South Coast

Status and Understanding of Groundwater Quality in the Santa Clara River Valley, 2007: California GAMA Priority Basin Project

U.S. Geological Survey (USGS) | September 26th, 2011

Groundwater quality in the approximately 460-square-mile Santa Clara River Valley study unit was investigated from April through June 2007 as part of the Priority Basin P

Groundwater quality in the approximately 460-square-mile Santa Clara River Valley study unit was investigated from April through June 2007 as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The GAMA Priority Basin Project is conducted by the U.S. Geological Survey (USGS) in collaboration with the California State Water Resources Control Board and the Lawrence Livermore National Laboratory. The Santa Clara River Valley study unit contains eight groundwater basins located in Ventura and Los Angeles Counties and is within the Transverse and selected Peninsular Ranges hydrogeologic province.

Status and Understanding of Groundwater Quality in the South Coast Interior Groundwater Basins, 2008: California GAMA Priority Basin Project

U.S. Geological Survey (USGS) | May 14th, 2014

Groundwater quality in the approximately 653-square-mile (1,691-square-kilometer) South Coast Interior Basins (SCI) study unit was investigated as part of the Priority Ba

Groundwater quality in the approximately 653-square-mile (1,691-square-kilometer) South Coast Interior Basins (SCI) study unit was investigated as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The South Coast Interior Basins study unit contains eight priority groundwater basins grouped into three study areas, Livermore, Gilroy, and Cuyama, in the Southern Coast Ranges hydrogeologic province. The GAMA Priority Basin Project is being conducted by the California State Water Resources Control Board in collaboration with the U.S. Geological Survey (USGS) and the Lawrence Livermore National Laboratory. The GAMA South Coast Interior Basins study was designed to provide a spatially unbiased assessment of untreated (raw) groundwater quality within the primary aquifer system, as well as a statistically consistent basis for comparing water quality between basins. The assessment was based on water-quality and ancillary data collected by the USGS from 50 wells in 2008 and on water-quality data from the California Department of Public Health (CDPH) database. The primary aquifer system was defined by the depth intervals of the wells listed in the CDPH database for the SCI study unit. The quality of groundwater in the primary aquifer system may be different from that in the shallower or deeper water-bearing zones; shallow groundwater may be more vulnerable to surficial contamination. The first component of this study, the status of the current quality of the groundwater resource, was assessed by using data from samples analyzed for volatile organic compounds (VOCs), pesticides, and naturally occurring inorganic constituents, such as trace elements and minor ions. This status assessment is intended to characterize the quality of groundwater resources within the primary aquifer system of the SCI study unit, not the treated drinking water delivered to consumers by water purveyors. Relative-concentrations (sample concentration divided by the health- or aesthetic-based benchmark concentration) were used for evaluating groundwater quality for those constituents that have Federal or California regulatory or non-regulatory benchmarks for drinking-water quality. A relative-concentration greater than 1.0 indicates a concentration greater than a benchmark, and a relative-concentration less than or equal to 1.0 indicates a concentration equal to or less than a benchmark. Relative-concentrations of organic constituents and special-interest constituents were classified as “high” (relative-concentration greater than 1.0), “moderate” (relative-concentration greater than 0.1 and less than or equal to 1.0), or “low” (relative-concentration less than or equal to 0.1). Relative-concentrations of inorganic constituents were classified as “high” (relative-concentration greater than 1.0), “moderate” (relative-concentration greater than 0.5 and less than or equal to 1.0), or “low” (relative-concentration less than or equal to 0.5). Aquifer-scale proportion was used as the primary metric in the status assessment for evaluating regional-scale groundwater quality. High aquifer-scale proportion is defined as the percentage of the area of the primary aquifer system with a relative-concentration greater than 1.0 for a particular constituent or class of constituents; percentage is based on an areal rather than a volumetric basis. Moderate and low aquifer-scale proportions were defined as the areal percentage of the primary aquifer system with moderate and low relative-concentrations, respectively. Two statistical approaches—grid-based and spatially weighted—were used to evaluate aquifer-scale proportions for individual constituents and classes of constituents. Grid-based and spatially weighted estimates were comparable in the SCI study unit (within 90-percent confidence intervals). Inorganic constituents (one or more) with health-based benchmarks were detected at high relative-concentrations in 29 percent of the primary aquifer system, at moderate relative-concentrations in 37 percent, and at low relative-concentrations in 34 percent. High aquifer-scale proportions of inorganic constituents primarily reflected high aquifer-scale proportions of nitrate (14 percent), boron (8.6 percent), molybdenum (8.6 percent), and arsenic (5.7 percent). In contrast, the relative-concentrations of organic constituents (one or more) were high in 1.6 percent, moderate in 2.0 percent, and low or not detected in 96 percent of the primary aquifer system. Of the 207 organic and special-interest constituents analyzed for, 15 constituents were detected. Perchlorate was found at moderate relative-concentrations in 34 percent of the aquifer. Two organic constituents were frequently detected (in greater than 10 percent of samples): the trihalomethane chloroform and the herbicide simazine. The second component of this study, the understanding assessment, identified natural and human factors that may have affected groundwater quality by evaluating land use, physical characteristics of the wells, and geochemical conditions of the aquifer. This evaluation was done by using statistical tests of correlations between these potential explanatory factors and water-quality data. Concentrations of arsenic, molybdenum, and manganese were generally greater in anoxic and pre-modern groundwater than other groundwater. In contrast, concentrations of nitrate and perchlorate were significantly higher in oxic and modern groundwater. Concentrations of simazine were greater in modern than pre-modern groundwater. Chloroform detections were positively correlated with greater urban land use. Boron concentrations and chloroform detections were higher in the Livermore study area than in the other study areas of the SCI; total dissolved solids and sulfate concentrations were greater in the Cuyama study area.

