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At least 397 records · Page 22Linked to original sources
USGS1996

Small watershed studies: Analytical approaches for understanding ecosystem response to environmental change

Biogeochemical studies in small watersheds provide an analytical approach to understand how ecosystems respond to natural climatic variations and human-induced environmental change. Small watersheds, usually less than 5 km2, are small enough to permit characterization and understanding of ecosystem processes within relatively simple, homogeneous biological and physical settings; yet they are large enough to incorporate more complex processes and element cycles than can be studied at plot scales. Watersheds comprise discrete hydrochemical environments allowing quantification of hydrologic, element, and energy budgets. Element budgets, or mass balances, can be quantified as the difference between the mass of a solute that enters a watershed in wet and dry deposition and leaves a watershed in streamflow. Element budgets are primary tools used to investigate biogeochemical processes. Monitoring various aspects of element budgets to assess ecosystem health and stability is analogous to measuring the pulse or blood chemistry of a patient. Monitoring streamwater chemistry, basic climate, soil, and biotic variables provide a means to integrate complex biogeochemical processes and evaluate trends in water quality. Small watershed studies provide a scientific basis to develop predictive models of watershed function. Major emphases of small watershed studies include investigation of hydrologic and chemical responses to natural climate variation, anthropogenic stressors, and alternate forest-management practices. The nature and significance of biogeochemical research in small watersheds is reviewed by Moldan and Cerny (1994). The U.S. Geological Survey, U.S. Department of Agriculture Forest Service, and other federal agencies support several long-term small watershed studies to provide insight into a variety of ecosystem processes. Long-term records are essential to distinguish trends resulting from natural climatic variations or other stressors. The following sites, with noted periods of records, are examples of intensively studied forested watersheds in eastern USA supported by federal agencies: ■ Coweeta Hydrologic Laboratory, North Carolina, (1939-present), Swank and Crossley (1988). ■ Hubbard Brook Experimental Forest, New Hampshire, (1956-present), Bormann and Likens (1979). ■ Sleepers River Research Watershed, Vermont, (1958-present), Shanley et al. (1995). ■ Walker Branch Watershed, Tennessee, (1967-present), Johnson and Van Hook (1989). ■ Catoctin Mountains Research Site, Maryland, (1982-present), Rice and Bricker (1995). ■ Catskill Stream Network, New York, (1983- present), Murdoch and Stoddard (1992). ■ Panola Mountain Research Watershed, Georgia, (1985-present), Huntington et al. (1993). Small watershed studies also provide essential baseline information for understanding variations in water quality and element cycling in "pristine" ecosystems that can be used as benchmarks to evaluate anthropogenic impacts and alternate watershed management practices. This paper provides examples of how analytical tools developed through watershed research provide insight into ecosystem processes and can contribute to the management of watershed resources.

Conference Paper↗
USGS2019

Evaluation of chemical and hydrologic processes in the eastern Snake River Plain Aquifer based on results from geochemical modeling, Idaho National Laboratory, eastern Idaho

