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At least 91 records · Page 5Linked to original sources
USGS1905

Preliminary list of deep borings in the United States

The first preliminary list of deep borings in the United States was issued as Water-Supply Papers Nos. 57 and 61. The present publication includes all of the wells listed in these two papers, together with many additional borings, mostly of recent date. Messrs. M. L. Fuller and A. C. Veatch, of the eastern section of hydrology, and other geologists of the Survey have contributed many new data. Descriptions of borings published in reports issued since 1901 have been incorporated as far as practicable. All the entries are by counties. The wells and borings reported in the paper are all more than 400 feet in depth. The information concerning them has been obtained partly from replies to circular letters sent to all parts of the United States and partly from geological reports and other published sources. Owing to the difficulty of obtaining replies to the circulars, to lack of knowledge on the part of correspondents, and to the incompleteness of published records, doubtless there are borings which have not been reported. In regions of oil and gas wells, where borings are numerous, the individual wells can not be listed here, but representative wells are given. References to logs or records of the wells or extended descriptions of them are given in footnotes, and after the list of wells in each State there is added a list of the principal publications relating to deep borings in that State. The bearing of the information given in the columns of the lists probably is apparent unless, perhaps, in the one headed "Height to which the water rises." In this column an entry such as "-45" indicates that the water rises to within 45 feet of the surface; "+45" indicates that it is a flowing well and has sufficient head to raise the water 45 feet above the surface in an open pipe 45 feet or more in height. The yield in gallons per minute usually is estimated. Depths and diameters often have been reported from memory and different sources of publication sometimes give different figures. Most wells which are not stated to be "for oil," "for gas," "brine," "abandoned," etc., in the remarks column, or "not any" in the yield column, generally afford more or less water. Many of the gas and oil wells, active or abandoned, yield salt water.

Water Supply Paper↗
USGS2009

Social, political, and institutional setting: Water management problems of the Rio Grande

This paper discusses various water management issues facing federal, state, and local agencies charged with managing the water resources of the Rio Grande River Basin and its major tributaries. The Rio Grande - 3,058 km (=1,900 mi) long - is the fourth longest river in the United States. The river's basin is 870,236 km 2 (=336,000 mi 2 ) and for roughly two-thirds of its length it forms the United States-Mexican border. It is a major recreational resource providing world class trout fishing near its headwaters in Colorado's San Juan Mountains and shoreline, angling, and boating opportunities near the Colorado-New Mexico border. The Rio Grande is the principal tourist attraction of Big Bend National Park and flows through downtown Albuquerque and El Paso. Many reaches are wide and broad, but almost all are relatively shallow and not navigable by commercial ships. Nevertheless, it is one of the most important renewable water resources of the southwestern United States and North America. The issue of the "manageability" of the river in the face of social forces and disparate administrative jurisdictions that adversely impact Rio Grande flows is a thread linking various sections of the paper together. The length of the river; the fact that major reaches lie in Colorado, New Mexico, and Texas; and its unique role as an international boundary pose complex management problems. The allocation status quo formed by the complex nexus of existing river laws make it difficult to reshape Rio Grande management. ?? 2009 ASCE.

Journal of Water Resources Planning and Management↗
USGS1998

Issues and prospects for the next generation of the spatial data transfer standard (SDTS)

The Spatial Data Transfer Standard (SDTS) was designed to be capable of representing virtually any data model, rather than being a prescription for a single data model. It has fallen short of this ambitious goal for a number of reasons, which this paper investigates. In addition to issues that might have been anticipated in its design, a number of new issues have arisen since its initial development. These include the need to support explicit feature definitions, incremental update, value-added extensions, and change tracking within large, national databases. It is time to consider the next stage of evolution for SDTS. This paper suggests development of an Object Profile for SDTS that would integrate concepts for a dynamic schema structure, OpenGIS interface, and CORBA IDL.

