DOCSLIB.ORG

Groundwater Resources and Groundwater Quality

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Groundwater Resources and Groundwater Quality Chapter 7: Groundwater Resources and Groundwater Quality Chapter 7 1 Groundwater Resources and 2 Groundwater Quality 3 7.1 Introduction 4 This chapter describes groundwater resources and groundwater quality in the 5 Study Area, and potential changes that could occur as a result of implementing the 6 alternatives evaluated in this Environmental Impact Statement (EIS). 7 Implementation of the alternatives could affect groundwater resources through 8 potential changes in operation of the Central Valley Project (CVP) and State 9 Water Project (SWP) and ecosystem restoration. 10 7.2 Regulatory Environment and Compliance 11 Requirements 12 Potential actions that could be implemented under the alternatives evaluated in 13 this EIS could affect groundwater resources in the areas along the rivers impacted 14 by changes in the operations of CVP or SWP reservoirs and in the vicinity of and 15 lands served by CVP and SWP water supplies. Groundwater basins that may be 16 affected by implementation of the alternatives are in the Trinity River Region, 17 Central Valley Region, San Francisco Bay Area Region, Central Coast Region, 18 and Southern California Region. 19 Actions located on public agency lands or implemented, funded, or approved by 20 Federal and state agencies would need to be compliant with appropriate Federal 21 and state agency policies and regulations, as summarized in Chapter 4, Approach 22 to Environmental Analyses. 23 Several of the state policies and regulations described in Chapter 4 have resulted 24 in specific institutional and operational conditions in California groundwater 25 basins, including the basin adjudication process, California Statewide 26 Groundwater Elevation Monitoring Program (CASGEM), California Sustainable 27 Groundwater Management Act (SGMA), and local groundwater management 28 ordinances, as summarized below. 29 7.2.1 Groundwater Basin Adjudication 30 Basin adjudications are determined through court decisions or pre-court mediation 31 on litigation that determine the groundwater rights of all the groundwater users 32 overlying the basins. The court identifies the extractors or well owners and the 33 amount of groundwater those well owners are allowed to extract, and appoints a 34 Watermaster whose role is to ensure that the basin is managed in accordance with 35 the court's decree. The Watermaster must report periodically to the court. There 36 are currently 23 adjudicated groundwater basins in California, most of which are Draft LTO EIS 7-1 Chapter 7: Groundwater Resources and Groundwater Quality 1 located in Southern California. Table 7.1 lists the adjudicated groundwater basins 2 located in the Study Area. 3 Table 7.1 Adjudicated Groundwater Basins in the Study Area Date of Final Court Basin Name Decision County Antelope Valley Groundwater Basin Under way Kern and Los Angeles Beaumont – Upper Santa Ana Groundwater 2004 Riverside Basin Brite Groundwater Basin 1970 Kern Central Subbasin of the Coastal Plain of 1965 Los Angeles Los Angeles Basin Chino Subbasin of the Upper Santa Ana Valley 1978 Riverside and San Basin Bernardino Cucamonga Subbasin of the Upper Santa Ana 1978 San Bernardino Valley Basin Cummings Valley Groundwater Basin 1972 Kern Goleta Groundwater Basin 1989 Santa Barbara San Jacinto Groundwater Basin 2013 Riverside Los Osos Valley Groundwater Basin Under way San Luis Obispo Mojave Basin Area (Lower Mojave River Valley, 1996 San Bernardino Middle Mojave River Valley, Upper Mojave River Valley, El Mirage Valley, and Lucerne Valley groundwater basins) San Gabriel Valley Groundwater Basin – 1973 Los Angeles excluding Raymond Groundwater Basin San Gabriel Valley Groundwater Basin – Puente 1985 Los Angeles Narrows Raymond Groundwater Basin 1944 Los Angeles Rialto-Colton Subbasin of the Upper Santa Ana 1961 San Bernardino Valley Basin Santa Margarita River Watershed – Santa 1966* Riverside and San Margarita Valley, Temecula Valley, and Cahuilla Diego Valley groundwater basins Santa Maria Valley Groundwater Basin 2008 San Luis Obispo and Santa Barbara Santa Paula Subbasin of the Santa Clara River 1996 Ventura Valley Groundwater Basin Six Basins Area in upper Santa Ana Valley 1998 Los Angeles