Nuclear research activities at the U.S. Department of Energy (DOE) Idaho National Laboratory (INL) produced liquid and solid chemical and radiochemical wastes that were disposed to the subsurface resulting in detectable concentrations of some waste constituents in the eastern Snake River Plain (ESRP) aquifer. These waste constituents may affect the water quality of the aquifer and may pose risks to the eventual users of the aquifer water. To understand these risks to water quality the U.S. Geological Survey, in cooperation with the DOE, conducted geochemical mass-balance modeling of the ESRP aquifer to improve the understanding of chemical reactions, sources of recharge, mixing of water, and groundwater flow directions in the shallow (upper 250 feet) aquifer at the INL. Modeling was conducted using the water chemistry of 127 water samples collected from sites at and near the INL. Water samples were collected between 1952 and 2017 with most of the samples collected during the mid-1990s. Geochemistry and isotopic data used in geochemical modeling consisted of dissolved oxygen, carbon dioxide, major ions, silica, aluminum, iron, and the stable isotope ratios of hydrogen, oxygen, and carbon. Geochemical modeling results indicated that the primary chemical reactions in the aquifer were precipitation of calcite and dissolution of plagioclase (An 60 ) and basalt volcanic glass. Secondary minerals other than calcite included calcium montmorillonite and goethite. Reverse cation exchange, consisting of sodium exchanging for calcium on clay minerals, occurred near site facilities where large amounts of sodium were released to the ESRP aquifer in wastewater discharge. Reverse cation exchange acted to retard the movement of wastewater-derived sodium in the aquifer. Regional groundwater inflow was the primary source of recharge to the aquifer underlying the Northeast and Southeast INL Areas. Birch Creek (BC), the Big Lost River (BLR), and groundwater from BC valley provided recharge to the North INL Area, and the BLR and groundwater from BC and Little Lost River (LLR) valleys provided recharge to the Central INL Area. The BLR, groundwater from the BLR and LLR valleys and the Lost River Range, and precipitation provided recharge to the Northwest and Southwest INL Areas. The primary source of recharge west and southwest of the INL was groundwater inflow from BLR valley. Upwelling geothermal water was a small source of recharge at two wells. Aquifer recharge from surface water in the northern, central, and western parts of the INL indicated that the aquifer in these areas was a dynamic, open system, whereas the aquifer in the eastern part of the INL, which receives little recharge from surface water, was a relatively static and closed system. Sources of recharge identified from isotope ratios and geochemical modeling (major ion concentrations) were nearly identical for the North, Northeast, Southeast, and Central INL Areas, which indicated that both methods probably accurately identified the sources of recharge in these areas. Conversely, isotope ratios indicated that the BLR and groundwater from the LLR valley provided most recharge to the western parts of the Northwest and Southwest INL Areas, whereas geochemical modeling results indicated a smaller area of recharge from the BLR and groundwater from the LLR valley, a larger area of recharge from the Lost River Range, and recharge of groundwater from the BLR valley that extended to the west INL boundary. The results from geochemical modeling probably were more accurate because major ion concentrations, but not isotope ratios, were available to characterize groundwater from the BLR valley and the Lost River Range. Sources of recharge identified with a groundwater flow model (using particle tracking) and geochemical modeling were similar for the Northeast and Southeast INL Areas. However, differences between the models were that the geochemical model represented (1) recharge of groundwater from the Lost River Range in the western part of the INL, whereas the flow model did not, (2) recharge of groundwater from the BC and BLR valleys extending farther south and east, respectively, than the flow model, and (3) more recharge from the BLR in the Southwest INL Area than the flow model. Mixing of aquifer water beneath the INL included (1) mixing of regional groundwater and water from the BC valley in the Northeast and Southeast INL Areas and (2) mixing of surface water (primarily from the BLR) and groundwater across much of the North, Central, Northwest, and Southwest INL Areas. Localized recharge from precipitation mixed with groundwater in the Northwest and Southwest INL Areas, and localized upwelling geothermal water mixed with groundwater in the Central and Northeast INL Areas. Flow directions of regional groundwater were south in the eastern part of the INL and south-southwest at downgradient locations. Groundwater from the BC and LLR valleys initially flowed southeast before changing to south-southwest flow directions that paralleled regional groundwater, and groundwater from the BLR valley initially flowed south before changing to a southsouthwest direction. Wastewater-contaminated groundwater flowed south from the Idaho Nuclear Technology and Engineering Center (INTEC) infiltration ponds in a narrow plume, with the percentage of wastewater in groundwater decreasing due to dilution, dispersion, and (or) degradation from about 60‒80 percent wastewater 0.7‒0.8 mile (mi) south of the INTEC infiltration ponds to about 1.4 percent wastewater about 15.5 mi south of the INTEC infiltration ponds. Wastewater contaminated groundwater flowed southeast and then southwest from the Naval Reactors Facility industrial waste ditch, with the percentage of wastewater in groundwater decreasing from about 100 percent wastewater adjacent to the waste ditch to about 2 percent wastewater about 0.6 mi south of the waste ditch.