Status of 2020 Agricultural Water Management Plans and Implementation of Efficient Water Management Practices Report

California Department of Water Resources (DWR) | January 25th, 2024

As required by the California Water Code (CWC), Agricultural Water Suppliers (AWS) must implement Efficient Water Management Practices (EWMPs) and submit an Agricultural

As required by the California Water Code (CWC), Agricultural Water Suppliers (AWS) must implement Efficient Water Management Practices (EWMPs) and submit an Agricultural Water Management Plan (AWMP) to the Department of Water Resources (DWR) every five years. Agricultural Water Suppliers subject to United States Bureau of Reclamation (Reclamation) requirements for a Water Conservation Plan (Reclamation Plan) may submit those plans to DWR in lieu of an AWMP. DWR then reports to the Legislature on the status of AWMPs, including outstanding elements, and implementation of EWMPs or Reclamation Best Management Practices (EWMPs/BMPs). This legislative report addresses the requirements for reporting on AWMPs and EWMPs in a single report that documents the status of AWMP submittals and the implementation of associated EWMPs. This report is the final Legislative report on EWMPs under CWC Section 10608.48(g).

Status of 2020 Urban Water Management Plans

California Department of Water Resources (DWR) | July 25th, 2023

As required by the California Water Code (CWC), every five years Urban Water Suppliers must submit an Urban Water Management Plan (UWMP) to the Department of Water Resour

As required by the California Water Code (CWC), every five years Urban Water Suppliers must submit an Urban Water Management Plan (UWMP) to the Department of Water Resources (DWR). DWR then reports to the Legislature on the status of UWMPs and Water Shortage Contingency Plans (WSCPs) and exemplary elements. Key Findings: * 95% (417 of 438) of Urban Water Suppliers submitted plans. * 97% (374 of 386) of Urban Retail Suppliers that submitted UWMPs met their water use reduction targets. * Statewide per capita urban water use was down 32% by 2020 from baseline period (suppliers identify a continuous 10-year or 15-year baseline period between 1995 and 2010). * 94% (393 of 417) of Urban Water Suppliers anticipate being able to manage any water shortages by implementing their Water Shortage Contingency Plans.

Stopping the Drain on Household Budgets: Addressing Tap Water Mistrust through Affordable Premise Plumbing Investments

University of California, Los Angeles (UCLA) | August 7th, 2019

This report focuses on the issue of tap water mistrust in the City of Los Angeles. While recent research into water quality of Los Angeles Department of Water and Power�

This report focuses on the issue of tap water mistrust in the City of Los Angeles. While recent research into water quality of Los Angeles Department of Water and Power (LADWP) indicates that water at the tap for their customers is safe to drink, the Los Angeles metropolitan region has one of the highest rates of household mistrust in tap water in the nation.

