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

At least 55 records · Page 3Linked to original sources

USGS2026

Improving estimates of spatially distributed agricultural land use using pesticide data

Accurate, spatially resolved agricultural land-use data are essential for estimating water demand, evaluating agricultural production, and understanding long-term changes in managed landscapes. However, existing land-use datasets are often temporally discontinuous, particularly for historical periods, and remotely sensed classifications face persistent challenges distinguishing spectrally similar crop types, capturing sub-annual rotations, and separating active from abandoned plantings. We developed the California Pesticide Use Reporting Land-Use Estimator (CalPUR-LUE), which converts grower-reported pesticide-application records into annual estimates of land use by crop class and cropped acreage at approximately 1-square-mile resolution across California. CalPUR-LUE performance was evaluated for 2018 using complementary spatial, categorical, and quantitative comparisons with California Department of Water Resources (CADWR) remotely sensed land-use data and county-level agricultural economic reports. At the county-meridian-township-range-section (COMTRS) scale, CalPUR-LUE and CADWR acreage estimates showed substantial proportional agreement (log-transformed Lin’s concordance correlation coefficient = 0.77) with a mean proportional bias of −15%. Crop-class agreement was high when CalPUR-LUE identified agricultural activity, with user’s accuracy exceeding 83% for all evaluated crop classes. Overall categorical agreement was 67% (Cohen’s kappa = 0.56). Grain crop underestimation contributed substantially to disagreement; however, there is evidence of CADWR systematic overestimation of grain during 2016–2019. County-level agricultural reports further corroborated CalPUR-LUE estimates and, in several cases, aligned more closely with CalPUR-LUE than with CADWR. These results demonstrate that pesticide-use reporting provides an independent and complementary source of agricultural land-use information that can corroborate contemporary estimates and reconstruct annual spatially distributed land use where historical data are limited.

California↗

USGS2026

3D broadband ground motion simulations of Cascadia megathrust earthquakes: Full-margin scenarios incorporating variable magnitudes and frontal thrust splay faulting

Great megathrust earthquakes (∼ M w 8–9) that rupture along the Cascadia Subduction Zone pose significant shaking and tsunami hazards to the U.S. Pacific Northwest. Although these large earthquakes are documented in the geologic record, none have been recorded with modern instrumentation, complicating regional seismic hazard assessments. To improve constraints on seismic hazard estimates for future earthquakes, we develop 3D broadband (0–10 Hz) ground‐motion simulations for 36 full‐margin megathrust earthquake scenarios through the Cascadia Coastlines and Peoples Hazards Research Hub. These simulations expand on the M9 Project ( Frankel et al. , 2018 ; Wirth, Frankel, et al. , 2018 ) by incorporating a broader range of rupture parameters—variable magnitudes, splay faulting, and geodetically informed slip distributions. Benchmarking these simulations against the Next Generation Attenuation Subduction (NGA‐Sub) ground‐motion models shows reasonable fits for non‐basin sites, although simulations predict stronger shaking at short (0–2 s) and long (6–10 s) periods. NGA‐Sub basin terms improve fits to synthetic shaking within the Seattle Basin but underpredict amplitudes by a factor of 2 at periods of 2–5 s. We also evaluate how rupture characteristics influence regional inland shaking variability and basin response in the Puget Lowlands. Larger magnitude scenarios generally cause stronger inland shaking due to farther inland extents of slip and larger strong‐motion‐generating fault patches but show little difference in basin amplification within the Puget Lowlands compared to smaller magnitude events. Along‐dip hypocenter location strongly influences overall inland shaking, with offshore (updip) hypocenters generating on average ∼45% higher shaking at long periods (>6 s) compared to onshore (downdip) hypocenters due to rupture directivity effects. Offshore splay faults minimally affect inland shaking but alter offshore deformation important for coupled ground‐shaking and tsunami scenarios. Finally, we show that rupture directivity increases amplification within the Seattle Basin through the generation and interaction of higher order mode surface waves, an effect of 3D basin geometry that cannot be captured using 1D approximations.

