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At least 955 records · Page 53Linked to original sources

USGS1989

Prairie basin wetlands of the Dakotas: a community profile

This description of prairie basin wetlands of the Dakotas is part of a series of community profiles on ecologically important wetlands of national significance. The shallow wetlands of the Dakotas form the bulk of the portion of the Prairie Pothole Region lying within the United States. This region is famous as the producer of at least half of North America's waterfowl and an unknown, but large, proportion of other prairie-dwelling marsh and aquatic birds.The wetlands described here lie in relatively small, shallow basins that vary greatly in their ability to maintain surface water, and in their water chemistry, which varies from fresh to hypersaline. These wetlands occur in a wide variety of hydrological settings, in an area where annual and seasonal precipitation varies greatly in form and amount. Thus the presence of surface water in these wetlands is largely unpredictable. Superimposed on these phenomena are the effects of a variety of land uses, including pasture, cultivation, mechanical forage removal, idle conditions and burning. All those factors greatly affect the plant and animal communities found in these basins.This profile covers lacustrine and palustrine basins with temporarily flooded, seasonally flooded, and semipermanently flooded water regimes. Basins with these water regimes compose about 90% of the basins in the Prairie Pothole Region of the Dakotas. This profile outlines the wetland subsystems, classes and subclasses that occur in these basins, and provides a useful reference to their geologic, climatic, hydrologic, and pedologic setting.Detailed information on the biotic environment of the wetlands dealt with in this profile will be useful to scientists and resource managers. Special recognition is paid to the macrophyte and invertebrate communities, which have dynamic qualities found in few other of the world's wetland ecosystems.The most noteworthy animal inhabitants of these basins are waterfowl, which are a resource of international concern. Because of the importance of this resource, much research on the habitat use and feeding ecology of breeding waterfowl has been conducted in the region. These topics receive special attention in this profile.The Prairie Pothole Region is a major world supplier of cereal grains. Consequently, wetlands in the region are often drained for crop production or otherwise cropped when water conditions permit. These practices degrade the value of wetlands for most species of wildlife and conflict with the aims of conservationists. The subject of human uses and impacts to prairie wetlands is thus an important part of this profile.

Biological Report↗

USGS2010

Simulation of lake evaporation with application to modeling lake level variations of Harney‐Malheur Lake, Oregon

A physically based eddy diffusion model for simulating the seasonal variation in lake temperature and evaporation is presented and validated. Because no lake‐specific fitting of the parameters of the model is necessary, the model can be used to simulate evaporation in studies of climate change and lake hydrology in a variety of settings. The eddy diffusion model is used to simulate evaporation for input to a simple lake level model that is applied to reconstruct recent fluctuations in the level of Harney‐Malheur Lake caused by climatic variations.

Oregon↗

USGS2012

Land-use and land-cover scenarios and spatial modeling at the regional scale

Land-use and land-cover (LULC) change has altered a large part of the earth's surface. Scenarios of potential future LULC change are required in order to better manage potential impacts on biodiversity, carbon fluxes, climate change, hydrology, and many other ecological processes. The U.S. Geological Survey is analyzing potential future LULC change in the United States, using an approach based on scenario construction and spatially explicit modeling. Similar modeling techniques are being used to produce historical LULC maps from 1940 to present. With the combination of backcast and forecast LULC data, the USGS is providing consistent LULC data for historical, current, and future time frames to support a variety of research applications.

Fact Sheet↗

USGS2021

Hierarchical clustering for paired watershed experiments: Case study in southeastern Arizona, U.S.A.

Watershed studies are often onerous due to a lack of data available to portray baseline conditions with which to compare results of monitoring environmental effects. A paired-watershed approach is often adopted to simulate baseline conditions in an adjacent watershed that can be comparable but assumes there is a quantifiable relationship between the control and treated watersheds. Finding suitably matched pairs that can most accurately depict similar responses is challenging and attributes are rarely quantified. In southeastern Arizona, United States, researchers are investigating the effectiveness of watershed restoration techniques employed by land managers. We selected Smith Canyon to develop a rigorous and quantitatively defensible paired-watershed experimental design. The Smith Canyon watershed consists of 91 structurally similar sub-basins that have a defined basin-like structure and flow channel, allowing for consideration as replicate units. We developed a statistical approach to group sub-basins based on similar structural, biophysical, and hydrologic traits. Our geospatial database consisted of 35 environmental variables, which we reduced to 12 through a correlation analysis. We identified three primary collections of paired sub-basins within the larger watershed. These clusters are being used to inform studies actively being employed in the watershed. Overall, we propose a hierarchical clustering protocol for justification of watershed pairing experiments.