and San Bernardino Tehachapi Valley West Basin and Tehachapi 1973 Kern Valley East Basin 7-2 Draft LTO EIS Chapter 7: Groundwater Resources and Groundwater Quality Date of Final Court Basin Name Decision County Upper Los Angeles River Area– 1979 Los Angeles San Fernando Valley Groundwater Basin Warren Valley Groundwater Basin 1977 San Bernardino West Coast Subbasin of the Coastal Plain of Los 1961 Los Angeles Angeles Basin Western San Bernardino – Upper Santa Ana 1969 San Bernardino Groundwater Basin 1 Sources: DWR 2003a, 2014a; LOCSD 2013 2 Note: 3 * Santa Margarita Watershed Adjudication addresses both groundwater and surface 4 water if water contributes to Santa Margarita River and its tributaries flows (SMRW 2014). 5 The agreements include interlocutory judgements for Murrieta-Temecula Groundwater 6 Basin that describes non-Indian water rights subject to court jurisdiction, land and water 7 rights not subject to court jurisdiction, reserved water rights for the Pechanga 8 Reservation, appropriative storage and diversion rights in conjunction with use of 9 groundwater by the Vail Company. 10 7.2.2 California Statewide Groundwater Elevation 11 Monitoring Program 12 Senate Bill X7-6, enacted in November 2009, mandates a statewide groundwater 13 elevation monitoring program to track seasonal and long-term trends in 14 groundwater elevations in California’s groundwater basins defined in 15 Bulletin 118. This amendment to Division 6 of the Water Code, specifically 16 Part 2.11 Groundwater Monitoring, requires the collaboration between local 17 monitoring entities and California Department of Water Resources (DWR) to 18 collect groundwater elevation data. The law requires local agencies to monitor 19 and report the groundwater elevation in the basins. To achieve this goal, DWR 20 developed the CASGEM Program to establish a permanent, locally-managed 21 program of regular and systematic monitoring in all of the state’s alluvial 22 groundwater basins. 23 DWR is required to establish a priority schedule for monitoring groundwater 24 basins, and to report to the Legislature on the findings from these investigations 25 (Water Code section 10920 et. seq). The 2012 CASGEM Status Report to the 26 Legislature describes that more than 400 monitoring entities have been identified 27 and water level data are being submitted to DWR (DWR 2012). The 28 prioritization of basins is to identify, evaluate, and determine the need for 29 additional groundwater level monitoring. The prioritization approach includes the 30 following eight criteria. 31 • Overlying population in the groundwater basin 32 • Projected growth of the overlying population 33 • Number of public water supply wells Draft LTO EIS 7-3 Chapter 7: Groundwater Resources and Groundwater Quality 1 • Total number of water supply wells 2 • Irrigated acreage overlying the groundwater basin 3 • Reliance on groundwater as the primary source of water by the overlying 4 land uses 5 • Impacts on groundwater, including overdraft, subsidence, saline intrusion, and 6 other water quality degradation 7 • Any other information relevant to the groundwater conditions 8 Groundwater basins designations in the study area are described for each basin in 9 the following subsection of this chapter (DWR 2014e). 10 7.2.3 Sustainable Groundwater Management Act 11 In September 2014, the SGMA was enacted. The SGMA establishes a new 12 structure for locally managing California’s groundwater in addition to existing 13 groundwater management provisions established by Assembly Bill (AB) 14 3030 (1992), Senate Bill (SB) 1938 (2002), and AB 359 (2011), as well as 15 SBX7-6 (2009). 16 The SGMA includes the following key elements: 17 • Provides for the establishment of a Groundwater Sustainability Agency (GSA) 18 by one or more local agencies overlying a designated groundwater basin or 19 subbasin identified in DWR Bulletin 118-03 20 • Requires all DWR Bulletin 118 groundwater basins found to be of “high” or 21 “medium” priorities to prepare Groundwater Sustainability Plans (GSPs) 22 • Provides for the proposed revisions, by local agencies, to the boundaries of a 23 DWR Bulletin 118 basin, including the establishment of new subbasins 24 • Provides authority for DWR to adopt regulations to evaluate GSPs, and 25 review the GSPs for compliance every 5 years 26 • Requires DWR to establish best management practices and technical measures 27 for GSAs to develop and implement GSPs 28 • Provides regulatory authority to the State Water Resources Control Board 29 (SWRCB) for developing and implementing interim groundwater 30 management plans under certain circumstances (such as lack of compliance 31 with development of GSPs by GSAs) 32 The SGMA defines sustainable groundwater management as “the management 33 and use of groundwater in a manner that can be maintained during the planning 34 and implementation horizon without causing undesirable results.” Undesirable 35 results are defined as any of the following effects. 