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At least 1,189 records · Page 66Linked to original sources
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↗
USGS2013

Transport and fate of microbial pathogens in agricultural settings

An understanding of the transport and survival of microbial pathogens (pathogens hereafter) in agricultural settings is needed to assess the risk of pathogen contamination to water and food resources, and to develop control strategies and treatment options. However, many knowledge gaps still remain in predicting the fate and transport of pathogens in runoff water, and then through the shallow vadose zone and groundwater. A number of transport pathways, processes, factors, and mathematical models often are needed to describe pathogen fate in agricultural settings. The level of complexity is dramatically enhanced by soil heterogeneity, as well as by temporal variability in temperature, water inputs, and pathogen sources. There is substantial variability in pathogen migration pathways, leading to changes in the dominant processes that control pathogen transport over different spatial and temporal scales. For example, intense rainfall events can generate runoff and preferential flow that can rapidly transport pathogens. Pathogens that survive for extended periods of time have a greatly enhanced probability of remaining viable when subjected to such rapid-transport events. Conversely, in dry seasons, pathogen transport depends more strongly on retention at diverse environmental surfaces controlled by a multitude of coupled physical, chemical, and microbiological factors. These interactions are incompletely characterized, leading to a lack of consensus on the proper mathematical framework to model pathogen transport even at the column scale. In addition, little is known about how to quantify transport and survival parameters at the scale of agricultural fields or watersheds. This review summarizes current conceptual and quantitative models for pathogen transport and fate in agricultural settings over a wide range of spatial and temporal scales. The authors also discuss the benefits that can be realized by improved modeling, and potential treatments to mitigate the risk of waterborne disease transmission.

Critical Reviews in Environmental Science and Tech↗
USGS2021

A review of algal toxin exposures on reserved federal lands and among trust species in the United States

Associated health effects from algal toxin exposure are a growing concern for human and animal health. Algal toxin poisonings may occur from contact with or consumption of water supplies or from ingestion of contaminated animals. The U.S. Federal Government owns or holds in trust about 259 million hectares of land, in addition to the Trust species obligations. We completed the first comprehensive review of potential toxin-producing algal blooms in surface waters on Federal lands and Trust species exposed to algal toxins. Events were sorted into three tiers based on potentially toxic algae abundance or toxin concentration and related effects on animal morbidity and mortality. At least 11.1% of Federal lands are known to have been affected by algal events, but exposure is likely underreported. The occurrence of potential toxin producers and their toxins (Tier 1) have been documented 337 times, health advisory threshold exceedances (Tier 2) were reported 943 times, and 86 events involved animal sickness or death linked to cyanobacteria or marine toxins (Tier 3). Trust species exposed to cyano- or algal toxins included marine mammals, migratory birds, threatened and endangered species, and species of concern. We report numerous data gaps ranging from potential effects on human health from consuming intoxicated animals to the infrequency of measuring and reporting certain toxins. Improvements to field and laboratory methods, more consistent evaluation of toxin exposure, decreased latency on data analysis, delivery and interpretation will be necessary to improve response and management strategies for protecting human and animal health where issues persist.

Critical Reviews in Environmental Science and Tech↗
USGS2021

Critical review of mercury methylation and methylmercury demethylation rate constants in aquatic sediments for biogeochemical modeling

Mercury is a toxin that causes neurological impairments in adults, is particularly harmful for fetuses and children, and is deadly in severe cases, making it a worldwide health concern. Methylmercury (MeHg) is the environmentally relevant form of mercury (Hg) because it biomagnifies along the food chain. Methylmercury is mainly produced in aquatic sediments via methylation of inorganic Hg (Hg(II)) and transformed back via demethylation. Because transformation rates determine MeHg concentrations, quantification of methylation and demethylation rates is needed to inform management of MeHg. Published rate constants for Hg(II) methylation ( 𝑘 𝑚 ) and MeHg demethylation ( 𝑘 𝑑 ) vary greatly, stemming partly from differences in experimental methods. We conducted a comprehensive review of rate laws, evaluated published rate constants, and performed biogeochemical simulations to assess variability in reported 𝑘 𝑚 and 𝑘 𝑑 . Based on selected studies employing the same pseudo-first-order rate law and similar experimental methods, we found that 𝑘 𝑚 = 0.04 ± 0.03 d −1 is a reasonable range for wetland sediments. Over a number of environments, maximum 𝑘 𝑑 was smaller at sites without Hg source ( 𝑘 𝑑 = 0.5 d −1 ) than at sites with identified Hg source ( 𝑘 𝑑 = 1.8 d −1 ). Larger variability and higher uncertainty in 𝑘 𝑑 compared to 𝑘 𝑚 highlight the need for more research on MeHg demethylation rates. This critical review: (a) aids the design of future experimental studies of 𝑘 𝑚 and 𝑘 𝑑 ; (b) provides guidance for comparing rate constants from different studies; (c) presents a biogeochemical reaction model to assess rate constants; and (d) informs selection of 𝑘 𝑚 and 𝑘 𝑑 values from the literature for use in model simulations.

