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USGS2025

USGS—An Unparalleled Scientific Asset

The U.S. Geological Survey (USGS) delivers information critical to powering our economy, managing our natural resources, and keeping Americans safe and healthy. 1 Mapping the Nation $21B Geologic maps save users an estimated 15% in annual costs: a value of between $14B and $21B. $25.6B in annual value to users of imagery from Landsat satellites, which were codeveloped by NASA and the USGS and operated through their lifespans by the USGS. $13.5B in annual benefits is generated by the USGS's 3D Elevation Program. Securing America’s Energy Independence 44% USGS-identified undiscovered geothermal energy is equal to 44% of current U.S. electricity generation. 29.4B barrels of oil and 391.6 trillion cubic feet of gas in recoverable resources are available on U.S. public lands based on USGS assessments. Protecting Americans’ Health and Safety $424B in recent wildland fire damages highlight the need for USGS fire science, which supports efforts to protect communities and reduce risk. USGS earthquake, volcano, landslide, and coastal hazard monitoring and information save lives and minimize costs; for example, $2.8M can be saved because of USGS enhanced information about a Mauna Loa eruption. $4.5B is the estimated cost of annual flooding. Through a network of over 11,885 streamgages, the USGS supports public safety and enables forecasts, early warning systems, and management actions that protect lives and property. Supporting National Security $3.1B The USGS identified a $3.1B risk to the American economy if China restricts gallium imports. This is one example underscoring the importance of the USGS mapping critical minerals, investigating supply chains, and producing the Nation’s critical minerals list. Enhancing Our Lands and Waters $21B in estimated annual costs results from invasive species. The USGS’s invasive species research informs approaches used to reduce their effects on agriculture, water infrastructure, disease transmission, fisheries, and outdoor recreation. USGS innovations support early warnings for harmful algal blooms—over $2M in yearly benefits are provided to Kansas alone. $45B USGS science informs the management of big game (such as deer and elk). The big-game hunting industry contributes $45B to the U.S. economy. Fostering American Prosperity $4.1T Mineral commodities are necessary for the $4.1T in value added to the GDP by major industries that consume processed mineral materials and employ 1 million workers. Because of this, USGS data on mineral supply, demand, and trade are highly valued. 45,000 metric tons Rare earths power the growing technology economy, including cell phones, electric vehicles, and medical devices. For over 70 years, USGS work has supported the discovery of rare earth resources in California’s Mountain Pass area, which produced 45,000 metric tons of rare earth concentrates in 2024—over 11% of the global supply. Guarding American Food Security $70.2B USGS science informs early warning systems and management strategies to mitigate disease outbreaks in agriculture—critical research on highly pathogenic avian influenza, for example, helps safeguard the $70B value in poultry and egg production. $11.8B USGS groundwater tools are vital for agriculture; for example, in the Mississippi Alluvial Plain, 65% of farming relies on groundwater to support its $11.8B annual industry. 1 Values throughout are given in billions (B), millions (M), and trillions (T) of U.S. dollars. GDP is “Gross Domestic Product.” Percentages are shown as %.

General Information Product↗

USGS1999

Characterizing backcountry camping impacts in Great Smoky Mountains National Park

This investigates resource impacts on backcounty campsites in the Great Smoky Mountains National Park, USA. Study objectives were to enhance our understanding of camping impacts and to improve campsite impact assessment procedures by means of multivariate techniques. Three-hundred and eight campsites at designated backcountry campgrounds, and 69 additional unofficial campsites were assessed. Factor analysis of 195 established campsites on eight impact indicator variables revealed three dimensions of campsite impact: area disturbance, soil and groundcover damage, and tree-related damage. Four distinctive backcountry campsite types were identified, three of which were derived from cluster analyses of factor scores. These four backcountry campsite types characterize the intensity and areal extent of resource impacts, and they vary in locational and environmental attributes. At an aggregate level, different campsite types contributed unequally to the cumulative level of impact. The dimensional structure and typology developed in this study demonstrates that campsite impacts can be viewed and examined holistically with the use of multivariate methods. Implications for assessment procedures, management and further research are discussed.

