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At least 991 records · Page 55Linked to original sources

USGS2008

Comment on the treatment of residual water content in “A consistent set of parametric models for the two-phase flow of immiscible fluids in the subsurface” by L. Luckner et al.

Luckner et al. [1989] (hereinafter LVN) present a clear summary and generalization of popular formulations used for convenient representation of porous media fluid flow characteristics, including water content ( θ ) related to suction ( h ) and hydraulic conductivity ( K ) related to θ or h. One essential but problematic element in the LVN models is the concept of residual water content ( θ r ; in LVN, θ w , r ). Most studies using θ r determine its value as a fitted parameter and make the assumption that liquid flow processes are negligible at θ values less than θ r . While the LVN paper contributes a valuable discussion of the nature of θ r , it leaves several problems unresolved, including fundamental difficulties in associating a definite physical condition with θ r , practical inadequacies of the models at low θ values, and difficulties in designating a main wetting curve.

Water Resources Research↗

USGS1997

Grain-size-induced weakening of H2O ices I and II and associated anisotropic recrystallization

Grain-size-dependent flow mechanisms tend to be favored over dislocation creep at low differential stresses and can potentially influence the rheology of low-stress, low-strain rate environments such as those of planetary interiors. We experimentally investigated the effect of reduced grain size on the solid-state flow of water ice I, a principal component of the asthenospheres of many icy moons of the outer solar system, using techniques new to studies of this deformation regime. We fabricated fully dense ice samples of approximate grain size 2±1 μm by transforming “standard” ice I samples of 250±50 μm grain size to the higher-pressure phase ice II, deforming them in the ice II field, and then rapidly releasing the pressure deep into the ice I stability field. At T ≤200 K, slow growth and rapid nucleation of ice I combine to produce a fine grain size. Constant-strain rate deformation tests conducted on these samples show that deformation rates are less stress sensitive than for standard ice and that the fine-grained material is markedly weaker than standard ice, particularly during the transient approach to steady state deformation. Scanning electron microscope examination of the deformed fine-grained ice samples revealed an unusual microstructure dominated by platelike grains that grew normal to the compression direction, with c axes preferentially oriented parallel to compression. In samples tested at T ≥220 K the elongation of the grains is so pronounced that the samples appear finely banded, with aspect ratios of grains approaching 50:1. The anisotropic growth of these crystallographically oriented neoblasts likely contributes to progressive work hardening observed during the transient stage of deformation. We have also documented remarkably similar microstructural development and weak mechanical behavior in fine-grained ice samples partially transformed and deformed in the ice II field.

Journal of Geophysical Research B: Solid Earth↗

USGS2005

Workgroup report: Drinking-water nitrate and health - Recent findings and research needs

Human alteration of the nitrogen cycle has resulted in steadily accumulating nitrate in our water resources. The U.S. maximum contaminant level and World Health Organization guidelines for nitrate in drinking water were promulgated to protect infants from developing methemoglobinemia, an acute condition. Some scientists have recently suggested that the regulatory limit for nitrate is overly conservative; however, they have not thoroughly considered chronic health outcomes. In August 2004, a symposium on drinking-water nitrate and health was held at the International Society for Environmental Epidemiology meeting to evaluate nitrate exposures and associated health effects in relation to the current regulatory limit. The contribution of drinking-water nitrate toward endogenous formation of N-nitroso compounds was evaluated with a focus toward identifying subpopulations with increased rates of nitrosation. Adverse health effects may be the result of a complex interaction of the amount of nitrate ingested, the concomitant ingestion of nitrosation cofactors and precursors, and specific medical conditions that increase nitrosation. Workshop participants concluded that more experimental studies are needed and that a particularly fruitful approach may be to conduct epidemiologic studies among susceptible subgroups with increased endogenous nitrosation. The few epidemiologic studies that have evaluated intake of nitrosation precursors and/or nitrosation inhibitors have observed elevated risks for colon cancer and neural tube defects associated with drinking-water nitrate concentrations below the regulatory limit. The role of drinking-water nitrate exposure as a risk factor for specific cancers, reproductive outcomes, and other chronic health effects must be studied more thoroughly before changes to the regulatory level for nitrate in drinking water can be considered.