Storing and managing water for the environment is more efficient than mimicking natural flows

Nature Portfolio (Springer Nature) | June 27th, 2024

Storm rainfall conditions for floods and debris flows from recently burned areas in southwestern Colorado and southern California

Geomorphology (Elsevier) | April 15th, 2008

Debris flows generated during rain storms on recently burned areas have destroyed lives and property throughout the Western U.S. Field evidence indicate that unli

Debris flows generated during rain storms on recently burned areas have destroyed lives and property throughout the Western U.S. Field evidence indicate that unlike landslide-triggered debris flows, these events have no identifiable initiation source and can occur with little or no antecedent moisture. Using rain gage and response data from five fires in Colorado and southern California, we document the rainfall conditions that have triggered post-fire debris flows and develop empirical rainfall intensity–duration thresholds for the occurrence of debris flows and floods following wildfires in these settings. This information can provide guidance for warning systems and planning for emergency response in similar settings. Debris flows were produced from 25 recently burned basins in Colorado in response to 13 short-duration, high-intensity convective storms. Debris flows were triggered after as little as six to 10 min of storm rainfall. About 80% of the storms that generated debris flows lasted less than 3 h, with most of the rain falling in less than 1 h. The storms triggering debris flows ranged in average intensity between 1.0 and 32.0 mm/h, and had recurrence intervals of two years or less. Threshold rainfall conditions for floods and debris flows sufficiently large to pose threats to life and property from recently burned areas in south-central, and southwestern, Colorado are defined by: I = 6.5D− 0.7 and I = 9.5D− 0.7, respectively, where I = rainfall intensity (in mm/h) and D = duration (in hours). Debris flows were generated from 68 recently burned areas in southern California in response to long-duration frontal storms. The flows occurred after as little as two hours, and up to 16 h, of low-intensity (2–10 mm/h) rainfall. The storms lasted between 5.5 and 33 h, with average intensities between 1.3 and 20.4 mm/h, and had recurrence intervals of two years or less. Threshold rainfall conditions for life- and property-threatening floods and debris flows during the first winter season following fires in Ventura County, and in the San Bernardino, San Gabriel and San Jacinto Mountains of southern California are defined by I = 12.5D−0.4, and I = 7.2D−0.4, respectively. A threshold defined for flood and debris-flow conditions following a year of vegetative recovery and sediment removal for the San Bernardino, San Gabriel and San Jacinto Mountains of I = 14.0D−0.5 is approximately 25 mm/h higher than that developed for the first year following fires. The thresholds defined here are significantly lower than most identified for unburned settings, perhaps because of the difference between extremely rapid, runoff-dominated processes acting in burned areas and longer-term, infiltration-dominated processes on unburned hillslopes.

Stormquakes

American Geophysical Union (AGU) | October 14th, 2019

Seismic signals from ocean-solid Earth interactions are ubiquitously recorded on our planet. However, these wavefields are typically incoherent in the time domain limiti

Seismic signals from ocean-solid Earth interactions are ubiquitously recorded on our planet. However, these wavefields are typically incoherent in the time domain limiting their utilization for understanding ocean dynamics or solid Earth properties. In contrast, we find that during large storms such as hurricanes and Nor’easters the interaction of long-period ocean waves with shallow seafloor features located near the edge of continental shelves, known as ocean banks, excites coherent transcontinental Rayleigh wave packets in the 20 to 50 s period band. These “stormquakes” migrate coincident with the storms, but are effectively spatiotemporally focused seismic point sources with equivalent earthquake magnitudes that can be greater than 3.5. Stormquakes thus provide new coherent sources to investigate Earth structure in locations that typically lack both seismic instrumentation and earthquakes. Moreover, they provide a new geophysical observable with high spatial and temporal resolution with which to investigate ocean wave dynamics during large storms.

Stormwater Capture: Enhancing Recharge and Direct Use Through Data Collection

Southern California Water Coalition | April 26th, 2018

The purpose of this 2018 white paper update is to gain a better understanding of actual stormwater runoff capture volumes, costs, benefits, and project performa

The purpose of this 2018 white paper update is to gain a better understanding of actual stormwater runoff capture volumes, costs, benefits, and project performance across the region to inform future discussions. This white paper augments prior efforts and uses the most recent and best available stormwater project data. Previously in January 2012, the SCWC published its first white paper on stormwater titled Stormwater Capture: Opportunities to Increase Water Supplies in Southern California (SCWC 2012). The purpose of the 2012 white paper was to examine existing statewide policies, goals, and regional plans related to integrated stormwater management; trends, structure, and requirements of MS4 permits as they pertain to both opportunities and constraints to maximizing stormwater capture for water supply purposes; and the advantages and disadvantages of two strategies of stormwater management: onsite low impact development and regional stormwater capture and infiltration. Lastly, the 2012 white paper largely focused on conceptual stormwater projects and technical strategies for increasing stormwater capture. Since the 2012 white paper, many of the proposed projects were constructed and in operation. Other plans such as Metropolitan’s 2015 Integrated Resources Plan (MWD 2016), the City of Los Angeles’s Stormwater Capture Master Plan (LADWP 2015), and Los Angeles County Flood Control District’s LA Basin Study (LACFCD 2016) also estimated stormwater capture and costs. The SCWC saw an opportunity to evaluate the costs and benefits of these constructed stormwater capture projects and pursued a white paper update.