Journal of Environmental Management↗

USGS2019

Reproductive failure in the Eastern Migratory Population: The interaction of research and management

The reintroduction of the Eastern Migratory Population of Whooping Cranes ( Grus americana ) has shown the most promise of any effort to date toward the establishment of a self-sustaining population. However, reproduction – including both nest success and chick survival – has been a major challenge. Here, we review the research and management efforts deployed to identify and address this challenge. While there is evidence that a proximal cause of nest failure is harassment by blood-feeding black flies ( Simulium spp. ), this is not likely to be the only contributing factor, and we present alternative hypotheses. There is less understanding of the causes of poor chick survival, and we present hypotheses for factors that may be contributing to chick mortality, including environmental, genetic, and behavioral factors. For both nest success and chick survival, we carried out a value of information analysis, using expert judgment, which allowed us to prioritize the alternative hypotheses for evaluation based on the expected management benefit of addressing each hypothesis. On the horizon are multiple opportunities to explore hypotheses about environmental factors as well as genetic and behavioral characteristics of the birds themselves that may contribute to poor reproduction. If bird-specific characteristics, such as genetics or rearing methods, are hindering reproduction, this has important implications for all efforts to restore Whooping Crane populations.

Book chapter↗

USGS2003

Support of total maximum daily load programs using spatially referenced regression models

The spatially referenced regressions on watershed attributes modeling approach, as applied to predictions of total nitrogen flux in three North Carolina river basins, addresses several information needs identified by a National Research Council evaluation of the total maximum daily load program. The model provides reach-level predictions of the probability of exceeding water-quality criteria, and estimates of total nitrogen budgets. Model estimates of point- and diffuse-source contributions and nitrogen loss rates in streams and reservoirs compared moderately well with literature estimates. Maps of reach-level predictions of nutrient inputs and delivery provide an intuitive and spatially detailed summary of the origins and fate of nutrients within a basin.

Journal of Water Resources Planning and Management↗

USGS2017

Reassessing rainfall in the Luquillo Mountains, Puerto Rico: Local and global ecohydrological implications

Mountains receive a greater proportion of precipitation than other environments, and thus make a disproportionate contribution to the world’s water supply. The Luquillo Mountains receive the highest rainfall on the island of Puerto Rico and serve as a critical source of water to surrounding communities. The area’s role as a long-term research site has generated numerous hydrological, ecological, and geological investigations that have been included in regional and global overviews that compare tropical forests to other ecosystems. Most of the forest- and watershed-wide estimates of precipitation (and evapotranspiration, as inferred by a water balance) have assumed that precipitation increases consistently with elevation. However, in this new analysis of all known current and historical rain gages in the region, we find that similar to other mountainous islands in the trade wind latitudes, leeward (western) watersheds in the Luquillo Mountains receive lower mean annual precipitation than windward (eastern) watersheds. Previous studies in the Luquillo Mountains have therefore overestimated precipitation in leeward watersheds by up to 40%. The Icacos watershed, however, despite being located at elevations 200–400 m below the tallest peaks and to the lee of the first major orographic barrier, receives some of the highest precipitation. Such lee-side enhancement has been observed in other island mountains of similar height and width, and may be caused by several mechanisms. Thus, the long-reported discrepancy of unrealistically low rates of evapotranspiration in the Icacos watershed is likely caused by previous underestimation of precipitation, perhaps by as much as 20%. Rainfall/runoff ratios in several previous studies suggested either runoff excess or runoff deficiency in Luquillo watersheds, but this analysis suggests that in fact they are similar to other tropical watersheds. Because the Luquillo Mountains often serve as a wet tropical archetype in global assessments of basic ecohydrological processes, these revised estimates are relevant to regional and global assessments of runoff efficiency, hydrologic effects of reforestation, geomorphic processes, and climate change.