36 • Chronic lowering of groundwater levels (not including overdraft during a 37 drought if a basin is otherwise managed) 38 • Significant and unreasonable reduction of groundwater storage 7-4 Draft LTO EIS Chapter 7: Groundwater Resources and Groundwater Quality 1 • Significant and unreasonable seawater intrusion 2 • Significant and unreasonable degraded water quality, including the
Load more

Recommended publications
  • (Ver. 1.1): Hydrogeologic Controls and Geochemical Indicators Of
    Prepared in cooperation with the East Bay Municipal Utility District, City of Hayward, and Alameda County Water District Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins, Alameda County, California Scientific Investigations Report 2018–5003 Version 1.1, February 2019 U.S. Department of the Interior U.S. Geological Survey Hydrogeologic Controls and Geochemical Indicators of Groundwater Movement in the Niles Cone and Southern East Bay Plain Groundwater Subbasins, Alameda County, California By Nick Teague, John Izbicki, Jim Borchers, Justin Kulongoski, and Bryant Jurgens Prepared in cooperation with the East Bay Municipal Utility District, City of Hayward, and Alameda County Water District Scientific Investigations Report 2018–5003 Version 1.1, February 2019 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior DAVID BERNHARDT, Acting Secretary U.S. Geological Survey William H. Werkheiser, Deputy Director exercising the authority of the Director U.S. Geological Survey, Reston, Virginia: 2019 First release: February 2018 Revised: February 2019 (ver. 1.1) For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment—visit http://www.usgs.gov or call 1–888–ASK–USGS. For an overview of USGS information products, including maps, imagery, and publications, visit http://store.usgs.gov. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text.
    [Show full text]
  • Appendix 4.15-1 Water Supply Assessment
    Appendix 4.15-1 Water Supply Assessment /lfCWD HLHHEOHCOUAIFYWHFEHO/SFH/CF DIRECTORS 43885 SOUTH GRIMMER BOULEVARD • FREMONT, CALIFORNIA 94538 MANAGEMENT (510) 668-4200 • FAX (510) 770-1793 • www.acwd.org ROBERT AZIZ AKBARI SHAVER General Manager JAMES G. GUNTHER KURT ARENDS JUDY C. HUANG Operations and Maintenance PAULSETHY LAURA J. HIDAS JOHN H. WEED Water Resources ED STEVENSON June 24, 2020 Engineering and Technology Services JONATHAN WUNDERLICH Finance VIA ELECTRONIC MAIL Carmela Campbell ([email protected]) Economic and Community Development Director City of Union City 34009 Alvarado-Niles Road Union City, CA 94587 Dear Ms. Campbell: Subject: Water Supply Assessment for Station East Project As requested by the City of Union City, Alameda County Water District (ACWD) has prepared a water supply assessment for the Station East Project (enclosed). The water supply assessment was adopted by the ACWD Board of Directors on June 11, 2020 (resolution enclosed). The water supply assessment was prepared pursuant to California Water Code Section §10910 which requires that a water supply assessment be provided to cities or counties for a project that is subject to the California Environmental Quality Act (CEQA), and which surpasses a threshold for the number of housing units and/or square feet of commercial/industrial buildings. The water supply assessment documents sources of water supply, quantifies water demands, evaluates drought impacts, and provides a comparison of water supply and demand that is the basis for an assessment of water supply sufficiency. The water supply assessment also includes provisions for Water Conservation to be implemented by the Project applicant. As noted in the assessment, these provisions will be a condition of water service to the Project.