Stormwater Funding Options Providing Sustainable Water Quality Funding in Los Angeles County

California Contract Cities Association (CCCA) | May 21st, 2014

The Los Angeles region faces critical, very costly, and seriously underfunded stormwater and urban runoff water quality challenges. The Los Angeles County Flood Control D

The Los Angeles region faces critical, very costly, and seriously underfunded stormwater and urban runoff water quality challenges. The Los Angeles County Flood Control District (LACFCD) led a multi-year effort to develop a sustainable revenue source for municipalities to manage stormwater programs and implement water quality improvement projects. This effort included special legislation and development of a proposed parcel fee, the “Clean Water, Clean Beaches Measure,” to fund clean water programs. At extended protest hearings on a proposed parcel fee in January and March of 2013, the Board of Supervisors heard concerns about the fee and the fee program from public schools, the business community, other stakeholders and the public. The Board moved to close the public hearing and determined to “not proceed at this time with the Clean Water, Clean Beaches measure as proposed.” In June 2013, the Board adopted a motion requesting collaborative participation with the County Sanitation Districts of Los Angeles County (LACSD) and other wastewater management agencies to evaluate methods, assess the a potential model governance structure, and to help identify and secure other sources of funding. In response to the Board’s actions, the City Managers Committees of the California Contract Cities Association (CCCA) and the League of California Cities, Los Angeles County Division (League) convened a City Managers meeting with representatives from public schools, environmental organizations, and the business community on June 27, 2013 to hear stakeholders’ concerns and suggestions directly. The City Managers attending the meeting authorized a Work Group to review stormwater funding options after the County’s proposed Clean Water, Clean Beaches funding initiative failed to move forward. The City Managers Work Group actively sought the input of key stakeholders from the environmental, public education, and business communities, and prepared this report to assist the Board, local decision makers, stakeholders, and the public in reaching a common understanding of the issues at hand and the potential solutions. The Managers found that to fully understand the issues, improved communication and education is necessary. This report describes the stormwater regulatory requirements speci c to the greater Los Angeles area, the complexities of funding stormwater programs, and the LACFCD’s funding initiative. It examines the regulatory framework for stormwater management, including the requirements of the National Pollution Discharge Elimination System (NPDES) MS4 permit (stormwater permit) and the total maximum daily load (TMDL) programs. The report also summarizes the impacts of the federal TMDL Consent Decree for the Los Angeles Region signed in 1999, which has indirectly regulated the LACFCD, 85 cities, and the unincorporated County since that time. Further, it reviews estimated stormwater program compliance costs, the “pros and cons” of various funding options, and evolving opportunities. The report concludes with a series of recommendations agreed upon by the City Managers. Suggestions from an Elected Officials Committee and individual City Attorneys are also included in this report. The Work Group found that funding urban runoff programs is so complex and dynamic, and the solutions so costly, that the County and the Cities cannot follow a single funding strategy at this time. One option, for example, is to examine institutional roles to determine whether other agencies, such as the County Sanitation Districts, either provide a useful governance model or could play a new or different role in managing stormwater in the future. During the report development process, the Sixth Appellate Court clarified the application of Proposition 218 regarding the imposition of fees for the capture and use of stormwater for groundwater recharge (Griffith v. Pajaro Water Management Agency). This ruling could have major implications on funding options. These are only two examples of the changing nature and complexities in charting a path forward. The City Managers Work Group recommends a “multi-pronged” approach to address urban runoff funding issues, since our communities may encounter several dead-ends. A number of the recommendations require active management and a higher degree of organization by local government. The recommended actions are voluntary. The report is not advocating that any city, group of cities, or the County adopt stormwater fees. The managers are committed to local control; if a regional fee moves forward, each community should make its own decision whether or not to participate in the regional effort. However, there are steps that local governments can take that will assist in funding the new stormwater mandates. For example, cities should organize and be active in the water bond discussions. This report suggests a voluntary framework through Contract Cities and the League to organize those communities that desire to engage in implementing the recommendations found in this report. It should be noted that the recommendations involving California Contract Cities, the Los Angeles County Division of the League of California Cities, and the State League of Cities have not been of cially endorsed by these organizations at this stage of the process. The City Managers Work Group and the Elected Of cials Committee held detailed discussions with staff from both organizations in order to re ect their input and concerns. Recommendations involving these organizations, such as changes in State legislation, would need to be reviewed and approved by each organization.