Luquillo Mountains↗

USGS2016

Assessing wildlife benefits and carbon storage from restored and natural coastal marshes in the Nisqually River Delta: Determining marsh net ecosystem carbon balance

Working in partnership since 1996, the U.S. Fish and Wildlife Service and the Nisqually Indian Tribe have restored 902 acres of tidally influenced coastal marsh in the Nisqually River Delta (NRD), making it the largest estuary-restoration project in the Pacific Northwest to date. Marsh restoration increases the capacity of the estuary to support a diversity of wildlife species. Restoration also increases carbon (C) production of marsh plant communities that support food webs for wildlife and can help mitigate climate change through long-term C storage in marsh soils. In 2015, an interdisciplinary team of U.S. Geological Survey (USGS) researchers began to study the benefits of carbon for wetland wildlife and storage in the NRD. Our primary goals are (1) to identify the relative importance of the different carbon sources that support juvenile chinook ( Oncorhynchus tshawytscha ) food webs and contribute to current and historic peat formation, (2) to determine the net ecosystem carbon balance (NECB) in a reference marsh and a restoration marsh site, and (3) to model the sustainability of the reference and restoration marshes under projected sea-level rise conditions along with historical vegetation change. In this fact sheet, we focus on the main C sources and exchanges to determine NECB, including carbon dioxide (CO 2 ) uptake through plant photosynthesis, the loss of CO 2 through plant and soil respiration, emissions of methane (CH 4 ), and the lateral movement or leaching loss of C in tidal waters.

Washington↗

USGS2006

Cumulative uncertainty in measured streamflow and water quality data for small watersheds

The scientific community has not established an adequate understanding of the uncertainty inherent in measured water quality data, which is introduced by four procedural categories: streamflow measurement, sample collection, sample preservation/storage, and laboratory analysis. Although previous research has produced valuable information on relative differences in procedures within these categories, little information is available that compares the procedural categories or presents the cumulative uncertainty in resulting water quality data. As a result, quality control emphasis is often misdirected, and data uncertainty is typically either ignored or accounted for with an arbitrary margin of safety. Faced with the need for scientifically defensible estimates of data uncertainty to support water resource management, the objectives of this research were to: (1) compile selected published information on uncertainty related to measured streamflow and water quality data for small watersheds, (2) use a root mean square error propagation method to compare the uncertainty introduced by each procedural category, and (3) use the error propagation method to determine the cumulative probable uncertainty in measured streamflow, sediment, and nutrient data. Best case, typical, and worst case data quality scenarios were examined. Averaged across all constituents, the calculated cumulative probable uncertainty (%) contributed under typical scenarios ranged from 6% to 19% for streamflow measurement, from 4% to 48% for sample collection, from 2% to 16% for sample preservation/storage, and from 5% to 21% for laboratory analysis. Under typical conditions, errors in storm loads ranged from 8% to 104% for dissolved nutrients, from 8% to 110% for total N and P, and from 7% to 53% for TSS. Results indicated that uncertainty can increase substantially under poor measurement conditions and limited quality control effort. This research provides introductory scientific estimates of uncertainty in measured water quality data. The results and procedures presented should also assist modelers in quantifying the quality of calibration and evaluation data sets, determining model accuracy goals, and evaluating model performance.

Transactions of the ASABE↗

USGS2010

Diet of lake trout and burbot in northern Lake Michigan during spring: Evidence of ecological interaction