British Columbia, California, Oregon, Washington↗

USGS2026

Hydrogeology and water quality of the unconsolidated aquifer system in the lower Fall Creek valley, Tompkins County, New York

The U.S. Geological Survey, in cooperation with Tompkins County and the Town of Dryden, conducted a hydrogeologic investigation of the lower Fall Creek unconsolidated aquifer system in Tompkins County, New York. This study is part of an ongoing effort to characterize major valley-fill aquifers in the region to support sustainable groundwater management. The lower Fall Creek valley, encompassing the Village of Freeville, the unincorporated communities of Etna, and the hamlets of McLean and Varna, has experienced moderate development and relies heavily on groundwater for residential, agricultural, and commercial use. The study area spans approximately 51 square miles along the boundary of the Allegheny Plateau and North Rim of the Allegheny Plateau physiographic provinces. The aquifer system, composed primarily of glacially derived sand and gravel deposits, includes both unconfined and confined aquifer units. For the approximately 2,300 people who live over the aquifers, groundwater is the sole source of drinking water. In some areas, such as the Village of Freeville, artesian conditions exist, with potentiometric heads exceeding 25 feet above land surface. This report describes the hydrogeologic framework, aquifer distribution, groundwater-flow dynamics, and water quality of the lower Fall Creek aquifer system. Groundwater is generally hard and contains elevated concentrations of redox-sensitive constituents, such as iron and manganese relative to U.S. Environmental Protection Agency secondary maximum contaminant levels. Arsenic was not detected above the U.S. Environmental Protection Agency maximum contaminant level during this study but remains a regional concern due to past detections in the study area and nearby aquifers. The findings provide data for local planners and resource managers to use in understanding and protecting this water resource.

New York↗

USGS2026

Diet and trophic ecology of invasive Blue Catfish Ictalurus furcatus in an eastern shore tributary of the Chesapeake Bay

Blue Catfish Ictalurus furcatus were first introduced to Virginia tributaries of the Chesapeake Bay in the 1970s and have greatly expanded in population size and distribution, prompting ecological and economic concerns. This study investigates the diet and trophic ecology of invasive Blue Catfish in tidal, low-salinity reaches of the Nanticoke River and Marshyhope Creek, on the Chesapeake Bay’s Eastern Shore (Maryland, USA), using complementary stomach content (SCA) and stable isotope (SIA) analyses. Stomach contents from Blue Catfish ( n = 363 non-empty stomachs) were collected opportunistically from October 2021 through November 2022. For SIA, 136 individuals across 21 fish species, blue crab Callinectes sapidus , and arrow arum Peltandra virginica were sampled between October 2021 and October 2023. SCA revealed considerable seasonal and size-based diet variability, suggesting a shift from omnivory to piscivory at 563 mm total length. Primary prey included fish, arrow arum seeds, Asian clams Corbicula fluminea , and amphipods, along with seasonally available species of economic and ecological importance (river herring Alosa spp., blue crab, White Perch Morone americana , and Atlantic Menhaden Brevoortia tyrannus ). Minimal isotopic niche overlap between large and small Blue Catfish size classes, alongside ontogenetic trends in δ 13 C and δ 15 N, substantiated SCA-detected diet shifts. Trophic level estimates derived from Blue Catfish δ 15 N ( n = 54 individuals) were higher than those from SCA, particularly for individuals <563 mm. Blue Catfish occupied a relatively high trophic level, and carbon and sulfur SIA indicated marine resource utilization, substantiating SCA results. This research describes localized trophic interactions of invasive Blue Catfish to inform fishery management planning regarding Blue Catfish’s potential influence on other species of management interest.

Delaware, Maryland↗

USGS2026

Fluvially-sourced sediment supply and climate modulate morphodynamics and state transitions in bistable aeolian dunefields

Alternative stable state theory in aeolian geomorphology describes the occurrence of bare and vegetated aeolian dunes in response to long-term climatic and ecological drivers. Transitions between states, as well as their co-occurrence (bistability), can arise from perturbations to drivers, disturbance, and associated biophysical feedbacks. Here, we examine the role of upwind fluvial sediment disturbance as a driver of aeolian state transitions. We analyze 24 source-bordering aeolian dunefields along 400 km of the Colorado River in Grand Canyon, USA, where active and inactive aeolian dune states occur downwind of fluvial sediment sources. Four decades of topographic change detection following upstream dam emplacement revealed that active aeolian dunes—which had indicators of recent aeolian transport—experienced four times more surface change than inactive dunes lacking such indicators of recent aeolian transport. Persistent aeolian activity occurred where bare upwind fluvial sandbars were maintained as sediment sources, whereas transitions toward inactivity accompanied the loss of bare sandbars and resulted in 50% less topographic change. Contrary to theory, the transition to aeolian inactivity did not correspond to significant reductions in erosion, despite decreased topographic changes. These results broadly demonstrate the effects of biophysical feedbacks within fluvially sourced aeolian environments. Specifically, they show that reductions in aeolian activity are not synonymous with geomorphic quiescence, as other sedimentary processes may become dominant agents of change within these coupled sedimentary systems that are ubiquitous throughout dryland regions on Earth.

