USGS Science⌕ Search

SEARCH · USGS Science

Results for “California Geographer”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 523 records · Page 29Linked to original sources
USGS2026

Dog attacks on wild desert tortoises: A risk model

We retrospectively compiled a database of 6,727 live, wild Agassiz's desert tortoises ( Gopherus agassizii ) and evaluated them for clinical signs of trauma to shell and limbs at 50 sites in the Mojave and Colorado (western Sonoran) deserts of California, USA, spanning the years 1977–2006. Our objectives were to 1) identify tortoises with severe trauma to shell, limbs, and gular horns typically seen in attacks from dogs ( Canis familiaris ); 2) identify locations where severe injuries occurred; and 3) develop a risk model based on distances of tortoises from settlements, towns, or cities. Our models identified multiple variables of importance for tortoises with severe damage to shells, limbs, and gular horns: relative age and sex of tortoises, decades of occurrence, and location. Females and very old tortoises were more vulnerable to attacks than other tortoises. In the decades between the 1970s and 2000s, the risk of severe overall trauma to shell and limbs increased 4 times and to gular horns 16.5 times. Compared to previous decades, by the early 2000s the percent of tortoises with severe trauma increased exponentially the closer a tortoise site was to a settlement; the exponential increase began at approximately 12 km from a settlement. We suggest that the risks may be higher now because of the growth of human populations within the geographic range of the tortoise. The threats to tortoises from dogs are based on whether dogs are off-leash in the Mojave and Colorado deserts.

Arizona, California, Nevada, Utah↗
USGS2022

Demographic and environmental correlates of home ranges and long-distance movements of Mohave ground squirrels

Space use by mammals can differ among age-classes, sexes, or seasons, and these processes are recognized as adaptive behavioral strategies. Semi-fossorial ground squirrels, in particular, have shown age- and sex-specific patterns in their aboveground movement behaviors. We studied space use of Mohave ground squirrels ( Xerospermophilus mohavensis ) at the Freeman Gulch study site in the central region of their range in the Mojave Desert, California. We documented the timing of their full annual cycle, investigated correlates of size of home ranges of adults and distance of long-distance movements by juveniles, and evaluated whether juvenile body masses and movements were related to interannual climatic variation. Adult males emerged from burrows and entered hibernation sooner than did adult females. Home ranges were larger for males ( ⁠ x ¯ "> x ¯ x¯ ± SD = 0.50 ± 0.40 km 2 ) than females (0.05 ± 0.03 km 2 ), especially during the mating season. Maximum distances moved by juveniles did not differ significantly between males (1.6 ± 2.3 km) and females (1.0 ± 1.8 km), and both sexes were equally likely to travel long distances from natal sites. The longest-distance movement we documented was 7.7 km by a juvenile male. Juveniles born in a year of low vegetation productivity gained significantly less mass (97 ± 7 g) and traveled shorter distances than those born in a year of higher vegetation productivity (177 ± 20 g). Our findings were similar to those documented in the Coso Range study site in the northern region of the geographic range of the species, indicating that movement patterns are similar range-wide. Mohave ground squirrels responded strongly to climate variation, and global climate change will likely result in a northward shift in suitable habitats. Informed conservation planning, therefore, will be essential for this rare, declining species.

California↗
USGS1998

Loose-coupling a cellular automaton model and GIS: Long-term urban growth prediction for San Francisco and Washington/Baltimore

Prior research developed a cellular automaton model, that was calibrated by using historical digital maps of urban areas and can be used to predict the future extent of an urban area. The model has now been applied to two rapidly growing, but remarkably different urban areas: the San Francisco Bay region in California and the Washington/Baltimore corridor in the Eastern United States. This paper presents the calibration and prediction results for both regions, reviews their data requirements, compares the differences in the initial configurations and control parameters for the model in the two settings, and discusses the role of GIS in the applications. The model has generated some long term predictions that appear useful for urban planning and are consistent with results from other models and observations of growth. Although the GIS was only loosely coupled with the model, the model's provision of future urban patterns as data layers for GIS description and analysis is an important outcome of this type of calculation.

California, Maryland↗
USGS2015

Defining population structure and genetic signatures of decline in the giant garter snake ( Thamnophis gigas ): implications for conserving threatened species within highly altered landscapes

