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At least 127 records · Page 7Linked to original sources
USGS2014

Toxicity and accumulation of silver nanoparticles during development of the marine polychaete Platynereis dumerilii

Pollutants affecting species at the population level generate ecological instability in natural systems. The success of early life stages, such as those of aquatic invertebrates, is highly affected by adverse environmental conditions. Silver released into the environment from emerging nanotechnology represents such a threat. Sediments are sinks for numerous pollutants, which aggregate and/or associate with depositing suspended particles. Deposit feeder such as the annelid Platynereis dumerilii, which has a large associated literature on its development, is an excellent model organism for exposure studies in coastal environments. We exposed eggs, larvae, juveniles and adults of P. dumerilii to various concentrations of citrate (cit-Ag NPs) or humic acid (HA-Ag NPs) capped silver nanoparticles (Ag NPs) as well to dissolved Ag (added as AgNO3). We showed that mortality and abnormal development rate increased with younger life stages. While adults and juvenile were the most tolerant life stages, fertilized eggs were highly sensitive to AgNO3, cit-Ag NPs and HA-Ag NPs. Exposures to HA-Ag NPs triggered the highest cute toxicity responses in P. dumerilii and in most cases both Ag NPs were more toxic than AgNO3. Uptake rate of HA-Ag NPs in adult worms was also higher than from other Ag forms, consistent with toxicity to other life stages. The early stages of the life cycle of marine coastal organisms are more affected by Ag NPs than the juvenile or adult life stages, indicating that exposure experiments at the larval level contribute to realistic eco-toxicological studies in aquatic environments.

Science of the Total Environment↗
USGS1981

Stratigraphy, sedimentology, and paleomagnetism of the Coral Ridge sand body, eastern Taylor Valley, Victoria Land, Antarctica

A body of moderately well sorted and well stratified ice-cemented sand, here informally called the Coral Ridge sand body, was deposited across eastern Taylor Valley before the deposition of a veneer of glaciogenic deposits related to late Pleistocene incursions of the Ross Sea ice sheet. The Coral Ridge sand body is more than 50 m thick where preserved in a north-south trending ridge that is transverse to the long axis of the valley. The ridge forms a drainage divide that stands 100 m above sea level and separates the basin of Lake Fryxell on the west from the seacoast to the east. An erosion surface having about 35 m of abrupt local relief was apparently developed on the sand body before the latest incursions of Ross Sea ice. The Coral Ridge sand body accumulated in a fluviatile or possibly fluviomarine deltaic environment following deposition of coarse diamictons and interbedded layers of sand in a fjord that once occupied the site of Taylor Valley. From its sedimentary characteristics and topographic distribution, the sand was deposited across the valley following filling of the fjord. The 1) comparatively high degree of sorting, 2) general lack of clay and silt, and of very coarse detritus, and 3) common fluviatile cross-stratification, argue for stream transport and for accumulation principally above sea level. Coarse glacial detritus, which must have existed in the source area, was not transported to the area of sand deposition. Very fine glacial detritus that presumably was transported with the sand was deposited some place beyond the area of sand deposition. Evidence bearing on the direction of transport, and thus the source area, has not yet been developed. The source could have been a grounded ice sheet in the Ross Sea to the east, or alternatively, the source could have lay to the west in the area of the Lake Fryxell basin at a time when the basin was occupied by a more extensive Taylor Glacier. Evidence bearing on the age of the Coral Ridge sand body also is not fully developed. West of the Coral Ridge divide, the upper 2-3 m of a 14-mthick section of Coral Ridge sand near the top of hole DVDP-11 is reversely polarized. All other beds of the ice-cemented sand have been found to be normally polarized. Two possibilities exist: 1) the Coral Ridge sand body was deposited during late Pliocene time, mainly during a time of normal polarity of the Gauss polarity epoch, or 2) the sand body is much younger and was deposited during the Bruhnes normal polarity epoch of Pleistocene time, less than 730,000 years ago (in which case, the reversely polarized strata are anomalous). Additional subsurface and surface geological and paleomagnetic study is required to resolve the problems of age and source, critical to deciphering the late Cenozoic glacial and structural history of Taylor Valley and environs.