Environmental Health Perspectives↗

USGS2022

Diatoms.org: Supporting taxonomists, connecting communities

Consistent identification of diatoms is a prerequisite for studying their ecology, biogeography, and successful application as environmental indicators. However, taxonomic consistency among observers has been difficult to achieve because taxonomic information is scattered across numerous literature sources, presenting challenges to the diatomist. Firstly, literature is often inaccessible because of cost or its location in journals that are not widely circulated. Secondly, taxonomic revisions of diatoms are taking place faster than floras can be updated. Finally, taxonomic information is often contradictory across literature sources. These issues can be addressed by developing a content creation community dedicated to making taxonomic, ecological, and image-based data freely available for diatom researchers. Diatoms.org represents such a content curation community, providing open, online access to a vast amount of recent and historical information on North American diatom taxonomy and ecology. The content curation community aggregates existing taxonomic information, creates new content, and provides feedback in the form of corrections and notices of literature with nomenclatural changes. The website not only addresses the needs of experienced diatom scientists for consistent identification but is also designed to meet users at their level of expertise, including engaging the lay public in the importance of diatom science. The website now contains over 1000 species pages contributed by over 100 content contributors, from students to established scientists. The project began with the intent to provide accurate information on diatom identification, ecology, and distribution using an approach that incorporates engaging design, user feedback, and advanced data access technology. In retrospect, the project that began as an ‘extended electronic book’ has emerged not only as a means to support taxonomists, but for practitioners to communicate and collaborate, expanding the size of and benefits to the content curation community. In this paper, we outline the development of diatoms.org , document key elements of the project, examine ongoing challenges and consider the unexpected emergent properties, including the value of diatoms.org as a source of data. Ultimately, if the field of diatom taxonomy, ecology, and biodiversity is to be relevant, a new generation of taxonomists needs to be trained and employed using new tools. We propose that diatoms.org is in a key position to serve as a hub of training and continuity for the study of diatom biodiversity and aquatic conditions.

Diatom Research↗

USGS2015

Megathrust earthquakes and sea-level change: A tribute to George Plafker

For numerous scientific disciplines that contribute to the understanding of megathrust earthquakes, 2014 was an anniversary year of two great, >M w 9, earthquakes; fifty years since the March 27 1964 earthquake in Alaska and ten years since the December 26 2004 Aceh-Andaman earthquake and attendant tsunami. 2014 was also the final year of International Geoscience Programme (IGCP) Project 588 “Preparing for Coastal Change”, which was the latest in the 25 year history of IGCP coastal change research.

Quaternary Science Reviews↗

USGS2022

Considerations for creating equitable and inclusive communication campaigns associated with ShakeAlert, the earthquake early warning system for the West Coast of the USA

Purpose The 2019 Global Assessment Report on Disaster Risk Reduction (GAR) cites earthquakes as the most damaging natural hazard globally, causing billions of dollars of damage and killing thousands of people. Earthquakes have the potential to drastically impact physical, social and economic landscapes; to reduce this risk, earthquake early warning (EEW) systems have been developed. However, these technical EEW systems do not operate in a vacuum; the inequities in social systems, along with the needs of diverse populations, must be considered when developing these systems and their associated communication campaigns. Design/methodology/approach This article reviews aspects of social vulnerability as they relate to ShakeAlert, the EEW system for the USA. The authors identified two theories (relationship management theory and mute group theory) to inform self-reflective questions for agencies managing campaigns for EEW systems, which can assist in the development of more inclusive communication practices. Finally, the authors suggest this work contributes to important conversations about diversity, equity and inclusion (DEI) issues within early warning systems and earthquake preparedness campaigns in general. Findings To increase inclusivity, Macnamara (2012) argues that self-reflective questioning while analyzing perspective, philosophy and approaches for a campaign can help. Specific to EEW campaigns, developers may find self-reflective questions a useful approach to increase inclusion. These questions are guided by two theories and are explored in the paper. Research limitations/implications Several research limitations exist. First, this work explores two theories to develop a combined theoretical model for self-reflective questions. Further research is required to determine if this approach and the combination of these two theories have adequately informed the development of the reflective questions. Orginality/value The authors could find little peer-reviewed work examining DEI for EEW systems, and ShakeAlert in particular. While articles on early warning systems exist that explore aspects of this, EEW and ShakeAlert, with its very limited time frames for warnings, creates unique challenges.