Anthropogenic habitat fragmentation can disrupt the ability of species to disperse across landscapes, which can alter the levels and distribution of genetic diversity within populations and negatively impact long-term viability. The giant gartersnake ( Thamnophis gigas ) is a state and federally threatened species that historically occurred in the wetland habitats of California’s Great Central Valley. Despite the loss of 93 % of historic wetlands throughout the Central Valley, giant gartersnakes continue to persist in relatively small, isolated patches of highly modified agricultural wetlands. Gathering information regarding genetic diversity and effective population size represents an essential component for conservation management programs aimed at this species. Previous mitochondrial sequence studies have revealed historical patterns of differentiation, yet little is known about contemporary population structure and diversity. On the basis of 15 microsatellite loci, we estimate population structure and compare indices of genetic diversity among populations spanning seven drainage basins within the Central Valley. We sought to understand how habitat loss may have affected genetic differentiation, genetic diversity and effective population size, and what these patterns suggest in terms of management and restoration actions. We recovered five genetic clusters that were consistent with regional drainage basins, although three northern basins within the Sacramento Valley formed a single genetic cluster. Our results show that northern drainage basin populations have higher connectivity than among central and southern basins populations, and that greater differentiation exists among the more geographically isolated populations in the central and southern portion of the species’ range. Genetic diversity measures among basins were significantly different, and were generally lower in southern basin populations. Levels of inbreeding and evidence of population bottlenecks were detected in about half the populations we sampled, and effective population size estimates were well below recommended minimum thresholds to avoid inbreeding. Efforts focused on maintaining and enhancing existing wetlands to facilitate dispersal between basins and increase local effective population sizes may be critical for these otherwise isolated populations.

Conservation Genetics↗
USGS2011

2010 bathymetric survey and digital elevation model of Corte Madera Bay, California

A high-resolution bathymetric survey of Corte Madera Bay, California, was collected in early 2010 in support of a collaborative research project initiated by the San Francisco Bay Conservation and Development Commission and funded by the U.S. Environmental Protection Agency. The primary objective of the Innovative Wetland Adaptation in the Lower Corte Madera Creek Watershed Project is to develop shoreline adaptation strategies to future sea-level rise based upon sound science. Fundamental to this research was the development of an of an up-to-date, high-resolution digital elevation model (DEM) extending from the subtidal environment through the surrounding intertidal marsh. We provide bathymetric data collected by the U.S. Geological Survey and have merged the bathymetry with a 1-m resolution aerial lidar data set that was collected by the National Oceanic and Atmospheric Administration during the same time period to create a seamless, high-resolution DEM of Corte Madera Bay and the surrounding topography. The bathymetric and DEM surfaces are provided at both 1 m and 10 m resolutions formatted as both X, Y, Z text files and ESRI Arc ASCII files, which are accompanied by Federal Geographic Data Committee compliant metadata.

California↗
USGS2014

Changes in vegetation and biological soil crust communities on sand dunes stabilizing after a century of grazing on San Miguel Island, Channel Island National Park, California

San Miguel Island is the westernmost of the California Channel Islands and one of the windiest areas on the west coast of North America. The majority of the island is covered by coastal sand dunes, which were stripped of vegetation and subsequently mobilized due to droughts and sheep ranching during the late 19th century and early 20th century. Since the removal of grazing animals, vegetation and biological soil crusts have once again stabilized many of the island's dunes. In this study, historical aerial photographs and field surveys were used to develop a chronosequence of the pattern of change in vegetation communities and biological soil crust levels of development (LOD) along a gradient of dune stabilization. Historical aerial photographs from 1929, 1954, 1977, and 2009 were georeferenced and used to delineate changes in vegetation canopy cover and active (unvegetated) dune extent among 5 historical periods (pre-1929, 1929–1954, 1954–1977, 1977–2009, and 2009–2011). During fieldwork, vegetation and biological soil crust communities were mapped along transects distributed throughout San Miguel Island's central dune field on land forms that had stabilized during the 5 time periods of interest. Analyses in a geographic information system (GIS) quantified the pattern of changes that vegetation and biological soil crust communities have exhibited on the San Miguel Island dunes over the past 80 years. Results revealed that a continuing increase in total vegetation cover and a complex pattern of change in vegetation communities have taken place on the San Miguel Island dunes since the removal of grazing animals. The highly specialized native vascular vegetation (sea rocket, dunedelion, beach-bur, and locoweed) are the pioneer stabilizers of the dunes. This pioneer community is replaced in later stages by communities that are dominated by native shrubs (coastal goldenbush, silver lupine, coyote-brush, and giant coreopsis), with apparently overlapping or cyclical succession pathways. Many of the dunes that have been stabilized the longest (since before 1929) are dominated by exotic grasses. Stands of biological soil crusts (cyanobacteria) are found only on dunes where vascular vegetation is already present. Biological soil crusts are not found on dunes exhibiting a closed vascular plant canopy, which may indicate that the role of soil crusts in dune stabilization on the island is transitory. Particle-size analyses of soil samples from the study area reveal that higher biological soil crust LOD is positively correlated with increasing fine grain content. The findings indicate that changes in vegetation communities may be the most rapid at earlier and later stages of dune stabilization and that regular monitoring of dunes may help to identify the interactions between vegetation and soil crusts, as well as the potential transitions between native and exotic plant communities.