Arizona↗

USGS1983

Evaluating environmental and economic consequences of alternative pest management strategies: results of modeling workshops

The U.S. Environmental Protection Agency (EPA) needs a comprehensive method to evaluate the human health and environmental effects of alternative agricultural pest management strategies. This project explored the utility of Adaptive Environmental Assessment (AEA) techniques for meeting this need. The project objectives were to produce models for environmental impact analysis, improve communications, identify research needs and data requirements, and demonstrate a process for resolving conflicts. The project was structured around the construction (in an initial 2 1/2-day workshop) and examination (in a second 2 1/2-day workshop) of a simulation model of a corn agroecosystem. The model conceptualized at the first workshop simulates the effect of corn agrecosystem decisions on crop production, economic returns, and environmental indicators. The model is composed of five interacting submodels: 1) a Production Strategies submodel which makes decisions concerning tillage, planting, fertilizer and pesticide applications, and harvest; 2) a Hydrology/Chemical Transport submodel which represents soil hydrology, erosion, and concentrations of fertilizers and pesticides in the soil, runoff, surface waters, and percolation; 3) a Vegetation submodel which simulates growth of agricultural crops (corns and soybeans) and weeds; 4) a Pests submodel which calculates pest population levels and resulting crop damage; and 5) an Environmental Effects submodel which calculates indicators of potential fish kills, human health effects, and wildlife habitat. The most persistent data gaps encountered in quantifying the model were coefficients to relate environmental consequences to alternative pest management strategies. While the model developed in the project is not yet accurate enough to be used for real-world decisions about the use of pesticides on corn, it does contain the basic structure upon which such a model could be built. More importantly at this stage of development, the project has shown that very complex systems can be modeled in short periods of time and that the process of building such models increases understanding among disciplinary specialists and between diverse institutional interests. This process can be useful to EPA as the agency cooperates with other institutions to meet its responsibilities in less costly ways. Activities at the second 2 1/2-day workshop included a review of the model, incorporation of necessary corrections, simulation of policy scenarios, and examination of techniques to address remaining institutional conflicts. Participants were divided into three groups representing environmental, production or industry, and regulatory interests. Each group developed scenarios that would be most appealing to their particular interest and the scenarios were simulated by the agroecosystem computer model. Negotiators from each of the interest groups decided whether a hypothetical herbicide should be relabeled and if certain restrictions should be imposed on its use. Other participants functioned as experts and consultants on caucus teams. A solution to the hypothetical problem was successfully negotiated. Workshop participants and project staff agreed that the model and processes developed during the project should be used in training students, extension specialists, farmers, researchers, and chemical producers in collaborative problem solving methods. More productive research can be planned, and more realistic models of complex systems can be built in this way. More importantly, greater trust of decisionmakers in computer models, better understanding by technical experts about disciplines other than their own, and improved cooperation between institutional interests can be achieved. This trust, understanding, and cooperation are critical ingredients in solving problems that are too complex to be resolved by independent disciplinary activity and unilateral decision authority.

Report↗

USGS1990

Modelling streamwater chemistry as a mixture of soilwater end-members - An application to the Panola Mountain catchment, Georgia, U.S.A.

Streamwater chemistry at Panola Mountain research catchment, Georgia, U.S.A., is explained as a mixture of representative soilwater solutions that are considered to be temporally invariant to a first approximation. The selection of three end-members from all sampled soil waters is evaluated by comparing the observed and predicted streamwater concentration of six solutes (alkalinity, sulfate, sodium, magnesium, calcium and dissolved silica), which are assumed to mix conservatively, and by assessing the consistency of the implied hydrograph separation with the hydrological mechanisms that are believed to be operating in this catchment. The percentage of variation in the streamwater solute concentrations explained by the end-member mixing analysis (EMMA) ranges from 82 to >97%, and the hydrograph separation is, intuitively, physically reasonable. If the correct end-members have been identified, the streamwater chemical response to different levels of acidic deposition can be predicted by examining the change in each end-member under different loads; no hydrological model is required. If a traditional hydrochemical model, which is driven by rainfall quantity and quality, is desired, this analysis provides an indication of the model structure that would be necessary to reproduce both streamwater and soilwater chemistry.