We used analyses of burbot ( Lota lota ) and lake trout ( Salvelinus namaycush ) diets taken during spring gill-net surveys in northern Lake Michigan in 2006-2008 to investigate the potential for competition and predator-prey interactions between these two species. We also compared our results to historical data from 1932. During 2006-2008, lake trout diet consisted mainly of alewives ( Alosa pseudoharengus ) and rainbow smelt ( Osmerus mordax ), whereas burbot utilized a much wider prey base including round goby ( Neogobius melanostomus ), rainbow smelt, alewives, and sculpins. Using the Schoener's diet overlap index, we found a higher potential for interspecific competition in 1932 than in 2006-2008, though diet overlap was not significant in either time period. No evidence of cannibalism by lake trout or lake trout predation on burbot was found in either time period. In 2006-2008, however, lake trout composed 5.4% (by weight) of burbot diet. To determine whether this predation could be having an impact on lake trout rehabilitation efforts in northern Lake Michigan, we developed a bioenergetic-based consumption estimate for burbot on Boulder Reef (a representative reef within the Northern Refuge) and found that burbot alone can consume a considerable proportion of the yearling lake trout stocked annually, depending on burbot density. Overall, we conclude that predation, rather than competition, is the more important ecological interaction between burbot and lake trout, and burbot predation may be contributing to the failed lake trout rehabilitation efforts in Lake Michigan.

Michigan↗

USGS2025

Changes in phosphorus concentration and flux from 2011 to 2023 in major U.S. tributaries to the Laurentian Great Lakes

Reducing phosphorus (P) flux to the Great Lakes is critical for improving water quality and controlling eutrophication. We used 13 water years (2011–2023) of U.S. Geological Survey data from 24 major U.S. tributaries (representing 47% of the U.S. Great Lakes watershed area) to evaluate temporal changes in orthophosphate (PO 4 -P) and total P (TP) using Weighted Regressions on Time, Discharge, and Season. We assessed actual and flow-normalized P concentrations and fluxes. Between 2011 and 2023, P concentrations and fluxes declined in many tributaries, although the extent and significance of these declines varied. Decreases were more common and statistically likely for TP than PO 4 -P, and several high-loading watersheds had modest or non-significant changes. Flow-normalized PO 4 -P:TP flux ratios increased in over half the tributaries, suggesting that even where P reductions occurred, reductions in the more bioavailable P fraction were proportionally smaller. Actual P fluxes were strongly correlated with streamflow, and year-to-year variability in actual fluxes was, on average, three times greater than variability related to trends in flow-normalized fluxes. This underscores the role of hydrology in modulating P export and highlights how changing precipitation and runoff patterns can obscure or counteract management progress. Spring accounted for the largest share of annual P flux in most tributaries, though many showed declining spring contributions. Our basin-wide analysis reveals that while management efforts may have yielded progress in reducing TP in many watersheds, additional strategies would be needed to address PO 4 -P reductions and account for changing hydrology, especially in high-contributing watersheds.

Journal of Great Lakes Research↗

USGS2007

Thermal infrared reflectance and emission spectroscopy of quartzofeldspathic glasses

This investigation seeks to better understand the thermal infrared (TIR) spectral characteristics of naturally-occurring amorphous materials through laboratory synthesis and analysis of glasses. Because spectra of glass phases differ markedly from their mineral counterparts, examination of glasses is important to accurately determine the composition of amorphous surface materials using remote sensing datasets. Quantitatively characterizing TIR (5-25 ??m) spectral changes that accompany structural changes between glasses and mineral crystals provides the means to understand natural glasses on Earth and Mars. A suite of glasses with compositions analogous to common terrestrial volcanic glasses was created and analyzed using TIR reflectance and emission techniques. Documented spectral characteristics provide a basis for comparison with TIR spectra of other amorphous materials (glasses, clays, etc.). Our results provide the means to better detect and characterize glasses associated with terrestrial volcanoes, as well as contribute toward understanding the nature of amorphous silicates detected on Mars. Copyright 2007 by the American Geophysical Union.