Victoria Land↗
USGS1999

Geology and evolution of lakes in north-central Florida

Fluid exchange between surficial waters and groundwater in karst environments, and the processes that control exchange, are of critical concern to water management districts and planners. High-resolution seismic data were collected from 30 lakes of north-central Florida. In each case study, lake structure and geomorphology were controlled by solution and/or mechanical processes. Processes that control lake development are twofold: (1) karstification or dissolution of the underlying limestone, and (2) the collapse, subsidence, or slumping of overburden to form sinkholes. Initial lake formation is directly related to the karst topography of the underlying host limestone. Case studies have shown that lakes can be divided by geomorphic types into progressive developmental phases: (1) active subsidence or collapse phase (young); (2) transitional phase (middle age); (3) baselevel phase (mature); and (4) polje (drowned prairie) – broad flat-bottom that have one or all phases of sinkhole. Using these criteria, Florida lakes can be classified by size, fill, subsurface features, and geomorphology.

Florida↗
USGS2017

Application of paleoecology to ecosystem restoration: A case study from south Florida’s estuaries

Paleoecological analyses of biotic assemblages from cores collected throughout south Florida’s estuaries indicate gradually increasing salinities over approximately the last 2000 years, consistent with rising sea level. Around the beginning of the twentieth century these gradual patterns of change began to shift, corresponding to the beginning of human alteration of the environment via canal construction, railroad construction and other land use changes. Between 1950 and 1960, at a time of significant construction of water management structures another distinctive shift in the biological assemblages occurred. Analysis of the assemblages provides essential information on long-term patterns of change in the estuaries and provides a basis for predicting future trajectories of change. Paleosalinity estimates derived from the cores are providing input to linear regression models to determine related freshwater flow into the estuaries of south Florida. These analyses are being used to help establish performance measures and targets for the Comprehensive Everglades Restoration, established following an Act of Congress in 2000. Restoration of south Florida’s ecosystems is slated to be a 30–50 year effort that will require detailed knowledge of past decadal to centennial-scale changes in climate, freshwater flow and salinity. This historical perspective provides information that allows land managers to set realistic and sustainable goals for restoration, and provides insight into the potential response of south Florida’s ecosystem to various future scenarios of global change.

Florida↗
USGS2008

Restoration of Circum-Arctic Upper Jurassic source rock paleolatitude based on crude oil geochemistry

Tectonic geochemical paleolatitude (TGP) models were developed to predict the paleolatitude of petroleum source rock from the geochemical composition of crude oil. The results validate studies designed to reconstruct ancient source rock depositional environments using oil chemistry and tectonic reconstruction of paleogeography from coordinates of the present day collection site. TGP models can also be used to corroborate tectonic paleolatitude in cases where the predicted paleogeography conflicts with the depositional setting predicted by the oil chemistry, or to predict paleolatitude when the present day collection locality is far removed from the source rock, as might occur due to long distance subsurface migration or transport of tarballs by ocean currents. Biomarker and stable carbon isotope ratios were measured for 496 crude oil samples inferred to originate from Upper Jurassic source rock in West Siberia, the North Sea and offshore Labrador. First, a unique, multi-tiered chemometric (multivariate statistics) decision tree was used to classify these samples into seven oil families and infer the type of organic matter, lithology and depositional environment of each organofacies of source rock [Peters, K.E., Ramos, L.S., Zumberge, J.E., Valin, Z.C., Scotese, C.R., Gautier, D.L., 2007. Circum-Arctic petroleum systems identified using decision-tree chemometrics. American Association of Petroleum Geologists Bulletin 91, 877-913]. Second, present day geographic locations for each sample were used to restore the tectonic paleolatitude of the source rock during Late Jurassic time (???150 Ma). Third, partial least squares regression (PLSR) was used to construct linear TGP models that relate tectonic and geochemical paleolatitude, where the latter is based on 19 source-related biomarker and isotope ratios for each oil family. The TGP models were calibrated using 70% of the samples in each family and the remaining 30% of samples were used for model validation. Positive relationships exist between tectonic and geochemical paleolatitude for each family. Standard error of prediction for geochemical paleolatitude ranges from 0.9?? to 2.6?? of tectonic paleolatitude, which translates to a relative standard error of prediction in the range 1.5-4.8%. The results suggest that the observed effect of source rock paleolatitude on crude oil composition is caused by (i) stable carbon isotope fractionation during photosynthetic fixation of carbon and (ii) species diversity at different latitudes during Late Jurassic time. ?? 2008 Elsevier Ltd. All rights reserved.

