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USGS2012

Trimming the UCERF2 hazard logic tree

The Uniform California Earthquake Rupture Forecast 2 (UCERF2) is a fully time‐dependent earthquake rupture forecast developed with sponsorship of the California Earthquake Authority (Working Group on California Earthquake Probabilities [WGCEP], 2007; Field et al., 2009). UCERF2 contains 480 logic‐tree branches reflecting choices among nine modeling uncertainties in the earthquake rate model shown in Figure 1. For seismic hazard analysis, it is also necessary to choose a ground‐motion‐prediction equation (GMPE) and set its parameters. Choosing among four next‐generation attenuation (NGA) relationships results in a total of 1920 hazard calculations per site. The present work is motivated by a desire to reduce the computational effort involved in a hazard analysis without understating uncertainty. We set out to assess which branching points of the UCERF2 logic tree contribute most to overall uncertainty, and which might be safely ignored (set to only one branch) without significantly biasing results or affecting some useful measure of uncertainty. The trimmed logic tree will have all of the original choices from the branching points that contribute significantly to uncertainty, but only one arbitrarily selected choice from the branching points that do not.

Seismological Research Letters↗

USGS2002

Statistical methods in water resources

Preface This book began as class notes for a course we teach on applied statistical methods to hydrologists of the Water Resources Division, U. S. Geological Survey (USGS). It reflects our attempts to teach statistical methods which are appropriate for analysis of water resources data. As interest in this course has grown outside of the USGS, incentive grew to develop the material into a textbook. The topics covered are those we feel are of greatest usefulness to the practicing water resources scientist. Yet all topics can be directly applied to many other types of environmental data. This book is not a stand-alone text on statistics, or a text on statistical hydrology. For example, in addition to this material we use a textbook on introductory statistics in the USGS training course. As a consequence, discussions of topics such as probability theory required in a general statistics textbook will not be found here. Derivations of most equations are not presented. Important tables included in all general statistics texts, such as quantiles of the normal distribution, are not found here. Neither are details of how statistical distributions should be fitted to flood data -- these are adequately covered in numerous books on statistical hydrology. We have instead chosen to emphasize topics not always found in introductory statistics textbooks, and often not adequately covered in statistical textbooks for scientists and engineers. Tables included here, for example, are those found more often in books on nonparametric statistics than in books likely to have been used in college courses for engineers. This book points the environmental and water resources scientist to robust and nonparametric statistics, and to exploratory data analysis. We believe that the characteristics of environmental (and perhaps most other 'real') data drive analysis methods towards use of robust and nonparametric methods. Exercises are included at the end of chapters. In our course, students compute each type of analysis (t-test, regression, etc.) the first time by hand. We choose the smaller, simpler examples for hand computation. In this way the mechanics of the process are fully understood, and computer software is seen as less mysterious. We wish to acknowledge and thank several other scientists at the U. S. Geological Survey for contributing ideas to this book. In particular, we thank those who have served as the other instructors at the USGS training course. Ed Gilroy has critiqued and improved much of the material found in this book. Tim Cohn has contributed in several areas, particularly to the sections on bias correction in regression, and methods for data below the reporting limit. Richard Alexander has added to the trend analysis chapter, and Charles Crawford has contributed ideas for regression and ANOVA. Their work has undoubtedly made its way into this book without adequate recognition. Professor Ken Potter (University of Wisconsin) and Dr. Gary Tasker (USGS) reviewed the manuscript, spending long hours with no reward except the knowledge that they have improved the work of others. For that we are very grateful. We also thank Madeline Sabin, who carefully typed original drafts of the class notes on which the book is based. As always, the responsibility for all errors and slanted thinking are ours alone.

