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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 1,405 records · Page 78Linked to original sources
USGS2026

Development and field testing of a UAS-based software-defined radar for measuring freshwater bathymetry

We provide an overview of an uncrewed aircraft system (UAS)-based software-defined radar (SDRadar) system for high-resolution geophysical observations. The radar transceiver is implemented on a Radio Frequency System-on-Chip (RFSoC) platform, along with an ultra-wideband Vivaldi antenna that has a starting operating frequency of 150 MHz, enabling the system to be used across different applications, including measurements of freshwater bathymetry. In addition to system design and subsystem performance assessments, this paper presents the results of field testing conducted along the Sacramento River near Glenn, California, USA. The radar-derived river depth measurements are compared with ground truth data collected from a crewed boat using an acoustic Doppler current profiler (ADCP). The results show good agreement, with a root mean square error (RMSE) of 0.079 m.

California↗
USGS2026

Satellite observations reveal widespread alteration of river thermal regimes by U.S. dams

Dams are well known to alter river thermal regimes, but assessments of downstream temperature changes have been constrained to single dams, single basins, or specific seasonal windows, thus limiting knowledge of their widespread impacts. We used satellite-based thermal infrared observations to quantify river surface temperature differences up- and downstream of 287 large dams in the United States from 2013 to 2024 across all seasons. We found downstream river temperature differences for the majority (71%) of longitudinal river profiles. These downstream changes were typically warmer (60%), and, on average, were sustained or continued to increase within 20 km downstream of the dam. We also found that the magnitude and frequency of downstream alterations varied by dam type, with 91% of extreme (≥ ±4°C) differences occurring at dams with reservoirs. This work documents the pervasive effects of large dams on downstream ecosystems across all seasons on a national scale.

Science Advances↗
USGS2026

Interacting effects of human presence and landscape modification on birds and mammals

Sustainable human–wildlife coexistence requires a mechanistic understanding of the many ways that humans affect animals. However, progress is hampered by the lack of accessible data measuring the dynamic presence of people. Here, we leverage mobile-device data to disentangle how human presence and landscape modification differentially influence the use of geographic and environmental space for 37 mammal and bird species across the United States. Human presence affected more than 65% of species, with substantial variation across species. For ~60% of species that responded to human activities, the effects were interdependent—animals tended to react more strongly to human presence in less modified habitats. Our results demonstrate that human presence and landscape modification have complex combined effects on wildlife, which need to be considered for effective management.

Science↗
USGS2026

Mars sample return campaign: Biological risk and a proposed sample safety assessment protocol

Returning surface samples from Mars to Earth has been a major planetary science objective, with the potential for the detection of microbiological life and the possibility of improving our understanding of the origins of life. The National Aeronautics and Space Administration and the European Space Agency assembled a team to assess the level of risk that returned samples could contain potential biohazards. The team was chartered with optimizing previous sample safety assessment strategies, defining what constitutes a biological hazard, developing a protocol to test for biohazards, and establishing a statistical framework to determine if samples may be safe for release from a high-containment facility. This report presents the biological context for a proposed three-step protocol for testing returned samples, including how to determine if microorganisms are present, and if they could be (or were recently) alive.

Applied and Environmental Microbiology↗
USGS2026

Upper Triassic igneous rocks of the southern Kenai Peninsula, Alaska – Prelude to Early Jurassic subduction along the western Wrangellia composite terrane margin