Arizona↗

USGS2026

Extensive glacier loss in the coterminous United States

Glaciers populate the mountain ranges of the western conterminous United States and despite their importance to alpine hydrology, their area and volume change have never been comprehensively evaluated. Since the mid-Twentieth Century about one-quarter of the glaciers have disappeared and the overall area and volume are reduced by one-third. The pattern of glacier shrinkage suggests most glaciers in the Conterminous US are largely maintained by local topographic influences due to their small size. These results are critical to understanding evolving high alpine hydrology and important to ecosystem processes.

conterminous United States↗

USGS2026

Climate change is reshaping seagrass futures: Novel environments and opportunities along coastlines and across oceans

Seagrasses are a highly productive ecosystem that supports biodiversity and fisheries, protects coastlines, and buries globally significant carbon stocks. Because seagrasses are increasingly stressed by warmer, darker, and more variable waters, established management strategies may not guarantee future success. Here, we depict a global outlook for seagrass futures by synthesizing how climate and non-climate human pressures may restructure meadow composition, food webs, fisheries, and blue carbon services. Current seagrass range shifts, adaptations, and acclimations to novel environmental conditions preview future states: climate-tolerant species often become dominant post-disturbance, seeds can disperse hundreds of kilometers, and local management can facilitate habitat persistence and large-scale restoration. To boost climate resilience, we propose a three-part framework involving (1) expanding seagrass mariculture and planting, (2) detecting and predicting shifting stressor gradients and species distributions, and (3) managing for seagrasses tolerant of novel environments. Together, these strategies offer proactive pathways for cultivating climate-adapted seagrass meadows worldwide.

BioScience↗

USGS2026

Phenological flexibility in nesting grassland birds over a half century informs timing of management

The timing of biological events for wildlife species reflects and influences ecological and evolutionary processes and helps guide management actions to meet conservation objectives. Climate change may cause phenological shifts across trophic levels and ecosystems, which can have broad ecological impacts. Shifts may also result in mistiming between management practices based on historical conditions and current biological events, reducing the effectiveness of natural resource management and conservation efforts. We analyzed nesting phenology patterns over recent decades across North America for 44 species of grassland-nesting birds, including waterfowl, upland gamebirds, shorebirds, and passerines, many of which have experienced precipitous population declines. Understanding nesting phenologies of these species is important to their conservation, as grassland management activities often conflict with reproductive periods leading to high nest and young mortality. We compiled a dataset of over 172,000 nest records spanning five decades and evaluated environmental factors influencing long-term shifts and short-term flexibility in nesting phenology. We found considerable variation in responses among species, with differences in both direction and magnitude of spatiotemporal effects on nest initiation dates. Notably, the community-level nesting season lengthened over time, but shifts exhibited spatial heterogeneity within this community of grassland birds. Nesting dates shifted asymmetrically across the breeding season with differential changes in early, peak, and late nesting dates whereas long-term changes were mediated by weather and geographic gradients. For example, nest initiation was earlier in warmer and wetter years. By applying a quantile-based analysis, we provide estimates of the full nesting period that could serve as a flexible tool for scheduling monitoring efforts and balancing management and human activities with periods of reduced nesting activity. Our collaborative effort illustrates the challenges and opportunities of collecting long-term data on avian communities necessary for answering questions across large regions but highlights the value of research coordination for bird conservation.