West Coast↗

USGS2017

Biocrust ecology: Unifying micro- and macro-scales to confront global change

Biological soil crusts (biocrusts) are communities of microbes, lichens and bryophytes living at the soil surface in drylands (Fig. 1; Belnap et al ., 2016). Biocrusts occur on all continents and can comprise a majority of cover in some systems (Belnap et al ., 2016). While species diversity and distributions have long been a research focus, interest in controls on community composition and cover has expanded as biocrusts are increasingly recognized for their roles in ecosystem functioning (Deane-Coe and Stanton, 2017). For example, biocrust organisms can stabilize soils (Belnap et al ., 2016; Faist et al ., 2017), fix atmospheric carbon (C) (Sancho et al ., 2016), and serve as the foremost source of ‘new’ soil nitrogen (N) in drylands, via N 2 fixation (Barger et al ., 2016) These contributions to gross primary production and soil fertility could be quite large, as high-end estimates suggest biocrusts and similar communities of bryophytes and lichens might account for 10% of terrestrial C- and 50% of N-fixation globally (Elbert et al ., 2012). Yet verifying these and other biocrust roles in ecosystem functioning is complicated by limited knowledge of biocrust cover and composition across the vast dryland biome (Ferrenberg et al ., 2017). It was against this backdrop that ‘Biocrust3: the 3 rd International workshop on biological soil crusts’ was held in Moab, UT, USA, on 26-30 September 2016. The workshop brought together over 50 scientists from 21 countries and six continents, and included numerous biocrust science pioneers (Fig. 2). The meeting was notable for its cross-scale focus, discussion of novel molecular and imaging techniques, and sessions on mapping and restoring biocrusts in a changing world. Here, we synthesize a central theme that emerged from Biocrust3, namely the potential for combining cutting edge tools with studies focused on organismal traits, ecosystem functions, and global change biology to advance the frontier of biocrust ecology.

New Phytologist↗

USGS1997

Activities of the United States Geological Survey in Pennsylvania

Since the late 1800's, when the U.S. Geological Survey first established a presence in Pennsylvania, the focus of our work has changed from general hydrologic and geologic appraisals to issue-oriented investigations; from predominantly data collection to a balanced program of data collection, interpretation, and research; and from traditional, hand-drawn mapping to digitally produced coverages with specialized themes. Yet our basic mission has not changed. It is as relevant to the resource issues of today as it was when our geologists first arrived in western Pennsylvania in 1884. Continuing in this proud heritage and tradition, the U.S. Geological Survey is moving confidently toward the next century, evolving organizationally and technologically to better meet the needs of our many constituencies. One major organizational change is the recent accession of employees from the former National Biological Service, who now form the Survey's fourth program division, the Biological Resources Division. These employees join forces with colleagues in our other three divisions: Water Resources, Geologic, and National Mapping. More than any other change in decades, the addition of this biological expertise creates new and exciting opportunities for scientific research and public service. This report provides an overview of recent activities in Pennsylvania conducted by the four program divisions and is intended to inform those interested in U.S. Geological Survey products and services. Additional information is available on our home page (at http://wwwpah2o.er.usgs.gov/). Together with numerous Federal, State, and local agencies and organizations who are our customers and partners, we at the U.S. Geological Survey look forward to providing continued scientific contributions and public service to Pennsylvania and the Nation.

