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

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At least 1,549 records · Page 86Linked to original sources
USGS2012

Distribution of potentially bioavailable natural organic carbon in aquifer sediments at a chloroethene-contaminated site

The distribution of natural organic carbon was investigated at a chloroethene-contaminated site where complete reductive dechlorination of tetrachloroethene (PCE) to vinyl chloride and ethene was observed. In this study, operationally defined potentially bioavailable organic carbon (PBOC) was measured in surficial aquifer sediment samples collected at varying depths and locations in the vicinity of a dense nonaqueous phase liquid (DNAPL) source and aqueous phase plume. The relationship between chloroethene concentrations and PBOC levels was examined by comparing differences in extractable organic carbon in aquifer sediments with minimal chloroethene exposure relative to samples collected in the source zone. Using performance-monitoring data, direct correlations with PBOC were also developed with chloroethene concentrations in groundwater. Results show a logarithm-normal distribution for PBOC in aquifer sediments with a mean concentration of 187 mg/kg. PBOC levels in sediments obtained from the underlying confining unit were generally greater when compared to sediments collected in the sandy surficial aquifer. Results demonstrated a statistically significant inverse correlation (p=0.007) between PBOC levels in aquifer sediments and chloroethene concentrations for selected monitoring wells in which chloroethene exposure was the highest. Results from laboratory exposure assays also demonstrated that sediment samples exhibited a reduction in PBOC levels of 35% and 73%, respectively, after a 72-h exposure period to PCE (20,000 μg/L). These results support the notion that PBOC depletion in sediments may be expected in chloroethene-contaminated aquifers, which has potential implications for the long-term sustainability of monitored natural attenuation.

South Carolina↗
USGS2011

Retesting of liquefaction and nonliquefaction case histories from the 1976 Tangshan earthquake

A field investigation was performed to retest liquefaction and nonliquefaction sites from the 1976 Tangshan earthquake in China. These sites were carefully investigated in 1978 and 1979 by using standard penetration test (SPT) and cone penetration test (CPT) equipment; however, the CPT measurements are obsolete because of the now nonstandard cone that was used at the time. In 2007, a modern cone was mobilized to retest 18 selected sites that are particularly important because of the intense ground shaking they sustained despite their high fines content and/or because the site did not liquefy. Of the sites reinvestigated and carefully reprocessed, 13 were considered accurate representative case histories. Two of the sites that were originally investigated for liquefaction have been reinvestigated for cyclic failure of fine-grained soil and removed from consideration for liquefaction triggering. The most important outcome of these field investigations was the collection of more accurate data for three nonliquefaction sites that experienced intense ground shaking. Data for these three case histories is now included in an area of the liquefaction triggering database that was poorly populated and will help constrain the upper bound of future liquefaction triggering curves.

Tangshan↗
USGS2022

On the role of climate in monthly baseflow changes across the continental United States

Baseflow is the portion of streamflow that comes from groundwater and subsurface sources. Although baseflow is essential for sustaining streams during low flow and drought periods, we have little information about how and why it has changed over large regions of the continental United States. The objective of this study was to evaluate how changes in the climate system have affected observed monthly baseflow records at 3,283 USGS gauges over the last 30 years (1989–2019). We developed a statistical modeling framework to determine the relationship between monthly baseflow and monthly climate predictors (i.e., precipitation, temperature, and antecedent wetness). Overall, we found that baseflow trends and the factors influencing them vary by region and month. In the US Northeast, increases were detected earlier in the year (February and March) and in the summer (May and June), and were likely due to increasing precipitation, warmer temperature, and subsequent changes in snowmelt. Increasing baseflow in the US Pacific Northwest and Midwest were associated with increases in precipitation and antecedent wetness throughout the year. Decreasing trends were located in the US Southeast and Southwest. Baseflow trends in the US Southeast were only detected in March, possibly as a result of decreased precipitation during the spring. On the other hand, decreases in baseflow in the Central Southwestern United States occurred throughout the year. These trends were associated with a lack of precipitation and increases in temperature. Finally, we examined the relationship between monthly baseflow trends and changes in total water storage using monthly Gravity Recovery and Climate Experiment mascon products from the Jet Propulsion Laboratory. In this study, trends in total water storage were strongly associated with baseflow trends across the United States. The spatial and temporal variability in baseflow response to climate reported here can aid water managers in adapting to future climate change.