    [Show full text]
  • Santa Margarita River Trail Preserve Acquisition
    COASTAL CONSERVANCY Staff Recommendation September 6, 2018 SANTA MARGARITA RIVER TRAIL PRESERVE ACQUISITION Project No. 18-015-01 Project Manager: Greg Gauthier RECOMMENDED ACTION: Authorization to disburse up to $9,750,000 to The Wildlands Conservancy for acquisition of approximately 1,390 acres along the Santa Margarita River for conservation and recreation purposes. LOCATION: Santa Margarita River, County of San Diego PROGRAM CATEGORY: Integrated Coastal and Marine Resource Protection EXHIBITS Exhibit 1: Project Location, Site Map, and APN Numbers Exhibit 2: Santa Margarita River Trail Preserve Photographs Exhibit 3: Project Letters RESOLUTION AND FINDINGS: Staff recommends that the State Coastal Conservancy adopt the following resolution pursuant to Chapter 5.5 of Division 21 of the Public Resources Code: “The State Coastal Conservancy hereby authorizes disbursement of an amount not to exceed nine million seven hundred fifty thousand dollars ($9,750,000) to The Wildlands Conservancy for acquisition of approximately 1,390 acres along the Santa Margarita River, as shown in Exhibit 1, for conservation and recreation purposes. This authorization is subject to the following conditions: 1. Prior to disbursement of any funds for acquisition of the property, The Wildlands Conservancy shall submit for the review and approval of the Executive Officer of the Conservancy: a) all relevant acquisition documents, including the appraisal, agreement of purchase and sale, escrow instructions, deeds, and documents of title; b) a baseline conditions report; c) a monitoring and reporting plan; and d) evidence that sufficient funds are available to complete the acquisition. 2. The Wildlands Conservancy shall not pay more than fair market value for the property acquired pursuant to this authorization, as established in an appraisal approved by the Executive Officer.
    [Show full text]
  • Attachment B-4 San Diego RWQCB Basin Plan Beneficial Uses
    Attachment B-4 San Diego RWQCB Basin Plan Beneficial Uses Regulatory_Issues_Trends.doc CHAPTER 2 BENEFICIAL USES INTRODUCTION .............................................................................................................................1 BENEFICIAL USES ..........................................................................................................................1 BENEFICIAL USE DESIGNATION UNDER THE PORTER-COLOGNE WATER QUALITY CONTROL ACT ..1 BENEFICIAL USE DESIGNATION UNDER THE CLEAN WATER ACT .................................................2 BENEFICIAL USE DEFINITIONS.........................................................................................................3 EXISTING AND POTENTIAL BENEFICIAL USES ..................................................................................7 BENEFICIAL USES FOR SPECIFIC WATER BODIES ........................................................................8 DESIGNATION OF RARE BENEFICIAL USE ...................................................................................8 DESIGNATION OF COLD FRESHWATER HABITAT BENEFICIAL USE ...............................................9 DESIGNATION OF SPAWNING, REPRODUCTION, AND/ OR EARLY DEVELOPMENT (SPWN) BENEFICIAL USE ...................................................................................................11 SOURCES OF DRINKING WATER POLICY ..................................................................................11 EXCEPTIONS TO THE "SOURCES OF DRINKING WATER" POLICY................................................11
    [Show full text]
  • Three Chumash-Style Pictograph Sites in Fernandeño Territory
    THREE CHUMASH-STYLE PICTOGRAPH SITES IN FERNANDEÑO TERRITORY ALBERT KNIGHT SANTA BARBARA MUSEUM OF NATURAL HISTORY There are three significant archaeology sites in the eastern Simi Hills that have an elaborate polychrome pictograph component. Numerous additional small loci of rock art and major midden deposits that are rich in artifacts also characterize these three sites. One of these sites, the “Burro Flats” site, has the most colorful, elaborate, and well-preserved pictographs in the region south of the Santa Clara River and west of the Los Angeles Basin and the San Fernando Valley. Almost all other painted rock art in this region consists of red-only paintings. During the pre-contact era, the eastern Simi Hills/west San Fernando Valley area was inhabited by a mix of Eastern Coastal Chumash and