Global Change Biology↗

USGS2026

Methodology for assessing the accuracy of long-term, annual land cover monitoring at national scale: Experiences from the Land Change Monitoring, Assessment, and Projection (LCMAP) initiative

Annual land cover monitoring using medium-resolution satellite imagery represents a transition from periodic mapping campaigns to continuous observation systems. This transition introduces accuracy assessment challenges not encountered in one-time mapping efforts, particularly when the initial monitoring period is extended forward in time. These challenges are not addressed in existing guidance, which remains largely framed around the evaluation of maps of a single date or maps showing changes between two dates. We present a set of methodological adaptations to adjust to this evolving paradigm, using as a case study the U.S. Geological Survey (USGS) Land Change Monitoring, Assessment, and Projection (LCMAP) initiative, which generated annual land cover and land cover change products across the historical Landsat archive. Assessing the accuracy of these products was an essential component of LCMAP and resulted in an extensive reference sample dataset that may be used for accuracy estimation, area estimation, or support in the development of new algorithms or models. We review the LCMAP methodology and highlight challenges encountered and lessons learned that are transferable to other long-term, temporally dense monitoring programs. This framework demonstrates that statistically rigorous assessment can scale to operational annual land cover production, while the experiences of the project clarify where existing good practice guidance should be extended to support the needs of ongoing, continuous land cover monitoring.

Remote Sensing of Environment↗

USGS2026

Environmental relationships with Silver Carp population ecology across the Mississippi River basin

Objective Silver Carp Hypophthalmichthys molitrix are of special concern to fisheries management agencies across the Mississippi River basin, but effective control of the species is challenging. Our objectives were to (1) identify spatial and environmental patterns among key Silver Carp demographic rates that could be exploited by removal programs and (2) develop predictive models of Silver Carp demographic rates using readily available environmental data that could potentially be used to quantify population ecology without expending the resources to conduct population assessments. Methods We collected Silver Carp from six rivers within the lower Mississippi River subbasin (i.e., Arkansas, Cache, Mississippi, St. Francis, White, and Yazoo rivers) and compiled raw data from populations in the upper Mississippi, Missouri, and Ohio River subbasins to estimate demographic rates (i.e., growth, mortality, and recruitment variability). We compared the demographic rates among subbasins and between main stems and tributaries using standard nonparametric tests. We used information-theoretic model selection to evaluate relationships among demographic rates, environmental conditions, and invasion stage. Results In general, lower Mississippi River subbasin populations exhibited faster growth and lower mortality than did those from the upper Mississippi River subbasin. Populations in main-stem rivers did not differ from those in tributaries. More established populations in warmer, free-flowing rivers (e.g., White River) generally experienced faster growth, lower mortality, and more stable recruitment than less established populations in cooler, impounded rivers (e.g., Illinois River). Conclusions The results indicated that variability in Silver Carp populations was related to environmental conditions and invasion stage. Our results suggested that the effectiveness of removal programs might be improved by targeting populations in warm hydrologically variable rivers, as they may have increased reproduction capacities and emigration rates. The equations provided here may be used to estimate population demographics for Silver Carp and help determine their potential sensitivity to management actions, without expending the resources that are required to collect population-specific biological data.

Mississippi River basin↗

USGS2026

Range-wide population trend analysis for greater sage-grouse ( Centrocercus urophasianus )—Updated 1960–2025

Greater sage-grouse ( Centrocercus urophasianus ; hereafter sage-grouse) are at the center of State and national land-use policies largely because of their unique life-history traits as an ecological indicator for the health of sagebrush ecosystems. This updated population analysis provides State and Federal land and wildlife managers with the best available science to help guide management and conservation plans aimed at benefitting sage-grouse populations and the ecosystems they inhabit. This analysis relied on previously published population modeling methodology from Coates and others (2021, 2022a) and incorporates population lek count data for 1960–2025. Included in this report are methodological updates to period terminology, expanded reporting of trends across all nadir-to-nadir combinations, and revised extirpation probability estimation that utilizes every historic population nadir to forecast abundance. Each of these updates are detailed under individual Modification sections. Additional updates include simulation analyses that evaluate the effects of progressively longer exclusions of Wyoming lek count data (Wyoming Game and Fish Department has not provided access to a complete lek count data set since 2023) on trends, extirpation probabilities, and targeted annual warning system signals. State-space models estimated a 2.7-percent average annual decline in sage-grouse populations between 1966 and 2021 (Period 1–7, six population oscillations) across their geographical range. The average annual decline among climate clusters for the same number of oscillations ranged between 2.0 and 3.5 percent. Cumulative declines were 42.4, 61.7, and 77.9 percent range-wide in Period 5–7 (19 years [two oscillations]), Period 3–7 (36 years [four oscillations]), and Period 1–7 (55 years), respectively. Between 2024 and 2025 (1-year, non-trend timeframe), range-wide population size declined 1.9 percent ( 95-percent credible interval [CRI]= −4.71–1.48). Simulations of missing data from Wyoming showed that progressively longer gaps produced more negative trend estimates and higher extirpation probabilities, predominantly within Wyoming. Effects on targeted annual warning system signals were more nuanced, with missed warnings occurring inside and outside Wyoming and false warnings occurring predominantly within Wyoming.