Georgia↗

USGS2019

Multiorder hydrologic position in the conterminous United States: A set of metrics in support of groundwater mapping at regional and national scales

The location of a point on the landscape within a stream network (hydrologic position) can be an important predictive measure in hydrology. Hydrologic position is defined here by two metrics: lateral position and distance from stream to divide, both measured horizontally. Lateral position (dimensionless) is the relative position of a point between the stream and its watershed divide. Distance from stream to divide (units of length) is an indicator of position within a watershed: generally small near a confluence and generally large in headwater areas. Watersheds and watershed divides are defined here by Thiessen polygons rather than topographic divides. Lateral position and distance from stream to divide are also defined in the context of hydrologic order. Hydrologic order “ n ” is defined as the network of streams, and associated divides, of order n and higher. And given that a point can have different positions in different hydrologic orders the term multiorder hydrologic position (MOHP) is used to describe the ensemble of hydrologic positions. MOHP was mapped across the conterminous United States for nine hydrologic orders at a spatial resolution of 30 m (about 8.7 billion pixels). There are 18 metrics for each pixel. Four case studies are presented that use MOHP metrics as explanatory factors in random forest machine learning models. The case studies show that lower order MOHP metrics can serve as indicators of hydrologic process while higher‐order metrics serve as indicators of location. MOHP is shown to have utility as a predictor variable across a large range of scales (50,000 to 8,000,000 km 2 ).

Water Resources Research↗

USGS2012

Wetland fire remote sensing research--The Greater Everglades example

Fire is a major factor in the Everglades ecosystem. For thousands of years, lightning-strike fires from summer thunderstorms have helped create and maintain a dynamic landscape suited both to withstand fire and recover quickly in the wake of frequent fires. Today, managers in the Everglades National Park are implementing controlled burns to promote healthy, sustainable vegetation patterns and ecosystem functions. The U.S. Geological Survey (USGS) is using remote sensing to improve fire-management databases in the Everglades, gain insights into post-fire land-cover dynamics, and develop spatially and temporally explicit fire-scar data for habitat and hydrologic modeling.

Florida↗

USGS2018

Evaluating and managing environmental water regimes in a water-scarce and uncertain future

While the number of environmental flows and water science programmes continues to grow across the globe, there remains a critical need to better balance water availability in support of human and ecological needs and to recognise the environment as a legitimate user of water. In water‐stressed areas, this recognition has resulted in friction between water users in the public and private sectors. An opportunity exists for practitioners to be on the forefront of the science determining best practices for supporting environmental water regimes. This Special Issue brings together a collection of environmental flows science and water management papers organised around three major themes: (1) method development and testing; (2) application case studies; and (3) efficacy evaluation. Contents of this Special Issue are intended to foster collaboration and broaden transferability of the information, technical tools, models and methods needed to support environmental water management programmes. The technical sophistication of methods and modelling tools, while important to the advancement of environmental water science, may come at the expense of easily interpretable outcomes that positively influence management decisions. Researchers need to be more proactive in translating the results of advanced modelling methodologies into user‐friendly tools and methods. This will allow stakeholders and water managers to proactively test alternative water allocation scenarios to help address growing human water demands in the face of droughts and changes in climatic patterns. The application of environmental flows science and water management strategies cannot be done in isolation. Implementation involves a complex decision‐making process that integrates ecological, hydrologic and social science across diverse multifaceted governance systems and requires active stakeholder involvement. Scientists and managers must strengthen partnerships at multiple scales to develop sensible science investment strategies so that collective knowledge can be translated into wise environmental water management decisions.