continental United States↗
USGS2012

Facilitating fish passage at ultra low head dams: An alternative to dam removal

Ecosystem sustainability and returning the biological integrity to rivers continue to change the landscape of fish passage technology. Installing a conventional fishways has a limited degree of success in accommodating fish passage needs. Recently, the option of total dam removal has been gaining momentum among resource managers, conservationists, and even engineers. Certain dams, however, cannot be removed, and conventional fishways are either too expensive to build or the real estate is simply not available; yet freedom of passage must be attained. At the Little Falls Dam on the Potomac River a notch in the crest of the dam was installed to accommodate passage of fish. The notch has three labyrinth weirs used for energy dissipation. Water velocities are maintained at less than about 4 m/s anywhere within the passage structure during migratory season of the target species (American shad). Construction of this novel design was recently completed (March 2000) and future biological evaluations are ongoing. Copyright ASCE 2004.

Conference Paper↗
USGS2012

Modeling and model validation of wind-driven circulation in Upper Klamath Lake, Oregon

The hydrodynamics in the Upper Klamath Lake (UKL) plays a significant role in the water quality conditions of the lake. In order to provide a quantitative evaluation of the impacts of hydrodynamics on water quality in UKL, a detailed hydrodynamic model was implemented using an unstructured grid 3-D hydrodynamic model known as the UnTRIM model. The circulation in UKL is driven primarily by wind. Wind speed and direction time-series records were used as input, the numerical model reproduced the wind "set-up" and "set-down" at down wind and upwind ends of the lake, respectively. Of the two acoustic Doppler current profiler (ADCP) records, the UnTRIM model reproduced the measured velocity at the deep station. At the shallow station, the model results showed diurnal patterns that correlated well with wind variations, but the measured velocity showed water velocity sustained at 3 to 5 cm/sec or above. Discrepancies between the model results and observations at the shallow ADCP station is discussed on the basis of correct physics. If the field measurements are inconsistent with the known physics, there exists the possibility that the field data are suspect or the field data are revealing some physical processes that are not yet understood. Copyright ASCE 2005.

Conference Paper↗
USGS2012

Physical modeling of river spanning rock structures: Evaluating interstitial flow, local hydraulics, downstream scour development, and structure stability

Rock weir and ramp structures uniquely serve a necessary role in river management: to meet water deliveries in an ecologically sound manner. Uses include functioning as low head diversion dams, permitting fish passage, creating habitat diversity, and stabilizing stream banks and profiles. Existing information on design and performance of in-stream rock structures does not provide the guidance necessary to implement repeatable and sustainable construction and retrofit techniques. As widespread use of rock structures increases, the need for reliable design methods with a broad range of applicability at individual sites grows as well. Rigorous laboratory testing programs were implemented at the U.S. Bureau of Reclamation (Reclamation) and at Colorado State University (CSU) as part of a multifaceted research project focused on expanding the current knowledge base and developing design methods to improve the success rate of river spanning rock structures in meeting project goals. Physical modeling at Reclamation is being used to measure, predict, and reduce interstitial flow through rock ramps. CSU is using physical testing to quantify and predict scour development downstream of rock weirs and its impact on the stability of rock structures. ?? 2009 ASCE.

Conference Paper↗
USGS2012

Competing risks and the development of adaptive management plans for water resources: Field reconnaissance investigation of risks to fishes and other aquatic biota exposed to endocrine disrupting chemicals (edcs) in lake mead, Nevada USA