Organic Geochemistry↗
USGS1994

Sources and migration pathways of natural gas in near-surface ground water beneath the Animas River valley, Colorado and New Mexico

In July 1990, the U.S. Geological Survey began a study of the occurrence of natural gas in near-surface ground water in the Animas River valley in the San Juan Basin between Durango, Colorado, and Aztec, New Mexico. The general purpose of the study was to identify the sources and migration pathways of natural gas in nearsurface ground water in the study area. The purpose of this report is to present interpretive conclusions for the study, primarily based on data collected by the U.S. Geological Survey from August 1990 to May 1991. Seventy of the 205 (34 percent) groundwater samples collected during August-November 1990 had methane concentrations that exceeded the reporting limit of 0.005 milligram per liter. The maximum concentration was 39 milligrams per liter, and the mean concentration was 1.3 milligrams per liter. Samples from wells completed in bedrock have greater mean concentrations of methane than samples from wells completed in alluvium. Correlations indicate weak or nonexistent associations between dissolved-methane concentrations and concentrations of dissolved solids, major ions, bromide, silica, iron, manganese, and carbon dioxide. Dissolved methane was associated with hydrogen sulfide. Soil-gas-methane concentrations were measurable at few of 192 ground-water sites, even at sites at which ground water contained large concentrations of dissolved methane, which indicates that soil-gas surveys are not useful to delineate areas of gas-affected ground water. The reporting limit of 0.005 milligram per liter of gas was equaled or exceeded by 40 percent of soil-gas measurements adjacent to 352 gas-well casings. Concentrations of at least 100 milligrams per liter of gas were measured at 25 (7 percent) of the sites. Potential sources of gases in water, soil, gas-well surface casings, and cathodic-protection wells were determined on the basis of their isotopic and molecular compositions and available information about gas-well construction or leaks. Biogenic and thermogenic sources of gas exist in the near-surface environment of the study area. Biogenic gas is present locally in the near-surface Animas and Nacimiento formations, and biogenic gas has been detected in water wells completed in those rocks. Most gas probably is thermogenic gas from deep reservoirs, including the Dakota Sandstone, Mesaverde Group, Lewis Shale, Pictured Cliffs Sandstone, and coals in the Fruitland Formation. Less important sources include sandstones in the upper Fruitland Formation and the Kirtland Shale. Although migration of gas by diffusion or through natural fractures is possible, manmade conduits probably account for most of the upward migration of gas to the near-surface environment of the study area. Primary migration pathways largely consist of 1) leaking, conventional gas wells and 2) uncemented annuli of conventional gas wells along coals in the Fruitland Formation. Secondary migration pathways are gas-well annuli, cathodic-protection wells, seismic-test holes, and bedrock water wells.