Techniques of Water-Resources Investigations↗

USGS1978

Evaluation and correlation of water-quality data for the North Fork Flathead River, northwestern Montana

This report is a compilation and evaluation of water-quality measurements that have been made by the U.S. Geological Survey at two stations on the North Fork Flathead River in Montana. Historical streamflow records show an annual mean daily discharge of 3,010 cubic feet per second near the mouth--a threefold increase compared to discharge at the international boundary. The chemical character of the water is dominated by calcium and magnesium cations and the bicarbonate anion. Base flow, in contrast to high flows from runoff, is characterized by higher dissolved constituents and lower concentrations of suspended sediment. The several lakes that contribute water throughout the middle and lower drainage have a dampening effect on both streamflow and constituent concentrations. Using the available data and computer techniques, regression equations were developed between certain water-quality variables. (Woodard-USGS)

Water-Resources Investigations Report↗

USGS2009

Development and application of a mark-recapture model incorporating predicted sex and transitory behaviour

We developed an extension of Cormack-Jolly-Seber models to handle a complex mark-recapture problem in which (a) the sex of birds cannot be determined prior to first moult, but can be predicted on the basis of body measurements, and (b) a significant portion of captured birds appear to be transients (i.e. are captured once but leave the area or otherwise become ' untrappable'). We applied this methodology to a data set of 4184 serins (Serinus serinus) trapped in northeastern Spain during 1985-96, in order to investigate age-, sex-, and time-specific variation in survival rates. Using this approach, we were able to successfully incorporate the majority of ringings of serins. Had we eliminated birds not previously captured (as has been advocated to avoid the problem of transience) we would have reduced our sample sizes by >2000 releases. In addition, we were able to include 1610 releases of birds of unknown (but predicted) sex; these data contributed to the precision of our estimates and the power of statistical tests. We discuss problems with data structure, encoding of the algorithms to compute parameter estimates, model selection, identifiability of parameters, and goodness-of-fit, and make recommendations for the design and analysis of future studies facing similar problems.

Bird Study↗

USGS2000

Water-surface profile and flood boundaries for the computed 100-year flood, lower Salt River, Lincoln County, Wyoming

The water-surface profile and flood boundaries for the computed 100-year flood were determined for a part of the lower Salt River in Lincoln County, Wyoming. Channel cross-section data were provided by Lincoln County. Cross-section data for bridges and other structures were collected and compiled by the U.S. Geological Survey. Roughness coefficients ranged from 0.034 to 0.100. The 100-year flood was computed using standard methods, ranged from 5,170 to 4,120 cubic feet per second through the study reach, and was adjusted proportional to contributing drainage area. Water-surface elevations were determined by the standard step-backwater method. Flood boundaries were plotted on digital basemaps.

Open-File Report↗

USGS1982

Multi-event urban runoff quality model

A computer model is presented for simulating the quality of surface runoff from urban watersheds. The model can simulate impervious area, pervious area, and precipitation contributions to runoff quality as well as the effects of street sweeping and (or) detention storage. Within-storm variations of runoff quality are simulated for user-specified storm-runoff periods. Between these storms, a daily accounting of the accumulation and washoff of water-quality constituents on effective impervious areas is maintained. The time step of the within-storm simulations can range from 1 to 60 minutes. The model can be operated as a lumped-parameter model or as a distributed-parameter model. As a lumped-parameter model, no spatial variations in model parameters are accounted for, and input to the model requires flow hydrographs only at the outlet of the watershed. The outlet hydrographs can be either observed or simulated. As a distributed-parameter model, the model requires flow hydrographs at many points in the watershed, as defined by basin segmentation. These hydrographs will normally be simulated by the Distributed Routing Rainfall-Runoff Model. This report includes a presentation of the theory and limitations of the model, as well as a program listing, instructions for running the program, and example simulations.