Idaho↗
USGS2023

Hydrologic modeling and river corridor applications of HY_Features concepts

The WaterML2: Part 3 - Surface Hydrology Features (HY_Features) Conceptual Model was published by OGC in 2018. This report documents the use of HY_Features concepts in support of two key tasks: (1) local to continental hydrologic modeling; and (2) referencing river corridor data to hydrographic networks. The presented use cases are applicable in hydroscience research and assessments, water resources engineering practices, and drought and flood responses. Before the HY_Features conceptual model there was no internationally recognized standard for the design of software and data for the hydroscience and engineering community. This report presents progress towards a logical data model that interprets the abstract HY_Features concepts for use in geospatial workflows, modeling applications, and web data systems that integrate hydrologic data. The use cases addressed include: (1) hydrologic model control volume definition; (2) hydrologic network connectivity; (3) characterization of catchments with landscape and atmospheric data; (4) river corridor characterization; (5) hydrologic location; and (6) flow network location. Each use case is described briefly along with an analysis of the information requirements. This report presents a summary of the logical model designed to satisfy the needs of these use cases and a summary of updates and changes proposed for HY_Features. Changes for consideration by the HY_Features Standards Working Group include the following. Provide more clarity on the inherited properties and associations of features that "realize" the catchment and nexus concepts from HY_Features. Add nexus realization feature types to represent the outlet of catchments that are "frontal" (terminate to the ocean or a large waterbody) or "inland sinks." Add a "HY_Flowline" feature as a superclass of HY_Flowpath providing linear referencing on waterbodies that are not catchment realizations. Add an association or interface to support connection between surface catchments and hydrogeologic units.

OGC Public Engineering Report↗
USGS2013

Ecological limit functions relating fish community response to hydrologic departures of the ecological flow regime in the Tennessee River basin, United States

Ecological limit functions relating streamflow and aquatic ecosystems remain elusive despite decades of research. We investigated functional relationships between species richness and changes in streamflow characteristics at 662 fish sampling sites in the Tennessee River basin. Our approach included the following: (1) a brief summary of relevant literature on functional relations between fish and streamflow, (2) the development of ecological limit functions that describe the strongest discernible relationships between fish species richness and streamflow characteristics, (3) the evaluation of proposed definitions of hydrologic reference conditions, and (4) an investigation of the internal structures of wedge-shaped distributions underlying ecological limit functions. Twenty-one ecological limit functions were developed across three ecoregions that relate the species richness of 11 fish groups and departures from hydrologic reference conditions using multivariate and quantile regression methods. Each negatively sloped function is described using up to four streamflow characteristics expressed in terms of cumulative departure from hydrologic reference conditions. Negative slopes indicate increased departure results in decreased species richness. Sites with the highest measured fish species richness generally had near-reference hydrologic conditions for a given ecoregion. Hydrology did not generally differ between sites with the highest and lowest fish species richness, indicating that other environmental factors likely limit species richness at sites with reference hydrology. Use of ecological limit functions to make decisions regarding proposed hydrologic regime changes, although commonly presented as a management tool, is not as straightforward or informative as often assumed. We contend that statistical evaluation of the internal wedge structure below limit functions may provide a probabilistic understanding of how aquatic ecology is influenced by altered hydrology and may serve as the basis for evaluating the potential effect of proposed hydrologic changes.

Tennessee River basin↗
USGS2008

A Compilation of Provisional Karst Geospatial Data for the Interior Low Plateaus Physiographic Region, Central United States

Geospatial data needed to visualize and evaluate the hydrogeologic framework and distribution of karst features in the Interior Low Plateaus physiographic region of the central United States were compiled during 2004-2007 as part of the Ground-Water Resources Program Karst Hydrology Initiative (KHI) project. Because of the potential usefulness to environmental and water-resources regulators, private consultants, academic researchers, and others, the geospatial data files created during the KHI project are being made available to the public as a provisional regional karst dataset. To enhance accessibility and visualization, the geospatial data files have been compiled as ESRI ArcReader data folders and user interactive Published Map Files (.pmf files), all of which are catalogued by the boundaries of surface watersheds using U.S. Geological Survey (USGS) eight-digit hydrologic unit codes (HUC-8s). Specific karst features included in the dataset include mapped sinkhole locations, sinking (or disappearing) streams, internally drained catchments, karst springs inventoried in the USGS National Water Information System (NWIS) database, relic stream valleys, and karst flow paths obtained from results of previously reported water-tracer tests.

Data Series↗
USGS2020

Sub-annual streamflow responses to rainfall and snowmelt inputs in snow-dominated watersheds of the western U.S.