Fernandeño. The style of the paintings at the three sites (CA-VEN-1072, VEN-149, and LAN-357) is clearly the same as that found in Chumash territory. If the quantity and the quality of rock art are good indicators, then it is probable that these three sites were some of the most important ceremonial sites for the region. An examination of these sites has the potential to help us better understand this area of cultural interaction. This article discusses the polychrome rock art at the Burro Flats site (VEN-1072), the Lake Manor site (VEN-148/149), and the Chatsworth site (LAN-357). All three of these sites are located in rock shelters in the eastern Simi Hills. The Simi Hills are mostly located in southeast Ventura County, although the eastern end is in Los Angeles County (Figure 1).
    [Show full text]
  • Santa Margarita River Watershed Annual Watermaster Report for the 2013-14 Water Year
    SANTA MARGARITA RIVER WATERSHED ANNUAL WATERMASTER REPORT WATER YEAR 2013-14 UNITED STATES OF AMERICA v. FALLBROOK PUBLIC UTILITY DISTRICT, ET AL. CIVIL NO. 51-CV-1247-GPC-RBB CHARLES W. BINDER WATERMASTER P. 0. BOX 631 FALLBROOK, CA 92088 (760) 728-1028 FAX (760) 728-1990 August 2015 WATERMASTER SANTA MARGARITA RIVER WATERSHED TABLE OF CONTENTS Page No. SECTION 1 - SUMMARY ............................................................................................... 1 SECTION 2 - INTRODUCTION ...................................................................................... 5 2.1 Background ......................................................................................................... 5 2.2 Authority .............................................................................................................. 5 2.3 Scope .................................................................................................................. 5 SECTION 3 - SURFACE WATER AVAILABILITY AND USE ......................................... 7 3.1 Surface Flow ........................................................................................................ 7 3.2 Surface Water Diversions .................................................................................. 13 3.3 Water Storage ................................................................................................... 13 SECTION 4- SUBSURFACE WATER AVAILABILITY ................................................. 19 4.1 General .............................................................................................................
    [Show full text]
  • 1 EVIDENCE THAT ACWD HAS OPERATED the NILES CONE SUB-BASIN 2-09.01 WITHIN ITS SUSTAINABLE YIELD the Alameda County Water Distri
    DRAFT EVIDENCE THAT ACWD HAS OPERATED THE NILES CONE SUB-BASIN 2-09.01 WITHIN ITS SUSTAINABLE YIELD The Alameda County Water District (ACWD) manages the Niles Cone Sub-basin 2-09.01 (Niles Cone) in the Cities of Fremont, Newark, Union City, and southern Hayward (map in Figure 1A and east-west cross-section in Figure 1B). Groundwater comprises approximately 40% of the supply to ACWD’s distribution system. ACWD operates production wells and artificial recharge facilities (also commonly referred to as managed-aquifer-recharge) in the Niles Cone. By integrating recharge and pumping operations, and implementing other vital programs, ACWD has operated the Niles Cone within its sustainable yield over the last five decades, including the most recent 10-year period from 2005 to 2015. To support this analysis, the following is provided: A description of the Niles Cone Groundwater Basin and its sustainable yield. A summary of ACWD programs that ensure that total pumping does not exceed the sustainable yield. Data on basin conditions over the last 10 years. Introduction – Sources of Information ACWD would like to emphasize that this document is based on existing and publically available information, including the Survey Report on Groundwater Conditions (published annually), the Groundwater Monitoring Report (published annually), Bulletins published by the California Department of Water Resources, reports of hydrogeologic investigations conducted by ACWD and financially supported by DWR, ACWD integrated planning and operations reports, and other studies. The Niles Cone Groundwater Basin and its Sustainable Yield The long-term average sustainable pumping yield of the Niles Cone, like any other groundwater basin, is determined by the amount of recharge to productive aquifers less natural (non-pumping) sinks from the aquifers.