The analysis and characterization of competing risks for water resources rely on a wide spectrum of tools to evaluate hazards and risks associated with their management. For example, waters of the lower Colorado River stored in reservoirs such as Lake Mead present a wide range of competing risks related to water quantity and water quality. These risks are often interdependent and complicated by competing uses of source waters for sustaining biological resources and for supporting a range of agricultural, municipal, recreational, and industrial uses. USGS is currently conducting a series of interdisciplinary case-studies on water quality of Lake Mead and its source waters. In this case-study we examine selected constituents potentially entering the Lake Mead system, particularly endocrine disrupting chemicals (EDCs). Worldwide, a number of environmental EDCs have been identified that affect reproduction, development, and adaptive behaviors in a wide range of organisms. Many EDCs are minimally affected by current treatment technologies and occur in treated sewage effluents. Several EDCs have been detected in Lake Mead, and several substances have been identified that are of concern because of potential impacts to the aquatic biota, including the sport fishery of Lake Mead and endangered razorback suckers (Xyrauchen texanus) that occur in the Colorado River system. For example, altered biomarkers relevant to reproduction and thyroid function in fishes have been observed and may be predictive of impaired metabolism and development. Few studies, however, have addressed whether such EDC-induced responses observed in the field have an ecologically significant effect on the reproductive success of fishes. To identify potential linkages between EDCs and species of management concern, the risk analysis and characterization in this reconnaissance study focused on effects (and attendant uncertainties) that might be expressed by exposed populations. In addition, risk reduction measures that may be of interest to resource managers are considered relative to emerging contaminants in treated effluents, interdependencies among biological resources at risk, and uses of reservoir waters derived from multiple inflows of widely varying qualities. ??2009 ASCE.

Nevada↗
USGS2012

Planned updates and refinements to the Central Valley hydrologic model with an emphasis on improving the simulation of land subsidence in the San Joaquin Valley

California's Central Valley has been one of the most productive agricultural regions in the world for more than 50 years. To better understand the groundwater availability in the valley, the U.S. Geological Survey (USGS) developed the Central Valley hydrologic model (CVHM). Because of recent water-level declines and renewed subsidence, the CVHM is being updated to better simulate the geohydrologic system. The CVHM updates and refinements can be grouped into two general categories: (1) model code changes and (2) data updates. The CVHM updates and refinements will require that the model be recalibrated. The updated CVHM will provide a detailed transient analysis of changes in groundwater availability and flow paths in relation to climatic variability, urbanization, stream flow, and changes in irrigated agricultural practices and crops. The updated CVHM is particularly focused on more accurately simulating the locations and magnitudes of land subsidence. The intent of the updated CVHM is to help scientists better understand the availability and sustainability of water resources and the interaction of groundwater levels with land subsidence.

California↗
USGS2013

The science, information, and engineering needed to manage water availability and quality in 2050

This chapter explores four water resources issues: 1) hydrologic variability, hazards, water supply and ecosystem preservation; 2) urban landscape design; 3) non-point source water quality, and 4) climate change, resiliency, and nonstationarity. It also considers what science, technology, and engineering practice may be needed in the coming decades to sustain water supplies and ecosystems in the face of increasing stresses from a growing demand for water. Dealing with these four water resource issues in the highly uncertain future would will demand predictive models that are rooted in real-world data. In a non-stationary world, continuity of observations is crucial. All watersheds are influenced by human actions through changes in land use, water use, and climate. The focus of water planning and management between today and 2050 will depend more than ever on collection and analysis of long-term data to learn about the evolving state of the system, understanding ecosystem processes in the water and on the landscape, and finding innovative ways to manage water as a shared resource. This includes sharing water with our neighbors on the landscape, sharing with the other species that depend on water, and sharing with future generations.

Book chapter↗
USGS2019

The Value of Data – The Qatar Geologic Mapping Project

The State of Qatar is in a period of rapid development, modernization, and population growth. One of the most important factors influencing the long-term success and sustainability of future development is a comprehensive understanding of the region’s geologic regime, geotechnical conditions, natural resources, and environmental constraints. To obtain this understanding, the Ministry of Municipality and Environment (MME) of the State of Qatar has undertaken the Qatar Geological Mapping Project (QGMP). The project was envisioned with the strategic foresight to compile and utilize existing and legacy subsurface data collected as part of its massive infrastructure and development projects as the foundation for developing modern scientific resources including geologic maps, digital thematic maps, and a 3-dimensional geological model of the Doha metropolitan area. Recently, the MME, in consultation with Gannett Fleming, Inc. (GF) and the United States Geological Survey (USGS) concluded the data collection and analysis phase (Phase I) of the two-phase QGMP. Phase I included: the development of a comprehensive geotechnical relational database populated with data digitized from more than 13,000 subsurface data logs; a detailed data quality analysis and distribution assessment; an extensive gap analysis and needs assessment; and careful design of the geologic mapping and subsurface investigation programs for the next phase of the project.