New U–Pb zircon geochronology identifies a latest Triassic (ca 214–201 Ma) igneous suite of tuff, hypabyssal dikes, and a pluton on the southern Kenai Peninsula, Alaska. The igneous suite was emplaced within Upper Triassic sedimentary rocks along the southern margin of Western Wrangellia, the western-most fragment of the Wrangellia composite terrane. The igneous rocks range from mafic (50.6% SiO 2 ) to felsic (78.3% SiO 2 ), characteristically have less than 1.55% K 2 O, and generally have low trace element abundances. The tonalitic and trondhjemitic magmas were largely sourced in mafic-rich lower crust and incompletely assimilated quartz and other mineral xenocrysts are common. Fractionation involving plagioclase and amphibole is indicated for some magmas and composite intrusions and igneous xenoliths indicate magma mixing was possible. Paleozoic and Precambrian inherited zircons and initial 87 Sr/ 86 Sr (0.704103–0.705609) and 143 Nd/ 144 Nd (0.512396–0.512777) ratios indicate that the Western Wrangellia crustal sources are heterogeneous and contain sialic components. The latest Triassic magmatism reflects processes that preceded Early Jurassic subduction along the Wrangellia composite terrane and Pacific Ocean plate boundary. These processes involved heating and melting of mantle lithosphere and lower crust as mantle instabilities accompanied the breaking of the plate boundary linkages. The Late Triassic transition to subduction along the Wrangellia composite terrane margin coincided with the transition to subduction cessation in the Late Triassic arcs of the western Intermontane terranes of Canada. The shift to subduction along the outboard Wrangellia composite terrane margin marks the beginning of the Pacific Ocean–Cordillera plate interactions that came to dominate the tectonic evolution of the northern Cordillera from the Early Jurassic to today.

Alaska↗
USGS2026

Geophysical architecture and geochronology of the Neoarchean Mentor anorthosite intrusive complex, northwestern Minnesota: Largest anorthosite complex of the Superior Province?

The Neoarchean Mentor anorthosite intrusive complex (MAIC) lies within the Wawa subprovince in northwestern Minnesota, in a region where the Wawa, Quetico, and Wabigoon subprovinces are juxtaposed in close proximity. Archean rocks are entirely concealed, and interpretations are developed from aeromagnetic, gravity, and borehole samples. The MAIC includes both anorthosite (dense, weakly magnetized) and oxide-rich gabbro (strongly magnetized) lithologies. Anorthosite is coarse-grained to megacrystic, intensely altered, and locally brecciated. Pervasive epidote alteration enhanced the density of the anorthosite via introduction of higher-density mineral assemblages, explaining why the MAIC produces a significant gravity high. Oxide-rich gabbro forms a border phase of the MAIC and has potential for vanadium, chromium, and titanium mineralization, and produces a strong aeromagnetic high. The MAIC is interpreted to extend over an area of 640 km 2 , making it the largest known anorthosite complex of the Superior Province, as measured by preserved areal extent. Modeling indicates the MAIC extends more than 6 km into the subsurface. A new Pb–Pb zircon age of 2737.2 ± 4.5 Ma is interpretated as the crystallization age of anorthosite within the MAIC, showing that the MAIC formed well before the ca. 2690 Ma Shebandowanian orogeny, and raising new questions about correlations with other parts of the Wawa subprovince. A low-density batholith, here informally called the Fertile batholith, is interpreted to intrude the southern part of the MAIC. A new Pb–Pb zircon age of 2701.1 ± 6 Ma is interpreted as the magmatic age of the Fertile batholith.

Minnesota↗
USGS2026

Decreased water transparency of nearshore Laurentian Great Lakes habitats is driven by increased dissolved organic carbon.

Little is understood of lake browning (due to increased dissolved organic carbon; DOC) in large lakes such as the Laurentian Great Lakes. Lake browning can alter whole lake ecosystems, including decreasing exposure to damaging ultraviolet radiation (UV-B) which is strongly and selectively attenuated by DOC more so than photosynthetically active radiation (PAR). We compared the changes in UV-B and PAR transparency to DOC data collected during the ice-free seasons from 62 nearshore sites in four of the five Great Lakes from 2002 to 2022 using linear mixed effects regression models based on backwards selected Bayesian information criteria. Regionally, DOC significantly increased from 2002 to 2022 by 0.5% per year on average. DOC strongly and inversely explained the variability of UV-B and PAR transparencies, as did seasons and offshore influence on these habitats. We provide regional evidence of lake browning within the nearshore habitats of the Great Lakes as a strong contrast to the well-documented increased offshore water transparency associated with the spread of invasive dreissenid mussels.