Colorado, New Mexico↗
USGS2001

Coastline complexity: A parameter for functional classification of coastal environments

To understand the role of the world's coastal zone (CZ) in global biogeochemical fluxes (particularly those of carbon, nitrogen, phosphorus, and sediments) we must generalise from a limited number of observations associated with a few well-studied coastal systems to the global scale. Global generalisation must be based on globally available data and on robust techniques for classification and upscaling. These requirements impose severe constraints on the set of variables that can be used to extract information about local CZ functions such as advective and metabolic fluxes, and differences resulting from changes in biotic communities. Coastal complexity (plan-view tortuosity of the coastline) is a potentially useful parameter, since it interacts strongly with both marine and terrestrial forcing functions to determine coastal energy regimes and water residence times, and since 'open' vs. 'sheltered' categories are important components of most coastal habitat classification schemes. This study employs the World Vector Shoreline (WVS) dataset, originally developed at a scale of 1:250 000. Coastline complexity measures are generated using a modification of the Angle Measurement Technique (AMT), in which the basic measurement is the angle between two lines of specified length drawn from a selected point to the closest points of intersection with the coastline. Repetition of these measurements for different lengths at the same point yields a distribution of angles descriptive of the extent and scale of complexity in the vicinity of that point; repetition of the process at different points on the coast provides a basis for comparing both the extent and the characteristic scale of coastline variation along different reaches of the coast. The coast of northwestern Mexico (Baja California and the Gulf of California) was used as a case study for initial development and testing of the method. The characteristic angle distribution plots generated by the AMT analysis were clustered using LOICZVIEW, a high dimensionality clustering routine developed for large-scale coastal classification studies. The results show distinctive differences in coastal environments that have the potential for interpretation in terms of both biotic and hydrogeochemical environments, and that can be related to the resolution limits and uncertainties of the shoreline data used. These objective, quantitative measures of coastal complexity as a function of scale can be further developed and combined with other data sets to provide a key component of functional classification of coastal environments. ?? 2001 Elsevier Science B.V. All rights reserved.

Conference Paper↗
USGS2005

Can superior natural amenities create high-quality employment opportunities? The case of nonconsumptive river recreation in central Idaho

Central Idaho has superior environmental amenities, as evidenced by exceptionally high-value tourism, such as guided whitewater rafting. The focus of our study concerns the attainment of high-quality jobs in a high-quality natural environment. We estimate cumulative wage rate effects unique to nonconsumptive river recreation in central Idaho for comparison with other sectors. The cumulative effects are based on a detailed survey of recreation spending and a modified synthesized input–output model. Cumulative wage rate effects support using the abundance of environmental amenities to expand and attract high-wage, environmentally sensitive firms, as opposed to expanded tourism to improve employment quality.

Society and Natural Resources↗
USGS2022

Long-term ocean observing for international capacity development around tsunami early warning

The 2004 magnitude (M) 9.1 Sumatra-Andaman Islands earthquake in the Indian Ocean triggered the deadliest tsunami ever, killing more than 230,000 people. In response, the United Nations Educational, Scientific, and Cultural Organization (UNESCO) established three additional Intergovernmental Coordination Groups (ICGs) for the Tsunami and Other Coastal Hazards Early Warning System: for the Caribbean and Adjacent Regions (ICG/CARIBE-EWS), for the Indian Ocean, and for the Northeastern Atlantic, Mediterranean, and Connected Seas. Along with the ICG for the Pacific Ocean, which was established in 1965, one of the goals of the new ICGs was to improve earthquake and tsunami monitoring and early warning. This need was further demonstrated by the 2011 Great East Japan (Tōhoku-oki) earthquake and tsunami, which killed more than 20,000 people, and other destructive tsunamis that occurred in the Solomon Islands, Samoa, Tonga, Chile, Indonesia, and Peru. In response to the call to action by the UN Decade of Ocean Science for Sustainable Development (2021–2030), as well as the desired safe ocean outcome (von Hillebrandt-Andrade et al., 2021), the Intergovernmental Oceanographic Commission (IOC) of UNESCO approved the Ocean Decade Tsunami Programme in June 2021. One of its goals is to develop the capability to issue actionable alerts for tsunamis from all sources with minimum uncertainty within 10 minutes (Angove et al., 2019). While laudable, this goal presents complexities. Currently, warning depends on quick detection as well as the location and initial magnitude estimates of an earthquake that may generate a tsunami. Other factors that affect tsunamis, such as the faulting mechanism (how the faults slide past each other) and areal extent of the earthquake, currently take at least 20–30 minutes to forecast and are still subject to large uncertainties. Hence, agencies charged with tsunami early warning need to broadcast public alerts within minutes after an earthquake occurs but may struggle to meet this 10-minute goal without further technological advances, some of which are outlined in this article. To reduce loss of life through adequate tsunami warning requires global ocean-based seismic, sea level, and geodetic initiatives to detect high-impact earthquakes and tsunamis, combined with sufficient communication and education so that people know how to respond when they receive alerts and warnings. The United Nations International Strategy for Disaster Reduction defines an early warning system as “a set of capacities needed to generate and disseminate timely and meaningful warning information to enable individuals, communities, and organizations threatened by a hazard to prepare and to act appropriately and in sufficient time to reduce the possibility of harm or loss” (UNISDR, 2012). In short, a successful early warning system requires technology coupled with human factors (Kelman and Glantz, 2014). In this article, we explore case studies from Japan and Canada, where scientists are leading the way in incorporating ocean observing capabilities in their early warning systems. We also explore advancements and challenges in the Caribbean, an area with a complex tectonic environment that would benefit greatly from increased global ocean observing capabilities. We also explore physical and social science interventions necessary to reduce loss of life.