Geophysical Research Letters↗

USGS2011

Elevated gas hydrate saturation within silt and silty clay sediments in the Shenhu area, South China Sea

Gas hydrate saturations were estimated using five different methods in silt and silty clay foraminiferous sediments from drill hole SH2 in the South China Sea. Gas hydrate saturations derived from observed pore water chloride values in core samples range from 10 to 45% of the pore space at 190–221 m below seafloor (mbsf). Gas hydrate saturations estimated from resistivity (R t ) using wireline logging results are similar and range from 10 to 40.5% in the pore space. Gas hydrate saturations were also estimated by P wave velocity obtained during wireline logging by using a simplified three-phase equation (STPE) and effective medium theory (EMT) models. Gas hydrate saturations obtained from the STPE velocity model (41.0% maximum) are slightly higher than those calculated with the EMT velocity model (38.5% maximum). Methane analysis from a 69 cm long depressurized core from the hydrate-bearing sediment zone indicates that gas hydrate saturation is about 27.08% of the pore space at 197.5 mbsf. Results from the five methods show similar values and nearly identical trends in gas hydrate saturations above the base of the gas hydrate stability zone at depths of 190 to 221 mbsf. Gas hydrate occurs within units of clayey slit and silt containing abundant calcareous nannofossils and foraminifer, which increase the porosities of the fine-grained sediments and provide space for enhanced gas hydrate formation. In addition, gas chimneys, faults, and fractures identified from three-dimensional (3-D) and high-resolution two-dimensional (2-D) seismic data provide pathways for fluids migrating into the gas hydrate stability zone which transport methane for the formation of gas hydrate. Sedimentation and local canyon migration may contribute to higher gas hydrate saturations near the base of the stability zone.

Journal of Geophysical Research B: Solid Earth↗

USGS2007

Wind River Watershed Restoration: Annual report April 2006 to March 2007

This report summarizes work completed by U.S. Geological Survey’s Columbia River Research Laboratory (USGS-CRRL) in the Wind River subbasin during the period April 2006 through March 2007 under Bonneville Power Administration (BPA) contract 26922. During this period, we collected temperature, flow, and habitat data to characterize physical habitat condition and variation within and among tributaries and mainstem sections in the Wind River subbasin. We also conducted electrofishing and snorkeling surveys to determine juvenile salmonid populations within select study areas throughout the subbasin. Portions of this work were completed with additional funding from U.S. Fish and Wildlife Service (USFWS) and the Lower Columbia Fish Enhancement Group (LCFEG). Funding from USFWS was for work to contribute to a study of potential interactions between introduced Chinook salmon Oncorhynchus tshawytscha and wild steelhead O. mykiss. Funding from LCFEG was for work to evaluate the effects of nutrient enrichment in small streams. A statement of work (SOW) was submitted to BPA in March 2006 that outlined work to be performed by USGS-CRRL. The SOW was organized by work elements, with each describing a research task. This report summarizes the progress completed under each work element.

Washington↗

USGS2024

A unified approach to long-term population monitoring of grizzly bears in the Greater Yellowstone Ecosystem

Long-term wildlife research and monitoring programs strive to maintain consistent data collections and analytical methods. Incorporating new techniques is important but can render data sets incongruent and limit their potential to discern trends in demographic parameters. Integrated population models (IPMs) can address these limitations by combining data sources that may span different periods into a unified statistical framework while providing a holistic view of population dynamics. We developed an IPM in a Bayesian framework for grizzly bears ( Ursus arctos ) in the Greater Yellowstone Ecosystem. We coupled demographic data with multiple, independent population count data to link annual changes in abundance with vital rates over 4 decades (1983–2023). Abundance increased threefold from an estimated 270 individuals in 1984 to 1030 individuals in 2023. Parameter estimates indicated survival of bears ≥2 years of age was high, contributing to robust population growth during the 1980s (λ = 1.023 [50 % interquartile range = 0.993–1.082]) and 1990s (λ = 1.064 [1.023–1.103]). A slowing of population growth started around 2000 (2000s: λ = 1.030 [0.989–1.068]) and continued into the 2010s (λ = 1.021 [0.985–1.057]), due primarily to reductions in survival of bears <2 years of age. These findings corroborate previous research that identified density-dependent effects as a likely cause. The IPM framework provided greater certainty and understanding regarding the dynamic demographic characteristics of the population and serves as a powerful monitoring tool for this long-lived species. Implementation of the IPM allows timely dissemination of demographic data to help inform adaptive management strategies and policy decisions necessary for the continued management and conservation of this population. This robust and flexible monitoring system allows scientists to investigate the effects of a changing ecosystem on population dynamics, incorporate new data sources and statistical models, and respond to changes in monitoring needs for the population. We highlight the efficacy of the IPM in estimating and tracking demographic parameters for a long-lived species, while accommodating shifts in monitoring techniques and data collections typical of long-term wildlife conservation programs worldwide.