Freshwater Biology↗

USGS1999

Vertical exchange of ground water and surface water in the Florida Everglades

Introduction and Project Objectives Knowledge about hydrologic exchange between surface water and ground water is critical to understanding the movement of water and dissolved chemical constituents (solutes) in the Florida Everglades. This fact sheet describes a study that will quantify vertical exchange of water and solutes in the Everglades as part of the U.S. Geological Survey's (USGS) South Florida Ecosystem Program. The two sites selected for the initial investigation are shown in the report. Those sites are the location of ongoing research projects concerned with movement and transformation of nutrients and mercury. Research results are being used by the South Florida Water Management District (SFWMD) to guide in the planning of Stormwater Treatment Areas, which will be large constructed wetlands designed to remove excess nutrients from agricultural drainage. The objectives of the project described here are to (1) quantify vertical exchange of water (also referred to as seepage) between ground water and surface water, (2) use seepage estimates to assist in the development of chemical mass balances for mercury and nutrients, and (3) relate seepage fluxes to subsurface hydrogeologic properties, management of surface-water levels in canals and water conservation areas, and the regional water balance in the northern Everglades.

Florida↗

USGS2008

Description of Existing Data for Integrated Landscape Monitoring in the Puget Sound Basin, Washington

This report summarizes existing geospatial data and monitoring programs for the Puget Sound Basin in northwestern Washington. This information was assembled as a preliminary data-development task for the U.S. Geological Survey (USGS) Puget Sound Integrated Landscape Monitoring (PSILM) pilot project. The PSILM project seeks to support natural resource decision-making by developing a 'whole system' approach that links ecological processes at the landscape level to the local level (Benjamin and others, 2008). Part of this effort will include building the capacity to provide cumulative information about impacts that cross jurisdictional and regulatory boundaries, such as cumulative effects of land-cover change and shoreline modification, or region-wide responses to climate change. The PSILM project study area is defined as the 23 HUC-8 (hydrologic unit code) catchments that comprise the watersheds that drain into Puget Sound and their near-shore environments. The study area includes 13 counties and more than four million people. One goal of the PSILM geospatial database is to integrate spatial data collected at multiple scales across the Puget Sound Basin marine and terrestrial landscape. The PSILM work plan specifies an iterative process that alternates between tasks associated with data development and tasks associated with research or strategy development. For example, an initial work-plan goal was to delineate the study area boundary. Geospatial data required to address this task included data from ecological regions, watersheds, jurisdictions, and other boundaries. This assemblage of data provided the basis for identifying larger research issues and delineating the study-area boundary based on these research needs. Once the study-area boundary was agreed upon, the next iteration between data development and research activities was guided by questions about data availability, data extent, data abundance, and data types. This report is not intended as an exhaustive compilation of all available geospatial data, rather, it is a collection of information about geospatial data that can be used to help answer the suite of questions posed after the study-area boundary was defined. This information will also be useful to the PSILM team for future project tasks, such as assessing monitoring gaps, exploring monitoring-design strategies, identifying and deriving landscape indicators and metrics, and visual geographic communication. The two main geospatial data types referenced in this report - base-reference layers and monitoring data - originated from numerous and varied sources. In addition to collecting information and metadata about the base-reference layers, the data also were collected for project needs, such as developing maps for visual communication among team members and with outside groups. In contrast, only information about the data was typically required for the monitoring data. The information on base-reference layers and monitoring data included in this report is only as detailed as what was readily available from the sources themselves. Although this report may appear to lack consistency between data records, the varying degree of details contained in this report are merely a reflection of varying source detail. This compilation is just a beginning. All data listed also are being catalogued in spreadsheets and knowledge-management systems. Our efforts are continual as we develop a geospatial catalog for the PSILM pilot project.

Open-File Report↗

USGS2013

Knowledge and understanding of dissolved solids in the Rio Grande–San Acacia, New Mexico, to Fort Quitman, Texas, and plan for future studies and monitoring

