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At least 919 records · Page 51Linked to original sources

USGS2015

Water-table and potentiometric-surface altitudes in the Upper Glacial, Magothy, and Lloyd aquifers of Long Island, New York, April-May 2013

The U.S. Geological Survey (USGS), in cooperation with State and local agencies, systematically collects groundwater data at varying measurement frequencies to monitor the hydrologic conditions on Long Island, New York. Each year during April and May, the USGS conducts a synoptic survey of water levels to define the spatial distribution of the water table and potentiometric surfaces within the three main water-bearing units underlying Long Island—the upper glacial, Magothy, and Lloyd aquifers (Smolensky and others, 1989)—and the hydraulically connected Jameco (Soren, 1971) and North Shore aquifers (Stumm, 2001). These data and the maps constructed from them are commonly used in studies of Long Island's hydrology and are utilized by water managers and suppliers for aquifer management and planning purposes. Water-level measurements made in 502 monitoring wells (observation and supply wells) and 16 streamgage locations across Long Island during April–May 2013 were used to prepare the maps in this report. Groundwater measurements were made by the wetted-tape method to the nearest hundredth of a foot. Contours of water-table and potentiometric-surface altitudes were created by using the groundwater measurements. The water-table contours were interpreted by using water-level data collected from 16 streamgages, 334 observation wells, and 1 supply well screened in the upper glacial aquifer or the shallow Magothy aquifer; the Magothy aquifer's potentiometric-surface contours were interpreted from measurements at 70 observation wells and 31 supply wells screened in the middle to deep Magothy aquifer and the contiguous and hydraulically connected Jameco aquifer. The Lloyd aquifer's potentiometric-surface contours were interpreted from measurements at 58 observation wells and 8 supply wells screened in the Lloyd aquifer and the contiguous and hydraulically connected North Shore aquifer. Many of the supply wells are in continuous operation and therefore, were turned off for a minimum of 24 hours before measurements were made to allow the water levels in the wells to recover to ambient (non-pumping) conditions. Full recovery time at some of these supply wells can exceed 24 hours; therefore, water levels measured at these wells are assumed to be less accurate than those measured at observation wells, which are not pumped (Busciolano, 2002). In addition to pumping stresses, elevated chloride concentrations (saline water) also lower the water levels measured in certain wells. This reduction in water level is the result of saline water being denser than freshwater (Lusczynski, 1961). In this report, all water-level altitudes are referenced to the National Geodetic Vertical Datum of 1929 (NGVD 29). The land surface or topography was downloaded from the National Map portal (http://nationalmap.gov), which represents the most currently available terrain representation as a 10-meter digital elevation model (DEM). The National Map terrain representation was combined with additional land surface terrain models of Suffolk County and New York City, which were collected using lidar to produce a high accuracy three-dimensional land surface altitude model based on the geospatial product for coastal flood mapping. The datum for land surface altitude is North American Vertical Datum of 1988 (NAVD 88). On Long Island NAVD 88 is approximately 1-foot lower than NGVD 29. Hydrographs are included on these maps for selected wells that have digital recording equipment. These hydrographs are representative of the 2013 water year to show the changes that have occurred throughout that period. The synoptic survey water level measured at the well is included on each hydrograph.

New York↗

USGS1952

Present and past ground-water conditions in the Morrison Formation in southwestern Colorado and southeastern Utah

