of poor‐quality water from deeper parts of the well may improve the quality of water from some wells without greatly reducing well yield.

The 1976–1977 California drought: A review

California Department of Water Resources (DWR) | May 1st, 1978

This is the fifth and final Department of Water Resources' report on the 1976-1977 California drought, the worst in the state's history, which saw 1076, the fourth driest

This is the fifth and final Department of Water Resources' report on the 1976-1977 California drought, the worst in the state's history, which saw 1076, the fourth driest year of record, give way to 1977, the driest ever. These reports provide the most comprehensive documentation of a drought in history.  

The 2025-26 Budget: Proposition 4 Spending Plan

Legislative Analyst's Office (LAO) | February 12th, 2025