Open-File Report↗

USGS1973

Water resources data for Wyoming, water year 1972; part 1, surface water records

Surface-water records for the 1972 water year for Wyoming, including records of streamflow or reservoir storage at gaging stations, partial-record stations, and miscellaneous sites, are given in this report. The locations of the gaging stations and partial-record stations are shown in figures 1 and 2. Records for a few pertinent gaging stations in bordering States also are included. These data represent that portion of the National Water Data System collected by the U.S. Geological Survey and cooperating State and Federal agencies in Wyoming. The records were collected and computed by the Water Resources Division of the U.S. Geological Survey under the direction of Robert L. Cushman, district chief. Wyoming district personnel who contributed significantly to the collection and preparation of data included in this report were: S.A. Druse, D. J. O'Connell, G. S. Craig, Jr., G. W. Armentrout, Jr., H. W. Lowham, B. H. Ringen, P. B. McCollam, C. F. Obert, W. R. Glass, T.W. Custis, R. L. Muench, J. 0. Ragsdale, M. D. Stevens, J. M. Johnson, and J. L. Lynch. Through September 30, 1960, the records of discharge and stage of streams and canals, and contents and stage of lakes or reservoirs, were published in an annual series of U.S. Geological Survey water-supply papers entitled "Surface Water Supply of the United States." Beginning with the 1961 water year, surface-water records have been released by the Geological Survey in annual reports on a State-boundary basis. Distribution of these reports is limited; they are designed primarily for rapid release of data shortly after the end of the water year to meet local needs. Records of discharge and reservoir storage for 1961-65 have been published in a Geological Survey water-supply paper series entitled "Surface Water Supply of the United States 1961-65." Records of discharge and reservoir storage for 1966-70 also will be published in a Geological Survey water-supply paper series entitled "Surface Water Supply of the United States 1966-70."

Wyoming↗

USGS1974

Water resources data for Wyoming, water year 1973; part 1, surface water records

Surface-water records for the 1973 water year for Wyoming, including records of streamflow or reservoir storage at gaging stations, partial-record stations, and miscellaneous sites, are given in this report. The locations of the gaging stations and partial-record stations are shown in figures 1 and 2. Records for a few pertinent gaging stations in bordering States also are included. These data represent that portion of the National Water Data System collected by the U.S. Geological Survey and cooperating State and Federal agencies in Wyoming. The records were collected and computed by the Water Resources Division of the U.S. Geological Survey under the direction of Robert L. Cushman, district chief. Wyoming district personnel who contributed significantly to the collection and preparation of data included in this report were: S.A. Druse, D. J. O'Connell, G. S. Craig, Jr., G. W. Armentrout, Jr., H. W. Lowham, J. G. Rankl, P. B. McCollam, C. F. Obert, W. R. Glass, T.W. Custis, R. L. Muench, J. O. Ragsdale, M. D. Stevens, R. C. Bauman, J. L. Lynch, and S. L. Green. Beginning with the 1961 water year, streamflow records and related data have been released by the Geological Survey in annual reports on a State-boundary basis. These reports are for limited distribution and are designed primarily for rapid release of data shortly after the end of the water year. Records of discharge and stage of streams and canals, and contents and stage of lakes or reservoirs, are published in a series of U.S. Geological Survey water-supply papers entitled "Surface Water Supply of the United States." Through September 30, 1960, these water-supply papers were in an annual series and since then are in a 5-year series. More information is given under the heading "Publications" on page 9.

Wyoming↗

USGS1975

Water resources data for Wyoming, water year 1974

Surface-water records for the 1974 water year for Wyoming, including records of streamflow or reservoir storage at gaging stations, partial-record stations, and miscellaneous sites, are given in this report. The locations of the gaging stations and partial-record stations are shown in figures 1 and 2. Records for a few pertinent gaging stations in bordering States also are included. These data represent that portion of the National Water Data System collected by the U.S. Geological Survey and cooperating State and Federal agencies in Wyoming. The records were collected and computed by the Water Resources Division of the U.S. Geological Survey under the direction of Sam W. West, district chief. Wyoming district personnel who contributed significantly to the collection and preparation of data included in this report were: S. A. Druse, D. J. O'Connell, G. S. Craig, Jr., G. W. Armentrout, Jr., H. W. Lowham, J. G. Rankl, P. B. McCollam, C. F. Obert, W. R. Glass, D. J. Pangburn, T. W. Custis, R. L. Muench, J. O. Ragsdale, M. D. Stevens, R. C. Bauman, D. J. Wangsness, L. W. Lenfest, B. C. Pedersen, M. T. O'Grady, and S. L. Green. Beginning with the 1961 water year, streamflow records and related data have been released by the Geological Survey in annual reports on a State-boundary basis. These reports are for limited distribution and are designed primarily for rapid release of data shortly after the end of the water year. Records of discharge and stage of streams and canals, and contents and stage of lakes or reservoirs, are published in a series of U.S. Geological Survey water-supply papers entitled "Surface Water Supply of the United States." Through September 30, 1960, these water-supply papers were in an annual series and since then are in a 5-year series. More information is given under the heading "Publications" on page 9.

