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267 records · Page 5Linked to original sources

Following the tug of the audience from complex to simplified hazards maps at Cascade Range volcanoes

Volcano-hazard maps are broadly recognized as important tools for forecasting and managing volcanic crises and for disseminating spatial information to authorities and people at risk. As scientists, we might presume that hazards maps can be developed at the time and with the methods of our discretion, yet the co-production of maps with stakeholder groups, who have programmatic needs of their own, can sway the timing, usability, and acceptance of map products. We examine two volcano hazard map-making efforts by staff at the U.S. Geological Survey. During the 1990s and early 2000s scientists developed a series of hazard assessments and maps with detailed zonations for volcanoes in Washington and Oregon. In 2009, the National Park Service expressed the need for simplified versions of the existing hazard maps for a high-profile visitor center exhibit. This request created an opportunity for scientists to rethink the objectives, scope, content, and map representations of hazards. The primary focus of this article is a discussion of processes used by scientists to distill the most critical information within the official parent maps into a series of simplified maps using criteria specified. We contextualize this project with information about development of the parent maps, public response to the simplified hazard maps, the value of user engagement in mapmaking, and with reference to the abundance of guidance available to the next generation of hazard-mapmakers. We argue that simplified versions of maps should be developed in tandem with any hazard maps that contain technical complexities, not as a replacement, but as a mechanism to broaden awareness of hazards. We found that when scientists endeavor to design vivid and easy-to-understand maps, people in many professions find uses for them within their organization’s information products, resulting in extensive distribution.

Washington

Remote sensing-based actual evapotranspiration assessment in a data-scarce area of Brazil: A case study of the Urucuia Aquifer System

The large groundwater reserves of the Urucuia Aquifer System (UAS) enabled agricultural development and economic growth in the western Bahia State, in northeastern Brazil. Over the last several years, concern has grown around the aquifer’s diminishing water levels, and water balance (WB) studies are in demand. Considering the lack of measured actual evapotranspiration (ET a ), a major component of the water cycle, this work uses the Operational Simplified Surface Energy Balance (SSEBop) model to estimate ET a , and compares it to basin-scale estimates from the Soil Moisture Accounting Procedure (SMAP) monthly model and from an annual WB closure method, based on gridded meteorological data and the Gravity Recovery and Climate Experiment (GRACE) product. Additionally, a comparative assessment of different versions of the SSEBop parameterization was performed. Moderate Resolution Imaging Spectroradiometer (MODIS) imagery was used to implement eight different versions of the SSEBop algorithm over the UAS between 2000 and 2013. SSEBop and SMAP ET a yielded similar seasonal patterns, with correlation coefficient (r) up to 0.65, mean difference (MD) of 0.8 mm/month and mean absolute difference (MAD) of 18.5 mm/month. Comparison of SSEBop annual ET a estimates to annual SMAP and WB closure estimates yielded low MD (12.1 and −7.3 mm/year, respectively) and MAD (82.5 and 82.8 mm/year, respectively), but also low r values (0.00 and 0.37, respectively). The comparison of the different SSEBop versions indicated the need to incorporate a calibration step of the aerodynamic heat resistance (r ah ) parameter. SSEBop results were also used for land cover and drought monitoring. Analysis indicates that agriculture, associated with an increasing trend of atmospheric evaporative demand, is responsible for the decrease in groundwater levels and streamflow in the studied time period.

Urucuia Aquifer System

Evaluation of solid bitumen created from marine oil shale bituminite under hydrous and anhydrous pyrolysis conditions