Field and laboratory studies of ground-water conditions in the carnotite-bearing Morrison formation in southwestern Colorado and southeastern Utah were undertaken to determine possible relations between ground waters and the carnotite deposits. The ore-bearing sandstone consists of lenticular sandstone strata, interbedded within discontinuous layers of mudstone; these strata were deposited in a stream environment. The porosity and permeability of the ore-bearing sandstone in one area are relatively low, porosity averaging about 15 percent and permeability ranging between 30 and 3300 millidarcys. Permeability studies in this same area show that sandstone classed as favorable for ore is slightly more permeable than and has nearly twice the transmissibility of sandstone classed as semifavorable; outcrop studies also suggest a lower transmissibility for sandstone that is unfavorable. Samples of water from the ore-bearing and associated strata show considerable variation in chemical charter. These water samples are generally low in uranium, vanadium, copper, and lead, most samples containing less than 1 part per million (ppm) of each metal. General geologic relations suggest that ground-water movement probably was active through the ore-bearing strata during their deposition and shortly afterward. Movement during this time probably occurred largely through the more permeable sand strata and in the general direction of initial dip and stream flow. During Cretaceous time, when several thousand feet of marine sediments accumulated over the Morrison, the water contained in the ore-bearing strata probably was immobile or nearly so and was protected from escape or contamination. Following Tertiary deformation and erosion, active ground-water circulation no doubt was restored, but because of the low permeability and the lenticular character and therefore low transmissibility of the ore-bearing sandstone, ground-water movement probably was slow. Faulting probably also influenced the direction and rate of ground-water movement during Tertiary time. Movement and localization of ground water would permit the concentration of metal-bearing solutions during Salt Wash and early Brushy Basin time in the beds that now contain ore deposits. It is more difficult to explain the formation of these deposits, which have a wide geographic distribution at a restricted stratigraphic position, from solutions circulating through the rocks at a later date. Whatever mode of origin is used to explain the deposits, geologists almost without exception, agree that the metals were transported by solutions that have migrated through the sediments for considerable distances. For this reason, a study of the horizontal and vertical transmissibility characteristics of all exposed sedimentary formations on the Colorado Plateau is planned.

Colorado, Utah↗

USGS1994

Hydrogeology of recharge areas and water quality of the principal aquifers along the Wasatch Front and adjacent areas, Utah

The principal basin-fill aquifers in Cache Valley, the lower Bear River area, and along the Wasatch Front provide ground water to about 84 percent of the population of Utah. Recharge areas for the principal aquifers were mapped to provide information needed for the implementation of ground-water quality regulations and a State ground-water protection plan. Water samples were collected and analyzed to provide baseline water- quality data for the principal aquifers. The study area includes five subareas: Cache Valley, the 1ower Bear River area, the East Shore area, Salt Lake Valley, and Utah and Goshen Valleys. Basin-fill deposits in each subarea are lithologically heterogeneous. The principal aquifers in most of the subareas are composed of multiple discontinuous unconfined and confined aquifers and confining layers. Primary recharge areas generally are located along adjacent mountain fronts and extend into the valleys at the mouths of major drainages. Secondary recharge areas are located on the benches and uplands of the valleys. Ground-water flow generally is from these recharge areas to the discharge areas in the topographically low parts of the valleys. In general, dissolved-solids concentrations in ground water range from less than 500 mg/L to about 3,000 mg/L. Of 73 water samples, 5 contained inorganic constituents in concentrations that exceeded State of Utah water-quality standards. None of the samples contained concentrations of organic compounds that exceeded State standards.

Water-Resources Investigations Report↗

USGS1998

Recharge-area delineation and hydrology, McCraken Springs, Fort Knox Military Reservation, Meade County, Kentucky

McCraken Springs, consisting of three perennial springs - Main, Bat Cave, and Rocky Springs—and several intermittent springs, are used as a source of public water by the Fort Knox Military Reservation in Meade County, Ky. The water supply provided by McCraken Springs is potentially vulnerable to natural and induced stresses on the karst aquifer and to degradation by contaminants introduced by stormwater entering sinkholes and a large sinking stream in the Springs' recharge area. The U.S. Department of the Army is preparing a spring-basin protection plan for McCraken Springs, in accordance with State water-supply regulations and as specified under U.S. Environmental Protection Agency Guidelines for the Wellhead Protection Program (U.S. Environmental Protection Agency, 1991). In order to provide the information needed to prepare the plan, the U.S. Geological Survey (USGS), in cooperation with the U.S. Army Corps of Engineers, conducted a hydrogeologic study of the McCraken Springs in 1997-98. This report presents the results of that investigation. Ground-water-tracer tests and the results of potentiometric-surface mapping were used to identify ground-water basins drained by major perennial springs and to delineate the approximate boundaries of the recharge area for McCraken Springs. Additional hydrologic data were collected to determine the discharge and recharge characteristics of the Springs. Karst aquifers and springs are widely recognized as being more sensitive to degradation to point- and nonpoint-source contamination than most granular and fractured-rock aquifers (Field, 1990). Delineation of the geographic area contributing recharge to a water-supply spring is a principal step in identifying potential sources of ground-water contamination and developing a strategy to ensure the availability and protect the sustainability of the water supply. Conventional methods of aquifer testing and numerical modeling are not sufficient to determine the flow boundaries of ground-water basins in conduit-dominated karst aquifers. Previous studies published by Quinlan and Ewers (1989); Mull and others (1990); Bayless and others (1994); and Schindel and others (1995) demonstrate the utility of ground-water tracer tests, used in combination with potentiometric-surface mapping, to identify flow directions in karst aquifers, and to delineate karst ground-water-basin boundaries.