Availability of water in the Rio Grande Basin has long been a primary concern for water-resource managers. The transport and delivery of water in the basin have been engineered by using reservoirs, irrigation canals and drains, and transmountain-water diversions to meet the agricultural, residential, and industrial demand. In contrast, despite the widespread recognition of critical water-quality problems, there have been minimal management efforts to improve water quality in the Rio Grande. Of greatest concern is salinization (concentration of dissolved solids approaching 1,000 mg/L), a water-quality problem that has been recognized and researched for more than 100 years because of the potential to limit both agricultural and municipal use. To address the issue of salinization, water-resource managers need to have a clear conceptual understanding of the sources of salinity and the factors that control storage and transport, identify critical knowledge gaps in this conceptual understanding, and develop a research plan to address these gaps and develop a salinity management program. In 2009, the U.S. Geological Survey (USGS) in cooperation with the U.S. Army Corps of Engineers (USACE), New Mexico Interstate Stream Commission (NMISC), and New Mexico Environment Department (NMED) initiated a project to summarize the current state of knowledge regarding the transport of dissolved solids in the Rio Grande between San Acacia, New Mexico, and Fort Quitman, Texas. The primary objective is to provide hydrologic information pertaining to the spatial and temporal variability present in the concentrations and loads of dissolved solids in the Rio Grande, the source-specific budget for the mass of dissolved solids transported along the Rio Grande, and the locations at which dissolved solids enter the Rio Grande. Dissolved-solids concentration data provide a good indicator of the general quality of surface water and provide information on the factors governing salinization within the Rio Grande study area. The pattern in dissolved-solids concentrations along the Rio Grande is one of increasing concentration with increasing distance downstream from Elephant Butte and Caballo Reservoirs. The concentration of dissolved solids in the Rio Grande doubles (approximately 500 to 1,000 mg/L) from below Elephant Butte Reservoir to El Paso and increases by more than a factor of 5 (approximately 500 to 3,200 mg/L) from below Elephant Butte Reservoir to Fort Quitman. Marked increases in the concentration of dissolved solids commonly coincide with contributions from agricultural drains, wastewater-treatment plants, regional groundwater, and upward-flowing saline groundwater. The greatest factor, from the surface-water system, in controlling dissolved solids in the Rio Grande is the amount of water that is being transported or stored. Annual variation in streamflow is influenced primarily by climate (precipitation and evaporation) and management of Elephant Butte and Caballo Reservoirs (water storage and release cycles). Seasonal variation in streamflow within the Rio Grande study area is generally categorized generally as irrigation (March–September) and nonirrigation (October–February) seasons; with streamflow in the Rio Grande is highest during the irrigation season and lowest during the nonirrigation season. Dissolved-solids loads during the irrigation season decrease between Leasburg and Fort Quitman primarily because of irrigation diversions and losses to the underlying alluvial aquifer. Conversely, dissolved-solids loads during the nonirrigation season increase between Caballo Dam and Fort Quitman primarily because of the inflow of dissolved solids from agricultural drains, wastewater-treatment plants, and groundwater with elevated concentrations of dissolved solids. Many studies have mass-balance budgets that account for the mass of dissolved solids transported along the Rio Grande. Results from mass-balance budgets developed for dissolved solids indicated that (1) the inflow of saline groundwater, inflow of regional groundwater, and chemical reactions between mineral phases are the primary sources controlling dissolved solids in the Rio Grande, and (2) groundwater pumping and mineral precipitation are causing a net storage of dissolved solids in the Leasburg to El Paso and El Paso to Fort Quitman reaches of the Rio Grande. Looking forward, multiple water-resource managers from State and local agencies in New Mexico and Texas and Federal agencies formed the Rio Grande Salinity Management Coalition with the goal to reduce the amount of dissolved solids that are transported and stored in the Rio Grande study area. The recommendations for additional monitoring to assist the coalition are as follows: -Monitoring: Couple water-quality and streamflow monitoring in the Rio Grande and agricultural drains; perform groundwater-seepage investigations in the Rio Grande and major agricultural drains; nonitor groundwater water-quality conditions in the Mesilla and Hueco Basins. -Focused Hydrogeology Studies at Inflow Sources: Map dissolved-solids concentrations in the Rio Grande and underlying alluvial aquifer; perform hydrogeologic characterization of subsurface areas containing unusually high concentrations of dissolved solids. -Modeling of Dissolved Solids: Develop models to simulate the transport and storage of dissolved solids in both surface-water and groundwater systems.