Great Lakes↗
USGS2026

Silver Carp Hypophthalmichthys molitrix broad movement patterns and dispersal dynamics in the upper Mississippi River

Rivers are important movement corridors for fishes that allow for population connectivity. Within the upper Mississippi River Basin, invasive Silver Carp ( Hypophthalmichthys molitrix ) use tributaries including the Des Moines, Iowa, and Cedar rivers; however, the extent Silver Carp move and intermix among these systems and pools of the upper Mississippi River (UMR) is largely unknown. We used acoustic telemetry and multistate models to (1) identify individual and spatial variability in movement strategies, (2) use survival and transition probability estimates to evaluate population dynamics and connectivity, and (3) evaluate the influence of temporal and environmental variables on survival and transition probabilities. Weekly transition probabilities generally increased with discharge and ranged between 0.01 from UMR Pool 20 to outside the study area at 575 m 3 /s to 0.75 from UMR Pool 18 to outside the study area at 7200 m 3 /s. Survival decreased as temperature increased from 0 to 30 °C and was higher in tributaries than mainstem pools correlated with lower discharge. Overall, Silver Carp displayed diverse movement strategies with high connectivity that can inform invasive species management strategies.

upper Mississippi River↗
USGS2026

Invasive hybridization has unpredicted and variable effects on trout survival in contrasting environments

Invasive hybridization between native and introduced species is widespread, especially in fishes, yet its effects on fitness-related traits across environments remain poorly understood. We combined individual genetic admixture estimates with capture–recapture data to quantify how hybridization between native Westslope Cutthroat Trout ( Oncorhynchus lewisi ) and invasive Rainbow Trout ( Oncorhynchus mykiss ) influences survival. We measured individual survival of 5186 trout across three populations in contrasting environments. Non-native admixture significantly affected survival in two populations, with positive effects during summer and negative effects during winter. Prior research has shown hybridization increases with stream temperature; however, survival patterns did not follow this trend. In a warmer stream, native trout in all size-classes had ≥20% higher annual survival than hybrids, whereas in a cooler stream, juvenile native trout had ≥20% lower survival than hybrids. These findings indicate that hybridization effects on survival are complex and vary among populations, environments, and size-classes. Landscape patterns of hybridization may therefore not reflect local survival (or fitness) outcomes, emphasizing that measures fitness-related traits across populations and environments could elucidate the eco-evolutionary consequences of invasive hybridization.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS2026

Detecting bumble bees in the wild using environmental DNA: Development and validation of a qPCR assay for the endangered Franklin’s bumble bee (Bombus franklini)

Environmental DNA (eDNA) sampling is a noninvasive alternative to conventional methods of surveying insects that may be particularly useful for detecting pollinators. We developed a quantitative polymerase chain reaction (qPCR) assay to detect the DNA of Franklin’s bumble bee ( Bombus franklini ) from flower samples and conducted an initial test of the assay using samples collected within and around the historical range of the species. We further analyzed all samples using metabarcoding. Our qPCR assay successfully amplified B. franklini DNA and exhibited no cross-reactivity with nontarget bumble bee DNA during in silico and in vitro testing. We did not detect B. franklini DNA from field-collected flower samples using either qPCR or metabarcoding. However, metabarcoding analysis revealed DNA of at least 16 other bumble bee species. This finding underscores the potential utility of eDNA sampling for surveying bumble bees. Nondetection of B. franklini from field-collected flower samples may be due to the extreme rarity of the species; B. franklini is endangered and has not been observed in the wild since 2006. Our B. franklini assay is among the first bee-specific qPCR assays ever developed and provides proof of concept for additional assays that may improve detection rates of rare and endangered bees.