Streamflow generation in mountain watersheds is strongly influenced by snow accumulation and melt, and multiple studies have found that snow loss leads to earlier snowmelt timing and declines in annual streamflow. However, hydrologic responses to snow loss are heterogeneous, and not all areas experience streamflow declines. This research examines whether streamflow generation is different for rainfall versus snowmelt inputs. We compiled a sample of 57 small U.S. Geological Survey watersheds in the western United States containing a Natural Resource Conservation Service Snow Telemetry site and having ratios of mean annual peak snow water equivalent to precipitation ratios >0.25. Daily streamflow was separated into quickflow and baseflow using a digital filter, and quickflow was then divided into quickflow response intervals using thresholds in quickflow slope. Each quickflow response interval was categorized by its fraction of input from snowmelt. Most sites exhibited two streamflow generation peaks each year, with one peak in the winter when runoff efficiency is greatest, and the second in the spring during peak snowmelt input. On average, study watersheds were dominated by snowmelt inputs (70%), and snowmelt and mixed inputs usually generated greater streamflow than rainfall because of higher inputs and longer durations. However, rainfall produced high streamflow generation in winter, when watersheds have their highest runoff efficiency (81%) across all input types. We demonstrate that while snowmelt is important for streamflow generation due to high input over long periods, increases in rain and mixed input during wet winter periods can countervail tendencies for reduced streamflow with declining snowpacks.

Water Resources Research↗
USGS2014

Report of the committee on runoff, 1936–37

Since the last meeting of the Section of Hydrology there has been a change in the organization and membership of some of the research‐committees, one relating to rainfall, of which Merrill Bernard is Chairman, and one relating to runoff, were created to replace the one committee which had functioned heretofore on both rainfall and runoff. This action by the officers provides for greater participation of the members of the Section in committees, and is a step well worth while. The personnel of the Committee as of May 1, 1937, is as follows: H. K. Barrows R. W. Davenport I. E. Houk F. T. Mavis F. F. Snyder M. M. Bernard R. S. Goodridge W. G. Hoyt A. F. Meyer H. C. Troxell E. S. Cullings R. E. Horton Joseph Jacobs C. R. Pettis C. O. Wisler I consider it an honor to act as Chairman of the Committee on Runoff but regret, however, that I have been unable as yet to coordinate thoroughly the work of the Committee or to inform myself adequately on many runoff‐experiments and research‐problems. Consequently, my report will be very brief and informal.

Eos, Transactions, American Geophysical Union↗
USGS2010

Ground-water flow related to streamflow and water quality

A ground-water flow system in southwestern Minnesota illustrates water movement between geologic units and between the land surface and the subsurface. The flow patterns indicate numerous zones of ground-water recharge and discharge controlled by topography, varying thicknesses of geologic units, variation in permeabilities, and the configuration of the basement rock surface. Variations in streamflow along a reach of the Yellow Medicine River agree with the subsurface flow system. Increases and decreases in runoff per square mile correspond, apparently, to ground-water discharge and recharge zones. Ground-water quality variations between calcium sulfate waters typical of the Quaternary drift and sodium chloride waters typical of the Cretaceous rocks are caused by mixing of the two water types. The zones of mixing are in agreement with ground-water flow patterns along the hydrologic section.

Water Resources Research↗
USGS2007

A monthly water-balance model driven by a graphical user interface

This report describes a monthly water-balance model driven by a graphical user interface, referred to as the Thornthwaite monthly water-balance program. Computations of monthly water-balance components of the hydrologic cycle are made for a specified location. The program can be used as a research tool, an assessment tool, and a tool for classroom instruction.

Open-File Report↗
USGS1994

Selected contributions to ground-water hydrology by C.V. Theis, and a review of his life and work