International Journal of Geographical Information ↗
USGS2011

Toward the next generation of research on earthquake-induced landslides: Current issues and future challenges

Although, thanks to the new developments in investigation techniques, modeling, and data analyses, much progress has been made in our understanding of collateral seismic hazards, important new lessons are still being learned from historic and recent earthquakes. By referring to the accompanying papers included in this Special Issue and other recent literature, we present an overview of current issues and future challenges of research on earthquake, triggered landsliding. We also offer some recommendations for future research priorities, as a proposed starting point for the next generation of research on earthquake-induced slope failures. These include i) the compilation of many more complete seismic landslide inventories with adequate contextual information, as well as of retrospective inventories; ii) the improvement of regional-scale assessments of seismic landslide susceptibility and hazard; iii) the development of new methods for regional scale analysis of hazards from large catastrophic landslides; and iv) the long-term monitoring of representative test slopes instrumented with an array of accelerometer stations.

Engineering Geology↗
USGS1998

The Soufriere Hills eruption, Montserrat, British West Indies: Introduction to special section, part 1

The special section on the eruption of Soufriere Hills volcano is a collection of 24 papers that summarises the early scientific work of the Montserrat Volcano Observatory. Part 1 of the special section, published in a previous issue of GRL , provided a sampling of the multidisciplinary investigations undertaken at Montserrat. The papers published in Part 1 included an overview of the eruption, investigations on seismicity, ground deformation studies, and petrology. The papers of this issue comprise Part 2 of the special section. These papers also cover a broad spectrum of topics, including various topics in seismology, petrology, pyroclastic flow models, gas chemistry, hydrothermal systems, and tsunami models. In general, papers in Part 1 may be said to be more observational- or data-orientated, and those of Part 2 more model-orientated, but indeed there is much overlap of descriptive material, data, and modelling within the individual contributions. Considered in total the collection presents a representative summary of the scientific effort carried out in Montserrat through much of 1997.

Geophysical Research Letters↗
USGS2012

Mysis diluviana and Hemimysis anomala : reviewing the roles of a native and invasive mysid in the Laurentian Great Lakes region

Mysis diluviana and Hemimysis anomala are the only two species of mysid shrimps in the order Mysidacea that are present in the Laurentian Great Lakes of North America. M. diluviana has inhabited the deep, cold waters of this region since Pleistocene-era glacial retreat and is widely considered to have a central role in the functioning of offshore food webs in systems they inhabit. More recently, the Great Lakes were invaded by the Ponto-Caspian native Hemimysis , a species that inhabits warmer water and shallower depths relative to M. diluviana . Hemimysis has rapidly expanded throughout the Great Lakes region and has become integrated into nearshore food webs as both food for planktivorous fish and predators and competitors of zooplankton. This special issue is composed of 14 papers that represent the most recent advances in our understanding of the ecological importance of both species of mysids to lake and river ecosystems in the Great Lakes region of North America. Topics discussed in this special issue will inform future research in all systems influenced by mysid ecology.

Lake Erie;Lake Huron;Lake Michigan;Lake Ontario;La↗
USGS2009

Modeling individual animal histories with multistate capture–recapture models

Many fields of science begin with a phase of exploration and description, followed by investigations of the processes that account for observed patterns. The science of ecology is no exception, and recent decades have seen a focus on understanding key processes underlying the dynamics of ecological systems. In population ecology, emphasis has shifted from the state variable of population size to the demographic processes responsible for changes in this state variable: birth, death, immigration, and emigration. In evolutionary ecology, some of these same demographic processes, rates of birth and death, are also the determinants of fitness. In animal population ecology, the estimation of state variables and their associated vital rates is especially problematic because of the difficulties in sampling such populations and detecting individual animals. Indeed, early capture–recapture models were developed for the purpose of estimating population size, given the reality that all animals are not caught or detected at any sampling occasion. More recently, capture–recapture models for open populations were developed to draw inferences about survival in the face of these same sampling problems. The focus of this paper is on multi‐state mark–recapture models (MSMR), which first appeared in the 1970s but have undergone substantial development in the last 15 years. These models were developed to deal explicitly with biological variation, in that animals in different “states” (classes defined by location, physiology, behavior, reproductive status, etc.) may have different probabilities of survival and detection. Animal transitions between states are also stochastic and themselves of interest. These general models have proven to be extremely useful and provide a way of thinking about a remarkably wide range of important ecological processes. These methods are now at a stage of refinement and sophistication where they can readily be used by biologists to tackle a wide range of important issues in ecology. In this paper, we draw together information on the state of the art in multistate mark–recapture methods, explaining the models and illustrating their use. We provide a modeling philosophy and a series of general principles on how to conduct analyses. We cover key issues and features, and we anticipate the ways in which we expect the models to develop in the years ahead.