New Mexico;Texas↗

USGS2013

Potential effects of climate change on inland glacial lakes and implications for lake-dependent biota in Wisconsin: final report April 2013

The economic vitality and quality of life of many northern Wisconsin communities is closely associated with the ecological condition of the abundant water resources in the region. Climate change models predict warmer temperatures, changes to precipitation patterns, and increased evapotranspiration in the Great Lakes region. Recently (1950-2006), many regions of Wisconsin have experienced warming, and precipitation has generally increased except in far northern Wisconsin. Modeling conducted by the University of Wisconsin Nelson Environmental Institute Center for Climate Research predicts an increase in annual temperature by the middle of the 21st century of approximately 6° F statewide, and an increase in precipitation of 1”–2”. However, summer precipitation in the northern part of the state is expected to be less and winter precipitation will be greater. By the end of the 21st century, the magnitude of changes in temperature and precipitation are expected to intensify. Such climatic changes have altered, and would further alter hydrological, chemical, and physical properties of inland lakes. Lake-dependent wildlife sensitive to changes in water quality, are particularly susceptible to lake quality-associated habitat changes and are likely to suffer restrictions to current breeding distributions under some climate change scenarios. We have selected the common loon (Gavia immer) to serve as a sentinel lake-dependent piscivorous species to be used in the development of a template for linking primary lake-dependent biota endpoints (e.g., decline in productivity and/or breeding range contraction) to important lake quality indicators. In the current project, we evaluate how changes in freshwater habitat quality (specifically lake clarity) may impact common loon lake occupancy in Wisconsin under detailed climate-change scenarios. In addition, we employ simple land-use/land cover and habitat scenarios to illustrate the potential interaction of climate and land-use/land cover effects. The methods employed here provide a template for studies where integration of physical and biotic models is used to project future conditions under various climate and land use change scenarios. Findings presented here project the future conditions of lakes and loons within an important watershed in northern Wisconsin – of importance to water resource managers and state citizens alike.

Wisconsin↗

USGS1996

Developing a temporal database of urban development for the Baltimore/Washington region