Oceanography↗
USGS2023

Assembling the right pieces: Developing an interdisciplinary team to study disease, decline, and recovery of a world-class Smallmouth Bass fishery

Managing and understanding fisheries dynamics are becoming more complex as new and seemingly more complicated environmental factors are identified. Often management requires resources beyond that of any one entity and calls for collaboration among partners with differing priorities and backgrounds to account for the complexity of factors influencing fisheries. We present a collaborative case study from the Susquehanna River basin, Pennsylvania, where Smallmouth Bass Micropterus dolomieu have faced population declines, mortality events, and notable signs of disease in recent years. Collaboration was required to study many facets of the fishery and the environment simultaneously to better understand risk factors and underlying relationships influencing Smallmouth Bass health. The outcomes from this interdisciplinary collaboration allowed for identification of contributing risk factors, led to the development of products and analytical techniques that were mutually beneficial to all partners involved, and provided knowledge that was integrated into fish health and fisheries management.

Maryland, New York, Pennsylvania↗
USGS2018

Before the storm: Antecedent conditions as regulators of hydrologic and biogeochemical response to extreme climate events

While the influence of antecedent conditions on watershed function is widely recognized under typical hydrologic regimes, gaps remain in the context of extreme climate events (ECEs). ECEs are those events that far exceed seasonal norms of intensity, duration, or impact upon the physical environment or ecosystem. In this synthesis, we discuss the role of source availability and hydrologic connectivity on antecedent conditions and propose a conceptual framework to characterize system response to ECEs at the watershed scale. We present four case studies in detail that span a range of types of antecedent conditions and type of ECE to highlight important controls and feedbacks. Because ECEs have the potential to export large amounts of water and materials, their occurrence in sequence can disproportionately amplify the response. In fact, multiple events may not be considered extreme in isolation, but when they occur in close sequence they may lead to extreme responses in terms of both supply and transport capacity. Therefore, to advance our understanding of these complexities, we need continued development of a mechanistic understanding of how antecedent conditions set the stage for ECE response across multiple regions and climates, particularly since monitoring of these rare events is costly and difficult to obtain. Through focused monitoring of critical ecosystems during rare events we will also be able to extend and validate modeling studies. Cross-regional comparisons are also needed to define characteristics of resilient systems. These monitoring, modeling, and synthesis efforts are more critical than ever in light of changing climate regimes, intensification of human modifications of the landscape, and the disproportionate impact of ECEs in highly populated regions.