Advances in Ecological Research↗
USGS2000

Strong-motion, site-effects and hazard issues in rebuilding Turkey: In light of the 17 August, 1999 earthquake and its aftershocks

The August 17, 1999 Izmit (Turkey) earthquake (Mw=7.4) will be remembered as one of the largest earthquakes of recent times that affected a large urban environment (U.S. Geological Survey, 1999). The shaking that caused the widespread damage and destruction was recorded only by a handful of accelerographs in the earthquake area operated by different networks. The characteristics of these records show that the recorded peak accelerations, even those from near field stations, are smaller than expected. On the other hand, smaller magnitude aftershocks yielded larger peak accelerations. This is attributed to the sparse networks, which possibly missed recording of larger motions during the main shock. As rebuilding of Turkey starts, strong-motion networks that yield essential data must be enlarged. In addition, attention must be paid to new developments elsewhere, such as earthquake zoning maps, earthquake hazard maps, liquefaction potentials and susceptibility. This paper aims to discuss these issues. Copyright??2000 IAHS.

International Journal for Housing Science and Its ↗
USGS2004

Ecological and political issues surrounding decommissioning of offshore oil facilities in the Southern California Bight

To aid legislators, resource managers, and the general public, this paper summarizes and clarifies some of the issues and options that the federal government and the state of California face in decommissioning offshore oil and gas production platforms, particularly as these relate to platform ecology. Both local marine ecology and political climate play a role in decommissioning offshore oil production platforms. Compared to the relatively supportive political climate in the Gulf of Mexico for “rigs-to-reefs” programs, conflicting social values among stakeholders in Southern California increases the need for understanding ecological impacts of various decommissioning alternatives (which range from total removal to allowing some or all of platform structure to remain in the ocean). Additional scientific needs in the decommissioning process include further assessment of platform habitat quality, estimation of regional impacts of decommissioning alternatives to marine populations, and determination of biological effects of any residual contaminants. The principal management need is a ranking of environmental priorities (e.g. species-of-interest and marine habitats). Because considerable numbers of economically important species reside near oil platforms, National Oceanic and Atmospheric Administration Fisheries should consider the consequences of decommissioning alternatives in their overall management plans. Management strategies could include designating reefed platforms as marine protected areas. The overarching conclusion from both ecological and political perspectives is that decommissioning decisions should be made on a case-by-case basis.

Ocean and Coastal Management↗
USGS2006

Introduction to ‘Antarctic climate evolution: View from the margin’