Wyoming↗

USGS2009

Discussion on remote sensing for aquatic monitoring

The special session on Remote Sensing for Aquatic Resource Monitoring concluded with an expert panel discussion. Panel members were Jennifer Bountry (hydraulic engineer, Bureau of Reclamation), Mimi D’Iorio (GIS analyst and database manager, National Oceanic and Atmospheric Administration), Russ Faux (president, Watershed Sciences, Inc.), Steve Lanigan (team leader, Aquatic and Riparian Effectiveness Monitoring Program, U.S. Forest Service), and Amar Nayegandhi (computer scientist, Jacobs Technology, contracted to U.S. Geological Survey). The panel was moderated by Ralph Haugerud (geologist, U.S. Geological Survey) and there were significant contributions from the audience. The dialogue is summarized below in question and answer format. This summary is followed by discussion of what we learned in the course of the special session and identification of some next steps for the Pacific Northwest aquatic monitoring community.

PNAMP Special Publication↗

USGS2011

Modeling sulfate reduction in methane hydrate-bearing continental margin sediments: Does a sulfate-methane transition require anaerobic oxidation of methane?

The sulfate‐methane transition (SMT), a biogeochemical zone where sulfate and methane are metabolized, is commonly observed at shallow depths (1–30 mbsf) in methane‐bearing marine sediments. Two processes consume sulfate at and above the SMT, anaerobic oxidation of methane (AOM) and organoclastic sulfate reduction (OSR). Differentiating the relative contribution of each process is critical to estimate methane flux into the SMT, which, in turn, is necessary to predict deeper occurrences of gas hydrates in continental margin sediments. To evaluate the relative importance of these two sulfate reduction pathways, we developed a diagenetic model to compute the pore water concentrations of sulfate, methane, and dissolved inorganic carbon (DIC). By separately tracking DIC containing 12 C and 13 C, the model also computes δ 13 C‐DIC values. The model reproduces common observations from methane‐rich sediments: a well‐defined SMT with no methane above and no sulfate below and a δ 13 C‐DIC minimum at the SMT. The model also highlights the role of upward diffusing 13 C‐enriched DIC in contributing to the carbon isotope mass balance of DIC. A combination of OSR and AOM, each consuming similar amounts of sulfate, matches observations from Site U1325 (Integrated Ocean Drilling Program Expedition 311, northern Cascadia margin). Without AOM, methane diffuses above the SMT, which contradicts existing field data. The modeling results are generalized with a dimensional analysis to the range of SMT depths and sedimentation rates typical of continental margins. The modeling shows that AOM must be active to establish an SMT wherein methane is quantitatively consumed and the δ 13 C‐DIC minimum occurs. The presence of an SMT generally requires active AOM.

Geochemistry, Geophysics, Geosystems↗

USGS1999

Conceptual Model and Numerical Simulation of the Ground-Water-Flow System in the Unconsolidated Sediments of Thurston County, Washington