California, Oregon↗
USGS2026

Magnetic storms and geoelectric hazards

Magnetic storms induce geoelectric fields at Earth's surface that can interfere with grounded long-line systems. The September 1859 storm disrupted global telegraph operations, the March 1989 storm caused a blackout in Canada and interfered with electric-power-transmission systems in the United States, and other storms have had related impacts. The geographic and temporal dependence of geoelectric fields are functions of both geomagnetic variation and local surface impedance, which differ considerably across different geological regions. These dependencies can be mapped across the contiguous United States by combining magnetotelluric impedance tensors with ground magnetometer time series. This review illustrates such mapping for the 1989 storm and shows that power-system interference was experienced where surface impedance is high, and when and where geoelectric fields were intense. Statistical analyses indicate that storms comparable to that of March 1989 occur roughly once every four solar cycles. Ongoing developments in numerical modeling and real-time monitoring are anticipated to enable prediction of geoelectric hazards. ▪ Magnetic storms can induced electric fields in the solid Earth that interfere with electric-power-transmission systems. ▪ Geoelectric hazards depend on the storm-time geomagnetic disturbance and the electrical conductivity structure of Earth. ▪ Historically, impacts on telecommunication and power-transmission systems in the United States have been concentrated in the East and Midwest. ▪ The future occurrence of a magnetic superstorm could cause widespread disruption of electric-power-transmission systems.

Annual Review of Earth and Planetary Sciences↗
USGS2026

New measurements indicate that natural geologic methane emissions from microseepage in the Michigan Basin are likely negligible

The magnitude of natural geologic methane (CH 4 ) emissions to the atmosphere (including emissions of fossil CH 4 from offshore and onshore gas and oil seeps, diffuse microseepage, mud volcanoes, volcanic vents, and geothermal areas) is highly uncertain. The largest component of geologic emissions is thought to be microseepage, which is the diffuse flux of CH 4 from soils across large areas of productive hydrocarbon basins. The accuracy of existing bottom-up estimates of microseepage is limited by low spatial coverage of published microseepage measurements. We present the first soil—atmosphere CH 4 flux measurements from Michigan Basin, USA. Results from 335 measurements taken during summer and winter seasons across a large portion of the basin suggest microseepage is nonexistent in the sampled region. Even areas with predictive features for microseepage (e.g., underlying mature, organically rich source rocks, proven gas accumulations, faults, and lineaments) yield null or negative fluxes, suggesting that CH 4 emissions from microseepage are negligible throughout our study region. A Monte Carlo method was used to place an upper limit on the regional-mean microseepage flux, in which synthetic patchy microseepage distributions were generated and tested against our observations to assess the impact of possible emission hot spots that were missed by our sampling strategy. Our analysis finds it is very unlikely that regional-mean emissions are as high as assumed in a previous global microseepage study. The observed lack of seepage may be explained by groundwater flow, active methanotrophy, glacial sediments, and bedded salt deposits, which could inhibit vertical gas migration and release to atmosphere.

Michigan↗
USGS2026

Relative activity of three bat species Impacted by white-nose syndrome on the Chesapeake and Ohio Canal National Historical Park

White-nose syndrome, a disease caused by the fungal-pathogen Pseudogymnoascus destructans , has caused drastic reductions in populations of several North American hibernating species of bats including Myotis lucifugus (Little Brown Bat), Myotis septentrionalis (Northern Long-eared Bat), and Perimyotis subflavus (Tricolored Bat). Recent data indicate that populations of Little Brown Bats may be stabilizing and/or increasing in the northeastern region of the US, while others, such as Northern Long-eared Bats, continue to decline. Whether these trends extend to the mid-Atlantic region is currently unknown. To better understand population changes over time, habitat associations, and species dynamics, we developed models of relative activity from bat acoustic data collected on the National Park Service's Chesapeake and Ohio Canal National Historical Park along the Potomac River Corridor in western Maryland between 2016 and 2022. Consistent with pre-disease habitat associations, Little Brown Bats and Tricolored Bats exhibited a positive correlation with proximity to water bodies. Notably, we found Little Brown Bat and Tricolored Bat populations potentially were increasing, whereas Northern Long-eared Bats showed no correlation with examined habitat covariates and had low detection levels, trends consistent with broader declines throughout their range.