The U.S. Geological Survey (USGS), the University of Maryland Baltimore County (UMBC), and the U.S. Bureau of the Census are working together as a multiagency, multidisciplinary team in developing a temporal database that documents the growth of the Baltimore-Washington metropolitan region. This database consists of urban development, principal transportation, shoreline, and population density change. The urban development theme, considered a primary data layer in the study of urban land transformation resulting from human impact on the land, is the focus of this paper. The Baltimore-Washington Spatial Dynamics and Human Impacts Study builds on earlier research efforts that mapped urban land use change for the San Francisco Bay area (Acevedo and Bell, 1994; Bell and others, 1995; Kirtland and others, 1994). In developing a temporal database (Acevedo and others, in press), the team participants hope to provide data that can be used to study patterns of urban growth; assess ecological, environmental, and climatic impacts of urban change; and model and predict future urbanization patterns and impacts (Clarke and others, 1996). Both the San Francisco and Baltimore-Washington regions were selected because of the rapid urban growth and resulting impacts on their ecosystems. The Chesapeake Bay region in particular has undergone extensive environmental agitation due to the hydrologic problems that have arisen from the increase in impermeable surfaces and structures, that is buildings and pavement that physically cover the soil. Because of the inability of water to percolate into the ground, little purification occurs by filtration. Water runs over paved surfaces and quickly washes high levels of toxins directly into the water system. Toxins like gasoline, oil, and fertilizer have dramatically affected the local streams, rivers, and the bay. ABSTRACT The U.S. Geological Survey, the University of Maryland Baltimore County, and the U.S. Bureau of the Census are developing a temporal database to study urban development in the Baltimore-Washington region. The primary data layer, the extent of urban or built-up areas, was compiled using a geographic information system and historical maps, remotely sensed data, digital land use data, and census information from a variety of sources. Urban land use change has been documented by the Baltimore-Washington Spatial Dynamics & Human Impact Study Team for the last 200 years. The methods, definitions, and collection criteria used to define urban or built-up areas were developed by a multi-disciplinary team that also ensures consistency in collection techniques and documentation methods for subsequent application in other regions. Animation techniques were used to visualize the database and to document the evolution of the region's urban landscape. The database is an important tool to urban and regional planners, ecologists, and global change researchers for measuring trends in urban sprawl, analyzing patterns of water pollution, understanding the impacts of development on ecosystems, and developing predictive modeling techniques to better forecast areas of urban growth. This paper describes the techniques used to map the extent of urban areas for Phase I and does not discuss Phase II in detail because the work is still in progress. In this study, urban development is defined as areas of intensive use, with much of the land covered by structures. The built-up areas are characterized by the existence of a systematic street pattern, and the relative concentration of buildings and associated intensive use areas, such as parking lots. Using this definition, urban development does not refer to political boundaries and may include incorporated or unincorporated areas as well as military reservations. ABSTRACT The U.S. Geological Survey, the University of Maryland Baltimore County, and the U.S. Bureau of the Census are developing a temporal database to study urban development in the Baltimore-Washington region. The primary data layer, the extent of urban or built-up areas, was compiled using a geographic information system and historical maps, remotely sensed data, digital land use data, and census information from a variety of sources. Urban land use change has been documented by the Baltimore-Washington Spatial Dynamics & Human Impact Study Team for the last 200 years. The methods, definitions, and collection criteria used to define urban or built-up areas were developed by a multi-disciplinary team that also ensures consistency in collection techniques and documentation methods for subsequent application in other regions. Animation techniques were used to visualize the database and to document the evolution of the region's urban landscape. The database is an important tool to urban and regional planners, ecologists, and global change researchers for measuring trends in urban sprawl, analyzing patterns of water pollution, understanding the impacts of development on ecosystems, and developing predictive modeling techniques to better forecast areas of urban growth. To build the urban component of the temporal database, a multidisciplinary team was assembled and a phased approach initiated. Expanding on procedures developed for the San Francisco Regional Study (Bell and others, 1995), the team developed data definitions, a classification scheme, compilation criteria, mapping specifications, guidelines for source materials, and metadata specifications to support development of a logically consistent dataset. Extensive documentation procedures were established to ensure consistency in data collection, and for subsequent application to other regions. Phase II was the implementation of the regional mapping effort. ABSTRACT The U.S. Geological Survey, the University of Maryland Baltimore County, and the U.S. Bureau of the Census are developing a temporal database to study urban development in the Baltimore-Washington region. The primary data layer, the extent of urban or built-up areas, was compiled using a geographic information system and historical maps, remotely sensed data, digital land use data, and census information from a variety of sources. Urban land use change has been documented by the Baltimore-Washington Spatial Dynamics & Human Impact Study Team for the last 200 years. The methods, definitions, and collection criteria used to define urban or built-up areas were developed by a multi-disciplinary team that also ensures consistency in collection techniques and documentation methods for subsequent application in other regions. Animation techniques were used to visualize the database and to document the evolution of the region's urban landscape. The database is an important tool to urban and regional planners, ecologists, and global change researchers for measuring trends in urban sprawl, analyzing patterns of water pollution, understanding the impacts of development on ecosystems, and developing predictive modeling techniques to better forecast areas of urban growth. The study area for Phase I consisted of an approximate area of 15- by 15-minute segment centered around the city of Baltimore (fig. 1). Phase I was used as a prototype for the technique development and integration that the multiagency collaborative effort would require. The regional study, Phase II, encompassed a 2-degree square centered on Washington, D.C. With more than 7 million people spread across 39 counties, the Baltimore-Washington region is one the Nation's fastest growing metropolitan areas. The two cities are rapidly merging into one.

Maryland↗

USGS2016

Geochemical evidence for seasonal controls on the transportation of Holocene loess, Matanuska Valley, southern Alaska, USA

Loess is a widespread Quaternary deposit in Alaska and loess accretion occurs today in some regions, such as the Matanuska Valley. The source of loess in the Matanuska Valley has been debated for more than seven decades, with the Knik River and the Matanuska River, both to the east, being the leading candidates and the Susitna River, to the west, as a less favorable source. We report here new stratigraphic, mineralogic, and geochemical data that test the competing hypotheses of these river sources. Loess thickness data are consistent with previous studies that show that a source or sources lay to the east, which rules out the Susitna River as a source. Knik and Matanuska River silts can be distinguished using Sc–Th–La, La N /Yb N vs. Eu/Eu ∗ , Cr/Sc, and As/Sb. Matanuska Valley loess falls clearly within the range of values for these ratios found in Matanuska River silt. Dust storms from the Matanuska River are most common in autumn, when river discharge is at a minimum and silt-rich point bars are exposed, wind speed from the north is beginning to increase after a low-velocity period in summer, snow depth is still minimal, and soil temperatures are still above freezing. Thus, seasonal changes in climate and hydrology emerge as critical factors in the timing of aeolian silt transport in southern Alaska. These findings could be applicable to understanding seasonal controls on Pleistocene loess accretion in Europe, New Zealand, South America, and elsewhere in North America.