California↗
USGS2006

Spatial and Temporal Migration Patterns of Neotropical Migrants in the Southwest Revealed by Stable Isotopes

Executive Summary We used stable hydrogen isotopes (?D) to investigate both temporal and spatial patterns during spring migration for three warbler species, Wilson's Warbler (Wilsonia pusilla), MacGillivray's Warbler (Oporornis tolmiei), and Nashville Warbler (Vermivora ruficapilla), across multiple migration routes in southwest North America. A strong correlation between stable hydrogen isotope values of feathers and the local precipitation at sites where feathers where collected across the breeding range for all three species reaffirmed that stable hydrogen isotopes were a good predictor of breeding locations. For the Wilson's Warbler, we found a significant negative relationship between the date when warblers passed through the sampling station and ?D values of their feathers, indicating that warblers who bred the previous season at southern latitudes migrated through the migration stations earlier than did warblers that had previously bred at more northern latitudes. This pattern was consistent across their southwestern migration route (5 sites sampled) and was consistent between years. Comparing ?D values between migration stations also showed a shift towards more negative ?D values from the western to the eastern migration stations sampled in this study, which corresponded to different geographical regions of the Wilson's Warblers' western breeding range. For MacGillivray's Warbler we found the same temporal pattern as Wilson's Warbler, with warblers that bred the previous season at southern latitudes migrating through the migration stations earlier than warblers that had previously bred at more northern latitudes. This pattern was consistent at the Lower Colorado River and Arivaca Creek, the two sites where sample sizes were adequate to test these hypotheses. Comparison of the ?D between the two sites indicated that the majority of warblers migrating through these stations were breeding within a geographically limited area of MacGillivray's Warblers' overall breeding range. This is in contrast to the larger range of ?D values for Wilson's Warblers at these two sites, which corresponded to a broader area across their breeding range. Feathers were also collected across MacGillivray's Warblers' wintering range, and stable hydrogen isotope analysis indicated a significant positive relationship with wintering latitude. Because the ?D value of MacGillivray's Warblers' feathers reflects the ?D value of their breeding locations, with more negative values representing more northerly breeding latitudes, this positive relationship between feather ?D and wintering latitude indicated that warblers wintering at more southern latitudes bred at more northern latitudes. This supports a leapfrog migration system for MacGillivray's Warblers and is the first documentation of such a pattern. We did not find a temporal pattern to the spring migration of Nashville Warblers. This lack of temporal pattern could be due to the reduced size of the breeding and wintering ranges of Nashville Warblers, both of which could decrease the advantages of a temporal migration pattern. A small population of Nashville Warblers also breeds on the California coast and the sporadic nature of migration for Nashville Warblers in the southwest suggests that in some years more Nashville Warblers may winter along the California coast. The information in this study has increased our understanding of both spatial and temporal patterns of migration for three neotropical migrant birds and has important implications for understanding the ecology and evolution of migrants and factors influencing overall population dynamics.

Open-File Report↗
USGS2015

Pathogen exposure varies widely among sympatric populations of wild and domestic felids across the United States

Understanding how landscape, host, and pathogen traits contribute to disease exposure requires systematic evaluations of pathogens within and among host species and geographic regions. The relative importance of these attributes is critical for management of wildlife and mitigating domestic animal and human disease, particularly given rapid ecological changes, such as urbanization. We screened >1,000 samples from sympatric populations of puma (Puma concolor), bobcat (Lynx rufus) and domestic cat (Felis catus) across urban gradients in six sites, representing three regions, in North America for exposure to a representative suite of bacterial, protozoal and viral pathogens (Bartonella sp., Toxoplasma gondii, feline herpesvirus-1, feline panleukopenea virus, feline calicivirus, feline immunodeficiency virus). We evaluated prevalence within each species, and examined host trait and land cover determinants of exposure-providing an unprecedented analysis of factors relating to potential for infections in domesticated and wild felids. Prevalence differed among host species (highest for puma and lowest for domestic cat) and was greater for indirectly transmitted pathogens. Sex was inconsistently predictive of exposure to directly transmitted pathogens only, and age infrequently predictive of both direct and indirectly transmitted pathogens. Determinants of pathogen exposure were widely divergent between the wild felid species. For puma, suburban landuse predicted increased exposure to Bartonella sp. in southern California, and FHV-1 exposure increased near urban edges in Florida. This may suggest inter-specific transmission with domestic cats via flea vectors (California) and direct contact (Florida) around urban boundaries. Bobcats captured near urban areas had increased exposure to T. gondii in Florida, suggesting an urban source of prey. Bobcats captured near urban areas in Colorado and Florida had higher FIV exposure, possibly suggesting increased intra-specific interactions through pile-up of home ranges. Beyond these regional and pathogen specific relationships, proximity to the wildland urban interface did not generally increase the probability of disease exposure in wild or domestic felids, emphasizing the importance of local ecological determinants. Indeed, pathogen exposure was often negatively associated with the wildland urban interface for all felids. Our analyses suggest cross-species pathogen transmission events around this interface may be infrequent, but followed by self-sustaining propagation within the new host species.