Maryland↗
USGS2026

Design, construction and application of an automated thermal chamber to determine critical thermal maxima in small anurans

Critical thermal maximum (CTMax) is a thermal threshold useful for understanding physiological boundaries and predicting anuran vulnerability to climate warming. Given the value of this metric, a comprehensive review of the literature on CTMax protocols (1962-2025) revealed widespread methodological inconsistencies and rare verification of ramping rate accuracy, essential to gauge the reliability of estimates and facilitate comparisons among studies. We engineered an inexpensive (<300 USD) automated CTMax chamber incorporating dual thermocouples, a programmable proportional integral derivative (PID) controller, and real-time software monitoring to address these deficiencies. Performance validation across eight trials demonstrated alignment between programmed and observed temperature ramping rate (0.40 vs. 0.39 °C/min; Z = 1.58, P > 0.05). As a proof-of-concept, we used the proposed system to generate CTMax estimates of six species of Eleutherodactylus in Puerto Rico, including first reports for E. brittoni, E. cochranae, E. wightmanae, and E. juanariveroi. CTMax values ranged from 36.30°C ± 0.52 (E. wightmanae) to 42.10°C ± 0.66 (E. cochranae), with warming tolerances ranging from 15.00°C ± 0.63 to 18.18°C ± 0.73. Our design provides an accurate, replicable, and ethical approach for CTMax measurement and enhances the capacity to assess small amphibian vulnerability to global warming.

SSRN↗
USGS2026

Resources to inform the 2026 Colorado Climate Preparedness Roadmap: Compound hazards and associated public health implications

Changing environmental conditions are increasing the frequency and severity of extreme weather and environmental hazards, including heat waves, wildfires, drought, reduced water quality, and degraded air quality from ozone (O3) and fine particulate matter pollution (AghaKouchak et al., 2020; Bolinger et al., 2024; Colorado Health Institute, 2023a; Fann et al., 2015; IPCC, 2023a; Nagamoto et al., 2024; Nolte et al., 2018, 2021; Zscheischler et al., 2020). Strong scientific evidence indicates that climate change will increase risks to public health and safety throughout the 21st century, particularly through compound climate events (AghaKouchak et al., 2020; Cascio, 2018; Childs et al., 2022; Ebi, 2025; IPCC, 2023a, 2023b; Ma et al., 2024; Marlier et al., 2026; National Academy of Medicine, 2025; Reid et al., 2016; Reid & Maestas, 2019; Simpson et al., 2023; van den Hurk et al., 2023; Volckens, 2024; Zscheischler et al., 2018, 2020). Compound hazards, which are co-occurring or sequential hazards such as heat waves occurring alongside drought, wildfire, and poor air quality from smoke, can amplify public health risks beyond the effects of individual hazards alone (Marlier et al., 2026; Zscheischler et al., 2020). In Colorado, compound climate events with clear implications for public health are already evident (see “Core definitions” section for additional context on compound climate events). Recent statewide assessments have documented increasing heat waves, drought, and wildfires linked to rising temperatures, while emerging data show that climate change is reversing decades of air quality improvements through increased O3 and fine particulate matter pollution due to wildfire, and increased aerosolized topsoil (i.e., dust) due to drought (Bolinger et al., 2024; Childs et al., 2022; Fann et al., 2015; Ghanbari et al., 2023; Larsen et al., 2022; Nolte et al., 2018, 2021; Volckens, 2024). These environmental shifts are associated with increases in eye and kidney-health related concerns, heat-related illness, exacerbations of asthma and other respiratory conditions, increased risk of infectious disease, cardiovascular stress, and mental health impacts, with disparities in risk for children, older adults, outdoor workers, and communities with existing health and economic vulnerabilities (Baraghoshi et al., 2023; Butler-Dawson et al., 2026; Cascio, 2018; Cleland et al., 2022; Colorado Health Institute, 2023a; Grover et al., 2024; Lee et al., 2023; Ma et al., 2024; Macaluso et al., 2024; Marlier et al., 2026; National Academy of Medicine, 2025; Patnaik et al., 2024; Peters et al., 2019; Reid et al., 2016; Reid & Maestas, 2019). The state is actively pursuing strategies to mitigate the risks of these compound climate events on the public, including expanding climate and health surveillance, strengthening early-warning systems and public communication around smoke and air quality, and developing integrated policy agendas that link climate mitigation, adaptation, and health equity (CDPHE, 2025; Colorado Health Institute, 2023b; Zemaitis & Bailey, 2024). For example, state and partner organizations have articulated cross-sector goals to prepare for health impacts related to extreme heat, wildfires, flooding, drought, declines in water quality, and poor air quality, including updating workplace safety protocols, enhancing community-based resilience, adapting clinical care assessments to include climate-related stressors, and improving access to mental and behavioral health services following climate-related disasters (Colorado Health Institute, 2023b; CDPHE, 2025; Zemaitis & Bailey, 2024). To better prepare for current risks and make informed decisions, more information is needed, including methods to analyze historical and projected conditions in near real time, characterize interactions among compound hazards, and translate climate and air quality science into actionable guidance for public health agencies, health care systems, and communities across Colorado (Ebi, 2025; Marlier et al., 2026; National Academy of Medicine, 2025; Simpson et al., 2023; Zscheischler et al., 2018). For this report, we focus on extreme heat and outdoor air quality (ozone [O3] and fine particulate matter [PM2.5]) as the main compound hazards causing compound climate events, given that 1) the state of Colorado has experienced poor air quality for some time, 2) these climate events are affecting large population numbers, and 3) there is capacity to consider and respond to these climate-driven events.