This publication highlights two previously unpublished papers by C.V. Theis; each is augmented with a discussion that explains why he wrote the paper, attempts to discern why he did not publish the paper, and amplifies the information with reference material not included by Theis. 'A Primer on Anisotropy' was written in the early 1970's to provide practicing hydrogeologists of the day with a method of analyzing ground-water problems involving anisotropic hydraulic-conductivity distribution without using tensor mathematics. The equations were developed for horizontal flow through dipping beds with differing conductivities parallel and perpendicular to the bedding and for flow through dipping beds having three different hydraulic conductivities, one perpendicular to the bedding and two others parallel to the bedding, at an angle to the strike of the beds. Although most colleagues who reviewed the primer in the early 1970's encouraged its publication enthusiastically, at least one suggested the addition of some examples in which the method would be demonstrated. Handwritten notes from Theis' files indicate that he may have worked on some examples and possibly other additions to the paper. The comments by Charles A. Appel include some examples of the primer's use and augment the presentation with references to relevant published papers, both those available to Theis but not cited by him, and subsequent publications. 'Aquifers, Ground-Water Bodies, and Hydrophers' was written in the early 1980's as an attempt to clarify the semantic and conceptual confusion in the use of the term aquifer, applied by some investigators to the saturated part of a permeable formation and by others to the entire permeable formation. The physical distinction between the aquifer and the ground-water body is emphasized, and the term hydropher is proposed to describe the saturated part of a permeable formation. Theis' interest in and familiarity with the French literature on ground water was the basis for a discussion of the French usage, which eschews the term aquifer. The analysis and critique of Theis' palzler explains the 1835 paper from which aquifer was reportedly derived, and provides further justification for the term hydropher. Theis' more important contributions to ground-water hydrology were outgrowths of his solutions to small local water problems based on field investigations. The biographical sketch, drawing extensively from a partial autobiography that Theis had dictated, reveals both the reasons for and the intellectual processes that led to his development of the nonequilibrium concept of ground-water hydraulics. The sketch also describes the background of the man, reviews his career, and portrays the admiration and respect he elicited from his colleagues and associates. The magnitude of Theis' contribution to the science of ground-water hydrology, to the appraisal of the water resources of New Mexico, and to the early research on ground disposal of radioactive wastes is evident from the bibliography of his writings, which includes 168 reports, many of them unpublished. The evolution of his thinking about the role of geologic inhomogeneities in mass transport, conceptualized but not quantified, was the major contribution of the latter part of his career.

Water Supply Paper↗
USGS2022

Editorial: Plant phenology shifts and their ecological and climatic consequences

Climate change is causing plant phenology to shift, with consequences for ecosystems and the Earth’s climate. Over the last decades, the timing of many important phenological events has advanced in spring, such as leaf emergence and flowering, or been delayed in fall, such as leaf coloration and leaf fall. The consequences of such phenological shifts are still largely unknown, but are hypothesized to have cascading effects on ecosystems, carbon and water cycles, and Earths’ climate. With this research topic, we aimed to synthesize and inspire innovative research in plant phenology to address research questions and challenges on the consequences of phenological shifts on ecosystem function and local hydrology. The articles presented here improve our understanding of the physiological mechanisms responsible for the current phenological changes in spring and fall and provide insight into some of the consequences of these changes on hydrological cycles and ecosystem functioning.

Frontiers in Plant Science↗
USGS2006

Applications of GIS and database technologies to manage a Karst Feature Database

This paper describes the management of a Karst Feature Database (KFD) in Minnesota. Two sets of applications in both GIS and Database Management System (DBMS) have been developed for the KFD of Minnesota. These applications were used to manage and to enhance the usability of the KFD. Structured Query Language (SQL) was used to manipulate transactions of the database and to facilitate the functionality of the user interfaces. The Database Administrator (DBA) authorized users with different access permissions to enhance the security of the database. Database consistency and recovery are accomplished by creating data logs and maintaining backups on a regular basis. The working database provides guidelines and management tools for future studies of karst features in Minnesota. The methodology of designing this DBMS is applicable to develop GIS-based databases to analyze and manage geomorphic and hydrologic datasets at both regional and local scales. The short-term goal of this research is to develop a regional KFD for the Upper Mississippi Valley Karst and the long-term goal is to expand this database to manage and study karst features at national and global scales.