California, Colorado, Idaho, Montana, Nevada, Nort↗

USGS2026

Mapping groundwater recharge potential and an assessment of available hydrogeologic data within five selected focus areas in eastern Nebraska

Groundwater recharge potential was mapped using airborne electromagnetic survey data collected over the previously glaciated part of eastern Nebraska. To evaluate the appropriate resolution at which airborne electromagnetic data should be interpolated (or represented), we compared a 500-meter cell raster and a filled contour shapefile to known geologic features, point estimates of groundwater recharge, and selected water-quality data. The median groundwater recharge rate for the estimates collected in areas mapped as having high groundwater recharge potential were higher compared to the groundwater recharge rate estimates collected in areas mapped as having moderate and low recharge potential. Selected water-quality data were examined to determine the influence of near-surface geology on water quality, groundwater geochemistry, and groundwater age. The strongest statistical correlations were produced when examining specific conductance values measured from wells in areas mapped as high, moderate, and low groundwater recharge potential. Within till-covered areas, statistically significant differences existed in nitrate, dissolved oxygen, manganese, and iron concentrations sampled from wells mapped in high, moderate, and low groundwater recharge potential areas. Boxplots indicate that till-covered areas mapped as low groundwater recharge potential generally have lower concentrations of nitrate and dissolved oxygen, but higher concentrations of manganese and iron. The Eastern Nebraska Water Resources Assessment project sponsors have identified five focus areas as locations facing unique and important groundwater resource management issues. These focus areas are experiencing the emergence of groundwater resource issues that include increased groundwater development, nitrate contamination, and the potential expansion of rural water districts. Hydrogeologic assessments were completed for the Dorchester-Sterling paleovalley aquifer, Dodge County, Knox County, Burt County, and the Fremont-Arlington-Leshara focus areas. Potential future studies to address data gaps were identified and discussed.

Nebraska↗

USGS2026

Improving predictions of insect harassment for barren-ground caribou in the Arctic

Many populations of barren-ground caribou ( Rangifer tarandus ) have declined or are declining, which is concerning given their ecological role in Arctic ecosystems and their societal role in northern communities. Insect harassment is an important driver of the behavior, energetics, and demographic rates of caribou, and yet, due to challenges in predicting harassment, there is limited understanding of how it is responding to changing Arctic conditions. We investigated environmental correlates of mosquito (Culicidae) and oestrid fly (Oestridae) harassment for the Porcupine caribou herd, with the aim of improving our ability to predict harassment. We collected field observations of mosquito activity and used video collars to detect oestrid fly activity across the summer range, which spans the Alaska–Yukon border. Additionally, we documented the composition of harassing insects collected in malaise traps using DNA metabarcoding. We developed predictive mosquito and oestrid fly harassment models using remotely sensed variables relevant to the insects' biology within a nonlinear modeling framework. We then used the top mosquito and oestrid fly models to hindcast predictions of harassment during 1950–2024 and investigate long-term changes in severity and phenology. The top mosquito harassment model included wind speed, temperature, days since snowmelt, precipitation, topographic position, and soil moisture. The top oestrid fly harassment model included temperature, cumulative growing degree days, and time of day. Harassment of both insects was limited at low temperatures (<10°C), with mosquitoes being additionally limited at high temperatures (>22°C) and wind speeds (>7 m/s). The phenology of mosquito and oestrid fly harassment exhibited curvilinear trends across the summer, peaking in midsummer based on the number of days since snowmelt and cumulative growing degree days, respectively. Mosquito harassment also increased with greater soil moisture, precipitation, and at lower relative elevations. Hindcasting indicated that insect harassment notably intensified and advanced over time. Intensifying harassment could decrease caribou foraging opportunities and body condition, and advancing harassment is likely to increasingly overlap with the calving season when calves are most vulnerable. Our results highlight climate-driven changes in insect harassment and provide improved indices for predicting harassment in the Arctic for future applications.