Conference Paper↗
USGS2026

Multireservoir allocation framework considering societal and ecological needs in a time-frequency domain

Existing reservoir management frameworks traditionally consider historical (predam) flow conditions to deliver environmental flows. Such frameworks may not be feasible because current demand and/or climate could be different from predam conditions. Hence, we developed a multireservoir framework that explicitly considers both human water demands and environmental flow requirements to minimize deviations under current hydroclimatic conditions and demand patterns. The multireservoir framework, Generalized Reservoir Analyses using Probabilistic Streamflow (GRAPS), was modified and implemented to solve the problem of minimizing the flow deviations using feasible sequential quadratic programming for three reservoirs in the Chattahoochee River Basin, Southeastern United States, which is known for its imperiled native biodiversity and productive estuarine ecosystem. Our results show that downstream reservoirs in the cascade system are less influenced by upstream reservoirs’ regulation because the downstream reservoirs receive a significant amount of natural flows. By comparing the average wavelet power spectrum at different periodicities between natural flows and downstream releases, we found that the current release policy and modified releases resulted in highly altered flows under shorter periodicities (e.g., less than 2 months) but synchronized flow variance between natural flow and downstream releases at longer periodicities (e.g., greater than 3 years). This framework of linking the multireservoir allocation model through the time–frequency analysis using wavelet power spectrum could not only advance sustainable water management policies to meet water for human and environmental needs but can also add additional value in meeting the downstream environmental demand at desired periodicities.

Alabama, Florida, Georgia↗
USGS2022

Maintaining wetland ecosystem services in a changing climate

A changing climate is causing challenges for soil and water management in many parts of the world. Current soil management practices need to be redesigned to effectively address present and future fluctuating climates. Soil Hydrology in a Changing Climate explores how soil management practices impact soil hydrological characteristics, and how we can improve our understanding of soil and water management under changing conditions. Soil hydrology includes water infiltration and soil water storage, which are critical for agricultural plant and animal production. With our future climate predicted to include hotter, drier conditions, increases in evapotranspiration as well as fewer, more intense storms, improved soil management and soil hydrology are critical to ensuring our agriculture production can meet human demand. This comprehensive book is a valuable resource for land managers, soil conservationists, researchers and others who wish to understand how different management practices affect soil and water dynamics and how these practices can be adjusted to enhance agricultural sustainability and environmental quality.

Book chapter↗
USGS2014

Spatial structuring within a reservoir fish population: implications for management

Spatial structuring in reservoir fish populations can exist because of environmental gradients, species-specific behaviour, or even localised fishing effort. The present study investigated whether white crappie exhibited evidence of improved population structure where the northern more productive half of a lake is closed to fishing to provide waterfowl hunting opportunities. Population response to angling was modelled for each substock of white crappie (north (protected) and south (unprotected) areas), the entire lake (single-stock model) and by combining simulations of the two independent substock models (additive model). White crappie in the protected area were more abundant, consisting of larger, older individuals, and exhibited a lower total annual mortality rate than in the unprotected area. Population modelling found that fishing mortality rates between 0.1 and 0.3 resulted in sustainable populations (spawning potential ratios (SPR) >0.30). The population in the unprotected area appeared to be more resilient (SPR > 0.30) at the higher fishing intensities (0.35–0.55). Considered additively, the whole-lake fishery appeared more resilient than when modelled as a single-panmictic stock. These results provided evidence of spatial structuring in reservoir fish populations, and we recommend model assessments used to guide management decisions should consider those spatial differences in other populations where they exist.