The demand for water in Thurston County has increased steadily in recent years because of a rapid growth in population. Surface-water resources in the county have been fully appropriated for many years and Thurston County now relies entirely on ground water for new supplies of water. Thurston County is underlain by up to 2,000 feet of unconsolidated glacial and non-glacial Quaternary sediments which overlie consolidated rocks of Tertiary age. Six geohydrologic units have been identified within the unconsolidated sediments. Between 1988 and 1990, median water levels rose 0.6 to 1.9 feet in all geohydrologic units except bedrock, in which they declined 1.4 feet. Greater wet-season precipitation in 1990 (43 inches) than in 1988 (26 inches) was the probable cause of the higher 1990 water levels. Ground-water flow in the unconsolidated sediments underlying Thurston County was simulated with a computerized numerical model (MODFLOW). The model was constructed to simulate 1988 ground-water conditions as steady state. Simulated inflow to the model area from precipitation and secondary recharge was 620,000 acre-feet per year (93 percent), leakage from streams and lakes was 38,000 acre-ft/yr (6 percent), and ground water entering the model along the Chehalis River valley was 5,800 acre-ft/yr (1 percent). Simulated outflow from the model was primarily leakage to streams, springs, lakes, and seepage faces (500,000 acre-ft/yr or 75 percent of the total outflow). Submarine seepage to Puget Sound was simulated to be 88,000 acre-ft/yr (13 percent). Simulated ground-water discharge along the Chehalis River valley was simulated to be 12,000 acreft/yr (2 percent). Simulated withdrawals by wells for all purposes was 62,000 acre-ft/yr (9 percent). The numerical model was used to simulate the possible effects of increasing ground-water withdrawals by 23,000 acre-ft/yr above the 1988 rate of withdrawal. The model indicated that the increased withdrawals would come from reduced discharge to springs, seepage faces, and offshore (total of 51 percent of increased pumping) and decreased flow to rivers (46 percent). About 3 percent would come from increased leakage from rivers. Water levels would decline more than 1 foot over most of the model area, more than 10 feet over some areas, and would be at a maximum of about 35 feet. Contributing areas for water discharging at McAllister and Abbott Springs and to pumping centers near Tumwater and Lacey were estimated using a particle-tracking post-processing computer code (MODPATH) and a MODFLOW model calibrated to steady-state (1988) conditions. Water discharging at McAllister and Abbot Springs was determined to come from water entering the ground-water system at the water table in an area of about 20 square miles (mi2) to the west and south of the springs. This water is estimated to come from recharge (both precipitation and secondary) and from leakage from Lake St. Clair and several other surface-water bodies. Southeast of Lacey, about 3,800 acre-ft of ground water were pumped from five municipal wells during 1988. The source of the pumped water was determined to be an area that covers about 1.1 mi2. The water was estimated to come from recharge (both precipitation and secondary) and leakage from surface-water bodies. Along the lower Deschutes River nearly 3,900 acre-ft/yr of ground water were pumped during 1988 from 15 wells for municipal and industrial use. The calculated source of this water was an area that covers about 1.3 mi2. Within the calculated contributing area the pumped ground water comes from recharge (both precipitation and secondary) and leakage from the Deschutes River and several other surface-water bodies.

Water-Resources Investigations Report↗

USGS2008

Origin and paleoclimatic significance of late Quaternary loess in Nebraska: Evidence from stratigraphy, chronology, sedimentology, and geochemistry

Loess is one of the most extensive surficial geologic deposits in midcontinental North America, particularly in the central Great Plains region of Nebraska. Last-glacial-age loess (Peoria Loess) reaches its greatest known thickness in the world in this area. New stratigraphic, geochronologic, mineralogic, and geochemical data yield information about the age and provenance of Peoria Loess, as well as evaluation of recent climate models. Sixteen new radiocarbon ages and recently acquired optically stimulated luminescence ages indicate that Peoria Loess deposition in Nebraska occurred between ca. 25,000 cal yr B.P. and ca. 13,000 cal yr B.P. After ca. 13,000 cal yr B.P. a period of pedogenesis began, represented by the dark, prominent Brady Soil. At some localities, further loess deposition was minimal. At other localities, sometime after ca. 11,000 cal yr B.P., there were additional episodes of loess deposition (Bignell Loess) intermittently throughout the Holocene. The spatial variability of particle size abundances in Peoria Loess shows a northwest-to-southeast fining in Nebraska, consistent with maps of previous workers that show a northwest-to-southeast thinning of loess. These observations indicate that paleowinds that deposited the loess were from the west or northwest and that the source or sources of Peoria Loess lay to the west or northwest. New mineralogical and geochemical data indicate that the most important sources of loess were likely Tertiary siltstones of the White River and Arikaree Groups, silt facies of Pliocene eolian sediments, and small contributions from Pierre Shale. It is likely that fine-grained silts were transported episodically through the Nebraska Sand Hills from Tertiary and Cretaceous bedrock sources to the north, in agreement with a model presented recently. The identification of Tertiary siltstones and silts as the primary sources of loess is consistent with isotopic data presented in a companion paper. Contributions of glaciogenic silt from the Platte and Missouri Rivers were limited to loess zones close to the valleys of those drainages. An earlier computer-based model of global dust generation during the last glacial period did not identify the Great Plains of North America as a significant source of nonglaciogenic eolian silt. However, a refined version of this model does simulate this region as a significant non-glacial dust source during the last glacial period, in good agreement with the results presented here.