    [Show full text]
  • Recovering California Steelhead South of Santa Cruz
    THE OSPREY • ISSUE NO. 75 MAY 2013 15 Recovering California Steelhead South of Santa Cruz By Kurt Zimmerman, Tim Frahm and Sam Davidson — California Trout, Trout Unlimited — Kurt Zimmerman is Southern Steelhead genetics evince unique documents, intended to help achieve California Regional Manager for characteristics region-by-region (and recovery goals by describing strate - California Trout. Tim Frahm and Sam even watershed-by-watershed), as the gies and recommended actions likely Davidson are California Central Coast fish adapted to the particular condi - required to restore viable wild popula - Steelhead Coordinator and California tions and climate factors of coastal tions. Communications Manager for Trout streams from the Baja Peninsula to In early 2012, after years of public Unlimited. Visit their web sites at: Alaska. Today, steelhead south of San and agency input, NMFS released the www.caltrout.org Mateo County in California are catego - Final Southern California Recovery www.tucalifornia.org rized by the National Marine Fisheries Plan for the SCC steelhead. Later that Service (NMFS) into two “Distinct year, the agency released for public any anglers consider Population Segments” (DPS): the comment a Review Draft of the the steelhead trout (O. “South Central California Coastal” Recovery Plan for the South Central mykiss) the “perfect Coastal steelhead. These two Recovery fish.” Steelhead are Plans identify area-wide threats as widely revered for well as threats specific to particular Mtheir power and grace in the water, and watersheds. Common threats are the Steelhead have for the high challenge of actually three “Ds”: Dams, Diversions and catching one. Sport fishing for steel - declined across much Diminished Aquatic and Riparian head is a major contributor to many Habitats.
    [Show full text]
  • Rosett 1 Tectonic History of the Los Angeles Basin: Understanding What
    Rosett 1 Tectonic history of the Los Angeles Basin: Understanding what formed and deforms the city of Los Angeles Anne Rosett The Los Angeles (LA) Basin is located in a tectonically complex region which has led to many, varying interpretations of its tectonic history. Current literature indicates that processes from rifting and extensional volcanism to pure dextral strike-slip displacement created the LA Basin. It appears that the best interpretation falls somewhere in between these two end-member explanations, with processes taking place simultaneously, including transtensional pull-apart faulting and clockwise rotation of large crustal blocks. With a comprehensive literature review, and paleomagnetic, seismic refraction, and low-fold reflection survey data, I intend to clarify what tectonic processes actually occurred in the LA Basin, and how that information can provide insight for other research in the region, as well as predicting future seismic hazards in the highly- populated, economically significant, and culturally rich city of Los Angeles. Introduction The Los Angeles Basin sits in a tectonically-active region, and thus, a large amount of research exists regarding its formation and tectonic history. However, due to several different fault systems, complex structures, and angles of slip currently affecting the area, the history of the LA Basin is not decisive; there are some discrepancies in the current literature regarding the tectonic and subsidence histories of the LA Basin. These include basin formation due to extensional rifting and basaltic volcanism (Crouch and Suppe, 1993; McCulloh and Beyer, 2003), transtensional pull-apart processes (Schneider et al., 1996), and dextral strike-slip faulting (Howard, 1996).