Colorado↗
USGS2026

Mississippi’s resiliency and changing environmental conditions

Mississippi is experiencing shifts in environmental conditions, many of which are expected to intensify in the coming decades, and will have important implications for ecosystems, species, and natural resource management across the state. Historical climate analyses and downscaled projections summarized for the state’s Environmental Protection Agency (EPA) level III Ecoregions show that Mississippi will likely face increases in extremely hot days, more intense heatwaves, greater evapotranspiration, and reductions in cold-season extremes. Temperature trends indicate that while Mississippi has warmed relatively little over the last century, recent years have been among the warmest on record. Projections suggest substantial increases in the number of days with maximum temperatures at or above 95°F across all Ecoregions, particularly under higher warming scenarios. Correspondingly, the number of freezing nights is expected to decline, with statewide decreases of 7–21 days depending on the global warming level and timeframe. These combined patterns are likely to reshape habitat conditions, influence species’ thermal stress, and alter ecological processes such as soil moisture retention and stream temperature regimes. Mississippi’s hydrological systems are also expected to be significantly affected. Extreme rainfall events, particularly the most intense 1% of precipitation days, are projected to increase across the state, raising risks of flooding, erosion, and altered stream flow. Coastal Mississippi faces additional stress from sea‑level rise, which is already contributing to more frequent high‑tide flooding; projections show continued increases in inundation risk throughout the century. These flooding patterns, combined with stronger hurricane rainfall rates and the potential for landfalling storms to stall, pose ongoing threats to coastal ecosystems and communities. The state is also vulnerable to extreme weather hazards such as tornadoes. Recent research shows a geographic shift in tornado activity toward the Southeast, with Mississippi experiencing some of the nation’s greatest increases in favorable tornado days and nighttime tornado frequency—hazards that have direct implications for wildlife, habitat stability, and human safety. Drought conditions may intensify as well: higher temperatures and increased evapotranspiration during dry spells could worsen water stress regardless of uncertainty in average annual precipitation. These changing environmental conditions have important consequences for Mississippi’s Species of Greatest Conservation Need (SGCN). Vulnerability assessments and ecological niche models indicate that several fish, mussel, crayfish, plant, amphibian, bird, and mammal species may face heightened stress due to warming temperatures, shifting hydrology, habitat loss, and increases in extreme events. For example, many cold‑water and moisture‑dependent species in the state’s rivers and wetlands are already near their thermal limits, and further warming could reduce suitable habitat. Birds breeding in bottomland hardwood forests, such as the Prothonotary Warbler, are increasingly susceptible to nest loss from flooding. Similarly, species like the Louisiana Black Bear may encounter higher risks from habitat inundation and shifting food availability. The “A Closer Look” section underscores the vulnerability of the Mississippi Alluvial Plain—one of the state’s most ecologically rich yet heavily altered Ecoregions. Its bottomland hardwood forests, wetlands, and floodplain habitats support diverse wildlife but are increasingly threatened by rising temperatures, hydrological changes, development pressures, and compounded disturbances. These habitats provide critical ecosystem services such as water filtration, flood attenuation, and biodiversity support, making their conservation particularly urgent under future conditions. Collectively, these findings indicate that Mississippi’s ongoing and projected environmental changes present both challenges and opportunities for natural resource management. Incorporating adaptation strategies into the State Wildlife Action Plan will be essential for sustaining habitats, mitigating risks, and supporting the long‑term resilience of Mississippi’s wildlife and ecosystems.