Biogeochemistry↗
USGS2015

A centroid model of species distribution with applications to the Carolina wren Thryothorus ludovicianus and house finch Haemorhous mexicanus in the United States

Drastic shifts in species distributions are a cause of concern for ecologists. Such shifts pose great threat to biodiversity especially under unprecedented anthropogenic and natural disturbances. Many studies have documented recent shifts in species distributions. However, most of these studies are limited to regional scales, and do not consider the abundance structure within species ranges. Developing methods to detect systematic changes in species distributions over their full ranges is critical for understanding the impact of changing environments and for successful conservation planning. Here, we demonstrate a centroid model for range-wide analysis of distribution shifts using the North American Breeding Bird Survey. The centroid model is based on a hierarchical Bayesian framework which models population change within physiographic strata while accounting for several factors affecting species detectability. Yearly abundance-weighted range centroids are estimated. As case studies, we derive annual centroids for the Carolina wren and house finch in their ranges in the U.S. We further evaluate the first-difference correlation between species’ centroid movement and changes in winter severity, total population abundance. We also examined associations of change in centroids from sub-ranges. Change in full-range centroid movements of Carolina wren significantly correlate with snow cover days (r = −0.58). For both species, the full-range centroid shifts also have strong correlation with total abundance (r = 0.65, and 0.51 respectively). The movements of the full-range centroids of the two species are correlated strongly (up to r = 0.76) with that of the sub-ranges with more drastic population changes. Our study demonstrates the usefulness of centroids for analyzing distribution changes in a two-dimensional spatial context. Particularly it highlights applications that associate the centroid with factors such as environmental stressors, population characteristics, and progression of invasive species. Routine monitoring of changes in centroid will provide useful insights into long-term avian responses to environmental changes.

Ecography↗
USGS2014

Development of a generic auto-calibration package for regional ecological modeling and application in the Central Plains of the United States

Process-oriented ecological models are frequently used for predicting potential impacts of global changes such as climate and land-cover changes, which can be useful for policy making. It is critical but challenging to automatically derive optimal parameter values at different scales, especially at regional scale, and validate the model performance. In this study, we developed an automatic calibration (auto-calibration) function for a well-established biogeochemical model—the General Ensemble Biogeochemical Modeling System (GEMS)-Erosion Deposition Carbon Model (EDCM)—using data assimilation technique: the Shuffled Complex Evolution algorithm and a model-inversion R package—Flexible Modeling Environment (FME). The new functionality can support multi-parameter and multi-objective auto-calibration of EDCM at the both pixel and regional levels. We also developed a post-processing procedure for GEMS to provide options to save the pixel-based or aggregated county-land cover specific parameter values for subsequent simulations. In our case study, we successfully applied the updated model (EDCM-Auto) for a single crop pixel with a corn–wheat rotation and a large ecological region (Level II)—Central USA Plains. The evaluation results indicate that EDCM-Auto is applicable at multiple scales and is capable to handle land cover changes (e.g., crop rotations). The model also performs well in capturing the spatial pattern of grain yield production for crops and net primary production (NPP) for other ecosystems across the region, which is a good example for implementing calibration and validation of ecological models with readily available survey data (grain yield) and remote sensing data (NPP) at regional and national levels. The developed platform for auto-calibration can be readily expanded to incorporate other model inversion algorithms and potential R packages, and also be applied to other ecological models.

Ecological Informatics↗
USGS1995

A survey of recent results in passive sampling of water and air by semipermeable membrane devices

A survey is presented of some recent results for passive sampling of water and air for trace organic contaminants using lipid-filled semipermeable membrane devices (SPMDs). Results of water sampling for trace organochlorine compounds using simultaneously exposed SPMDs and the most universally applied biomonitor (bivalves) are discussed. In general, the total amounts of accumulated analytes available for analysis in bivalves and SPMDs were comparable. However, SPMD controls typically had negligible levels of contamination, which was not always the case for transplanted bivalves, even after prolonged depuration prior to exposure. In surveys of the spatial trends of organochlorines at a series of sites, data from bivalves and SPMDs provided the same picture of contaminant distribution and severity. An exception was ionizable contaminants such as the chlorinated phenolic compounds and their transformation products found in pulp mill effluents. In these cases the two monitoring approaches compliment each other, i.e. what is not found in bivalves appears in SPMDs and vice versa. SPMDs have also been applied in environments where biomonitoring is not feasible. SPMDs have shown their utility in studies of trace levels of polyaromatic hydrocarbons by locating and characterizing point sources. An example is given of their application to the calculation of contaminant half-lives from aqueous SPMD residues, a direct measurement of the persistence of contaminants in an environmental compartment. Similarly, results of air sampling with SPMDs in a relatively pristine coastal location are cited which reveal a tremendous enhancement in p,p′ -DDE relative to open ocean values.