This special issue on “Antarctic Climate Evolution—view from the margin” presents results from modelling studies and reports on geoscience data aimed at improving our understanding of the behaviour of the Antarctic ice sheet and the climate of the region. This research field is of interest because of the sensitivity of the polar regions to global warming, and because of the influence of the Antarctic ice sheet on global sea level and climate through most if not all of the Cenozoic Era. The Antarctic ice sheet both responds to and forces changes on global climate and sea level. We need to be aware of the scale and frequency of these changes if we are to understand past patterns of environmental change elsewhere on earth. It was only three decades ago that we discovered from strata drilled in shelf basins on the Antarctic margin that the Antarctic ice sheet had a history that predated the Quaternary ice ages by over 20 million years ( Hayes et al., 1975 ). Later that year the first interpretation of Antarctic glacial history through the Cenozoic Era from oxygen isotopes, recorded in foraminifera from deep-sea sediment cores, was published ( Shackleton and Kennett, 1975 ). Revisions with a more extensive database have modified the story a little ( Miller et al., 1987 , Zachos et al., 2001 ), and there have been recent attempts to resolve the temperature–ice volume ambiguity ( Lear et al., 2000 ). However, reports on strata drilled on the Antarctic margin have unambiguously shown the character of this huge ice sheet, which was oscillating in the Oligocene ( Barrett et al., 1987 , Barrett, 1999 ) with a period and magnitude comparable with the Northern Hemisphere ice sheets of the Quaternary ( Naish et al., 2001a , Naish et al., 2001b ). In this issue we present further research on the history of the Antarctic ice sheet from Oligocene to recent times, most of them from the Antarctic margin, but with some on the nature of the deep-sea isotope record, and others using recently developed modeling techniques to investigate the influence of atmosphere, ocean and biosphere on past Antarctic climate. This special issue is the third in three years on the theme of Antarctic Climate Evolution. The first followed a workshop in Erice, Sicily, in 2001 to report on results from ANTOSTRAT, a SCAR-sponsored project for gathering and analysing circum-Antarctic seismic data for planning and promoting offshore drilling for climate history. The introduction to that issue (Florindo et al., 2003) provides a review of the recent history of circum-Antarctic drilling by the Ocean Drilling Program (Legs 113, 114, 119, 120, 177, 178, 188 and 189) and the Cape Roberts Project. For a more comprehensive review of earlier drilling in the Ross Sea region (Deep Sea Drilling Project Leg 28, Dry Valley Drilling Project, McMurdo Sound Sediment and Tectonic Studies, Cenozoic Investigations in the western Ross Sea) see Hambrey and Barrett (1993). The first of these issues (Florindo et al., 2003) featured a global plate reconstruction of the Southern Hemisphere through Cenozoic time with emphasis on evolution of Cenozoic seaways (Lawver and Gahagan, 2003) along with a study of the inception and early evolution of the EAIS using a new coupled global climate (GCM)–dynamic ice sheet model (DeConto and Pollard, 2003b), as well as data from recent drilling around the margin covering time period from Cretaceous to the present. A second special issue on the same theme (Florindo et al., 2005) also featured a mix of modelling and data papers with a focus on the Eocene–Oligocene boundary and the initiation of ice sheet growth, including a pioneering attempt to evaluate the relative influence of fluvial versus glacial processes in shaping the landscape of the Prydz Bay sector of Antarctica (Jamieson et al., 2005). The remainder of the issue comprised further papers on seismic stratigraphy and reports from drilling around the margin. The papers to be found in this special issue, like the previous two, maintain the mix of modelling- and data-oriented papers that reflect the range of this research.

Palaeogeography, Palaeoclimatology, Palaeoecology↗
USGS2011

Diel biogeochemical processes in terrestrial waters

Many biogeochemical processes in rivers and lakes respond to the solar photocycle and produce persistent patterns of measureable phenomena that exhibit a day–night, or 24-h, cycle. Despite a large body of recent literature, the mechanisms responsible for these diel fluctuations are widely debated, with a growing consensus that combinations of physical, chemical, and biological processes are involved. These processes include streamflow variation, photosynthesis and respiration, plant assimilation, and reactions involving photochemistry, adsorption and desorption, and mineral precipitation and dissolution. Diel changes in streamflow and water properties such as temperature, pH, and dissolved oxygen concentration have been widely recognized, and recently, diel studies have focused more widely by considering other constituents such as dissolved and particulate trace metals, metalloids, rare earth elements, mercury, organic matter, dissolved inorganic carbon (DIC), and nutrients. The details of many diel processes are being studied using stable isotopes, which also can exhibit diel cycles in response to microbial metabolism, photosynthesis and respiration, or changes in phase, speciation, or redox state. In addition, secondary effects that diel cycles might have, for example, on biota or in the hyporheic zone are beginning to be considered. This special issue is composed primarily of papers presented at the topical session “Diurnal Biogeochemical Processes in Rivers, Lakes, and Shallow Groundwater” held at the annual meeting of the Geological Society of America in October 2009 in Portland, Oregon. This session was organized because many of the growing number of diel studies have addressed just a small part of the full range of diel cycling phenomena found in rivers and lakes. This limited focus is understandable because (1) fundamental aspects of many diel processes are poorly understood and require detailed study, (2) the interests and expertise of individual scientists typically do not encompass the wide diversity and range of processes that produce diel cycles, and (3) the logistics of making field measurements for 24-h periods has limited recognition and understanding of these important cycles. Thus, the topical session brought together hydrologists, biologists, geochemists, and ecologists to discuss field studies, laboratory experiments, theoretical modeling, and measurement techniques related to diel cycling. Hopefully with the cross-disciplinary synergy developed at the session as well as by this special issue, a more comprehensive understanding of the interrelationships between the diel processes will be developed. Needless to say, understanding diel processes is critical for regulatory agencies and the greater scientific community. And perhaps more importantly, expanded knowledge of biogeochemical cycling may lead to better predictions of how aquatic ecosystems might react to changing conditions of contaminant loading, eutrophication, climate change, drought, industrialization, development, and other variables.