Pennsylvania↗

USGS2020

Editorial: Contributions of behavior and physiology to conservation biology

Conservation biology is a rapidly evolving discipline, with its synthetic, multidisciplinary framework expanding extensively in recent years. Seemingly disparate disciplines, such as behavior and physiology, are being integrated into this discipline's growing portfolio, resulting in diverse tools that can help develop conservation solutions. Behavior and physiology have traditionally been considered separate fields, yet their integration can provide a more comprehensive approach to developing solutions to conservation and management problems. However, demonstrations are needed of how behavior and physiology—either separately or combined—have contributed to conservation success. Examining species' vulnerabilities to extinction through the lenses of behavior and physiology can provide insight into the mechanisms that drive population declines and extirpations. Our goal is to increase awareness of the benefit of combining behavioral and physiological tools to improve conservation management decisions. Such studies can also help strengthen the basis for evidence-based conservation which, in some cases, has been previously lacking. The diverse studies in our Research Topic illustrate key examples of ways that behavior and physiology can be incorporated into conservation biology. Three main themes emerged from the invited papers with respect to their relevance to conservation: (1) Stress physiology, (2) indicators of health and disease dynamics, (3) and movement ecology. But these themes were also intertwined, thus showing the importance of integrating multiple fields of research to successfully address questions about conservation biology. Two mini reviews discuss the importance of examining how stress physiology may affect individual fitness and capacity to cope with change which, ultimately, affects the resiliency of populations. Walls and Gabor, in their mini review, promoted combining studies of behavior and physiology to aid in developing conservation strategies for amphibians, which could provide conservation managers with workable solutions to global environmental change. Walls and Gabor also pointed out that studies of behavior are useful to understand how native amphibian species respond to invasive predators. This is supported by Roznik et al. who combined physiology and behavior for a more holistic understanding of the impacts of competition between native and invasive frogs. These authors found that invasive Cuban tree frogs outperformed two native species in jump length and speed, offsetting the costs of dehydration. This work also ties in well to a review by Joly, who indicated the importance of exploring movement ecology (on multiple spatial scales) of invasive species to provide insights for invasive species management. Walls and Gabor also emphasized that more studies on phenological shifts of species in response to recent climate change are needed, as explored by Bókony et al. with birds. These authors found that bird species varied their migratory behaviors in response to contemporary climate change which, in turn, influenced subsequent trends in population size.

Frontiers in Ecology and Evolution↗

USGS2023

Effects of environment and metacommunity delineation on multiple dimensions of stream fish beta diversity

Introduction: Beta diversity represents changes in community composition among locations across a landscape. While the effects of human activities on beta diversity are becoming clearer, few studies have considered human effects on the three dimensions of beta diversity: taxonomic, functional, and phylogenetic. Including anthropogenic factors and multiple dimensions of biodiversity may explain additional variation in stream fish beta diversity, providing new insight into how metacommunities are structured within different spatial delineations. Methods: In this study, we used a 350 site stream fish abundance dataset from South Carolina, United States to quantify beta diversity explainable by spatial, natural environmental, and anthropogenic variables. We investigated three spatial delineations: (1) a single whole-state metacommunity delineated by political boundaries, (2) two metacommunities delineated by a natural geomorphic break separating uplands from lowlands, and (3) four metacommunities delineated by natural watershed boundaries. Within each metacommunity we calculated taxonomic, functional, and phylogenetic beta diversity and used variation partitioning to quantify spatial, natural environmental, and anthropogenic contributions to variations in beta diversity. Results: We explained 25–81% of the variation in stream fish beta diversity. The importance of these three factors in structuring metacommunities differed among the diversity dimensions, providing complementary perspectives on the processes shaping beta diversity in fish communities. The effect of spatial, natural environmental, and anthropogenic factors varied among the spatial delineations, which indicate conclusions drawn from variation partitioning may depend on the spatial delineation chosen by researchers. Discussion: Our study highlights the importance of considering human effects on metacommunity structure, quantifying multiple dimensions of beta diversity, and careful consideration of user-defined metacommunity boundaries in beta diversity analyses.