Nebraska↗

USGS2012

Streamflow depletion by wells--Understanding and managing the effects of groundwater pumping on streamflow

Groundwater is an important source of water for many human needs, including public supply, agriculture, and industry. With the development of any natural resource, however, adverse consequences may be associated with its use. One of the primary concerns related to the development of groundwater resources is the effect of groundwater pumping on streamflow. Groundwater and surface-water systems are connected, and groundwater discharge is often a substantial component of the total flow of a stream. Groundwater pumping reduces the amount of groundwater that flows to streams and, in some cases, can draw streamflow into the underlying groundwater system. Streamflow reductions (or depletions) caused by pumping have become an important water-resource management issue because of the negative impacts that reduced flows can have on aquatic ecosystems, the availability of surface water, and the quality and aesthetic value of streams and rivers. Scientific research over the past seven decades has made important contributions to the basic understanding of the processes and factors that affect streamflow depletion by wells. Moreover, advances in methods for simulating groundwater systems with computer models provide powerful tools for estimating the rates, locations, and timing of streamflow depletion in response to groundwater pumping and for evaluating alternative approaches for managing streamflow depletion. The primary objective of this report is to summarize these scientific insights and to describe the various field methods and modeling approaches that can be used to understand and manage streamflow depletion. A secondary objective is to highlight several misconceptions concerning streamflow depletion and to explain why these misconceptions are incorrect.

Circular↗

USGS1973

Water resources data for Kansas, water year 1972; Part 1, Surface water records

Surface-water records for the 1972 water year for Kansas, including records of streamflow or reservoir storage at gaging stations and partial-record stations, are given in this report. The locations of the stations are on figures 1 and 2. Records for a few pertinent gaging stations in bordering States also are included. These data represent that part of the National Water Data System collected by the U. S. Geological Survey and cooperating State and Federal agencies in Kansas. The records were collected and computed by the Water Resources Division of the U. S. Geological Survey under the direction of C. W. Lane, district chief. Kansas district personnel who contributed significantly to the collection and preparation of data included in this report were: J. L. Ebling, C. 0. Geiger, K. D. Medina, L. E. Stuliken, C. 0. Peek, J. D. Craig, L. L. Jones, A. T. Klamm, J. P. Marshall, C. W. Kennedy, W. J. Carswell, D. L. Lacock, G. G. Quy II, J. T. Religa, R. D. Thomas, S. V. Bond, S. T. Green, C. G. Sauer, A. B. Evans, A. F. Browning, M. J. Goetz, M. L. Penny, and M. Pabst. Through September 30, 1960, the records of discharge and stage of streams and canals and contents and stage of lakes or reservoirs were published in an annual series of U. S. Geological Survey water-supply papers entitled "Surface Water Supply of the United States." Beginning with the 1961 water year, surface-water records have been released by the Geological Survey in annual reports on a State-boundary basis. Distribution of these reports is limited; they are designed primarily for rapid release of data shortly after the end of the water year to meet local needs. The discharge and reservoir storage records for 1961-65 also have been published in a Geological Survey water-supply paper series entitled "Surface Water Supply of the United States 1961-65."

Kansas↗

USGS2002

Weathering reactions and hyporheic exchange controls on stream water chemistry in a glacial meltwater stream in the McMurdo Dry Valleys