Critical Reviews in Environmental Science and Tech↗
USGS2004

A Simplified Method for Sampling and Analysis of High Volume Surface Water for Organic Contaminants Using XAD-2

A simple compressed-gas driven system for field processing and extracting water for subsequent analyses of hydrophobic organic compounds is presented. The pumping device is a pneumatically driven pump and filtration system that can easily clarify at 4L/min. The extraction device uses compressed gas to drive filtered water through two parallel XAD-2 resin columns, at about 200 mL/min. No batteries or inverters are required for water collection or processing. Solvent extractions were performed directly in the XAD-2 glass columns. Final extracts are cleaned-up on Florisil cartridges without fractionation and contaminants analyzed by GC-MS. Method detection limits (MDLs) and recoveries for dissolved organic contaminants, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and pesticides are reported along with results of surface water analysis for the San Francisco Bay, CA.

Journal of Environmental Science and Health - Part↗
USGS2019

Case studies in groundwater contaminant fate and transport

A case study of groundwater contamination is a detailed study of a single site contaminated with a chemical or mixture that is known to be a problem at many sites. The goal of case studies is to provide insights into the physical, chemical, and biological processes controlling migration, natural attenuation, or remediation of common groundwater contaminants. Ideally, processes occurring at a case study site are representative of other sites so that knowledge gained from these intensive studies can be applied at thousands of sites where fewer data are available. Several characteristics of case studies contribute to their value. First, they may have tens to hundreds of monitoring wells, compared to fewer than ten wells at some contaminated sites. Second, some case studies continue for many years or even decades, providing insights into temporal progression of slow processes. Third, analytical methods prohibitively expensive for routine use or under development may be tested at case study sites. Finally, the ongoing characterization typical of case study sites builds a foundation of knowledge that facilitates sophisticated experimental design and testing of new methods. This article is divided into sections based on the contaminant type because the chemical and biological processes required for remediation vary for each contaminant. Most importantly, some contaminants can be biodegraded whereas metals and radionuclides cannot be destroyed but can be immobilized or rendered less toxic. The emphasis is on case studies of natural processes that control the fate and transport of contaminants in groundwater rather than on active remediation methods. The principles learned from these studies may form the basis for design of remedial strategies. The organic contaminants are divided into: petroleum hydrocarbons, fuel oxygenates, coal tar and wastes from manufactured gas plants, and chlorinated solvents. The inorganic contaminants covered are metals and radionuclides, arsenic, and nitrate. Case studies of mixed waste plumes from landfills are also described. Experimental sites where contaminants have been introduced into an aquifer as an emplaced source or a controlled release may not meet the above definition of case studies, but some are included because the overall goal is to impart lessons learned from detailed field studies. It is impossible to cover all case studies in this short format. Conversely, focusing on one or two does not convey the breadth of research results in entire range of case studies. Instead, the strategy is to describe the evolution of knowledge for each contaminant class while providing citations of relevant case studies. Much of the progress in understanding of the fate of contaminants in groundwater is based on laboratory studies; thus whenever possible, papers that included both field and laboratory results have been included among the citations. Two topics of growing importance have not been covered. These are the fate of pharmaceuticals in groundwater and discharge of contaminant plumes to surface water. These topics merit coverage in the future as knowledge grows and case studies increase in number.