California, Colorado,Florida↗
USGS1978

Reconstruction of crustal blocks of California on the basis of initial strontium isotopic compositions of Mesozoic granitic rocks

Initial 87Sr/ 86 Sr was determined for samples of Mesozoic granitic rocks in the vicinity of the Garlock fault zone in California. These data along with similar data from the Sierra Nevada and along the San Andreas fault system permit a reconstruction of basement rocks offset by the Cenozoic lateral faulting along both the San Andreas and Garlock fault systems. The location of the line of initial 87Sr/ 86 Sr = 0.7060 can be related to the edge of the Precambrian continental crust in the western United States. Our model explains the present configuration of the edge of Precambrian continental crust as the result of two stages of rifting that occurred about 1,250 to 800 m.y. ago, during Belt sedimentation, and about 600 to 350 m.y. ago, prior to and during the development of the Cordilleran geosyncline and to left-lateral translation along a locus of disturbance identified in the central Mojave Desert. The variations in Rb, Sr, and initial 87Sr/ 86 Sr of the Mesozoic granitic rocks are interpreted as due to variations in composition and age of the source materials of the granitic rocks. The variations of Rb, Sr, and initial 87Sr/ 86 Sr in Mesozoic granitic rocks, the sedimentation history during the late Precambrian and Paleozoic, and the geographic position of loci of Mesozoic magmatism in the western United States are related to the development of the continental margin and different types of lithosphere during rifting.

Professional Paper↗
USGS1995

Evaluation of a monitoring program for assessing the effects of management practices on the quantity and quality of drainwater from the Panoche Water District, western San Joaquin Valley, California

An evaluation was made of an existing monitoring program in the Panoche Water District for 1986-93. The Panoche Water District is an agricultural area located in the western San Joaquin Valley of California. Because irrigation drainage from this area has high concentrations of dissolved solids and selenium, management strategies have been developed to improve the quality of drainwater discharge. The purpose of the Panoche Water District's monitoring program is to assess the effects of water- and land-use practices on local ground water and drain flow from the district. Drainflow from the district consists of the discharge from 50 separate on-farm underground tile-drainage systems. The Panoche Water District maintains information on water deliveries, planned and actual crop types, and planned and actual acreages planted each year. In addition, the water district monitors ground-water and drainage-system discharges using a variety of data-collection methods. A total of 62 observation well sites are used to monitor ground-water level and quality. A total of 42 sites were monitored for drainflow quantity, and drain flow quality samples were collected from the outlets of each of the 50 drainage systems. However, these data were collected inconsistently and (or) intermittently during the period studied. All data obtained from the water district were compiled and stored in a geographic information system database. Water delivered for irrigation by the Panoche Water District is a mix of imported water and local ground water pumped directly into delivery canals. Although delivered water is a mix, information on the proportion of water from the two sources is not reported. Also, individual growers pump directly to their crops unknown quantities of ground water, the total of which could be greater than 60 percent of total applications during years when water district deliveries are greatly reduced (for example, the years during and following a drought). To evaluate the effects of irrigation on ground-water and drainflow quality, data on the combined chemical characteristics and the volume of water applied to crops are needed as part of the district's monitoring program. For example, without these data, this study could estimate only the effects of irrigation on ground-water recharge for 1986 (60.4 106 m3/y), 1987 (74.2 106 m3/y), and 1988 (56.0 106 m3/y) in the Panoche Water District water years when the amount of ground water pumped by individual growers was probably small. Water-level data show a significant decline of the water table in the upslope, undrained parts of the study area, and little or no significant change in the down slope, drained parts of the study area. Pumping from productions wells, most of which are located in the upslope part of the study area, may have contributed to the decline of the water table in the upslope area. The quantities of drainflow, dissolved solids, and selenium discharged from the study area decreased during the study period. However, drainflow, dissolved solids, and selenium discharged from individual on-farm drainage systems did not decrease. These data also illustrate the need for consistent and regular monitoring of the factors that affect drainage in the western San Joaquin Valley.

Open-File Report↗
USGS2001

Geologic map and digital database of the Porcupine Wash 7.5 minute Quadrangle, Riverside County, southern California