To test the influence of environmental conditions on aromaticity of solid bitumen generated during petroleum generation, four organic-rich (26–36 wt% total organic carbon) oil shale samples collected from the Neoproterozoic–Lower Cambrian restricted marine Salt Range Formation in the upper Indus Basin, Pakistan, were pyrolyzed under hydrous and anhydrous conditions. Experiments used closed system batch reactors at subcritical water temperatures between 300 and 370°C for 72 h. Thermal conversion of bituminite in the Salt Range oil shales created a newly formed solid bitumen, similar to previous observations from experiments on the Eocene lacustrine Green River Formation Mahogany zone oil shale. Newly formed solid bitumen in the Salt Range Formation oil shales generally has higher reflectance (R o ) in hydrous residues compared to anhydrous experiments subjected to the same time-temperature conditions, also similar to prior observations. This finding supports the hypothesis that radical disproportionation is favored in the presence of hydrogen contributed by water, promoting aromatization in the solid bitumen residue with concomitant increased expulsion of saturated hydrocarbons. Indigenous solid bitumen (and vitrinite in a comparison sample) also shows higher reflectance values in hydrous versus anhydrous residues, indicating that additional aromatization in the presence of exogenous hydrogen occurs both in newly formed organic matter and in organic matter that is present throughout the experiment. Despite similarities in their bulk rock geochemical screening parameters, R o evolution shows different trajectories amongst the four Salt Range oil shales, suggesting as-yet undetermined differences in kinetic properties which are probably related to differences in a priori chemical composition. These results have implications for the use of solid bitumen reflectance (BR o ) as a thermal proxy, suggesting BR o values and appearance could vary as a function of the concentration of water. Variation in water concentration may be present at the reservoir or formation scale, but may also be present at a much finer scale in tight oil shales where permeability is several orders of magnitude lower than conventional reservoirs. Therefore, local variations in the presence of water potentially could explain substantial variation in BR o values and appearance in closely spaced source rock samples and even within an individual microscope field.

Journal of Analytical and Applied Pyrolysis

Central Valley Hydrologic Model version 2 (CVHM2): Decision support tool for groundwater and land subsidence management

The San Joaquin Valley (SJV) of California is one of the world’s most productive agricultural regions. Reliance on groundwater has led to some of the greatest rates of human-induced land subsidence in the world in the 20th century, as well as more recently. The United States Geological Survey (USGS) has recently developed an integrated surface–subsurface hydrologic model, the Central Valley Hydrologic Model 2 (CVHM2), that represents the major components of the hydrologic system of California’s Central Valley. In this study, CVHM2 was applied as a decision support tool while simulating various management strategies to mitigate the land subsidence caused by the extraction of groundwater. CVHM2 was extended through to 2073 and applied to simulate management scenarios in terms of three primary drivers and their impact on subsidence along the Delta–Mendota Canal (DMC), a critical piece of infrastructure in the western SJV. The drivers considered were agricultural water demands, managed aquifer recharge (MAR), and changes in future climate. The results show that future subsidence is most sensitive to water demands, second most sensitive to future changes in climate, and relatively insensitive to MAR when it is applied as a surface application in the western SJV. However, we demonstrate via proof-of-concept scenarios that the MAR is capable of arresting subsidence when implemented via injection below the Corcoran Clay Member of the Tulare Formation instead of as a surface application. We also examine the uncertainty that is the result of climate variability and how to use the tool to identify the most appropriate strategies to constrain future subsidence to acceptable levels.

California

Reaction kinetics and accelerant effects of sulfides in early mature hydrocarbon generation using hydrous pyrolysis