Environmental Science↗
USGS2019

Wildfire as a catalyst for hydrologic and geomorphic change

Wildfire has been a constant presence on the Earth since at least the Silurian period, and is a landscape-scale catalyst that results in a step-change perturbation for hydrologic systems, which ripples across burned terrain, shaping the geomorphic legacy of watersheds. Specifically, wildfire alters two key landscape properties: (1) overland flow, and (2) soil erodibility. Overland flow and soil erodibility have both been seen to increase after wildfires, resulting in order-of-magnitude increases in erosion rates during rainstorms with relatively frequent recurrence intervals. On short timescales, wildfire increases erosion and leads to natural hazards that are costly and threatening to society. Over longer timescales, wildfire-induced erosion can account for the majority of total denudation in certain settings with long- term implications for landscape evolution. There is a special focus on debris flows in this document because they are the most destructive geomorphic process that is observed to follow wildfires after high severity burns. In the past several decades researchers have investigated important aspects of post-wildfire debris flows, such as: the provenance of sediment that is moved in debris flows, the hydrologic and soil properties required to produce debris flows, and debris flow initiation mechanisms. Herein we highlight the relevant research articles showing the current state of progress in debris flow research as well as pointing to the fundamental research on post-wildfire hydrology and erosion that is necessary for understanding how water and sediment behave after wildfires.

Environmental Science↗
USGS2021

USGS CEOS analysis ready data for land achievements and future plans

The efforts of the Committee on Earth Observation Satellites (CEOS) to bring CEOS Analysis Ready Data for Land (CARD4L) products to countries and international organizations quickly and easily continues to receive important support from the U.S. Geological Survey (USGS). As part of its engagement with CARD4L, the USGS worked to address specific Threshold and Target Product Family Specification (PFS) requirements for its Landsat Collection 2 Level-2 science products and in July 2020, received formal CEOS endorsement for 100 percent CARD4L-compliance at the Threshold level for Collection 2 surface reflectance and surface temperature. This endorsement ensures these products meet a level of interoperability with data from other Earth-observing platforms, such as Europe's Sentinel-2 satellites, as the European Space Agency also works toward CARD4L-compliant products. In addition to the Collection 2 Level-2 land surface data products, the USGS recognizes Landsat's potential to make a valuable contribution to aquatic science and environmental monitoring capabilities for aquatic ecosystems, especially in coastal and inland waters. Working with subject matter experts, the USGS has been coordinating an international agency effort to establish a new CARD4L PFS for aquatic reflectance to be considered for CEOS endorsement in 2021.

Conference Paper↗
USGS2005

Potential for intrinsic bioremediation of a DNT-contaminated aquifer

Microorganisms indigenous to a shallow aquifer, which underlies an explosives-contaminated site, mineralized 28% of [U-ring- 14 C] 2,4–dinitrotoluene to 14 CO 2 within 28 days under aerobic conditions. Approximately 20% of added 2,4–dinitrotoluene remained undegraded at the end of the incubation while approximately 22% and 6% were transformed to 4–amino-2–nitrotoluene and 2–amino-4–nitrotoluene, respectively. In aquifer microcosms containing 2,6–dinitrotoluene, approximately 67% of the substrate remained undegraded and approximately 14% was transformed to 2–amino-6–nitrotoluene. The radiolabeled study indicated that about 8% of the 2,6–dinotrotoluene was mineralized to CO 2 . The demonstrated degradation and subsequent mineralization of dinitrotoluene compounds by aquifer microorganisms are consistent with the decline in dissolved dinitrotoluene concentrations observed along the general ground-water flowpath at the site. The results indicate that intrinsic bioremediation may be a viable alternative for remediating contaminated ground water at this site.

Environmental Science & Technology↗
USGS2020

Variation of lead isotopic composition and atomic weight in terrestrial materials (IUPAC Technical Report)

The isotopic composition and atomic weight of lead are variable in terrestrial materials because its three heaviest stable isotopes are stable end-products of the radioactive decay of uranium ( 238 U to 206 Pb; 235 U to 207 Pb) and thorium ( 232 Th to 208 Pb). The lightest stable isotope, 204 Pb, is primordial. These variations in isotope ratios and atomic weights provide useful information in many areas of science, including geochronology, archaeology, environmental studies, and forensic science. While elemental lead can serve as an abundant and homogeneous isotopic reference, deviations from the isotope ratios in other lead occurrences limit the accuracy with which a standard atomic weight can be given for lead. In a comprehensive review of several hundred publications and analyses of more than 8000 samples, published isotope data indicate that the lowest reported lead atomic weight of a normal terrestrial materials is 206.1462 ± 0.0028 ( k = 2), determined for a growth of the phosphate mineral monazite around a garnet relic from an Archean high-grade metamorphic terrain in north-western Scotland, which contains mostly 206 Pb and almost no 204 Pb. The highest published lead atomic weight is 207.9351 ± 0.0005 ( k = 2) for monazite from a micro-inclusion in a garnet relic, also from a high-grade metamorphic terrain in north-western Scotland, which contains almost pure radiogenic 208 Pb. When expressed as an interval, the lead atomic weight is [206.14, 207.94]. It is proposed that a value of 207.2 be adopted for the single lead atomic-weight value for education, commerce, and industry, corresponding to previously published conventional atomic-weight values.