Kentucky↗

USGS2023

Prioritizing the risk and management of introduced species in a landscape with high indigenous biodiversity

Risk analysis protocols for prioritizing the management of non-native species are numerous, yet few incorporate risk and management in the same analysis or accommodate a broad diversity of taxa outside of a specific geographic area. We adapted a protocol that accounts for these factors to address non-native animal species in the Southern California/Northern Baja California Coast Ecoregion near the international border in San Diego County, an area with high indigenous biodiversity and high numbers of species of conservation concern. This stepwise, semi-quantitative protocol is applicable to any animal group in any predefined geographic area, relies on consensus-building among taxonomic experts, and has been vetted through previous use and in peer-reviewed literature. Our results show that the final prioritization was driven mainly by management feasibility, with top-ranked species having multitrophic effects that favor other non-native invaders over native residents. Conditions within the assessment area required some modification to the protocol as it was originally designed, namely a shift in emphasis from eradication to control, given that eradication is implausible for most non-native species in the assessment area. We call attention to taxon-specific issues that surfaced during the analysis, identify areas for improvement in this first-ever risk assessment for invasive animal species in the Natural Communities Conservation Plan/Habitat Conservation Plan (NCCP/HCP) reserve system of San Diego County, and provide suggestions for further refinement of the protocol. This study builds on the effort to standardize risk analysis for invasive species globally, given that many of the same invaders present threats to indigenous biodiversity worldwide.

California↗

USGS2026

The development of long-term mean annual total nitrogen and total phosphorus load models for Mississippi, U.S., using RSPARROW

Water-quality degradation from nutrient pollution remains a major challenge for resource managers. Developing effective strategies requires tools to characterize nutrient sources and transport. This study used the RSPARROW framework to develop and assess new, smaller-scale models for Total Nitrogen (TN) and Total Phosphorus (TP) transport across Mississippi (MS). These state-level models were built using 15 years (2005–2020) of observation data and considered variables including multiple nutrient sources, land characteristics, and attenuation processes. The MS models demonstrated comparable accuracy to larger regional SPARROW models, validating the use of smaller-scale models for local management. Results showed agricultural sources are the major contributors to TN, dominated by fertilizer in northern MS and livestock manure in the south. Urban land cover also significantly influenced TN and was the second most significant source of TP, following geologic material (background P). Fertilizer and manure were also important TP sources. This study provides valuable, spatially explicit data on nutrient distribution in MS streams, supporting the state’s nutrient reduction planning. It concludes by highlighting the need for future model improvements via updated source data and mean annual flow estimates.

Alabama, Georgia, Louisiana, Mississippi, North Ca↗

USGS2018

Cumulative spring discharge and survey effort influence occupancy and detection of a threatened freshwater mussel, the Suwannee Moccasinshell

Freshwater mussels (Unionidae) are among the most imperiled groups of organisms in the world, and the lack of information regarding species distributions, life-history characteristics, and ecological and biological requirements may limit the protection of remaining mussel populations. We examined the influence of hydrologic factors on the occurrence of the Suwannee Moccasinshell Medionidus walkeri, a federally threatened freshwater mussel species, endemic to the Suwannee River Basin in Georgia and Florida. We also evaluated the influence of survey effort on detection of Suwannee Moccasinshell during field surveys. We compiled all recent (2013–2016) mussel survey records in the Suwannee River Basin. We calculated cumulative discharge contributed by upstream springs for each of 220 survey locations. We combined the spring discharge predictor variable with Suwannee Moccasinshell detection and nondetection data from each survey location to develop a suite of occupancy models. Modeling results indicated that detection of Suwannee Moccasinshell during surveys was strongly and positively related to survey effort. Modeling results also indicated that sites with cumulative spring discharge inputs exceeding ∼28 cubic meters per second were most likely (i.e., predicted occupancy probabilities >0.5) to support Suwannee Moccasinshell populations. However, occupancy declined in the lowermost reaches of the Suwannee mainstem despite high spring discharge inputs, presumably due to greater tidal influences and differences in physicochemical habitat conditions. Historical localities where Suwannee Moccasinshell has presumably been extirpated are all devoid of springs in their upstream watersheds. We hypothesize that springs may buffer extremely tannic, and at times polluted, surface waters, in addition to maintaining adequate flows during periods of drought, thereby promoting the persistence of Suwannee Moccasinshell populations. Our study suggests that springs are a critical resource for Suwannee Moccasinshell and may be more important for conservation planning than was previously recognized.