Alaska↗

USGS2018

Regionalization of groundwater residence time using metamodeling

Groundwater residence-time distributions (RTDs) are critical for assessing susceptibility of water resources to degradation. A novel combination of numerical modeling and statistical methods allows estimation of regional RTDs with unprecedented speed. In this method, particle RTDs are generated in 30 type locales in the northeastern glaciated U.S using automated generalized finite-difference groundwater flow and advective transport models. Targets for statistical learning were created from particle RTDs by fitting Weibull, gamma, and inverse Gaussian distributions. Whole-basin flux-weighted RTDs were well fit by one-component Weibull distributions. Flux-weighted RTDs at stressed receptors such as wells often produced more complicated RTDs that required a two-component mixture to fit. A Multitask Lasso regression was trained on the parametric RTDs using hydrogeographic features of the modeled areas as explanatory features. In this way, RTDs are regionalized using mappable physical features such as recharge and aquifer volume. The shape, location, and scale parameters of the parametric RTDs are strongly related to the mean exponential age. The shape parameter of the distribution, which controls deviation from exponential, is additionally a function of aquifer heterogeneity and hydrologic features. Regionalized RTDs provide useful metrics with respect to groundwater lag times and solute loading to streams. The lag time between input and output contained in the RTD is critical to understanding the relation between the land surface and human and ecological receptors.

Water Resources Research↗

USGS2020

Inundation exposure assessment for Majuro Atoll, Republic of the Marshall Islands using a high-accuracy digital elevation model

Majuro Atoll in the central Pacific has high coastal vulnerability due to low-lying islands, rising sea level, high wave events, eroding shorelines, a dense population center, and limited freshwater resources. Land elevation is the primary geophysical variable that determines exposure to inundation in coastal settings. Accordingly, coastal elevation data (with accuracy information) are critical for assessments of inundation exposure. Previous research has demonstrated the importance of using high-accuracy elevation data and rigorously accounting for uncertainty in inundation assessments. A quantitative analysis of inundation exposure was conducted for Majuro Atoll, including accounting for the cumulative vertical uncertainty from the input digital elevation model (DEM) and datum transformation. The project employed a recently produced and validated DEM derived from structure-from-motion processing of very-high-resolution aerial imagery. Areas subject to marine inundation (direct hydrologic connection to the ocean) and low-lying lands (disconnected hydrologically from the ocean) were mapped and characterized for three inundation levels using deterministic and probabilistic methods. At the highest water level modeled (3.75 ft, or 1.143 m), more than 34% of the atoll study area is likely to be exposed to inundation (68% chance or greater), while more than 20% of the atoll is extremely likely to be exposed (95% chance or greater). The study demonstrates the substantial value of a high-accuracy DEM for assessing inundation exposure of low-relief islands and the enhanced information from accounting for vertical uncertainty.

Majuro Atoll↗

USGS2020

A socio-environmental geodatabase for integrative research in the transboundary Rio Grande/Río Bravo basin

Management of water resources in the transboundary Rio Grande/Río Bravo Basin (the Basin) presents challenges for state and Federal entities in the United States and Mexico making management decisions on shared water resources. Damming, channelization, water availability, and allocation are governed by water rights and water-sharing agreements. Data and information sharing are important aspects of transboundary cooperation, but differences in format, content, spatial and temporal resolution, and language hinder collaboration. In addition, data on the kinds and geographic distribution of water governance and management institutions across the Basin have not been consistently documented. Existing data disparities parallel the hydrological and social fragmentation of the Basin. Seeking to underscore the interdependence between social and environmental processes in the Basin, anthropologists and modelers collaborated to develop a socio-environmental geodatabase. This geodatabase is a first step in modeling the social components of decision making and their connectivity to environmental processes across the Basin. The geodatabase is available in an open-access domain and contains geospatial data related to water and land governance, hydrology, water use and hydraulic infrastructure, socioeconomics, and the biophysical environment necessary to advance the understanding of basin dynamics. Having these data documented and compiled in a central location serves as a resource to help decision makers better understand upstream and downstream social-environmental characteristics. This knowledge is useful for developing sustainable water management policies in a region where water resources are increasingly under pressure from climatic, environmental, and human-related changes.

Chihuahua, New Mexico, Texas↗