Hydrocarbon generation in organic-rich sediments is influenced by the molecular organic composition and relative abundance of associated minerals. Certain mineral-derived elements act as catalysts and reaction intermediaries, facilitating early-stage hydrocarbon formation in potential source rocks. This study investigated the role of sulfur contributed from pyrite as an accelerant in thermal reaction, focusing on its effects on early maturation and consequent hydrocarbon generation from gilsonite (low-sulfur solid petroleum). Hydrous pyrolysis (HP) experiments were conducted on mixtures of gilsonite and pyrite in varying ratios (1:0.1, 1:0.5, 1:1, 1:2, and 1:10 w/w gilsonite:pyrite) at 320, 350, and 370 °C for 72 h. Untreated and thermally altered residues were analyzed using solid bitumen reflectance (BR o , %), total organic carbon (TOC) content, programmed temperature pyrolysis, scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), and X-ray diffraction (XRD) to evaluate the potential accelerant role of pyritic sulfur in hydrocarbon formation. The results show HP residues at 320 and 350 °C with greater pyrite concentrations had higher BR o , while reflectance values were similar in the 370 °C residues, regardless of pyrite concentration, suggesting enhanced reaction at lower thermal conditions. Increasing pyrite content systematically decreased hydrogen index (HI) values while increasing the transformation ratio (TR) and production index (PI), indicating enhanced conversion of organic matter to hydrocarbons with increasing pyrite concentrations. Gas yields increased with pyrite addition, particularly at 350 °C, confirming secondary cracking effects. However, gas production stabilized or declined at higher pyrite loadings (1:10), suggesting alternative reaction pathways such as coke formation. Our data indicate the presence of pyrite lowers the activation energy for thermal cracking, shifting peak experimental hydrocarbon generation temperatures downward by 20–30 °C, with the most pronounced accelerant effects observed at moderate pyrite concentrations (1:0.5 and 1:1). The thermodynamic framework reveals that pyrite stability is influenced by experimental conditions, with pyrrhotite formation favored in the presence of gilsonite due to reduced oxygen fugacity. Pyrite transformation to pyrrhotite, as observed through XRD, SEM-EDS, and predicted by thermodynamic data, further supports the accelerant role of S, as pyrrhotite exhibits a higher hydrogen transfer potential, promoting early oil generation. These findings highlight the importance of pyrite in modulating hydrocarbon generation pathways in organic-rich systems.

Journal of Analytical and Applied Pyrolysis

Eruptive history within the vicinity of Al Madīnah in northern Harrat Rahat, Kingdom of Saudi Arabia

The northernmost part of the Harrat Rahat volcanic field contains early Pleistocene to Holocene mafic eruptive products within the vicinity of the city of Al Madīnah, Kingdom of Saudi Arabia. A detailed geologic investigation into the eruptive history of a 570 square kilometer (km 2 ) area covering Al Madīnah and the surrounding area has yielded 33 mapped Quaternary volcanic units consisting of lava flows, scoria cones, and shield volcanoes. These eruptive products consist of continental, intraplate alkalic and minor transitional basalts, hawaiites, and a single mugearite that were emplaced from at least 1,014±14 thousand years ago (ka) to a single Holocene eruption in 1256 C.E. Lava flows are generally 10 to 15 kilometers (km) long (but can reach 23 km long), 1 to 3 km wide, and at least 10 meters thick. Most of the mapped units erupted episodically between 400 and 340 ka and 180 and 100 ka. Despite small individual volumes (less than 1 cubic kilometers dense rock equivalent), each unit represents eruption of a distinct magma batch that was strongly influenced by clinopyroxene, olivine, and plagioclase fractionation. Some of these units are interpreted to have undergone magma mixing pre- and (or) syneruptively. Integrating eruption ages, geochemistry, and paleomagnetic data yields evidence that some eruptions were temporally and (or) spatially clustered. Aligned scoria cones and elongate vent edifices were constructed atop fissure vent systems that reflect the local stress field, which controls dike ascent through the middle and upper crust.

Professional Paper

Evaluation of ground-water flow and hydrologic budget for Lake Five-O, a seepage lake in northwestern Florida

Temporal and spatial distributions of ground-water inflow to, and leakage from Lake Five-O, a softwater, seepage lake in northwestern Florida, were evaluated using hydrologic data and simulation models of the shallow ground-water system adjacent to the lake. The simulation models indicate that ground-water inflow to the lake and leakage from the lake to the ground-water system are the dominant components in the total inflow (precipitation plus ground-water inflow) and total outflow (evaporation plus leakage) budgets of Lake Five-O. Simlulated ground-water inflow and leakage were approximately 4 and 5 times larger than precipitation inputs and evaporative losses, respectively, during calendar years 1989-90. Exchanges of water between Lake Five-O and the ground-water system were consistently larger than atmospheric-lake exchanges. A consistent pattern of shallow ground-water inflow and deep leakage was also evident throughout the study period. The mean time of travel from ground-water that discharges at Lake Five-O (time from recharge at the water table to discharge at the lake) was estimated to be within a range of 3 to 6 years. Flow-path evaluations indicated that the intermediate confining unit probably has a negligible influence on the geochemistry of ground-water inflow to Lake Five-O. The hydrologic budgets and flow-path evaluations provide critical information for developing geochemical budgets for Lake Five-O and for improving the understanding of the relative importance of various processes that regulate the acid-neutralizing capacity of softwater seepage lakes in Florida.