Idaho, Montana, Wyoming↗

USGS2002

Alien invasions in aquatic ecosystems: Toward an understanding of brook trout invasions and potential impacts on inland cutthroat trout in western North America

Experience from case studies of biological invasions in aquatic ecosystems has motivated a set of proposed empirical “rules” for understanding patterns of invasion and impacts on native species. Further evidence is needed to better understand these patterns, and perhaps contribute to a useful predictive theory of invasions. We reviewed the case of brook trout ( Salvelinus fontinalis )invasions in the western United States and their impacts on native cutthroat trout ( Oncorhynchus clarki ). Unlike many biological invasions, a considerable body of empirical research on brook trout and cutthroat trout is available. We reviewed life histories of each species, brook trout invasions, their impacts on cutthroat trout, and patterns and causes of segregation between brook trout and cutthroat trout. We considered four stages of the invasion process: transport, establishment, spread, and impacts to native species. Most of the research we found focused on impacts. Interspecific interactions, especially competition, were commonly investigated and cited as impacts of brook trout. In many cases it is not clear if brook trout invasions have a measurable impact. Studies of species distributions in the field and a variety of experiments suggest invasion success of brook trout is associated with environmental factors, including temperature, landscape structure, habitat size, stream flow, and human influences. Research on earlier stages of brook trout invasions (transport, establishment, and spread) is relatively limited, but has provided promising insights. Management alternatives for controlling brook trout invasions are limited, and actions to control brook trout focus on direct removal, which is variably successful and can have adverse effects on native species. The management applicability of research has been confounded by the complexity of the problem and by a focus on understanding processes at smaller scales, but not on predicting patterns at larger scales. In the short-term, an improved predictive understanding of brook trout invasions could prove to be most useful, even if processes are incompletely understood. A stronger connection between research and management is needed to identify more effective alternatives for controlling brook trout invasions and for identifying management priorities.

western United States↗

USGS2016

Using scenarios to assess possible future impacts of invasive species in the Laurentian Great Lakes

The expected impacts of invasive species are key considerations in selecting policy responses to potential invasions. But predicting the impacts of invasive species is daunting, particularly in large systems threatened by multiple invasive species, such as North America’s Laurentian Great Lakes. We developed and evaluated a scenario-building process that relied on an expert panel to assess possible future impacts of aquatic invasive species on recreational fishing in the Great Lakes. To maximize its usefulness to policy makers, this process was designed to be implemented relatively rapidly and consider a range of species. The expert panel developed plausible, internally-consistent invasion scenarios for 5 aquatic invasive species, along with subjective probabilities of those scenarios. We describe these scenarios and evaluate this approach for assessing future invasive species impacts. The panel held diverse opinions about the likelihood of the scenarios, and only one scenario with impacts on sportfish species was considered likely by most of the experts. These outcomes are consistent with the literature on scenario building, which advocates for developing a range of plausible scenarios in decision making because the uncertainty of future conditions makes the likelihood of any particular scenario low. We believe that this scenario-building approach could contribute to policy decisions about whether and how to address the possible impacts of invasive species. In this case, scenarios could allow policy makers to narrow the range of possible impacts on Great Lakes fisheries they consider and help set a research agenda for further refining invasive species predictions.