This data set maps and describes the geology of the Porcupine Wash 7.5 minute quadrangle, Riverside County, southern California. The quadrangle, situated in Joshua Tree National Park in the eastern Transverse Ranges physiographic and structural province, encompasses parts of the Hexie Mountains, Cottonwood Mountains, northern Eagle Mountains, and south flank of Pinto Basin. It is underlain by a basement terrane comprising Proterozoic metamorphic rocks, Mesozoic plutonic rocks, and Mesozoic and Mesozoic or Cenozoic hypabyssal dikes. The basement terrane is capped by a widespread Tertiary erosion surface preserved in remnants in the Eagle and Cottonwood Mountains and buried beneath Cenozoic deposits in Pinto Basin. Locally, Miocene basalt overlies the erosion surface. A sequence of at least three Quaternary pediments is planed into the north piedmont of the Eagle and Hexie Mountains, each in turn overlain by successively younger residual and alluvial deposits. The Tertiary erosion surface is deformed and broken by north-northwest-trending, high-angle, dip-slip faults and an east-west trending system of high-angle dip- and left-slip faults. East-west trending faults are younger than and perhaps in part coeval with faults of the northwest-trending set. The Porcupine Wash database was created using ARCVIEW and ARC/INFO, which are geographical information system (GIS) software products of Envronmental Systems Research Institute (ESRI). The database consists of the following items: (1) a map coverage showing faults and geologic contacts and units, (2) a separate coverage showing dikes, (3) a coverage showing structural data, (4) a scanned topographic base at a scale of 1:24,000, and (5) attribute tables for geologic units (polygons and regions), contacts (arcs), and site-specific data (points). The database, accompanied by a pamphlet file and this metadata file, also includes the following graphic and text products: (1) A portable document file (.pdf) containing a navigable graphic of the geologic map on a 1:24,000 topographic base. The map is accompanied by a marginal explanation consisting of a Description of Map and Database Units (DMU), a Correlation of Map and Database Units (CMU), and a key to point-and line-symbols. (2) Separate .pdf files of the DMU and CMU, individually. (3) A PostScript graphic-file containing the geologic map on a 1:24,000 topographic base accompanied by the marginal explanation. (4) A pamphlet that describes the database and how to access it. Within the database, geologic contacts , faults, and dikes are represented as lines (arcs), geologic units as polygons and regions, and site-specific data as points. Polygon, arc, and point attribute tables (.pat, .aat, and .pat, respectively) uniquely identify each geologic datum and link it to other tables (.rel) that provide more detailed geologic information.

California↗
USGS2009

Groundwater availability of the Central Valley Aquifer, California

California's Central Valley covers about 20,000 square miles and is one of the most productive agricultural regions in the world. More than 250 different crops are grown in the Central Valley with an estimated value of $17 billion per year. This irrigated agriculture relies heavily on surface-water diversions and groundwater pumpage. Approximately one-sixth of the Nation's irrigated land is in the Central Valley, and about one-fifth of the Nation's groundwater demand is supplied from its aquifers. The Central Valley also is rapidly becoming an important area for California's expanding urban population. Since 1980, the population of the Central Valley has nearly doubled from 2 million to 3.8 million people. The Census Bureau projects that the Central Valley's population will increase to 6 million people by 2020. This surge in population has increased the competition for water resources within the Central Valley and statewide, which likely will be exacerbated by anticipated reductions in deliveries of Colorado River water to southern California. In response to this competition for water, a number of water-related issues have gained prominence: conservation of agricultural land, conjunctive use, artificial recharge, hydrologic implications of land-use change, and effects of climate variability. To provide information to stakeholders addressing these issues, the USGS Groundwater Resources Program made a detailed assessment of groundwater availability of the Central Valley aquifer system, that includes: (1) the present status of groundwater resources; (2) how these resources have changed over time; and (3) tools to assess system responses to stresses from future human uses and climate variability and change. This effort builds on previous investigations, such as the USGS Central Valley Regional Aquifer System and Analysis (CV-RASA) project and several other groundwater studies in the Valley completed by Federal, State and local agencies at differing scales. The principal product of this new assessment is a tool referred to as the Central Valley Hydrologic Model (CVHM) that accounts for integrated, variable water supply and demand, and simulates surface-water and groundwater-flow across the entire Central Valley system. The development of the CVHM comprised four major elements: (1) a comprehensive Geographic Information System (GIS) to compile, analyze and visualize data; (2) a texture model to characterize the aquifer system;(3) estimates of water-budget components by numerically modeling the hydrologic system with the Farm Process (FMP); and (4) simulations to assess and quantify hydrologic conditions.

Professional Paper↗
USGS2001

Preliminary evaluation of the importance of existing hydraulic-head observation locations to advective-transport predictions, Death Valley regional flow system, California and Nevada

When a model is calibrated by nonlinear regression, calculated diagnostic statistics and measures of uncertainty provide a wealth of information about many aspects of the system. This report presents a method of ranking the likely importance of existing observation locations using measures of prediction uncertainty. It is suggested that continued monitoring is warranted at more important locations, and unwarranted or less warranted at less important locations. The report develops the methodology and then demonstrates it using the hydraulic-head observation locations of a three-layer model of the Death Valley regional flow system. The predictions of interest are subsurface transport from beneath Yucca Mountain and 14 Underground Test Areas. The advective component of transport is considered because it is the component most affected by the system dynamics represented by the scale model being used. The problem is addressed using the capabilities of the U.S. Geological Survey computer program MODFLOW-2000, with its ADVective-Travel Observation (ADV) Package, and an additional computer program developed for this work. The methods presented in this report are used in three ways. (1) The ratings for individual observations are obtained by manipulating the measures of prediction uncertainty, and do not involve recalibrating the model. In this analysis, observation locations are each omitted individually and the resulting increase in uncertainty in the predictions is calculated. The uncertainty is quantified as standard deviations on the simulated advective transport. The increase in uncertainty is quantified as the percent increase in the standard deviations caused by omitting the one observation location from the calculation of standard deviations. In general, observation locations associated with larger increases are rated as more important. (2) Ratings for largely geographically based groups are obtained using a straightforward extension of the method used for individual observation locations. This analysis is needed where observations are clustered to determine whether the area is important to the predictions of interest. (3) Finally, the method is used to evaluate omitting a set of 100 observation locations. The locations were selected because they had low individual ratings and were not one of the few locations at which hydraulic heads from deep in the system were measured. The major results of the three analyses, when applied to the three-layer DVRFS ground-water flow system, are described in the following paragraphs. The discussion is labeled using the numbers 1 to 3 to clearly relate it to the three ways the method is used, as listed above. (1) The individual observation location analysis indicates that three observation locations are most important. They are located in Emigrant Valley, Oasis Valley, and Beatty. Of importance is that these and other observations shown to be important by this analysis are far from the travel paths considered. This displays the importance of the regional setting within which the transport occurs, the importance of including some sites throughout the area in the monitoring network, and the importance of including sites in these areas in particular. The method considered in this report indicates that the 19 observation locations that reflect hydraulic heads deeper in the system (in model layers 1, 2, and 3) are not very important. This appears to be because the locations of these observations are in the vicinity of shallow observation locations that also generally are rated as low importance, and because the model layers are hydraulically well connected vertically. The value of deep observations to testing conceptual models, however, is stressed. As a result, the deep observations are rated higher than is consistent with the results of the analysis presented, and none of these observations are omitted in the scenario discussed under (3) below. (2) The geographic grouping of th