Chemical Geology↗
USGS2005

Comment on "How can seismic hazard around the New Madrid seismic zone be similar to that in California?" by Arthur Frankel

A recent paper in the September/October 2004 issue of Seismological Research Letters, “How Can Seismic Hazard around the New Madrid Seismic Zone Be Similar to That in California?”, by Arthur Frankel, concludes “I have demonstrated how probabilistic seismic hazard for New Madrid can be greater than that at San Francisco at low probabilities for PGA and similar at low probabilities for 5 Hz S.A. By low probabilities, I mean annual probabilities less than the reciprocal of the return time of the New Madrid characteristic source, that is, 1/500. This is a consequence of the higher ground motions, for PGA and 5 Hz S.A. (and other high-frequency measures), expected for large New Madrid characteristic earthquakes compared to San Andreas earthquakes with similar magnitudes.” His conclusion is confusing and not necessarily true. The fundamental differences in assessing seismic hazard between San Francisco and the New Madrid seismic zone are the uncertainties, especially the uncertainties associated with the ground-motion attenuation relationship. The larger ground-motion uncertainties in both the median and its standard deviation derive a higher hazard in the New Madrid area. The larger standard deviation, in particular, derives a higher hazard at low annual probabilities of exceedance. Moreover, Frankel also equated the hazard (annual probability of exceedance) defined in probabilistic seismic hazard analysis (PSHA) with the average recurrence rate defined in engineering risk analysis. There is a fundamental difference in defining risk between PSHA and the engineering risk analysis. The risks—10%, 5%, and 2% probability of exceedance (PE) in 50 years—defined in PSHA are not interchangeable with those defined in engineering risk analysis. Hence, though Frankel's stated intention was to improve understanding of PSHA among nonpractitioners, the paper may cause more confusion and problems for users of the U.S. Geological Survey national seismic hazard maps.

Seismological Research Letters↗
USGS2012

The ChemCam Instrument Suite on the Mars Science Laboratory (MSL) Rover: Science objectives and mast unit description

ChemCam is a remote sensing instrument suite on board the "Curiosity" rover (NASA) that uses Laser-Induced Breakdown Spectroscopy (LIBS) to provide the elemental composition of soils and rocks at the surface of Mars from a distance of 1.3 to 7 m, and a telescopic imager to return high resolution context and micro-images at distances greater than 1.16 m. We describe five analytical capabilities: rock classification, quantitative composition, depth profiling, context imaging, and passive spectroscopy. They serve as a toolbox to address most of the science questions at Gale crater. ChemCam consists of a Mast-Unit (laser, telescope, camera, and electronics) and a Body-Unit (spectrometers, digital processing unit, and optical demultiplexer), which are connected by an optical fiber and an electrical interface. We then report on the development, integration, and testing of the Mast-Unit, and summarize some key characteristics of ChemCam. This confirmed that nominal or better than nominal performances were achieved for critical parameters, in particular power density (>1 GW/cm 2 ). The analysis spot diameter varies from 350 μm at 2 m to 550 μm at 7 m distance. For remote imaging, the camera field of view is 20 mrad for 1024×1024 pixels. Field tests demonstrated that the resolution (˜90 μrad) made it possible to identify laser shots on a wide variety of images. This is sufficient for visualizing laser shot pits and textures of rocks and soils. An auto-exposure capability optimizes the dynamical range of the images. Dedicated hardware and software focus the telescope, with precision that is appropriate for the LIBS and imaging depths-of-field. The light emitted by the plasma is collected and sent to the Body-Unit via a 6 m optical fiber. The companion to this paper (Wiens et al. this issue) reports on the development of the Body-Unit, on the analysis of the emitted light, and on the good match between instrument performance and science specifications.