Florida↗

USGS1989

Recent progress on hydrodynamic modeling of San Francisco Bay, California

A hydrodynamic modeling study of the effects of freshwater inflow on circulation and mixing in San Francisco Bay has been underway since 1985. This paper describes the multidimensional hydrodynamic models being used on the study and review recent progress with their applications. Particular modeling considerations for San Francisco Bay and future modeling plans are discussed.

Conference Paper↗

USGS2006

Tidal saltmarsh fragmentation and persistence of San Pablo Song Sparrows (Melospiza melodia samuelis): Assessing benefits of wetland restoration in San Francisco Bay

The San Pablo Song Sparrow (Melospiza melodia samuelis) is one of three morphologically distinct Song Sparrow subspecies in tidal marshes of the San Francisco Bay estuary. These subspecies are rare, because as the human population has grown, diking and development have resulted in loss of 79% of the historic tidal marshes. Hundreds of projects have been proposed in the past decade to restore tidal marshes and benefit endemic populations. To evaluate the value of these restoration projects for Song Sparrows, we developed a population viability analysis (PVA) model to examine persistence of samuelis subspecies in relation to parcel size, connectivity, and catastrophe in San Pablo Bay. A total of 101 wetland parcels were identified from coverages of modern and historic tidal marshes. Parcels were grouped into eight fragments in the historical landscape and 10 in the present landscape. Fragments were defined as a group of parcels separated by >1 km, a distance that precluded regular interchange. Simulations indicated that the historic (circa 1850) samuelis population was three times larger than the modern population. However, only very high levels (>70% mortality) of catastrophe would threaten their persistence. Persistence of populations was sensitive to parcel size at a carrying capacity of <10 pairs, but connectivity of parcels was found to have little importance because habitats were dominated by a few large parcels. Our analysis indicates little risk of extinction of the samuelis subspecies with the current extent of tidal marshes, but the vulnerability of the small-est parcels suggests that restoration should create larger continuous tracts. Thus, PVA models may be useful tools for balancing the costs and benefits of restoring habitats for threatened tidal-marsh populations in wetland restoration planning.

Studies in Avian Biology↗

USGS2010

Restoration and revegetation associated with control of saltcedar and Russian olive: Chapter 7

Rationales for controlling or eliminating saltcedar and Russian olive from sites, river reaches, or entire streams include implicit or explicit assumptions that natural recovery or applied restoration of native plant communities will follow exotic plant removal (McDaniel and Taylor, 2003; Quimby and others, 2003). The vegetation that replaces saltcedar and Russian olive after treatment (“replacement vegetation”), with or without restoration actions, strongly influences the extent to which project objectives are successfully met. It is often assumed or implied that saltcedar and Russian olive removal alone is “restoration,” and many reports equate restoration success with areal extent of nonnative plants treated (for example, Duncan and others, 1993). However, removal of nonnative species alone does not generally constitute restoration. In this chapter, the term “restoration” refers to conversion of saltcedar- and Russian olive-dominated sites to a replacement vegetation type that achieves specific management goals and helps return parts of the system to a desired state. The degree to which a site is “restored” following removal of saltcedar or Russian olive typically depends upon a range of factors, such as (1) the site’s potential for restoration (such as extant soil conditions, site hydrology), (2) the direct and indirect effects of removal (for example, mechanical impacts to the site, effects of herbicides on nontarget vegetation), (3) the efficacy of restoration activities (for example, grading, reseeding, pole planting), and (4) the maintenance of processes that support native vegetation and prevent re-colonization by nonnative communities over the long term. This chapter summarizes and synthesizes the published literature on the topic of restoring native riparian vegetation following saltcedar and Russian olive control or removal. Most of the studies reviewed here are from saltcedar removal, revegetation, and river restoration projects in semiarid and arid parts of the Western United States. The paucity of literature on Russian olive prevents thorough evaluation of specific considerations for restoration following Russian olive removal; however, a few field studies are highlighted. Furthermore, the basic principles of restoration following vegetation removal and the considerations and lessons learned from saltcedar case studies are broadly applicable to sites across the Western United States. We begin with a brief discussion of planning and objective setting. Next, we discuss site factors and context, which are important to consider when selecting and prioritizing sites for restoration. We then review and synthesize the literature on restoration approaches and methods or combinations of methods to apply to particular sites. Throughout this chapter, we highlight what is known on the topics of restoring soils, vegetation, and site conditions following nonnative species removal, as well as future research needs.