California, Nevada↗
USGS2019

Gopherus agassizii (Cooper 1861) – Agassiz’s Desert Tortoise, Mojave Desert Tortoise

The Mojave Desert Tortoise, Gopherus agassizii (Family Testudinidae), is a large terrestrial species that can reach >370 mm in straight midline carapace length (CL) but most individuals are smaller. Both sexes reach adulthood at 12 to 21 years and ca. 180 mm CL. The species is sexually dimorphic, with males typically larger than females; sexual characteristics of males become more obvious with increasing size and age. Females lay from 1 to 10 eggs per clutch and from 0 to 3 clutches annually, with eggs hatching after 67 to 104 days. Populations of G. agassizii have declined rapidly over the last several decades. Habitat throughout the geographic range has experienced major losses, degradation, and fragmentation as a result of urban and agricultural development, livestock grazing, military activities, transportation and utility corridors, high levels of visitor use, vehicle-oriented recreation, and energy development. Disturbed habitats were vulnerable to invading non-native grasses and forbs, creating an unnatural and destructive grass-fire cycle. When consumed by tortoises as their only diet, non-native (and native) grasses are harmful because of limited nutrients. Additionally, subsidized predators (Common Ravens, Coyotes, and dogs), infectious diseases, drought, and vandalism, add to the catastrophic effects of habitat loss and degradation. Tortoise populations have declined rapidly in density, and most populations are below viability, with fewer than 3.9 adults/km2. These declines occurred despite protections afforded by federal and state laws and regulations, ca. 26,000 km2 of federally designated critical habitat units, two Recovery Plans, and efforts to reduce the negative impacts of human activities. As noted by Allison and McLuckie (2018), the negative population trends in most of the critical habitat units suggest that under current conditions G. agassizii is on the path to extinction. Distribution. – USA. Distributed in parts of the southern Great Basin, Mojave, and western Sonoran deserts in southeastern California, southern Nevada, northwestern Arizona, and southwestern Utah, north and west of the Grand Canyon/Colorado River complex, with the exception of a small population east of the Colorado River. Synonymy. – Xerobates agassizii Cooper 1861, Testudo agassizii, Gopherus agassizii, Gopherus polyphemus agassizii, Scaptochelys agassizii, Xerobates lepidocephalus Ottley and Velázques Solis 1989. Subspecies . – None currently recognized. Status. – IUCN 2019 Red List: Vulnerable (VU A1acde+2cde; assessed 1996) ; TFTSG Provisional Red List: Critically Endangered (CR; assessed 2011, 2018); CITES: Appendix II (Testudinidae spp.); US ESA: Threatened.