Florida

Remote compositional analyses of space-weathered lunar maria

Visible-to-shortwave infrared (VSWIR) reflectance spectroscopy has revolutionized our understanding of planetary surface compositions. However, space-weathering processes on airless bodies complicate quantitative compositional analyses. Here, we present a framework to isolate the signatures of space weathering in VSWIR spectra of lunar maria by leveraging radiative transfer modeling under the assumptions that (i) a space-weathered target can be expressed as a mixture of fresh and fully space-weathered components and (ii) remaining signatures can be modeled by including agglutinates as an end-member component. We first validate this approach against laboratory spectra of space-weathered Apollo mare soils of known mineral compositions using a probabilistic Markov Chain Monte Carlo implementation of the Hapke radiative transfer model. Second, we illustrate how this approach can be applied to orbital Moon Mineralogy Mapper data. The proposed space-weathering correction workflow for lunar maria could be expanded to other lunar lithologies and applied to existing and future data sets.

Planetary Science Journal

Complex hydrology and variability of nitrogen sources in a karst watershed

Streams draining karst areas with rapid groundwater transit times may respond relatively quickly to nitrogen reduction strategies, but the complex hydrologic network of interconnected sinkholes and springs is challenging for determining the placement and effectiveness of management practices. This study aims to inform nitrogen reduction strategies in a representative agricultural karst setting of the Chesapeake Bay watershed (Fishing Creek watershed, Pennsylvania) with known elevated nitrate contamination and a previous documented groundwater residence time of less than a decade. During baseflow conditions, streamflow did not increase with drainage area. Headwaters and the main stem lost substantial flow to sinkholes until eventually discharging along large springs downstream. Seasonal hydrologic conditions shift the flow and nitrogen load spatially among losing and gaining stream sections. A compilation of nitrogen source inputs with the geochemistry and the pattern of enrichment of δ 15 N and δ 18 O suggest that the nitrogen in streams and springs during baseflow represents a mixture of manure, fertilizer, and wastewater sources with low potential for denitrification. The pH and calcite saturation index increased along generalized flow paths from headwaters to springs and indicate shorter groundwater residence times in baseflow during the spring versus summer. Given the substantial investment in management practices, fixed monitoring sites could incorporate synoptic water sampling to properly monitor long-term progress and help inform management actions in karst watersheds. Although karst watersheds have the potential to respond to nitrogen reduction strategies due to shorter groundwater residence times, high nitrogen inputs, effectiveness of conservation practices, and release of legacy nutrients within the karst cavities could confound progress of water quality goals.

Pennsylvania

Recycling radiogenic osmium by crustal foundering in subduction zones: Evidence from pyroxenite xenoliths in the north Andean arc

Removal of mafic-ultramafic lower crust (e.g., via delamination) is fundamental to making andesitic continental crust, yet direct evidence of this process remains elusive. A unique suite of garnet clinopyroxenite and hornblendite (arclogite) xenoliths from the northern volcanic zone of the Andes, erupted to the surface in the mid-Pleistocene, have bulk-rock geochemistry and osmium (Os) isotopic compositions that demonstrate their crustal affinity, yet have equilibration pressures and temperatures below the arc Mohorovičić discontinuity (~53 km) and some as deep as within the sub-arc mantle wedge (~105 km). Garnet websterites from the same xenolith suite, sourced from depths approaching the Wadati-Benioff zone (~140 km), have elemental and isotopic compositions indicative of a mantle origin, likely formed as products of peridotite-liquid reactions above the subducting slab. Variability in bulk-rock 143 Nd/ 144 Nd values and garnet oxygen isotope ratios ( 𝛿 18 O) for these samples is attributed to minor assimilation of subducted components and/or older crustal material, but assimilation alone cannot account for the highly radiogenic Os isotopic compositions. These results provide direct petrologic evidence for modern arclogite formation and foundering in the Andean orogen, the archetypal active continental subduction system. Elevated 187 Os/ 188 Os values of Mercaderes arclogites imply that recycling of gravitationally unstable arc cumulates during continental crust formation introduces highly radiogenic Os into the convective mantle, which has implications for mass fluxes across the crust-mantle boundary as well as the sources and evolution of mantle heterogeneity as seen in orogenic peridotite massifs and in the sources of oceanic basalts