Book chapter↗

USGS1991

USFWS selected geographic analyses

The geographic information system (GIS) used by the National Wetlands Research Center (NWRC) of the U.S. Fish and Wildlife Service has been valuable in assisting natural resource managers in planning and managing coastal fish and wildlife resources. In the past 5 years, NWRC has conducted about 60 studies employing this technology. Applications have ranged from simple natural resource inventories to documentation of trends in wetland changes and complex predictive modeling of impacts of harbor expansion on biological resources. Maps, tables, and data bases from these studies have been presented before local, State, and Congressional committees as well as numerous scientific and public organizations. This paper describes and summarizes selected GIS projects related to resource inventories, analyses of wetland change, and cartographic modeling of coastal areas of the United States.

Conference Paper↗

USGS2024

Planned geological investigations of the Europa Clipper mission

Geological investigations planned for the Europa Clipper mission will examine the formation, evolution, and expression of geomorphic structures found on the surface. Understanding geologic features, their formation, and any recent activity are key inputs in constraining Europa’s potential for habitability. In addition to providing information about the moon’s habitability, the geologic study of Europa is compelling in and of itself. Here we provide a high-level, cross-instrument, and cross-discipline overview of the geologic investigations planned within the Europa Clipper mission. Europa’s fascinating collection of ice-focused geology provides an unparalleled opportunity to investigate the dynamics of icy shells, ice-ocean exchange processes, and global-scale tectonic and tidal stresses. We present an overview of what is currently known about the geology of Europa, from global to local scales, highlighting outstanding issues and open questions, and detailing how the Europa Clipper mission will address them. We describe the mission’s strategy for searching for and characterizing current activity in the form of possible active plumes, thermal anomalies, evidence for surface changes, and extremely fresh surface exposures. The complementary and synergistic nature of the data sets from the various instruments and their integration will be key to significantly advancing our understanding of Europa’s geology.

Space Science Reviews↗

USGS1982

Tilt networks of Mount Shasta and Lassen Peak, California

In response to recent eruptions at Mount St. Helens and with support from the USGS Volcanic Hazards Program, the Cascades Volcano Observatory (CVO) has initiated a program to monitor all potentially-active volcanoes of the Cascade Range. As part of that effort, we installed tilt networks and obtained baseline measurements at Mount Shasta and Lassen Peak, California during July 1981. At the same time, baseline electronic distance measurements (EDM) were made and fumarole surveys were conducted by other crews from CVO. Annual surveys are planned initially, with subsequent visits as conditions warrant. These geodetic and geochemical measurements supplement a program of continuous seismic monitoring of Cascade volcanoes by the USGS Office of Earthquake Studies in cooperation with local universities. Other tilt networks were established at Mount Baker in 1975 and at Mount St. Helens in 1981. EDM networks were established at Mount Baker in 1975, Mount St. Helens in 1980, and Crater Lake in 1981. Additional tilt and/or EDM networks are planned for Mount Rainier, Mount Hood, Glacier Peak, Three Sisters, and Crater Lake as funds permit.