Space Science Reviews↗
USGS2009

Biostratigraphy of selected K/T boundary sections in southwestern North Dakota, USA: Toward a refinement of palynological identification criteria

The Cretaceous/Tertiary ( K / T ) boundary corresponds to one of the very few unique events in the geological record discovered to date, representing a single traceable timeline across the world. This timeline, coincident with the geochemical and mineralogical singularities caused by the impact of a large extraterrestrial body, is also coincident with the end-Cretaceous extinction event in North America. This precise timeline gives an ideal context for comparing the trends recorded by the different groups of the terrestrial fossil record during the K / T extinction event. However, in southwestern North Dakota , numerous studies conducted on excellent exposures of the K / T boundary showed that the geochemical and mineralogical criteria associated with the impact are rarely preserved. For that reason, palynology is preferred as a simple and efficient way for identifying the K / T boundary . In this context, a previously undescribed outcrop section from southwestern North Dakota was found to preserve an extensive record of the continental K / T boundary with miospores and plant megafossils, as well as microvertebrates and large vertebrate elements. Preliminary studies on the fossil associations recovered from this site showed an inconsistency between the Paleocene age given by the vertebrate and megafloral component and the Cretaceous age given by the palynological record. This issue is investigated in this paper, with a major emphasis on the description and analysis of the palynological record associated with sedimentological and paleoenvironmental data. Results shows that palynologically, the K / T boundary is placed more accurately using relative abundance variations of selected taxa.

North Dakota↗
USGS2021

Mangroves and people: Impacts and interactions

Mangroves have long been associated with human populations, as coastal communities rely on the various ecosystem services that mangroves provide. However, human degradation and destruction of mangrove forests is common, despite and because of our reliance on them as valuable ecosystems. Mangrove research and management must elucidate and reconcile these conflicts to maintain mangrove forests and the services that humans depend on. To better understand the complex dynamics, interactions and relationships that exist between mangroves and coastal communities, the 5th Mangrove Macrobenthos and Management (MMM5) conference was held in Singapore in July 2019, with the theme “ Mangroves and People: Impacts and Interactions”. This theme was chosen because Southeast Asia is the epicentre of ongoing mangrove loss, and a large number of coastal communities in the region rely on the ecosystem services that mangroves provide. The 32 papers published in this Special Issue represent the breadth of mangrove research presented at MMM5, including topics in faunal biology, ecosystem ecology, genetics, physical geography, biogeochemistry, remote sensing and the social sciences. The articles are characterized under the following topics: 1) mangrove ecosystem functioning; 2) range expansion of mangroves; 3) ecosystem services of mangroves; 4) anthropogenic and natural threats to mangroves; and 5) the management and social-ecology of mangroves. This Special Issue highlights the current state of the art of mangrove research and application, and describes a number of emerging new ideas and research opportunities that will continue to advance mangrove ecosystem science into the future.

Estuarine, Coastal and Shelf Science↗
USGS2013

Appraising options to reduce shallow groundwater tables and enhance flow conditions over regional scales in an irrigated alluvial aquifer system

Some of the world’s key agricultural production systems face big challenges to both water quantity and quality due to shallow groundwater that results from long-term intensive irrigation, namely waterlogging and salinity, water losses, and environmental problems. This paper focuses on water quantity issues, presenting finite-difference groundwater models developed to describe shallow water table levels, non-beneficial groundwater consumptive use, and return flows to streams across two regions within an irrigated alluvial river valley in southeastern Colorado, USA. The models are calibrated and applied to simulate current baseline conditions in the alluvial aquifer system and to examine actions for potentially improving these conditions. The models provide a detailed description of regional-scale subsurface unsaturated and saturated flow processes, thereby enabling detailed spatiotemporal description of groundwater levels, recharge to infiltration ratios, partitioning of ET originating from the unsaturated and saturated zones, and groundwater flows, among other variables. Hybrid automated and manual calibration of the models is achieved using extensive observations of groundwater hydraulic head, groundwater return flow to streams, aquifer stratigraphy, canal seepage, total evapotranspiration, the portion of evapotranspiration supplied by upflux from the shallow water table, and irrigation flows. Baseline results from the two regional-scale models are compared to model predictions under variations of four alternative management schemes: (1) reduced seepage from earthen canals, (2) reduced irrigation applications, (3) rotational lease fallowing (irrigation water leased to municipalities, resulting in temporary dry-up of fields), and (4) combinations of these. The potential for increasing the average water table depth by up to 1.1 and 0.7 m in the two respective modeled regions, thereby reducing the threat of waterlogging and lowering non-beneficial consumptive use from adjacent fallow and naturally-vegetated lands, is demonstrated for the alternative management intervention scenarios considered. Net annual average savings of up to about 9.9 million m 3 (8000 ac ft) and 2.3 million m 3 (1900 ac ft) of non-beneficial groundwater consumptive use is demonstrated for the study periods in each of the two respective study regions. Alternative water management interventions achieve varying degrees of benefits in each of the two regions, suggesting a need to adopt region-specific interventions and avoid a ‘one-size-fits-all’ approach. Impacts of the considered interventions on return flows to the river were predicted to be significant, highlighting the need for flow augmentation to comply with an interstate river compact and portending beneficial impacts on solute loading.