Marine and Freshwater Research↗
USGS2000

Seagrass responses to and recovery (?) from seven years of brown tide

Most harmful algal blooms are relatively short, violent paroxysms to aquatic systems. The Texas brown tide was unique in its 7-year domination of upper Laguna Madre wherein it reduced light penetrating 1 m from 31 to 63% on an annual basis between June 1990 and May 1997. In response, seagrasses declined in biomass in deep areas for two years. Over the next three years, bare areas opened up in the deepest areas of the seagrass meadow and the outer seagrass boundary retreated landward. In the last two years of the brown tide, regression of the dominant species, Halodule wrightii, slowed and stopped, and Halophila engelmanni, a previously minor species, revegetated some areas. Subsequent to cessation of meadow retreat, water clarity improved to pre-brown tide levels, consistent with the hypothesis that regeneration of nutrients from retreating seagrass meadow may have been the source of the nutrient subsidy required to sustain the brown tide at high concentration. However, after a short interlude of clear water and Halodule recovery, a resurgence of the bloom occurred and areas of regrowth succumbed. Although human activities did not seem to be involved in initiation or persistence of the brown tide, nutrients brought in by runoff from agricultural lands may have contributed to the return of bloom conditions.

Texas↗
USGS2020

Linking nest microhabitat selection to nest survival within declining pheasant populations in the Central Valley of California

Context: The ring-necked pheasant ( Phasianus colchicus ) has experienced considerable population declines in recent decades, especially in agricultural environments of the Central Valley of California. Although large-scale changes in land cover have been reported as an important driver of population dynamics, the effects of microhabitat conditions on specific demographic rates (e.g. nesting) are largely unknown. Aims: Our goal was to identify the key microhabitat factors that contribute to wild pheasant fitness by linking individual-level selection of each microhabitat characteristic to the survival of their nests within the California Central Valley. Methods: We radio- or GPS-marked 190 female ring-necked pheasants within five study areas and measured nest-site characteristics and nest fates during 2013–2017. Specifically, we modeled microhabitat selection using vegetation covariates measured at nest sites and random sites and then modeled nest survival as a function of selecting each microhabitat characteristic. Key results: Female pheasants tended to select nest sites with greater proportions of herbaceous cover and avoided areas with greater proportions of bare-ground. Specifically, perennial grass cover was the most explanatory factor with regard to nest survival, but selection for increasing visual obstruction alone was not shown to have a significant effect on survival. Further, we found strong evidence that pheasants selecting sites with greater perennial grass height were more likely to have successful nests. Conclusions: Although pheasants will select many types of vegetation available as cover, our models provided evidence that perennial grasses are more beneficial than other cover types to pheasants selecting nesting sites. Implications: Focusing management actions on promoting perennial grass cover and increased heights at the microsite level, in lieu of other vegetative modifications, may provide improved quality of habitat for nesting pheasants and, perhaps, result in increased productivity. This is especially important if cover is limited during specific times of the nesting period. Understanding how microhabitat selection influences fitness can help land managers develop strategies to increase the sustainability of hunted populations of this popular game-bird species.

California↗
USGS2023

Movement ecology of adult and juvenile spotted turtles (Clemmys guttata) in a seasonally dynamic environment

Context Understanding the temporal and spatial scales at which wildlife move is vital for conservation and management. This is especially important for semi-aquatic species that make frequent inter-wetland movements to fulfil life-history requirements. Aims We aimed to investigate the drivers of movement and space-use of the imperilled spotted turtle ( Clemmys guttata ), a seasonal wetland specialist, in three large, isolated wetland complexes in Virginia, USA. Methods We used VHF radio-transmitters to radio-locate adult and juvenile turtles, and estimated movement and space-use during their active and aestivation seasons (March–August). We then used generalised linear mixed models to examine how movement and space-use varied, based on intrinsic turtle characteristics and extrinsic wetland and climatic factors. Key results We show that, on average, individual spotted turtles used five wetlands per year (range 3–13), and that their inter-wetland movement and movement distance varied seasonally in accordance with wetland availability and breeding phenology. Spotted turtle movement and space-use was influenced by the arrangement and size of the wetland complexes, with turtles moving further and occupying larger home-ranges as size and distance between wetlands increased. Inter-wetland movement was not influenced by intrinsic turtle effects but larger adult turtles moved further, used more wetlands, and had larger home-ranges than smaller turtles. Conclusions Turtle responses to variation in season and wetland configuration highlight the need for complex and dynamic landscapes required to sustain this species. Implications This study has important conservation implications showing that spotted turtles rely on a large number of diverse wetlands, as well as upland habitat, to fulfil their resource needs – and that these habitat associations vary seasonally. Results from our study can aid the understanding of spatial and temporal variation in patch characteristics (e.g. quality and extent) and inter-patch movement by organisms, which is critical for the conservation and management of semi-aquatic species and other organisms that occupy patchy habitat complexes.