Journal of Cave and Karst Studies↗
USGS2014

Basin-scale simulation of current and potential climate changed hydrologic conditions in the Lake Michigan Basin, United States

The Great Lakes Restoration Initiative (GLRI) is the largest public investment in the Great Lakes in two decades. A task force of 11 Federal agencies developed an action plan to implement the initiative. The U.S. Department of the Interior was one of the 11 agencies that entered into an interagency agreement with the U.S. Environmental Protection Agency as part of the GLRI to complete scientific projects throughout the Great Lakes basin. The U.S. Geological Survey, a bureau within the Department of the Interior, is involved in the GLRI to provide scientific support to management decisions as well as measure progress of the Great Lakes basin restoration efforts. This report presents basin-scale simulated current and forecast climatic and hydrologic conditions in the Lake Michigan Basin. The forecasts were obtained by constructing and calibrating a Precipitation-Runoff Modeling System (PRMS) model of the Lake Michigan Basin; the PRMS model was calibrated using the parameter estimation and uncertainty analysis (PEST) software suite. The calibrated model was used to evaluate potential responses to climate change by using four simulated carbon emission scenarios from eight general circulation models released by the World Climate Research Programme’s Coupled Model Intercomparison Project phase 3. Statistically downscaled datasets of these scenarios were used to project hydrologic response for the Lake Michigan Basin. In general, most of the observation sites in the Lake Michigan Basin indicated slight increases in annual streamflow in response to future climate change scenarios. Monthly streamflows indicated a general shift from the current (2014) winter-storage/snowmelt-pulse system to a system with a more equally distributed hydrograph throughout the year. Simulated soil moisture within the basin illustrates that conditions within the basin are also expected to change on a monthly timescale. One effect of increasing air temperature as a result of the changing climate was the appreciable increase in the length of the growing season in the Lake Michigan Basin. The increase in growing season will cause an increase in evapotranspiration across the Lake Michigan Basin, which will directly affect soil moisture and late growing season streamflows. Output from the Lake Michigan Basin PRMS model is available through an online dynamic web mapping service available at (http://pubs.usgs.gov/sir/2014/5175/). The map service includes layers for the each of the 8 global climate models and 4 carbon emission scenarios combinations for 12 hydrologic model state variables. The layers are pre-rendered maps of annual hydrologic response from 1977 through 2099 that provide an easily accessible online method to examine climate change effects across the Lake Michigan Basin.

Indiana, Illinois, Michigan, Wisconsin↗
USGS2007

Toward a transport-based analysis of nutrient spiraling and uptake in streams

Nutrient addition experiments are designed to study the cycling of nutrients in stream ecosystems where hydrologic and nonhydrologic processes determine nutrient fate. Because of the importance of hydrologic processes in stream ecosystems, a conceptual model known as nutrient spiraling is frequently employed. A central part of the nutrient spiraling approach is the determination of uptake length ( S w ), the average distance traveled by dissolved nutrients in the water column before uptake. Although the nutrient spiraling concept has been an invaluable tool in stream ecology, the current practice of estimating uptake length from steady‐state nutrient data using linear regression (called here the “ S w approach”) presents a number of limitations. These limitations are identified by comparing the exponential S w equation with analytical solutions of a stream solute transport model. This comparison indicates that (1) S w is an aggregate measure of uptake that does not distinguish between main channel and storage zone processes, (2) S w is an integrated measure of numerous hydrologic and nonhydrologic processes—this process integration may lead to difficulties in interpretation when comparing estimates of S w , and (3) estimates of uptake velocity and areal uptake rate ( v f and U ) based on S w are not independent of system hydrology. Given these findings, a transport‐based approach to nutrient spiraling is presented for steady‐state and time‐series data sets. The transport‐based approach for time‐series data sets is suggested for future research on nutrient uptake as it provides a number of benefits, including the ability to (1) separately quantify main channel and storage zone uptake, (2) quantify specific hydrologic and nonhydrologic processes using various model parameters (process separation), (3) estimate uptake velocities and areal uptake rates that are independent of hydrologic effects, and (4) use shortterm, non‐plateau nutrient additions such that the effects of regeneration and mineralization are minimized. In summary, the transport‐based, time‐series approach provides a means of estimating traditional measures of nutrient uptake ( S w , v f , U ) while providing additional information on the location and magnitude of uptake (main channel versus storage zone). Application of the transport‐based approach to time‐series data from Green Creek, Antarctica, indicates that the bulk of nitrate uptake (~74% to 100%) occurred within the main channel where benthic uptake by algal mats is a likely process. Substantial uptake (~26%) also occurred in the storage zone of one reach, where uptake is attributed to the microbial community.