Arizona, California, Nevada, Utah↗
USGS2013

Tectonic map of the Circum-Pacific region, Pacific basin sheet

Circum-Pacific Map Project : The Circum-Pacific Map Project was a cooperative international effort designed to show the relationship of known energy and mineral resources to the major geologic features of the Pacific basin and surrounding continental areas. Available geologic, mineral, and energy-resource data are being complemented by new, project-developed data sets such as magnetic lineations, seafloor mineral deposits, and seafloor sediment. Earth scientists representing some 180 organizations from more than 40 Pacific-region countries are involved in this work. Six overlapping equal-area regional maps at a scale of 1:10,000,000 form the cartographic base for the project: the four Circum-Pacific Quadrants (Northwest, Southwest, Southeast, and Northeast), and the Antarctic and Arctic Sheets. There is also a Pacific Basin Sheet at a scale of 1:17,000,000. The Base Map Series and the Geographic Series (published from 1977 to 1990), the Plate-Tectonic Series (published in 1981 and 1982), the Geodynamic Series (published in 1984 and 1985), and the Geologic Series (published from 1984 to 1989) all include six map sheets. Other thematic map series in preparation include Mineral-Resources, Energy-Resources and Tectonic Maps. Altogether, more than 50 map sheets are planned. The maps were prepared cooperatively by the Circum-Pacific Council for Energy and Mineral Resources and the U.S. Geological Survey and are available from the Branch of Distribution, U. S. Geological Survey, Box 25286, Federal Center, Denver, Colorado 80225, U.S.A. The Circum-Pacific Map Project is organized under six panels of geoscientists representing national earth-science organizations, universities, and natural-resource companies. The six panels correspond to the basic map areas. Current panel chairmen are Tomoyuki Moritani (Northwest Quadrant), R. Wally Johnson (Southwest Quadrant), Ian W.D. Dalziel (Antarctic Region), vacant. (Southeast Quadrant), Kenneth J. Drummond (Northeast Quadrant), and George W. Moore (Arctic Region). Project coordination and final cartography was being carried out through the cooperation of the Office of the Chief Geologist of the U.S. Geological Survey, under the direction of General Chairman, George Gryc of Menlo Park, California. Project headquarters were located at 345 Middlefield Road, MS 952, Menlo Park, California 94025, U.S.A. The framework for the Circum-Pacific Map Project was developed in 1973 by a specially convened group of 12 North American geoscientists meeting in California. The project was officially launched at the First Circum-Pacific Conference on Energy and Mineral Resources, which met in Honolulu, Hawaii, in August 1974. Sponsors of the conference were the AAPG, Pacific Science Association (PSA), and the Coordinating Committee for Offshore Prospecting for Mineral Resources in Offshore Asian Areas (CCOP). The Circum-Pacific Map Project operates as an activity of the Circum-Pacific Council for Energy and Mineral Resources, a nonprofit organization that promotes cooperation among Circum-Pacific countries in the study of energy and mineral resources of the Pacific basin. Founded by Michel T. Halbouty in 1972, the Council also sponsors conferences, topical symposia, workshops and the Earth Science Series books. Tectonic Map Series : The tectonic maps distinguish areas of oceanic and continental crust. Symbols in red mark active plate boundaries, and colored patterns show tectonic units (volcanic or magmatic arcs, arc-trench gaps, and interarc basins) associated with active plate margins. Well-documented inactive plate boundaries are shown by symbols in black. The tectonic development of oceanic crust is shown by episodes of seafloor spreading. These correlate with the rift and drift sequences at passive continental margins and episodes of tectonic activity at active plate margins. The recognized episodes of seafloor spreading seem to reflect major changes in plate kinematics. Oceanic plateaus and other prominences of greater than normal oceanic crustal thickness such as hotspot traces are also shown. Colored areas on the continents show the ages of deformation and metamorphism of basement rocks and the emplacement of igneous rocks. Transitional tectonic (molassic) and reactivation basins are shown by a colored boundary, and if they are deformed, a colored horizontal line pattern indicates the age of deformation. Colored bands along basin boundaries indicate age of inception, and isopachs indicate thickness of platform strata on continental crust and cover on oceanic crust. Colored patterns at separated continental margins show the age of inception of rift and drift (breakup) sequences. Symbols mark folds and faults, and special symbols show volcanoes and other structural features. Affiliations are as of compilation of the data. This map was created in quadrants and then compiled together. They are the Northwest land, Northwest Marine (different compilers), Northeast, Southwest and Southeast, and parts in plate-boundary sections.

Circum-Pacific Map↗
USGS2013

Geologic map of the Valley Mountain 15’ quadrangle, San Bernardino and Riverside Counties, California

The Valley Mountain 15’ quadrangle straddles the Pinto Mountain Fault, which bounds the eastern Transverse Ranges in the south against the Mojave Desert province in the north. The Pinto Mountains, part of the eastern Transverse Ranges in the south part of the quadrangle expose a series of Paleoproterozoic gneisses and granite and the Proterozoic quartzite of Pinto Mountain. Early Triassic quartz monzonite intruded the gneisses and was ductiley deformed prior to voluminous Jurassic intrusion of diorite, granodiorite, quartz monzonite, and granite plutons. The Jurassic rocks include part of the Bullion Mountains Intrusive Suite, which crops out prominently at Valley Mountain and in the Bullion Mountains, as well as in the Pinto Mountains. Jurassic plutons in the southwest part of the quadrangle are deeply denuded from midcrustal emplacement levels in contrast to supracrustal Jurassic limestone and volcanic rocks exposed in the northeast. Dikes inferred to be part of the Jurassic Independence Dike Swarm intrude the Jurassic plutons and Proterozoic rocks. Late Cretaceous intrusion of the Cadiz Valley Batholith in the northeast caused contact metamorphism of adjacent Jurassic plutonic rocks. The Tertiary period saw emplacement of basanitoid basalt at about 23 Ma and deposition of Miocene and (or) Pliocene ridge-capping gravels. An undated east-dipping low-angle normal fault zone in the Pinto Mountains drops hanging-wall rocks eastward and may account for part of the contrast in uplift history across the quadrangle. The eastern Transverse Ranges are commonly interpreted as severely rotated clockwise tectonically in the Neogene relative to the Mojave Desert, but similar orientations of Jurassic dike swarms suggest that any differential rotation between the two provinces is small in this quadrangle. The late Cenozoic Pinto Mountain Fault and other strike-slip faults cut Quaternary deposits in the quadrangle, with two northwest-striking faults cutting Holocene deposits. Geographic Information System and metadata on most geologic features are available on the Geologic map of the Sheep Hole Mountains 30’ by 60’ quadrangle, U.S. Geological Survey map MF–2234, scale 1:100,000, available at http://pubs.usgs.gov/mf/2002/2344/.