South Carolina↗

USGS2016

Arctic sea ice decline contributes to thinning lake ice trend in northern Alaska

Field measurements, satellite observations, and models document a thinning trend in seasonal Arctic lake ice growth, causing a shift from bedfast to floating ice conditions. September sea ice concentrations in the Arctic Ocean since 1991 correlate well ( r = +0.69, p < 0.001) to this lake regime shift. To understand how and to what extent sea ice affects lakes, we conducted model experiments to simulate winters with years of high (1991/92) and low (2007/08) sea ice extent for which we also had field measurements and satellite imagery characterizing lake ice conditions. A lake ice growth model forced with Weather Research and Forecasting model output produced a 7% decrease in lake ice growth when 2007/08 sea ice was imposed on 1991/92 climatology and a 9% increase in lake ice growth for the opposing experiment. Here, we clearly link early winter 'ocean-effect' snowfall and warming to reduced lake ice growth. Future reductions in sea ice extent will alter hydrological, biogeochemical, and habitat functioning of Arctic lakes and cause sub-lake permafrost thaw.

Alaska↗

USGS2016

High-latitude dust in the Earth system

Natural dust is often associated with hot, subtropical deserts, but significant dust events have been reported from cold, high latitudes. This review synthesizes current understanding of high-latitude (≥50°N and ≥40°S) dust source geography and dynamics and provides a prospectus for future research on the topic. Although the fundamental processes controlling aeolian dust emissions in high latitudes are essentially the same as in temperate regions, there are additional processes specific to or enhanced in cold regions. These include low temperatures, humidity, strong winds, permafrost and niveo-aeolian processes all of which can affect the efficiency of dust emission and distribution of sediments. Dust deposition at high latitudes can provide nutrients to the marine system, specifically by contributing iron to high-nutrient, low-chlorophyll oceans; it also affects ice albedo and melt rates. There have been no attempts to quantify systematically the expanse, characteristics, or dynamics of high-latitude dust sources. To address this, we identify and compare the main sources and drivers of dust emissions in the Northern (Alaska, Canada, Greenland, and Iceland) and Southern (Antarctica, New Zealand, and Patagonia) Hemispheres. The scarcity of year-round observations and limitations of satellite remote sensing data at high latitudes are discussed. It is estimated that under contemporary conditions high-latitude sources cover >500,000 km2 and contribute at least 80–100 Tg yr−1 of dust to the Earth system (~5% of the global dust budget); both are projected to increase under future climate change scenarios.

Reviews of Geophysics↗

USGS2016

Application of genetics and genomics to wildlife epidemiology

Wildlife diseases can have significant impacts on wildlife conservation and management. Many of the pathogens that affect wildlife also have important implications for domestic animal and human health. However, management interventions to prevent or control wildlife disease are hampered by uncertainties about the complex interactions between pathogens and free-ranging wildlife. We often lack crucial knowledge about host ecology, pathogen characteristics, and host–pathogen dynamics. The purpose of this review is to familiarize wildlife biologists and managers with the application of genetic and genomic methodologies for investigating pathogen and host biology to better understand and manage wildlife diseases. The genesis of this review was a symposium at the 2013 annual Wildlife Society Conference. We reviewed the scientific literature and used our personal experiences to identify studies that illustrate the application of genetic and genomic methods to advance our understanding of wildlife epidemiology, focusing on recent research, new techniques, and innovative approaches. Using examples from a variety of pathogen types and a broad array of vertebrate taxa, we describe how genetics and genomics can provide tools to detect and characterize pathogens, uncover routes of disease transmission and spread, shed light on the ways that disease susceptibility is influenced by both host and pathogen attributes, and elucidate the impacts of disease on wildlife populations. Genetic and increasingly genomic methodologies will continue to contribute important insights into pathogen and host biology that will aid efforts to assess and mitigate the impacts of wildlife diseases on global health and conservation of biodiversity.