Limnology and Oceanography: Methods↗
USGS2011

Recent and historic drivers of landscape change in the Everglades ridge, slough, and Tree Island mosaic

More than half of the original Everglades extent formed a patterned peat mosaic of elevated ridges, lower and more open sloughs, and tree islands aligned parallel to the dominant flow direction. This ecologically important landscape structure remained in a dynamic equilibrium for millennia prior to rapid degradation over the past century in response to human manipulation of the hydrologic system. Restoration of the patterned landscape structure is one of the primary objectives of the Everglades restoration effort. Recent research has revealed that three main drivers regulated feedbacks that initiated and maintained landscape structure: the spatial and temporal distribution of surface water depths, surface and subsurface flow, and phosphorus supply. Causes of recent degradation include but are not limited to perturbations to these historically important controls; shifts in mineral and sulfate supply may have also contributed to degradation. Restoring predrainage hydrologic conditions will likely preserve remaining landscape pattern structure, provided a sufficient supply of surface water with low nutrient and low total dissolved solids content exists to maintain a rainfall-driven water chemistry. However, because of hysteresis in landscape evolution trajectories, restoration of areas with a fully degraded landscape could require additional human intervention.

Critical Reviews in Environmental Science and Tech↗
USGS2000

Relationships among sea-floor structure and benthic communities in Long Island Sound at regional and benthoscape scales

Long Island Sound is comprised of a rich and spatially heterogeneous mix of sea-floor environments which provide habitat for an equally diverse set of assemblages of soft-sediment communities. Information from recent research on the geomorphological and chemical attributes of these environments, as well as from studies of the hydrodynamics of the Sound, provide the opportunity to develop a landscape, or "benthoscape" framework for understanding the soft-sediment ecology of this estuary and for guiding future research focusing on structure and function at multiple spatial scales. This contribution reviews past research on benthic communities in Long Island Sound and addresses how they may be shaped by sea-floor characteristics at regional and benthoscape scales. At the regional scale (i.e. the entire Sound), differences in benthic community composition correspond to the distribution of general sedimentary environments. However, significant variation in community structure also occurs at the benthoscape scale (within regions) related to local variations in sediment properties, and physical and biogenic topographic features. Several topical areas in particular need further research in Long Island Sound, including temporal dynamics of benthic communities relative to sea-floor structure and the interaction between the dynamics of benthoscapes and hydrologic seascapes.

Connecticut, New York↗
USGS1965

Geological Survey research, 1965, Chapter D

Scientific notes and summaries of investigations by members of the Conservation, Geologic, and Water Resources Divisions tn geology, hydrology, and related fields.

Professional Paper↗
USGS1994

Assessment of the hydrologic interaction between Imikpuk Lake and the adjacent airstrip site near Barrow, Alaska, 1993

Imikpuk Lake serves as the drinking water source for the Ukpeagvik Inupiat Corporation-National Arctic Research Laboratory (UIC-NARL), formerly known as the Naval Arctic Research Laboratory, near Barrow, Alaska. During the 1970's and 1980's, accidental releases of more than 1,300 cubic meters of various types of fuel occurred at the airstrip site adjacent to the lake. To aid an assessment of the potential risk 10 the quality of water in the lake posed by fuel remaining in the subsurface, the hydrologic interaction between the lake and ground water at the airstrip site was examined. The study area lies within the region of continuous permafrost where hydrologic processes are largely controlled by the short annual thaw season and the presence of near-surface permafrost. Runoff occurs for only a short period each year, typically from early or mid-June to late September, and a shallow ground- water system develops during approximately the same period as a result of shallow thawing of the subsurface. During the spring and summer of 1993, snowpack and surface-water data were collected throughout the Imikpuk Lake basin, and subsurface- flow-system data were collected at the airstrip site. The total annual inflow to the lake was estimated 10 be approximately 300,000 cubic meters per year, based on four methods of estimation. The ground-water flow system at the airstrip site is complex, primarily because of variations in local land-surface topography. Subsurface frost-elevation data indicate that a permafrost ridge exists beneath one of the elevated building pads at the site. Similar ridges beneath elevated roadways at the site may act as impediments to ground-water flow, reducing the flux of subsurface water to Imikpuk Lake. However, on the basis of the assumption that such impediments do not reduce flux substantially, the ground-water flux from the airstrip site was estimated to be approximately 173 cubic meters per year--less than 0.1 percent of the estimated annual inflow to Imikpuk Lake.

Open-File Report↗