California↗
USGS2021

Exploring the regional dynamics of U.S. irrigated agriculture from 2002 to 2017

The United States has a geographically mature and stable land use and land cover system including land used as irrigated cropland; however, changes in irrigation land use frequently occur related to various drivers. We applied a consistent methodology at a 250 m spatial resolution across the lower 48 states to map and estimate irrigation dynamics for four map eras (2002, 2007, 2012, and 2017) and over four 5-year mapping intervals. The resulting geospatial maps (called the Moderate Resolution Imaging Spectroradiometer (MODIS) Irrigated Agriculture Dataset or MIrAD-US) involved inputs from county-level irrigated statistics from the U.S. Department of Agriculture, National Agricultural Statistics Service, agricultural land cover from the U.S. Geological Survey National Land Cover Database, and an annual peak vegetation index derived from expedited MODIS satellite imagery. This study investigated regional and periodic patterns in the amount of change in irrigated agriculture and linked gains and losses to proximal causes and consequences. While there was a 7% overall increase in irrigated area from 2002 to 2017, we found surprising variability by region and by 5-year map interval. Irrigation land use dynamics affect the environment, water use, and crop yields. Regionally, we found that the watersheds with the largest irrigation gains (based on percent of area) included the Missouri, Upper Mississippi, and Lower Mississippi watersheds. Conversely, the California and the Texas–Gulf watersheds experienced fairly consistent irrigation losses during these mapping intervals. Various drivers for irrigation dynamics included regional climate fluctuations and drought events, demand for certain crops, government land or water policies, and economic incentives like crop pricing and land values. The MIrAD-US (Version 4) was assessed for accuracy using a variety of existing regionally based reference data. Accuracy ranged between 70% and 95%, depending on the region.

Conterminous United States↗
USGS2007

Native Fish Sanctuary Project - Sanctuary Development Phase, 2007 Annual Report

Notable progress was made in 2007 toward the development of native fish facilities in the Lower Colorado River Basin. More than a dozen facilities are, or soon will be, online to benefit native fish. When this study began in 2005 no self-supporting communities of either bonytail or razorback sucker existed. Razorback suckers were removed from Rock Tank in 1997 and the communities at High Levee Pond had been compromised by largemouth bass in 2004. This project reversed that trend with the establishment of the Davis Cove native fish community in 2005. Bonytail and razorback sucker successfully produced young in Davis Cove in 2006. Bonytail successfully produced young in Parker Dam Pond in 2007, representing the first successful sanctuary established solely for bonytail. This past year, Three Fingers Lake received 135 large razorback suckers, and Federal and State agencies have agreed to develop a cooperative management approach dedicating a portion of that lake toward grow-out and (or) the establishment of another sanctuary. Two ponds at River's Edge Golf Course in Needles, California, were renovated in June and soon will be stocked with bonytail. Similar activities are taking place at Mohave Community College, Cerbat Cliffs Golf Course, Cibola High Levee Pond, Office Cove, Emerald Canyon Golf Course, and Bulkhead Cove. Recruitment can be expected as fish become sexually mature at these facilities. Flood-plain facilities have the potential to support 6,000 adult razorback suckers and nearly 20,000 bonytail if native fish management is aggressively pursued. This sanctuary project has assisted agencies in developing 15 native fish communities by identifying specific resource objectives for those sites, listing and prioritizing research opportunities and needs, and strategizing on management approaches through the use of resource-management plans. Such documents have been developed for Davis Cove, Cibola High Levee Pond, Parker Dam Pond, and Three Fingers Lake. We anticipate similar documents will be developed in the near future for River's Edge Golf Course Ponds, Office Cove, Emerald Canyon Golf Course Ponds, Bulkhead Cove, Mohave Community College, and Cerbat Cliffs Golf Course ponds as these facilities come on line or are developed in the future. The following report discusses the process that went into the development of these facilities. Sites were visited, assessed as to their suitability based on the control of nonnative predators, habitat suitability, conversion cost, logistics, geographical location, and willingness of landowners. They were then prioritized according to their suitability, cost, timely conversion, and willingness of landowners. Existing native fish facilities were included in this evaluation for their value in helping to determine physical and biological parameter ranges. This report describes the approaches that led to success, those leading to failure, and some of the biological, institutional, and management issues of implementing native fish sanctuary development.

Open-File Report↗