Journal of Wildlife Management↗

USGS2025

Changes in aeolian saltation cloud properties with wind speed and ripples

Aeolian sediment transport shapes landscapes on Earth and other planetary surfaces, yet key uncertainties remain in how the near-bed saltation cloud responds to changing wind and surface conditions. Leveraging recent advances in image-based particle tracking, we conducted wind tunnel experiments using high-speed imaging and Particle Tracking Velocimetry to quantify sand grain trajectories in saturated saltation clouds over both flat and rippled beds. Our open-source PTV workflow resolved particle motions within millimeters of the bed across a range of wind speeds. Supporting previous results, we find that mean particle velocities do not scale linearly with wind speed; instead, changes in particle velocity distributions—including skewness and kurtosis—emerge as wind strength and sediment flux increase. At higher transport rates, distinctions among saltation, reptation, and creep within the particle distribution become more smoothed, suggesting a continuum spectrum of particle behavior rather than discrete transport modes. Our new dataset of particle trajectories over an active rippled bed shows distinctions in particle speed across the aspects. On ripple stoss slopes, fast saltating grains co-occur with slow creeping particles, while lee slopes are depleted of slower grains, consistent with shadowing effects. These observations support a feedback between ripple morphology and near-bed particle trajectories, with implications for how splash events redistribute sediment momentum. This study contributes new high-resolution empirical data that illuminate how saltation cloud structure evolves with wind forcing and bedform development, advancing our understanding of aeolian sediment transport under complex, dynamic conditions.

Aeolian Research↗

USGS2020

Monthly suspended-sediment apportionment for a western Lake Erie agricultural tributary

Black Creek, a headwater to the Maumee River and western Lake Erie, is an agricultural basin with a mix of cropland (66%), pasture (19%), and forest (7%) linked by a road network to the rural community. Suspended sediment was collected monthly during the 2018 water year for the main stem and two sub-basins using in-situ, passive samplers that integrated a range of streamflow conditions. Sediment fingerprinting used 44 indicators to apportion samples among five sources: cropland, pasture, forest, road dirt, and streambanks. Cropland, pasture, and streambanks had similar ranges in sediment-bound phosphorus (679-1670 ppm). Cropland contributed 21 ± 15% (monthly mean ± standard deviation; 0-46% among individual months) of suspended sediment during the year. Fall and spring peaks in cropland contribution highlight the ongoing importance of on-field management, but this small contribution of suspended sediment relative to the expanse of cropland may reflect implementation of best-management practices. Pasture contributed 0-66% (16±19%) of suspended-sediment and roads 0-26% (6±6%). Streambanks contributed 12-100% (55±25%) and was the only source identified in all sediment samples. In this basin, most cropland-adjacent streambanks are protected by a riparian setback. However, streams traversing other land-use types are not as consistently protected, and these setbacks do not protect the stream channel from discharge of water from sump pumps, road culverts, or tile drains. The contribution of sediment from other land uses combined with that from the agricultural drainage network (as streambank material) underscores the need to consider water movement in the basin as a whole.