Pure and Applied Chemistry↗
USGS2021

Using machine learning to develop a predictive understanding of the impacts of extreme water cycle perturbations on river water quality

This whitepaper addresses to two focal areas – (3) Insight gleaned from complex data using Artificial Intelligence (AI), and other advanced techniques (primary), and (2) Predictive modeling through the use of AI techniques and AI-derived model components (secondary). This topic is directly relevant to four DOE Earth and Environmental Systems Science Division Grand Challenges: integrated water cycle, biogeochemistry, drivers and responses in the Earth system, and data-model integration.

Technical Report↗
USGS2004

Science data in support of environmental health studies in the U.S.-Mexico border region

The border region of the United States and Mexico encompasses a vast and diverse array of physical settings and habitats that include wetlands, deserts, rangeland, mountains, and forests, which are unique in terms of the diversity of their water, mineral, and biological resources. The region is interconnected economically, politically, and socially owing to its binational heritage. In 1995, nearly 11 million people lived immediately adjacent to the border. By one account, that population could more than double by 2020. This rapid population growth and consequent economic development and land-use changes are pushing the limits of environmental sustainability and quality. Infrastructure development has lagged behind the rapid growth of the region, resulting in a shortage of water for municipal, agricultural, and industrial uses. These stressors threaten the quality of life in the region and raise concerns about the interdependence of environmental quality and human health. To allow for continued economic growth while protecting the area’s natural resources and fostering a high quality of life, the United States and Mexico need an improved understanding of the threats posed by these anthropogenic changes. Issues of particular concern include (1) contaminants in ground water, surface water, and biota from agricultural, municipal, and industrial activities; (2) airborne pollutants from fossil-fuel combustion and other activities; (3) contaminants from past and present mining activities and mineral deposits; and (4) pathogens, pharmaceuticals, hormones, and other contaminants released in treated and untreated human and animal wastewaters.

Fact Sheet↗
USGS2022

GSPy: A new toolbox and data standard for Geophysical Datasets

The diversity of geophysical methods and datatypes, as well as the isolated nature of various specialties (e.g., electromagnetic, seismic, potential fields) leads to a profusion of separate data file formats and documentation conventions. This can hinder cooperation and reduce the impact of datasets researchers have invested in heavily to collect and prepare. An open, portable, and well-supported community data standard could greatly improve the interoperability, transferability, and long-term archival of geophysical data. Airborne geophysical methods particularly need an open and accessible data standard, and they exemplify the complexity that is common in geophysical datasets where critical auxiliary information on the survey and system parameters are required to fully utilize and understand the data. Here, we propose a new Geophysical Standard, termed the GS convention, that leverages the well-established and widely used NetCDF file format and builds on the Climate and Forecasts (CF) metadata convention. We also present an accompanying open-source Python package, GSPy, to provide methods and workflows for building the GS-standardized NetCDF files, importing and exporting between common data formats, preparing input files for geophysical inversion software, and visualizing data and inverted models. By using the NetCDF format, handled through the Xarray Python package, and following the CF conventions, we standardize how metadata is recorded and directly stored with the data, from general survey and system information down to specific variable attributes. Utilizing the hierarchical nature of NetCDF, GS-formatted files are organized with a root Survey group that contains global metadata about the geophysical survey. Data are then organized into subgroups beneath Survey and are categorized as Tabular or Raster depending on the geometry and point of origin for the data. Lastly, the standard ensures consistency in constructing and tracking coordinate reference systems, which is vital for accurate portability and analysis. Development and adoption of a NetCDF-based data standard for geophysical surveys can greatly improve how these complex datasets are shared and utilized, making the data more accessible to a broader science community. The architecture of GSPy can be easily transferred to additional geophysical datatypes and methods in future releases.