Earth and Planetary Science Letters

The impact of burial diagenesis on soil-formed minerals in paleosols using stable isotopes of phyllosilicates and carbonate clumped isotopes

To understand the effects of burial diagenesis on the stable isotope geochemistry of soil-formed clay and carbonate minerals in paleosols, samples were collected from seven cores, spanning middle- to upper-Pennsylvanian strata of the Illinois Basin, with varied maximum burial depths of 1–3 km. Mixed-layer illite-smectite and kaolinite mixtures give δ 2 H and δ 18 O values of −83 ‰ to −36 ‰ and 11.9 ‰ to 21.1 ‰ (VSMOW), respectively. After carbonates were screened petrographically for diagenetic textures using transmitted light and cathodoluminescence, measured clumped isotope Δ 47 values range from 0.504 to 0.563 ‰ (I-CDES). Resulting mineral formation temperatures for phyllosilicate mineral mixtures are 28 to 66 °C (mean = 47 °C), whereas T(Δ 47 ) estimates for calcites are 36 to 61 °C (mean = 45 °C). Calculated δ 18 O water values from which phyllosilicate minerals and calcites precipitated under isotopic equilibrium ranges from −7.1 to −1.2 ‰ and − 1.4 to +4.9 ‰, respectively. Closed and open-system phyllosilicate-fluid exchange modeling indicates that phyllosilicate alteration occurred in the presence of a low temperature brine or meteoric water and is interpreted to occur in a layer-by-layer illitization transformation. Due to the lack of diagenetic textures and positively correlated T(Δ 47 ) and δ 18 O water , calcites are interpreted to have undergone solid-state bond reordering. Despite low to moderate temperatures (<125 °C) and varying depths of shallow burial (1–3 km), solid-state transformation of phyllosilicates and calcites indicates paleosols had prolonged exposure to burial conditions which has implications for the use of paleosol minerals for paleoenvironmental reconstructions.

Illinois, Indiana, Kentucky

Detrital zircons and the magmatic history of Viti Levu, Fiji

We integrate the existing detrital zircon data from multiple modern river sediment samples on Viti Levu, Fiji, with the most current available geological and topographic mapping of the respective river drainage basins to compare detrital populations with potential bedrock sources. The temporal and spatial variations in zircon geochemistry supplement what is known from igneous rocks and confirm the petrological differences between plutonic and volcanic rocks from the Eocene to early Oligocene (Yavuna age, >30 Ma), middle Oligocene to middle Miocene (Wainimala age, 30–12.5 Ma), late Miocene (Colo age, 12.5–6.5 Ma) and latest Miocene (Namosi age, 6.5–5 Ma). The >30 Ma Yavuna-age zircons are restricted to areas that drain the previously mapped Yavuna Group. The 30–12.5 Ma zircons are found across central Viti Levu from west to east, and the 30–15 Ma zircons have distinctively low U/Yb and high Dy/Yb ratios. They are the best radiometric evidence of widespread early to middle Miocene arc magmatism in Fiji that was relatively U-poor. Peak deconvolution of the Colo age zircons from individual basins suggests the following ages for undated or poorly dated plutons from central Viti Levu. The large Mavuvu pluton is probably composed of multiple intrusions in the 12–10 Ma range, the Waiqa pluton is probably ca 10 Ma, and the Noikoro pluton is probably ca 9 Ma. There are zircons from unknown plutonic or volcanic sources between 8 and 7 Ma in western Viti Levu that have distinct Eu/Eu* ratios. We attribute the highest U/Yb ratios in some Colo age zircons to crustal anatexis. Namosi-age zircons are abundant in the Medrausucu Group and can be found scattered across Viti Levu.