Alaska↗

USGS2026

Duck nesting response to experimental management of upland habitats in California

Habitat loss and limited upland nesting cover likely constrain waterfowl productivity in intensively managed wetland landscapes in California, USA. We evaluated whether experimental manipulations of upland habitats, including the seeding of native plants, dense nesting cover, or cereal grains, could enhance nesting vegetation and improve duck nest density and nest survival in a Mediterranean climate. During 2008 to 2013, we used a before-after-control-impact (BACI) experimental design within 15 upland grassland fields (each 12–28 ha in size) at a state wildlife area to evaluate habitat management treatment effects on nest site vegetation, vegetation structure, and reproductive performance of mallard ( Anas platyrhynchos ) and gadwall ( Mareca strepera ). The BACI design allowed vegetation and duck nesting responses in treated fields to be compared to untreated control fields both before and after treatment implementation. Prior to treatment implementation, all study fields consisted of upland grasslands dominated primarily by non-native annual grasses typical of Mediterranean-climate ecosystems in California. Relative to control fields, we observed only limited improvement to duck nest success in fields seeded with cereal grains and dense nesting cover, whereas fields seeded with native plants showed persistently lower duck nest survival. Vegetation composition after treatment application shifted rapidly from plants that were purposefully seeded to non-native grasses (e.g., Italian ryegrass [ Lolium multiflorum ]) by the second and third years after treatment. Vegetation structural metrics (i.e., visual obstruction height, lateral density, and canopy density) also showed limited or no improvement attributable to the experimental treatments. Across nearly all treatment and control fields, duck nest densities increased during the first several years following treatment implementation but later declined towards pre-treatment levels by the fourth year after treatment. However, mallard nest densities increased much more markedly in native fields than in control fields in the early post-treatment years but declined again in later post-treatment years, suggesting limited long-term benefit. Clutch size, nest initiation date, and egg hatching success were not affected by treatments. Our results indicate that vegetation management and direct seeding had limited short-term and no measurable long-term benefits to the vegetation's structure, duck nesting densities, or duck nest survival, and upland habitat conditions showed little sustained improvement during later breeding seasons (years 2–4 post-treatment). Upland restoration efforts in agricultural landscapes may need more continued, multi-year habitat management to improve nesting conditions for waterfowl over the long-term.

California↗

USGS2026

On the fidelity of oxygen isotope-based sea level reconstructions: A case study of Marine Isotope Stage 3

Although foraminiferal oxygen isotope records (δ 18 O F ) have long been used to develop time-continuous estimates of past global ice volume, growing evidence indicates that the ice volume and temperature contributions to δ 18 O F diverge considerably over the last glacial cycle. Across Marine Isotope Stage 3 (MIS 3; 57 to 29 ka), estimates of peak global sea level based on δ 18 O F are ∼30 m lower than reconstructions based on recent glacial geology, geologic sea-level records, and glacial isostatic adjustment (GIA) modeling approaches. Here we address this mismatch by quantifying uncertainties in converting δ 18 O F to global sea level during MIS 3. We review the geochemical tools to assess the contributions of ocean temperature, diagenesis, and the isotopic composition of ice sheets to δ 18 O F records across MIS 3. We show that recent advances in our understanding of these and other factors that contribute uncertainty (e.g., global sea level during the Last Glacial Maximum) help to explain the MIS 3 gap between global sea level estimates based on δ 18 O F and GIA analyses of geologic sea-level records. We find that the accuracy and precision of MIS 3 ocean temperature reconstructions is likely a key contributor, and various MIS 3 temperature reconstructions can reduce the “gap” by 30%–70% (∼10–20 m). Future improvements in the precision of temperature reconstructions will better constrain the ice volume component of δ 18 O F records. Ultimately, assessing the fidelity of δ 18 O F as a proxy for global ice volume is key to disentangling the feedbacks between climate and ice sheets over the Pleistocene.