Great Lakes, Lake Superior, Lake Huron, Lake Michi↗

USGS2019

Visualizing populations of North American sea ducks: Maps to guide research and management planning

North American sea ducks generally breed in mid- to northern-latitude regions and nearly all rely upon marine habitats for much of their annual cycle. Most sea duck species remained poorly studied until the 1990s when declines were noted in several species and populations. Subsequent research, much of which was funded by the Sea Duck Joint Venture, began in the late 1990s with an emphasis on defining use areas throughout the annual cycle, migration patterns, and determining if there were distinct populations, within species, across North America. These studies relied largely upon satellite telemetry information to identify winter, breeding, and molting areas of sea ducks. New information from band recovery and genetic markers was added, contributing to hypotheses and initial conclusions about population delineation. Information on population units across North America is critical for identifying appropriate scales for evaluating population status and trends through annual monitoring surveys, harvest assessments, habitat protection and measuring effectiveness of management applications. Previous descriptions of population segments were for single species or smaller groups of similar species. Here, we summarize current knowledge on the general distribution and population segments of 13 species of sea ducks in North America by comparing range maps to long-term band recovery, genetic, and satellite telemetry data to inform population delineation assessments and future research. These comparisons show a high degree of consistency in population patterns for most species across the independent data types. These maps provide a foundation for developing new hypothesis-driven research to address remaining knowledge gaps and questions about population differentiation, annual cycle distribution, habitat use, and harvest assessment.

North America↗

USGS2014

Evaluation of a mass-balance approach to determine consumptive water use in northeastern Illinois

A principal component of evaluating and managing water use is consumptive use. This is the portion of water withdrawn for a particular use, such as residential, which is evaporated, transpired, incorporated into products or crops, consumed by humans or livestock, or otherwise removed from the immediate water environment. The amount of consumptive use may be estimated by a water (mass)-balance approach; however, because of the difficulty of obtaining necessary data, its application typically is restricted to the facility scale. The general governing mass-balance equation is: Consumptive use = Water supplied - Return flows . This study explored a mass-balance field-based computation of consumptive use in a residential setting at the scale of a sanitary sewer service area (sewershed). In addition, the feasibility (cost and difficulty) and relative uncertainties (accuracies) associated with applying the approach at this scale were evaluated. The study was conducted during 2011–13 within a 3.5-square mile (mi 2 ) sewershed confined to a predominantly residential area of Elk Grove Village, Illinois. Following background evaluation of the geohydrologic setting, sewershed infrastructure, and possible components of supplied and returned water, the identified primary components were 1. public water deliveries by the Elk Grove Village Department of Public Works, 2. self-served groundwater withdrawals in an included unincorporated neighborhood with public sanitary sewer service, 3. return flows to the sanitary sewer system, and 4. direct return of water discharged from swimming pools to Salt Creek. Water volumes principally were reported for deliveries, measured for sanitary sewer returns by using an acoustic Doppler current-velocity meter, and estimated for domestic withdrawals and swimming pool discharges to storm sewers. All water volumes required some degree of estimation. Observation wells were installed adjacent to sewer pipelines (lines) to determine the depth of the water table relative to that of the sewer lines and to collect water samples for detection of optical brighteners, as they are routinely discharged as clotheswashing waste to sanitary sewers. These data provided qualitative information on gains (inflow and infiltration) and losses (exfiltration) of sewer flow by pipe leakage, which might otherwise not be considered in the sewer flow return measurements. Hydrographs of sewer flow also were evaluated to identify and estimate storm-associated inputs to sewer flow. The volume of sanitary sewer return flow (778 million gallons per year [Mgal/yr]) was determined to substantially exceed the volume of supplied water (566 Mgal/yr), thus, for this study setting, voiding the utility of the applied mass-balance approach for estimating consumptive water use. Mass-balance components, including sanitary sewer flow and supplied-water use, were estimated within reasonable limits of uncertainty. Evidence of a water table that is typically shallower than the area’s sewer lines, yet is sometimes depressed near more deeply buried sewer lines, suggests groundwater infiltration into the sewers contributes to the excess volume of return flow. Technical obstacles and project resources precluded accurate quantification of infiltration volumes and other gains and losses to sanitary sewer flow. As estimated from various simplified methods, a minimum of 26 percent of return flow measured in the sanitary sewer represented groundwater infiltration and stormwater inflow; separately, about 2 percent of return flow was estimated as inflow. On the basis of the alternative winter base-rate method, consumptive use in the sewershed was estimated as 13 percent, which compares favorably with that used by the State of Illinois for Lake Michigan allocation accounting (10 percent) and other States and Canadian Provinces in the Great Lakes region (generally 10-15 percent). The study also provided other findings considered useful to studies of water use and to performance evaluation of sanitary sewer infrastructure. In urban residential settings, the comparatively small volumes of nonpublic sources of water (self-supplied) and direct (nonsanitary) return flow potentially can be ignored in the estimation of consumptive use. An acoustic Doppler current-velocity meter can be used in sanitary sewers to accurately measure discharge and reasonably estimate storm-associated inflows. Hourly to daily patterns of water use can be readily identified and quantified in the return flow record for the sanitary sewers. Relative volumes of infiltration gains (and exfiltration losses) can be substantial, even in sewer systems of communities making significant investments in system upgrades to limit sewer line leakage. Monitoring of optical brighteners in groundwater (and potentially in sanitary sewer flow) can provide a useful means of identifying probable leakage from (and to) sewer lines. Accurate quantification of gains and losses to sanitary sewer flow at the sewershed scale will require additional research effort and technical advances. Under ideal conditions, accurate quantification of consumptive use at the sewershed scale by the described mass-balance approach might be possible. Under most prevailing conditions, quantification likely would be more costly and time consuming than that of the present study, given the freely contributed technical support of the host community and relatively appropriate conditions of the study area. Essentials to quantification of consumptive use are a fully cooperative community, storm and sanitary sewers that are separate, and newer sewer infrastructure and (or) a robust program for limiting infiltration, exfiltration, and inflow.