Viti Levu

A diatom-based quantitative sea-ice proxy for the Bering and Chukchi seas

Sea ice affects Earth's climate system on both regional and global scales. Its incorporation into climate can be used to achieve more accurate predictions of future climate. However, instrumental records of sea-ice concentration do not extend earlier than 1978. In an effort to extend this record, we constructed a proxy using the generalized additive model based on relative abundances of five easy-to-identify diatom species found in sediment samples across the Bering and Chukchi seas. Here we present the first quantitative diatom-based sea-ice proxy developed for Beringia. The developed proxy has been applied to two sediment cores in the Bering Sea ranging from 0 to 25.7 ka (HLY0204 51JPC) and 369 to 430 ka (IODP Exp 323 Site U1345) and one in the Chukchi Sea ranging from 2.7 to 10 ka (HLY0204 24JPC). The obtained reconstructions of sea-ice concentrations are similar, but not identical to previously published qualitative and nearby records based on other proxies. Because our results are quantitative, they can be incorporated into regional climate models. The proxy is publicly available as an R Shiny application (app) and can be applied to any diatom count from marine sediments in the region.

Bering Sea, Chukchi Sea

Framework for implementing damping scaling factors in U.S. Geological Survey National Seismic Hazard Models

Traditionally, probabilistic seismic hazard analysis (PSHA) has focused on calculating ground motion hazard curves for elastic, 5%-damped pseudo spectral accelerations, Sa(T,5%), which are used as the basis for engineering design parameters and targets for ground motion selection and modification. However, structures and geotechnical systems can exhibit a wide range of damping ratios both above and below the 5% level, depending on the construction material, structural system, nonstructural elements, or subsurface soil properties. When spectral parameters at such damping levels are required for certain applications, 5%-damped accelerations have traditionally been extracted from PSHA-based hazard curves and adjusted outside of the hazard integral using damping scaling factors (DSF) such as those from Newmark & Hall (1982). Recent advances in the development of more rigorous and comprehensive damping scaling models (e.g., Rezaeian et al., 2014; Rezaeian et al., 2021) have allowed for the modeling of means and standard deviations of DSFs as functions of earthquake source and path properties for crustal, intraslab, and subduction interface tectonic environments. These DSF models can be applied to ground motion model (GMM) estimates of Sa(T,5%) for a given earthquake rupture scenario to produce a corresponding mean and standard deviation Sa at a specified damping ratio β, Sa(T,β). In this study, the DSF models of Rezaeian et al. (2014) and Rezaeian et al. (2021) are implemented within the U.S. Geological Survey National Seismic Hazard Model (NSHM) PSHA framework to calculate probabilistic hazard curves for spectral accelerations at damping ratios from 0.5% to 30%. The DSF models are applied directly to the mean and standard deviation of Sa(T,5%) predictions from each GMM in the NSHM logic tree. Resulting hazard curves and uniform hazard and risk spectra for Sa(T,β) are presented for several geographic locations and compared with corresponding spectra estimated using current design practices by applying the same DSFs outside of the PSHA calculation. Key differences between the two methods for estimating Sa(T,β) are discussed, and potential strategies are presented for the implementation and usage of the hazard-consistent Sa(T,β) in building codes. Comparing the results to those from DSFs used in current design practices that are mainly based on Newmark & Hall (1982) is not explored in this study.

Conference Paper

Subduction zone earthquake catalog separation tool: Implementation in the USGS 2025 Puerto Rico and U.S. Virgin Islands National Seismic Hazard Model

The U.S. Geological Survey (USGS) periodically releases updates to National Seismic Hazard Model (NSHM) for the United States and its territories leveraging current scientific knowledge and methodologies to guide public policy, building codes, and risk assessments regarding potential ground shaking due to earthquakes that may result in infrastructure damage. In subduction zones, there is a need to separate the earthquake catalog into tectonic regimes to create specific seismicity models for which the most appropriate ground‐motion models are then applied. Here, we describe newly developed methods and software, called CatSep, that classifies subduction zone events into three primary tectonic regimes: crustal, interface, and intraslab. This method incorporates information about the location of the earthquake relative to the subducting slab, the depth of the Mohorovičić discontinuity, and the earthquake’s moment tensor. Applying this method is a first step in the NSHM workflow for regions covering U.S. subduction zones. Results using this subduction zone earthquake catalog separation tool for the 2025 Puerto Rico and U.S. Virgin Islands NSHM earthquake catalog are presented and analyzed.