Frontiers in Earth Science - Environmental Informa↗
USGS2018

Exploring the impacts of seagrass on coupled marsh-tidal flat morphodynamics

Intertidal coastal environments are prone to changes induced by sea level rise, increases in storminess, temperature, and anthropogenic disturbances. It is unclear how changes in external drivers may affect the dynamics of low energy coastal environments because their response is non-linear, and characterized by many thresholds and discontinuities. As such, process-based modeling of the ecogeomorphic processes underlying the dynamics of these ecosystems is useful, not only to predict their change through time, but also to generate new hypotheses and research questions. Here, we used a three-point dynamic model to investigate how seagrass might affect the behavior of coupled marsh-tidal flat systems. The model directly incorporates ecogeomorphological feedbacks among wind waves, salt marsh vegetation, allochthonous sediment loading, seagrasses and sea level rise. The model was applied to examine potential behaviors of salt marsh systems in the Virginia coastal bays. Differences due to the presence or absence of seagrass and stochastic vs. constant drivers lead to the emergence of complex behaviors in the coupled salt marsh-tidal flat system. In intertidal areas without seagrass, small tidal flats are unlikely to expand and provide enough sediment to the salt marshes to combat sea level rise. However, as the tidal flat expands, the concurrent increase in sediment supply due to wave-induced processes allows for the salt marsh to maintain pace with sea level at the expense of salt marsh extent. The presence of seagrass has two effects: (1) it decreases near bed shear stresses thus reducing the sediment flux to the salt marsh platform; (2) it reduces the wave energy acting on the salt marsh scarp, thus reducing boundary erosion. Model results indicate that the reductions in wave power and near bed shear stresses when seagrass is present provide an overall stabilizing effect on the coupled marsh-tidal flat system; but as water depth increases due to sea level rise or as external sediment supply increases, light conditions decline and the system reverts to that of a bare tidal flat.

Frontiers in Environmental Science↗
USGS2019

Monarch habitat as a component of multifunctional landscape restoration using continuous riparian buffers

Stabilizing the eastern, migratory population of monarch butterflies (Danaus plexippus) is expected to require substantial habitat restoration on agricultural land in the core breeding area of the Upper Midwestern U.S. Previous research has considered the potential to utilize marginal land for this purpose because of its low productivity, erodible soils, and high nutrient input requirements. This strategy has strong potential for restoring milkweed (Asclepias spp.), but may be limited in terms of its ability to generate additional biophysical and socioeconomic benefits for local communities. Here we explore the possibility of restoring milkweed via the creation of continuous riparian buffer strips around rivers and streams throughout the region. We use a GIS-based analysis to consider the potential of several different buffer-width scenarios to meet milkweed restoration targets. We further estimate the ability of these habitat areas to provide additional functionality in the form of crop pollination and water quality regulation across the entire region. Finally, we estimate the conservative economic value of these ecosystem services and compare it with the lost value of crops associated with each scenario. Results suggest that riparian buffers could be used to meet 10-43% of the total milkweed restoration target of 1.3 billion new stems with moderate management. The value of water quality and pollination benefits provided by buffers is estimated to exceed costs only for our smallest buffer-width scenario, with a cost-benefit ratio of 1:2. Larger buffer widths provide more milkweed, but costs to farmers exceed the benefits we were able to quantify. The large-scale restoration of multifunctional riparian corridors thus has the potential to be a win-win scenario, adding milkweed stems while also providing a variety of other valuable benefits. This suggests the potential to leverage monarch habitat restoration efforts for the benefit of a wider variety of species and broader coalition of beneficiaries.

Iowa, Minnesota, Michigan, Wisconsin, Ohio, Indian↗
USGS2019

Soil aggregates as a source of dissolved organic carbon to streams: An experimental study on the effect of solution chemistry on water extractable carbon