In the McMurdo Dry Valleys, Antarctica, dilute glacial meltwater flows down well‐established streambeds to closed basin lakes during the austral summer. During the 6–12 week flow season, a hyporheic zone develops in the saturated sediment adjacent to the streams. Longer Dry Valley streams have higher concentrations of major ions than shorter streams. The longitudinal increases in Si and K suggest that primary weathering contributes to the downstream solute increase. The hypothesis that weathering reactions in the hyporheic zone control stream chemistry was tested by modeling the downstream increase in solute concentration in von Guerard Stream in Taylor Valley. The average rates of solute supplied from these sources over the 5.2 km length of the stream were 6.1 × 10 −9 mol Si L −1 m −1 and 3.7 × 10 −9 mol K L −1 m −1 , yielding annual dissolved Si loads of 0.02–1.30 mol Si m −2 of watershed land surface. Silicate minerals in streambed sediment were analyzed to determine the representative surface area of minerals in the hyporheic zone subject to primary weathering. Two strategies were evaluated to compute sediment surface area normalized weathering rates. The first applies a best linear fit to synoptic data in order to calculate a constant downstream solute concentration gradient, dC / dx (constant weathering rate contribution, CRC method); the second uses a transient storage model to simulate dC / dx , representing both hyporheic exchange and chemical weathering (hydrologic exchange, HE method). Geometric surface area normalized dissolution rates of the silicate minerals in the stream ranged from 0.6 × 10 −12 mol Si m −2 s −1 to 4.5 × 10 −12 mol Si m −2 s −1 and 0.4 × 10 −12 mol K m −2 s −1 to 1.9 × 10 −12 mol K m −2 s −1 . These values are an order of magnitude lower than geometric surface area normalized weathering rates determined in laboratory studies and are an order of magnitude greater than geometric surface area normalized weathering rates determined in a warmer, wetter setting in temperate basins, despite the cold temperatures, lack of precipitation and lack of organic material. These results suggest that the continuous saturation and rapid flushing of the sediment due to hyporheic exchange facilitates weathering in Dry Valley streams.

Water Resources Research↗

USGS2025

Constraining large magnitude event source and path effects using ground motion simulations

The purpose of this study is to use ground motion simulations to investigate ways in which source and path effects for large magnitude events can be represented in non-ergodic GMMs. While we initially developed computation techniques using CyberShake simulations, the range of magnitudes and source-site combinations is not adequate to replicate what is observed empirically. We therefore designed a new ground motion simulation study, which includes earthquakes with a large range of magnitudes distributed uniformly on a fault plane, and sites covering a large range of rupture distances and azimuths. After running a large suite of simulations (M4-M7), we then develop a non-ergodic GMM with the simulation data. We find that the within-site residuals are dominated by the radiation pattern, rupture directivity, and slip patterns. Next, we modify an existing rupture directivity model to fit and remove the observed radiation pattern and rupture directivity from the residuals. We also minimize the contributions of slip patterns by averaging the within-site residuals among multiple source realizations. Finally, after removing the source effects from the within-site residuals, we compare the path effects computed with different magnitude groups using two approaches. The first approach only considers the small events that have the same shortest path to a site with the large events, while the second approach considers all small events on the fault plane. The results indicate that the path effects of large events cannot be satisfactorily approximated with that of small events using either approach.

Conference Paper↗

USGS2025

Apportionment of oxygen demand contributions from aircraft and pavement deicer freezing point depressants in airport runoff, Milwaukee, Wisconsin, 2005–2022

Aircraft anti-icers and pavement deicers improve the safety of airport operations during winter precipitation events. Runoff containing these products can contribute elevated biochemical oxygen demand (BOD) to receiving streams. We monitored runoff from Milwaukee Mitchell International Airport at one upstream site, three outfall sites, and one downstream site from 2005 to 2022 for BOD, chemical oxygen demand (COD), and freezing point depressants used in deicing and anti-icing fluids to determine the primary sources of BOD and COD in the receiving stream. The greatest concentrations of BOD, COD, and freezing point depressants occurred at the primary outfall, which drains the main terminal area, and the secondary outfall, which drains cargo operations. The greatest loadings occurred at the primary outfall; loadings were an order of magnitude less at the secondary outfall due to a small drainage area with relatively low flow volumes. At the three outfalls, median concentrations of five-day BOD (BOD 5 ) and COD were 100–1,300 mg L −1 and 200–2,100 mg L −1 respectively. Apportionment computations indicated that propylene glycol from aircraft deicers and anti-icers was responsible for at least half of the BOD 5 and COD concentrations and loadings. Acetate from pavement deicers contributed another 7%–15% at each site. These findings suggest that management actions in the primary outfall drainage area that target propylene glycol–containing deicers have the greatest potential to decrease BOD 5 in airport runoff. This work demonstrates the usefulness of BOD and COD apportionment for identifying the deicing products and locations within an airport to prioritize for reduction or recovery and treatment.

Wisconsin↗