Puerto Rico, U.S. Virgin Islands

Remote sensing enables basin-scale inventories of coal mine methane

Underground coal mines are important global sources of methane, but emission estimates are uncertain. We show that emission estimates for individual mines from aircraft remote-sensing surveys in the United States agree within 40% with direct measurements used for national emission reporting (IPCC Tier 3 estimate). Such direct measurements are unavailable in most countries, which rely on estimated emission factors (EFs) applied to coal-production rates. We find that EFs from IPCC Tier 1 and the Model for Calculating Coal Mine Methane (MC2M) methods overestimate U.S. emissions 3-fold due to incorrect dependence on mine depth. An IPCC Tier 2 method using measured basin-specific mine gas content agrees with direct emission measurements but does not account for gob well emissions and requires gas content data that are generally unavailable. We show that aircraft remote sensing for a small sample of mines can successfully estimate basin-specific EFs for ventilation shafts and gob wells, enabling estimates of basin- and national-scale emissions. We discuss how the method can be applied with satellite remote sensing to quantify coal emissions worldwide.

Alabama, Colorado, Kentucky, New Mexico, Ohio, Pen

Computational electromagnetic geophysics for groundwater system studies: A review on established practices and recent advances

Identifying effective solutions for locating groundwater resources and ensuring the quality of drinking water is increasingly urgent, given the challenges posed by climate change and population growth. This review investigates electromagnetic geophysical imaging techniques, in both time- and frequency-domain, that can provide valuable insights for groundwater assessment. We explore computational electromagnetic methods used to evaluate electromagnetic data and several recent hydrogeophysical case studies. As open-source frameworks for modeling electromagnetic geophysical problems become available, a broader range of researchers can interpret their data with computationally advanced software. We provide an overview of documented open-source codes for evaluating electromagnetic data and analyze various hydrological targets in relation to their electromagnetic surveying technique and the computational method applied. Furthermore, we evaluate the potential of advanced computational techniques, including three-dimensional modeling, non-deterministic inversion and machine learning, to couple geophysical with numerical groundwater modeling and apply it in groundwater system studies. Despite obstacles such as complexity and resource demands, our findings indicate that the quantification and integration of predictive uncertainties from both electromagnetic and hydrological data and simulations would significantly improve the reliability of hydrogeophysical models. This can lead to a deeper understanding of groundwater systems and improved management practices.

Journal of Hydrology

ARCHI: A new R package for automated imputation of regionally correlated hydrologic records

Missing data in hydrological records can limit resource assessment, process understanding, and predictive modeling. Here, we present ARCHI (Automated Regional Correlation Analysis for Hydrologic Record Imputation), a new, open-source software package in R designed to aggregate, impute, cluster, and visualize regionally correlated hydrologic records. ARCHI imputes missing data in “target” records by linear regression using more complete “reference” records as predictors. Automated imputation is implemented using a novel, iterative algorithm that allows each site to be considered a target or reference for regression, growing the pool of complete references with each imputed record until viable gap-filling ceases. Users can limit artifacts from spurious correlations by specifying model-acceptance criteria and applying geospatial, correlation, and group-based filters to control reference selection. ARCHI provides additional functions for visualizing results, clustering records with similar correlation structures, evaluating holdout data, and interactive parameterization with an accessible and intuitive graphical user interface (GUI). This methods brief provides an overview of the ARCHI package, modeling guidelines, and benchmarking on two regional groundwater-level datasets from the Central Valley, CA and Long Island, NY. We evaluate ARCHI alongside widely used multivariate imputation software to highlight and contextualize its computational efficiency, imputation accuracy, and model transparency when applied to large, groundwater-level datasets.

California, New York