Wildlife Research↗
USGS2024

Mesocarnivores in residential yards: Influence of yard features on the occupancy, relative abundance, and overlap of coyotes, grey fox, and red fox

Context As conversion of natural areas to human development continues, there is a lack of information about how developed areas can sustainably support wildlife. While large predators are often extirpated from areas of human development, some medium-bodied mammalian predators (hereafter, mesocarnivores) have adapted to co-exist in human-dominated areas. Aims How human-dominated areas such as residential yards are used by mesocarnivores is not well understood. Our study aimed to identify yard and landscape features that influence occupancy, relative abundance and spatial-temporal overlap of three widespread mesocarnivores, namely, coyote ( Canis latrans ), grey fox ( Urocyon cineroargenteus ) and red fox ( Vulpes vulpes ). Methods Over the summers of 2021 and 2022, we deployed camera-traps in 46 and 96 residential yards, spanning from low-density rural areas (<1 home per km 2 ) to more urban areas (589 homes per km 2 ) in north-western Arkansas, USA. Key results We found that mesocarnivore occupancy was marginally influenced by yard-level features as opposed to landscape composition. Fences reduced the occupancy probability of coyotes, although they were positively associated with the total area of potential shelter sites in a yard. We found that relative abundance of grey fox was highest in yards with poultry, highlighting a likely source of conflict with homeowners. We found that all three species were primarily nocturnal and activity overlap between the species pairs was high. Conclusions Thus, these species may be using spatio-temporal partitioning to avoid antagonistic encounters and our data supported this, with few examples of species occurring in the same yards during the same 24-h period. Implications As the number of residential yards continues to grow, our results suggested that there are ways in which our yards can provide resources to mesocarnivores and that homeowners also have agency to mitigate overlap with mesocarnivores through management of their yard features.

Arkansas, Missouri↗
USGS2007

A cold phase of the East Pacific triggers new phytoplankton blooms in San Francisco Bay

Ecological observations sustained over decades often reveal abrupt changes in biological communities that signal altered ecosystem states. We report a large shift in the biological communities of San Francisco Bay, first detected as increasing phytoplankton biomass and occurrences of new seasonal blooms that began in 1999. This phytoplankton increase is paradoxical because it occurred in an era of decreasing wastewater nutrient inputs and reduced nitrogen and phosphorus concentrations, contrary to the guiding paradigm that algal biomass in estuaries increases in proportion to nutrient inputs from their watersheds. Coincidental changes included sharp declines in the abundance of bivalve mollusks, the key phytoplankton consumers in this estuary, and record high abundances of several bivalve predators: Bay shrimp, English sole, and Dungeness crab. The phytoplankton increase is consistent with a trophic cascade resulting from heightened predation on bivalves and suppression of their filtration control on phytoplankton growth. These community changes in San Francisco Bay across three trophic levels followed a state change in the California Current System characterized by increased upwelling intensity, amplified primary production, and strengthened southerly flows. These diagnostic features of the East Pacific "cold phase" lead to strong recruitment and immigration of juvenile flatfish and crustaceans into estuaries where they feed and develop. This study, built from three decades of observation, reveals a previously unrecognized mechanism of ocean-estuary connectivity. Interdecadal oceanic regime changes can propagate into estuaries, altering their community structure and efficiency of transforming land-derived nutrients into algal biomass.

California↗