Illinois↗

USGS2010

Understanding the role of fog in forest hydrology: Stable isotopes as tools for determining input and partitioning of cloud water in montane forests

Understanding the hydrology of tropical montane cloud forests (TMCF) has become essential as deforestation of mountain areas proceeds at an increased rate worldwide. Passive and active cloud‐water collectors, throughfall and stemflow collectors, visibility or droplet size measurements, and micrometeorological sensors are typically used to measure the fog water inputs to ecosystems. In addition, stable isotopes may be used as a natural tracer for fog and rain. Previous studies have shown that the isotopic signature of fog tends to be more enriched in the heavier isotopes 2 H and 18 O than that of rain, due to differences in condensation temperature and history. Differences between fog and rain isotopes are largest when rain is from synoptic‐scale storms, and fog or orographic cloud water is generated locally. Smaller isotopic differences have been observed between rain and fog on mountains with orographic clouds, but only a few studies have been conducted. Quantifying fog deposition using isotope methods is more difficult in forests receiving mixed precipitation, because of limitations in the ability of sampling equipment to separate fog from rain, and because fog and rain may, under some conditions, have similar isotopic composition. This article describes the various types of fog most relevant to montane cloud forests and the importance of fog water deposition in the hydrologic budget. A brief overview of isotope hydrology provides the background needed to understand isotope applications in cloud forests. A summary of previous work explains isotopic differences between rain and fog in different environments, and how monitoring the isotopic signature of surface water, soil water and tree xylem water can yield estimates of the contribution of fog water to streamflow, groundwater recharge and transpiration. Next, instrumentation to measure fog and rain, and methods to determine isotopic concentrations in plant and soil water are discussed. The article concludes with the identification of some of the more pressing research questions in this field and offers various suggestions for future research.

Hydrological Processes↗