Marine Pollution Bulletin↗
USGS2006

Channel formation by flow stripping: large-scale scour features along the Monterey East Channel and their relation to sediment waves

The Monterey East system is formed by large-scale sediment waves deposited as a result of flows stripped from the deeply incised Monterey fan valley (Monterey Channel) at the apex of the Shepard Meander. The system is dissected by a linear series of steps that take the form of scour-shaped depressions ranging from 3·5 to 4·5 km in width, 3 to 6 km in length and from 80 to 200 m in depth. These giant scours are aligned downstream from a breech in the levee on the southern side of the Shepard Meander. The floor of the breech is only 150 m above the floor of the Monterey fan valley but more than 100 m below the levee crests resulting in significant flow stripping. Numerical modeling suggests that the steps in the Monterey East system were created by Froude-supercritical turbidity currents stripped from the main flow in the Monterey channel itself. Froude-supercritical flow over an erodible bed can be subject to an instability that gives rise to the formation of cyclic steps, i.e. trains of upstream-migrating steps bounded upstream and downstream by hydraulic jumps in the flow above them. The flow that creates these steps may be net-erosional or net-depositional. In the former case it gives rise to trains of scours such as those in the Monterey East system, and in the latter case it gives rise to the familiar trains of upstream-migrating sediment waves commonly seen on submarine levees. The Monterey East system provides a unique opportunity to introduce the concept of cyclic steps in the submarine environment to study processes that might result in channel initiation on modern submarine fans.

California↗
USGS2006

Numerical Simulation of the Hydrologic Effects of Redistributed and Additional Ground-Water Withdrawal, Island of Molokai, Hawaii

Because of increased demand for water associated with a growing population, projected increases in demand over the next few decades, and rising salinity of the water pumped from some existing wells, the County of Maui Department of Water Supply (DWS) is currently (2006) considering drilling additional wells to replace or supplement existing wells on the Island of Molokai, Hawaii. Redistributed and additional ground-water withdrawals will affect ground-water levels, discharge of ground water to the nearshore environment, and, possibly, salinity of the water pumped from existing wells. For this study, an existing numerical ground-water-flow model was used to estimate water-level and coastal-discharge changes, relative to 2005 base-case conditions, caused by withdrawals in the area between Kualapuu and Ualapue on Molokai. For most of the scenarios tested, total withdrawals were either equal to or 0.28 million gallons per day greater than those in the 2005 base case. Model results indicate that a redistribution of withdrawals causes a corresponding redistribution of water levels and coastal discharge. Water levels rise and coastal discharge increases near sites of reduced withdrawal, whereas water levels decline and coastal discharge decreases near sites of increased withdrawal. The magnitude and areal extent of hydrologic changes caused by a redistribution of withdrawals increase with larger changes in withdrawal rates. Simulated water-level changes are greatest at withdrawal sites and decrease outward with distance elsewhere. Simulated water-level declines at proposed withdrawal sites generally were less than 0.5 feet. The low-permeability dike complex of East Molokai Volcano impedes the spread of water-level changes to perennial streams in the northeastern part of the island, and discharge to these streams in the dike complex therefore is unaffected by the proposed withdrawals. Simulated coastal-discharge changes generally are greatest immediately downgradient from sites of withdrawal change. Simulated coastal-discharge reductions generally are less than 30,000 gallons per day (and everywhere less than 75,000 gallons per day) within model elements for scenarios that exclude the Hawaii Department of Hawaiian Home Lands reservation (2.905 million gallons per day). (Model elements cover discrete 1,640-feet by 1,640-feet square areas.) Simulated coastal-discharge reductions generally represent less than 5 percent change relative to 2005 base-case conditions. Simulated discharge to some fishponds and springs increased in response to decreased withdrawal at upgradient sites, and simulated discharge to other fishponds and springs decreased in response to increased withdrawal. Simulated water-level declines associated with the Hawaii Department of Hawaiian Home Lands reservation were as much as 4 feet at three arbitrarily selected withdrawal sites, and simulated reductions in coastal discharge between Umipaa and Kamiloloa along the south coast exceeded 200,000 gallons per day from several model elements.