Open-File Report↗

USGS2011

Potentiometric surface in the Central Oklahoma (Garber-Wellington) aquifer, Oklahoma, 2009

A study of the hydrogeology of the Central Oklahoma aquifer was started in 2008 to provide the Oklahoma Water Resources Board (OWRB) hydrogeologic data and a groundwater flow model that can be used as a tool to help manage the aquifer. The 1973 Oklahoma water law requires the OWRB to do hydrologic investigations of Oklahoma's aquifers (termed 'groundwater basins') and to determine amounts of water that may be withdrawn by permitted water users. 'Maximum annual yield' is a term used by OWRB to describe the total amount of water that can be withdrawn from a specific aquifer in any year while allowing a minimum 20-year life of the basin (Oklahoma Water Resources Board, 2010). Currently (2010), the maximum annual yield has not been determined for the Central Oklahoma aquifer. Until the maximum annual yield determination is made, water users are issued a temporary permit by the OWRB for 2 acre-feet/acre per year. The objective of the study, in cooperation with the Oklahoma Water Resources Board, was to study the hydrogeology of the Central Oklahoma aquifer to provide information that will enable the OWRB to determine the maximum annual yield of the aquifer based on different proposed management plans. Groundwater flow models are typically used by the OWRB as a tool to help determine the maximum annual yield. This report presents the potentiometric surface of the Central Oklahoma aquifer based on water-level data collected in 2009 as part of the current (2010) hydrologic study. The U.S. Geological Survey (USGS) Hydrologic Investigations Atlas HA-724 by Christenson and others (1992) presents the 1986-87 potentiometric-surface map. This 1986-87 potentiometric-surface map was made as part of the USGS National Water-Quality Assessment pilot project for the Central Oklahoma aquifer that examined the geochemical and hydrogeological processes operating in the aquifer. An attempt was made to obtain water-level measurements for the 2009 potentiometric-surface map from the wells used for the 1986-87 potentiometric-surface map. Well symbols with circles on the 2009 potentiometric-surface map (fig. 1) indicate wells that were used for the 1986-87 potentiometric-surface map.

Scientific Investigations Map↗

USGS2023

Estimating peak-flow quantiles for selected annual exceedance probabilities in Illinois

This report presents the methods, results, and applications of an updated flood-frequency study for the State of Illinois. This study, which uses data through September 2017, updates two previous studies that used data through 1999 and 2009, respectively. Flood-frequency estimates are used for a variety of land-use planning and infrastructure design purposes, including for the hydraulic design of bridges. The flood frequencies presented are the stream discharges (or quantiles) that are exceeded each year with a given probability, called the annual exceedance probability (AEP). Estimates are provided for eight AEPs: 0.5, 0.2, 0.1, 0.04, 0.02, 0.01, 0.005, and 0.002. The basic data used are the annual maximum discharges (peak flows) at streamgages in and near Illinois and the measurable physical properties (basin characteristics) of the basins upstream from those streamgages. The logarithms of the peak flow records at qualifying streamgages were fit to the Pearson Type 3 distribution using federally recommended methods, providing one of the two primary products of the study, which is the set of peak-flow quantiles at the streamgages and their uncertainties. The other primary product is sets of equations, determined by least-squares regression, that relate the peak-flow quantiles and the basin characteristics. There is one set of equations for each of Illinois’ seven hydrologic regions, and, for each region, one equation for each AEP. These regional equations allow the estimation of peak-flow quantiles at ungaged locations throughout the state and their uncertainties. A set of illustrative example applications is provided, and tables of all results at all study streamgages and regions are provided in associated data releases. The study results are also being made available in a web application, StreamStats.

Illinios↗

USGS2005

Observations of plan-view sand ripple behavior and spectral wave climate on the inner shelf of San Pedro Bay, California