    [Show full text]
  • Introduction I-1 Adopted by City Council 1/25/93
    Introduction INTRODUCTION A. Overview of the City of Palmdale 1. Location and Regional Setting The City of Palmdale is located in the High Desert region of Los Angeles County, approximately 60 freeway miles north of downtown Los Angeles (see Exhibit I-1). Palmdale is one of two incorporated cities and several unincorporated communities within the Antelope Valley. The City is bordered by the City of Lancaster and unincorporated community of Quartz Hill to the north; unincorporated communities of Lake Los Angeles and Littlerock to the east; the unincorporated community of Acton to the south; and the unincorporated community of Leona Valley to the west (see Exhibit I- 2). The City of Palmdale Planning Area encompasses approximately 174 square miles within a transitional area between the foothills of the San Gabriel and Sierra Pelona Mountains and the Mojave Desert to the north and east (see Exhibit I-3). As a result, the Planning Area contains a variety of plant and animal communities, slope conditions, soil types and other physical characteristics. In general, the Planning Area slopes from south to north-northeast, with surface flows and subsurface flows trending away from the foothills to Rosamond Dry Lake. The major watercourses flowing through Palmdale are Amargosa Creek, Anaverde Creek, Little Rock Wash and Big Rock Wash. While foothill areas within and adjacent to the City contain significant slopes, a majority of the Planning Area is relatively flat. The climate of Palmdale and the Antelope Valley is dominated by the region’s Pacific high pressure system, which contributes to the area’s hot, dry summers and relatively mild winters.
    [Show full text]
  • 1. NEOGENE TECTONICS of SOUTHERN CALIFORNIA . the Focus of This Research Project Is to Investigate the Timing of Rotation of T
    1. NEOGENE TECTONICS OF SOUTHERN CALIFORNIA. The focus of this research project is to investigate the timing of rotation of the Transverse Ranges and the evolution of the 3-D architecture of the Los Angeles basin. Objectives are to understand better the seismicity of the region and the relationships between petroleum accumulations and the structure and stratigraphic evolution of the basin. Figure 1 shows the main physiographic and structural features of the Los Angeles basin region, the epicenter of recent significant earthquakes and the our initial study area in the northeastern Los Angeles basin. Los Angeles basin tectonic model: Most tectonic models attribute the opening of the Los Angeles basin to lithospheric extension produced by breakaway of the Western Transverse Ranges from the Peninsular Ranges and 90 degrees or more of clockwise rotation from ca. 18 Ma to the present. Evidence of this extension includes crustal thinning on tomographic profiles between the Santa Ana Mountains and the Santa Monica Mountains and the presence in the Los Angeles basin of Middle Miocene volcanic rocks and proto-normal faults. Detailed evidence of the 3-D architecture of the rift created by the breakaway and the timing of the rift phase has remained elusive. The closing of the Los Angeles basin in response to N-S contraction began at ca. 8 Ma and continues today (Bjorklund, et al., 2002). A system of active faults has developed that pose significant seismic hazards for the greater Los Angeles region. Crustal heterogeneities that developed during the extension phase of basin development may have strongly influenced the location of these faults.
    [Show full text]
  • Arroyo Chub Survey Report 2010
    Western Riverside County Multiple Species Habitat Conservation Plan (MSHCP) Biological Monitoring Program Arroyo chub (Gila orcutti) Survey Report 2010 23 March 2011 Arroyo Chub Survey Report 2010 TABLE OF CONTENTS INTRODUCTION ...............................................................................................................................................1 GOALS AND OBJECTIVES...............................................................................................................2 METHODS ........................................................................................................................................................2 PROTOCOL DEVELOPMENT............................................................................................................2 PERSONNEL AND TRAINING ..........................................................................................................2 STUDY SITE SELECTION .................................................................................................................3 ESTABLISHING SAMPLING UNITS ..................................................................................................5 SURVEY METHODS .......................................................................................................................5 RESULTS..........................................................................................................................................................6 DISCUSSION .....................................................................................................................................................9
    [Show full text]