Scientific Investigations Report↗
USGS2012

Automating calibration, sensitivity and uncertainty analysis of complex models using the R package Flexible Modeling Environment (FME): SWAT as an example

Parameter optimization and uncertainty issues are a great challenge for the application of large environmental models like the Soil and Water Assessment Tool (SWAT), which is a physically-based hydrological model for simulating water and nutrient cycles at the watershed scale. In this study, we present a comprehensive modeling environment for SWAT, including automated calibration, and sensitivity and uncertainty analysis capabilities through integration with the R package Flexible Modeling Environment (FME). To address challenges (e.g., calling the model in R and transferring variables between Fortran and R) in developing such a two-language coupling framework, 1) we converted the Fortran-based SWAT model to an R function (R-SWAT) using the RFortran platform, and alternatively 2) we compiled SWAT as a Dynamic Link Library (DLL). We then wrapped SWAT (via R-SWAT) with FME to perform complex applications including parameter identifiability, inverse modeling, and sensitivity and uncertainty analysis in the R environment. The final R-SWAT-FME framework has the following key functionalities: automatic initialization of R, running Fortran-based SWAT and R commands in parallel, transferring parameters and model output between SWAT and R, and inverse modeling with visualization. To examine this framework and demonstrate how it works, a case study simulating streamflow in the Cedar River Basin in Iowa in the United Sates was used, and we compared it with the built-in auto-calibration tool of SWAT in parameter optimization. Results indicate that both methods performed well and similarly in searching a set of optimal parameters. Nonetheless, the R-SWAT-FME is more attractive due to its instant visualization, and potential to take advantage of other R packages (e.g., inverse modeling and statistical graphics). The methods presented in the paper are readily adaptable to other model applications that require capability for automated calibration, and sensitivity and uncertainty analysis.

Environmental Modelling and Software↗
USGS2019

Individual based modelling of fish migration in a 2-D river system: Model description and case study

Context: Diadromous fish populations in the Pacific Northwest face challenges along their migratory routes from declining habitat quality, harvest, and barriers to longitudinal connectivity. These stressors complicate the prioritization of proposed management actions intended to improve conditions for migratory fishes including anadromous salmon and trout. Objectives: We describe a multi-scale hybrid mechanistic–probabilistic simulation model linking migration corridor conditions to fish fitness outcomes. We demonstrate the model’s utility using a case study of salmon and steelhead adults in the Columbia River migration corridor exposed to spatially- and temporally-varying stressors. Methods: The migration corridor simulation model is based on a behavioral decision tree that governs individual interactions with the environment, and an energetic submodel that estimates the hourly costs of migration. Emergent properties of the migration corridor simulation model include passage time, energy use, and survival. Results: We observed that the simulated fish’s initial energy density, the migration corridor temperatures they experienced, and their history of behavioral thermoregulation were the primary determinants of their fitness outcomes. Insights gained from use of the model might be exploited to identify management interventions that increase successful migration outcomes. Conclusions: This paper describes new methods that extend the suite of tools available to aquatic biologists and conservation practitioners. We have developed a 2-dimensional spatially-explicit behavioral and physiological model and illustrated how it can be used to simulate fish migration within a river system. Our model can be used to evaluate trade-offs between behavioral thermoregulation and fish fitness at population scales.

Landscape Ecology↗