Indiana↗

USGS1983

Seasonal food of juvenile lake trout in U.S. waters of Lake Ontario

Stomach contents of 3,554 lake trout ( Salvelinus namaycush ), 100 to 449 mm in total length, captured with bottom trawls during April through October 1978–81 along the south shore of Lake Ontario were examined. Invertebrates appeared to be an important food of lake trout less than 200 mm long but were only occasionally eaten by larger fish. For all seasons and size groups of juvenile lake trout combined, the slimy sculpin ( Cottus cognatus ) was the principal forage fish, making up 42% (by weight) of identifiable fish remains. Young-of-the-year slimy sculpins were a major food of recently stocked yearling lake trout during July through October. Alewives ( Alosa pseudoharengus ) were the principal forage during April and May, and made up 28% (by weight) of the identifiable fish remains. They were rarely eaten during July and August, however, when lake trout remained in the hypolimnion and alewives were above it. Over 99% of the alewives eaten from April through August were yearlings and over 99% eaten during October were young-of-the-year. Rainbow smelt ( Osmerus mordax ) were the primary forage during July and August, but contributed only a small part of the diet during other seasons; overall, they made up 25% of identifiable fish remains. Johnny darters ( Etheostoma nigrum ) made up 4% of identifiable fish remains and were most common in stomachs of small lake trout during October.

Journal of Great Lakes Research↗

USGS2021

The finicky nature of earthquake shaking-triggered submarine sediment slope failures and sediment gravity flows

Since 2011, seafloor temperatures, pressures, and seismic ground motions have been measured by the seafloor cabled Dense Oceanfloor Network system for Earthquakes and Tsunamis (DONET) on the Nankai margin. These measurements, high-resolution bathymetry, and abundant contextual information make the DONET region seem ideally suited to provide constraints on seismic shaking-triggered sediment slope failures and gravity flows, particularly since numerous published studies have linked paleo- to modern earthquakes to failures and flows within the DONET. The occurrences of the local 2016 M6.0 Mie-ken and regional M7.0 Kumamoto earthquakes within and at regional distances, respectively, from the DONET data set provided an opportunity to explore this potential. We used DONET seismic recordings of the posited triggering shaking and to search for submarine slide signals and continuous temperature and pressure data to detect pulses of warm and densified water indicative of passing flows. We developed and applied a variety of analytical methods to eliminate signals generated by water column processes, while leaving slope failures and sediment gravity flow anomalies as residuals. Our explorations yielded no evidence that earthquake shaking initiated either phenomenon, which we suggest reflects the finicky nature both of the detection of and the physical processes that contribute to slope failures and flows (i.e., both require satisfying precise suites of conditions). Nonetheless, this negative result, our analyses, and the estimates of physical properties we derived for them, provide useful lessons and inputs for future studies.

Journal of Geophysical Research↗

USGS2025

Permafrost and rain influence summer hydrologic flowpaths in boreal catchments

Flowpaths of water through catchments influence water quality and flow regimes of streams. Depths of dominant flowpaths respond to variation in climate and catchment characteristics, such as topography, vegetation, and soil type. In high-latitude regions, the depth and spatial extent of permafrost influences catchment hydrology, and thawing permafrost might change sources and pathways of water supplying solutes and flow to streams. We estimated contributions of precipitation, soil water, and groundwater flowpaths to streams during the open-water period after snowmelt by applying a Bayesian mixing model to 4–6 years of observed solute concentrations in five catchments of boreal Alaska. The relative contribution of groundwater to streams varied from 12% to 82% across catchments and years and declined as spatial extent of permafrost increased from 25% to 58% across catchments, indicating potential for increased infiltration and drainage as permafrost thaws. Temporal patterns in precipitation also influenced flowpaths. The mean annual contribution of precipitation to streamflow increased in years with more rain. Groundwater contribution increased, on average, in years with few large storms, suggesting deepening flows due to seasonal ground thaw or loss of shallow water to evapotranspiration. In contrast, groundwater contributed less in years when large storms delivered most of the year's rain in late summer or autumn. Overall, spatial and temporal variation in relative flowpath contributions to streams suggest that permafrost thaw will deepen flowpaths, but increasing precipitation expected in high-latitude regions under warming climate might obscure this effect by routing water via shallow flowpaths following large storms.

Alaska↗