Mississippi↗
USGS2026

Detecting occurrence and timing of grizzly bear parturition based on anomalies in accelerometer data

Documenting natality of brown (grizzly) bears ( Ursus arctos ) is an important component of many population monitoring and research programs. Brown bears give birth during hibernation, so observation of litters is generally not feasible until females exit dens, and detection of litters can be compromised by poor observability. Using triaxial accelerometer activity data stored on radiocollars, we developed a technique that predicts births by the presence of brief upsurges in activity likely associated with postnatal maternal behaviors. We developed presence criteria with a training sample of known parturient females ( n = 22) to detect anomalies within time-series of daily motion-counts (i.e., activity readings >0 measured at 10-min intervals) during 25 December–7 March. To test performance, we applied criteria to a blinded sample of activity data obtained from female grizzly bears (captured and collared during 2012–2022) in 4 populations in interior North America ( n = 295). We assigned predicted status and compared assignments to reproductive status at first visual observation. The true positive rate was 91% ( n = 47 females observed with cubs of the year) and the false-positive rate was 17% ( n = 65 females observed with older offspring). Births were predicted for 50% of females with unknown reproductive status ( n = 48), 21% of females observed without offspring ( n = 114), and 10% of subadult females considered too young to reproduce ( n = 21). Dates of predicted births varied from 27 December to 28 February. Our anomaly detection technique was successful at estimating parturition events, and despite some error, indicated that a number of litters were born but not observed, presumably due to mortality in or shortly after den emergence. This technique provides an additional tool for supplementing visual observations for natality estimation and population modeling, provided that potential biases stemming from increased detection rates are considered.

Alaska, British Columbia, Idaho, Montana↗
USGS2026

Scenarios to assess the future water availability in the Mississippi River Valley Alluvial Aquifer for the Cache River and Grand Prairie Regions of Arkansas

The U.S. Geological Survey, as part of the Arkansas Groundwater Initiative, developed forecast scenarios using previously calibrated MODFLOW 6 groundwater models that focused on the Cache and Grand Prairie Critical Groundwater Areas to assess the impact of future climate and water management strategies on the Mississippi River Valley alluvial aquifer. A Soil Water Balance model was used to forecast recharge and irrigation water use. The forecast scenario period was from January 1, 2019, through December 31, 2055, with monthly stress periods. Twenty scenarios were simulated and included seven alternate climate forecasts, five 13 general groundwater pumping reduction scenarios (round 1), and groundwater pumping reduction scenarios by crop type and for the Bayou Meto Water Management Project and Grand Prairie Area Demonstration Project (round 2). Declines in saturated thickness within the Cache Critical Groundwater Area were larger for 18 of the 20 scenarios as compared to outside of the Critical Groundwater Area. The largest average increase in saturated thickness inside the Critical Groundwater Area was 6.4 m which occurred for the round 1, 50 percent reduction scenario. Automatic reductions in groundwater pumping by MODFLOW 6 in the Cache simulation ranged from 0.02 to 13.1 percent of total groundwater pumping. For the Grand Prairie model domain, the average change in saturated thickness of the Mississippi River Valley alluvial aquifer inside the Critical Groundwater Area for the forecast period ranged between -6.6 to 1.7 m. The average saturated thickness of the Mississippi River Valley alluvial aquifer inside the Grand Prairie Critical Groundwater Area declined for 16 of the 20 scenarios. The average reduction in requested groundwater pumping for all scenarios inside the Grand Prairie Critical Groundwater Area was 25.1 percent, and the largest reduction was 46.5 percent.

ESS Open Archive↗