Concurrent video images of sand ripples and current meter measurements of directional wave spectra are analyzed to study the relations between waves and wave-generated sand ripples. The data were collected on the inner shelf off Huntington Beach, California, at 15 m water depth, where the sea floor is comprised of well-sorted very fine sands (D50=92 ??m), during the winter of 2002. The wave climate, which was controlled by southerly swells (12-18 s period) and westerly wind waves (5-10 s period), included three wave types: (A) uni-modal, swells only; (B) bi-modal, swells dominant; and (C) bi-modal, wind-wave dominant. Each wave type has distinct relations with the plan-view shapes of ripples that are classified into five types: (1) sharp-crested, two-dimensional (2-D) ripples; (2) sharp-crested, brick-pattern, 3-D ripples; (3) bifurcated, 3-D ripples; (4) round-crested, shallow, 3-D ripples; and (5) flat bed. The ripple spacing is very small and varies between 4.5 and 7.5 cm. These ripples are anorbital as ripples in many field studies. Ripple orientation is only correlated with wave directions during strong storms (wave type C). In a poly-modal, multi-directional spectral wave environment, the use of the peak parameters (frequency, direction), a common practice when spectral wave measurements are unavailable, may lead to significant errors in boundary layer and sediment transport calculations. ?? 2004 Elsevier Ltd. All rights reserved.

Continental Shelf Research↗

USGS2002

Logs and data from trenches across the Hayward Fault at Tyson's Lagoon (Tule Pond), Fremont, Alameda County, California

INTRODUCTION The purpose of this publication is to make available detailed trench logs (sheets 1, 2), radiocarbon dates (table 1) and pollen data (fig. 1) obtained as a result of an intensive subsurface investigation of the Hayward Fault at Tyson's Lagoon (Tule Pond) from August to November 2000 (figs. 1, 2 on sheet 1). The Hayward Fault is recognized to be among the most hazardous in the United States (Working Group on California Earthquake Probabilities, 1999). This document makes available geologic evidence for historical and prehistoric surfacerupturing earthquakes that were recorded at the site. Prehistoric earthquakes deduced from geologic evidence are called paleoearthquakes. Establishing a chronology of paleoearthquakes is of immediate use in resolving the level of hazard posed by the Hayward Fault for producing large earthquakes in the future. Preliminary findings of this investigation have been presented in Lienkaemper and others (2001). A formal report on our conclusions based on these data is in preparation. The investigation at Tyson's Lagoon is ongoing, so these products should not be considered final. Lienkaemper, Dawson, and Personius interpreted the geology and logged the trenches. Seitz and Reidy performed analyses on radiocarbon and pollen samples, respectively. Schwartz led the critical-review field team. Previous trenching work was done at Tyson's Lagoon (figs. 2, 3 on sheet 1). Lienkaemper (1992) references the location of most of those trenches. The earlier trenching was generally for the evaluation of local faultrupture hazard, except for the study of Williams (1993), which was a paleoearthquake investigation. An unpublished study by J.N. Alt in 1998 (shown on our site map as trenches 98A and 98B, fig. 3, on sheet 1), also sought evidence of paleoearthquakes. Alt's study and one by Woodward-Clyde and Associates (1970; trenches 70A to 70G, fig. 3) were located south of Walnut Avenue in one of the few areas that still remain undisturbed and were, thus, useful in planning our work in 2000.

Miscellaneous Field Studies Map↗

USGS2007

Water- and air-quality monitoring of the Sweetwater Reservoir Watershed, San Diego County, California-Phase One results, continued, 1999-2001

In 1998, the U.S. Geological Survey, in cooperation with the Sweetwater Authority, began a study to assess the overall health of the Sweetwater watershed with respect to chemical contamination. The study included regular sampling of air and water at Sweetwater Reservoir for chemical contaminants, including volatile organic compounds, polycyclic aromatic hydrocarbons, pesticides, and major and trace elements. Background water samples were collected at Loveland Reservoir for volatile organic compounds and pesticides. The purpose of this study was to monitor changes in contaminant composition and concentration in the air and water resulting from the construction and operation of State Route 125 near Sweetwater Reservoir. To accomplish this, the study was divided into two phases. Phase One sampling was designed to establish baseline conditions for target compounds in terms of detection frequency and concentration in air and water. Phase Two sampling is planned to continue at the established monitoring sites during and after construction of State Route 125 to assess the chemical impact this roadway alignment project may have on the water quality in the reservoir. In addition to the ongoing data collection, several special studies were initiated to assess the occurrence of specific chemicals of concern, such as low-use pesticides, trace metals, and wastewater compounds. This report describes the study design, and the sampling and analytical methods, and presents the results for the second and third years of the study (October 1999 to September 2001). Data collected during the first year of sampling (October 1998 to September 1999) were published in 2002.

California↗