Colorado↗
USGS2010

Gravity-driven groundwater flow and slope failure potential: 2. Effects of slope morphology, material properties, and hydraulic heterogeneity

Hillslope morphology, material properties, and hydraulic heterogeneities influence the role of groundwater flow in provoking slope instability. We evaluate these influences quantitatively by employing the elastic effective stress model and Coulomb failure potential concept described in our companion paper (Iverson and Reid, this issue). Sensitivity analyses show that of four dimensionless quantities that control model results (i.e., Poisson's ratio, porosity, topographic profile, and hydraulic conductivity contrast), slope profiles and hydraulic conductivity contrasts have the most pronounced and diverse effects on groundwater seepage forces, effective stresses, and slope failure potentials. Gravity-driven groundwater flow strongly influences the shape of equilibrium hillslopes, which we define as those with uniform near-surface failure potentials. For homogeneous slopes with no groundwater flow, equilibrium hillslope profiles are straight; but with gravity-driven flow, equilibrium profiles are concave or convex-concave, and the largest failure potentials exist near the bases of convex slopes. In heterogeneous slopes, relatively slight hydraulic conductivity contrasts of less than 1 order of magnitude markedly affect the seepage force field and slope failure potential. Maximum effects occur if conductivity contrasts are of four orders of magnitude or more, and large hydraulic gradients commonly result in particularly large failure potentials just upslope from where low-conductivity layers intersect the ground surface.

Water Resources Research↗
USGS2010

Occam's shadow: levels of analysis in evolutionary ecology - where to next?

Evolutionary ecology is the study of evolutionary processes, and the ecological conditions that influence them. A fundamental paradigm underlying the study of evolution is natural selection. Although there are a variety of operational definitions for natural selection in the literature, perhaps the most general one is that which characterizes selection as the process whereby heritable variation in fitness associated with variation in one or more phenotypic traits leads to intergenerational change in the frequency distribution of those traits. The past 20 years have witnessed a marked increase in the precision and reliability of our ability to estimate one or more components of fitness and characterize natural selection in wild populations, owing particularly to significant advances in methods for analysis of data from marked individuals. In this paper, we focus on several issues that we believe are important considerations for the application and development of these methods in the context of addressing questions in evolutionary ecology. First, our traditional approach to estimation often rests upon analysis of aggregates of individuals, which in the wild may reflect increasingly non-random (selected) samples with respect to the trait(s) of interest. In some cases, analysis at the aggregate level, rather than the individual level, may obscure important patterns. While there are a growing number of analytical tools available to estimate parameters at the individual level, and which can cope (to varying degrees) with progressive selection of the sample, the advent of new methods does not reduce the need to consider carefully the appropriate level of analysis in the first place. Estimation should be motivated a priori by strong theoretical analysis. Doing so provides clear guidance, in terms of both (i) assisting in the identification of realistic and meaningful models to include in the candidate model set, and (ii) providing the appropriate context under which the results are interpreted. Second, while it is true that selection (as defined) operates at the level of the individual, the selection gradient is often (if not generally) conditional on the abundance of the population. As such, it may be important to consider estimating transition rates conditional on both the parameter values of the other individuals in the population (or at least their distribution), and population abundance. This will undoubtedly pose a considerable challenge, for both single- and multi-strata applications. It will also require renewed consideration of the estimation of abundance, especially for open populations. Thirdly, selection typically operates on dynamic, individually varying traits. Such estimation may require characterizing fitness in terms of individual plasticity in one or more state variables, constituting analysis of the norms of reaction of individuals to variable environments. This can be quite complex, especially for traits that are under facultative control. Recent work has indicated that the pattern of selection on such traits is conditional on the relative rates of movement among and frequency of spatially heterogeneous habitats, suggesting analyses of evolution of life histories in open populations can be misleading in some cases.

Journal of Applied Statistics↗