Over the past two decades, headwater streams of the northern hemisphere have shown increased amounts of dissolved organic carbon (DOC), coinciding with decreased acid deposition. The exact nature of the mechanistic link between precipitation composition and stream water DOC is still widely debated in the literature. We hypothesize that soil aggregates are the main source of stream water DOC and that DOC release is greater in organic rich, riparian soils vs. hillslope soils. To test these hypotheses, we collected soils from two main landscape positions (hillslope and riparian zones) from the acid-impacted Sleepers River Research Watershed in northeastern Vermont. We performed aqueous soil extracts with solutions of different ionic strength (IS) and composition to simulate changes in soil solution. We monitored dynamic changes in soil particle size, aggregate architecture and composition, leachate DOC concentrations, dissolved organic matter (DOM) characteristics by fluorescence spectroscopy and trends in bioavailability. In low IS solutions, extractable DOC concentrations were significantly higher, particle size (by laser diffraction) was significantly smaller and organic material was separated from mineral particles in scanning electron microscope observations. Furthermore, higher DOC concentrations were found in Na + compared to Ca 2+ solutions of the same IS. These effects are attributed to aggregate dispersion due to expanding diffuse double layers in decreased IS solutions and to decreased bridging by divalent cations. Landscape position impacted quality but not quantity of released DOC. Overall, these results indicate that soil aggregates might be one important link between Critical Zone inputs (i.e., precipitation) and exports in streams.

Vermont↗
USGS2019

Wind sheltering impacts on land-atmosphere fluxes over fens

Wetlands and their ability to mitigate climate change motivates restorative and protective action; however, scientific understanding of land-atmosphere interactions is restricted by our limited continuous observations of gaseous fluxes. Many wetlands are small in spatial scale and embedded in forested landscapes. Yet, little is known about how the relative sheltering of forests affects net carbon (C) and energy balance. Here, we analyze coterminous USGS and Ameriflux eddy covariance flux tower observations over three years in two shrub fens in Northern Wisconsin, one more sheltered (US-ALQ) than the other (US-Los). Unsurprisingly, the open site showed higher overall wind speeds. This should have implications for atmospheric fluxes in wetlands as wind-forced processes are essential in promoting gas exchange over water. While both sites had similar half-hourly net ecosystem exchange of CO2 (NEE) during daytime, there were significant differences in nighttime NEE, as well as in net radiation partitioning in early spring and late summer. Sensible heat (H) fluxes were smaller at the sheltered fen except for the months of July-September. In contrast, latent heat (LE) fluxes were higher in every month except July. Additionally, sheltered fen ecosystem respiration had a weaker linear correlation with air temperature (R: 0.08 versus 0.57 for the open fen). Our work suggests that canopy sheltering does not cause significant differences in half-hourly NEE during the day, but rather the largest differences such as lower CO2 emissions occur at nighttime due to higher variance at very low wind speeds. Sheltering also influenced direction of air flow, mean wind speeds in day versus night, energy balance, and sensible and latent heat fluxes. We discuss implications of these findings for wetland restoration.

Wisconsin↗
USGS2020

Estimating late 19th century hydrology in the Greater Everglades Ecosystem: An integration of paleoecologic data and models

Determining hydrologic conditions prior to instrumental records is a challenge for restoration of freshwater ecosystems worldwide. Paleoecologic data provide this information on past conditions and when these data are used to adjust hydrologic models, allow conditions to be hindcast that may not be directly estimated from the paleo-data alone. In this context, the paleo-data provide real-world estimates as input to the models. Restoration of the Greater Everglades Ecosystem requires this understanding of the hydrology of the natural system prior to significant alterations due to water management and land use. Large scale models such as the Natural Systems Model (NSM 4.6.2) have been used by the South Florida Water Management District and other agencies responsible for restoration to estimate past hydrologic conditions; however, these models typically portray a drier natural system for the beginning of the 20th century than what is indicated by paleoecologic analyses and historical data. The purpose of this study is to estimate pre-20th century water levels, hydroperiods and flow in the freshwater wetlands of the Everglades by using pollen assemblage data in three sediment cores to adjust the Natural Systems Model. This study is designed to further test estimates of flow through the Everglades derived from analysis of sediment cores collected in Florida Bay. The results demonstrate that the NSM 4.6.2 underestimates water levels and hydroperiods in the Everglades compared to the paleo-adjusted NSM 4.6.2 model outputs. Flow models that use the paleo-adjusted water levels as input indicate flow through Shark River Slough in the late 19th century was approximately two times flow between 1990 and 2000, and flow through Taylor Slough was approximately three times flow between 1990 and 2000. The flow estimates derived from this study agree with the estimates derived from earlier studies using estuarine cores. This integration of paleoecologic information and hydrologic models provides resource managers with the best available estimates of past conditions and allows them to set realistic targets for restoration of freshwater ecosystems.

Florida↗