Paleoceanography and Paleoclimatology↗

USGS2026

Arctic Grayling, scared to death: Are Brown Trout an impediment to Arctic Grayling reintroduction success in Michigan?

Introduction: Arctic Grayling Thymallus arcticus were extirpated from Michigan in 1936. Their demise was caused by over-fishing, habitat destruction from large-scale logging, and Brook Trout Salvelinus fontinalis and Brown Trout Salmo trutta. Subsequently, Brook and Brown trout have become the dominant salmonid species in Michigan streams. Past attempts to restore Grayling to Michigan have been unsuccessful perhaps due to competition with these now resident salmonids. Objective: To determine the impacts of competition between age-0 Arctic Grayling and age-0 Brook and Brown Trout on Grayling growth and survival. Methods: Competition trials were performed in experimental streams, lasting two months, across three years, with three treatment types: the control, 10 Grayling with 10 Grayling; the Brook Trout treatment, 10 Grayling with 10 Brook Trout; and the Brown Trout treatment, 10 Grayling with 10 Brown Trout. Results: Brown Trout had a significant effect on Arctic Grayling growth and mortality, while Brook Trout had no effect on Arctic Grayling growth or mortality. Conclusion: Age-0 Brown Trout negatively impacted growth, condition, and survival of age-0 Arctic Grayling, while the impacts of age-0 Brook Trout or conspecifics were negligible. This suggests reintroduction of Arctic Grayling may be more successful in streams with few or no Brown Trout.

Michigan↗

USGS2026

Detecting polar bears on land using satellite imagery and deep learning

Summer land use is increasing for polar bears in the Beaufort Sea, which may lead to increases in human-bear interactions. Remote methods may enable noninvasive approaches to monitor polar bear abundance and distribution on land. We examined the potential of using very high-resolution optical satellite imagery to detect polar bears on land from images collected at three sites on the Beaufort Sea coast of Alaska. Additionally, we evaluated the use of deep learning models to automate detection of polar bears in these images and the degree to which detection of polar bears differed among three very high-resolution optical satellite missions. Pléiades Neo images exhibited 90% average precision in validation analyses using a faster region-based convolutional neural network model, which was 55% and 11% greater than the average precision using WorldView-2 or -3 images, respectively. Applying the Pléiades Neo training set to new imagery exhibited lower precision (35%), but high recall (100%), which indicates that deep learning could be used to expedite the visual detection of polar bears in imagery. Very high-resolution optical satellite imagery provides a remote method for monitoring polar bears on land where they occur in high densities, but satellite mission, off-nadir angle, pansharpening methods, and image resolution are important considerations.

Alaska↗

USGS2026

Quality of groundwater used for domestic supply in the western Central Valley, California—2023

More than 2 million Californians rely on groundwater from domestic wells for their drinking-water supply. This report summarizes a 2023 California Groundwater Ambient Monitoring and Assessment Priority Basin Project water-quality survey of 44 domestic and small-system drinking-water supply wells in the western Sacramento Valley (basin number 5-021) and San Joaquin Valley (basin number 5-022) groundwater basins in the Central Valley, California, where more than 88,000 residents are estimated to utilize privately owned, domestic wells. The study area includes the Corning, Colusa, Yolo, and Solano subbasins (subbasin numbers 5-021.51, 5-021.52, 5-021.67, and 5-021.66, respectively) of the Sacramento Valley groundwater basin, and the East Contra Costa, Tracy, Delta-Mendota, and Westside subbasins (subbasin numbers 5-022.19, 5-022.15, 5-022.07, and 5-022.09, respectively) of the San Joaquin Valley groundwater basin. The study was focused on groundwater resources used for domestic drinking-water supply, which are mostly drawn from shallower parts of the aquifer system rather than groundwater resources used for public drinking-water supply, which are typically drawn from deeper parts. This assessment characterized the quality of ambient groundwater used for domestic supply, rather than the quality of drinking water at a tap or faucet, which may be filtered or treated after extraction. To provide context, concentrations of constituents in groundwater were compared to Federal and State of California regulatory and non-regulatory benchmarks for drinking-water quality. Regulatory benchmarks were U.S. Environmental Protection Agency and State of California maximum contaminant levels (MCLs) for drinking water. Non-regulatory benchmarks were State of California secondary maximum contaminant levels (SMCLs) for managing aesthetic conditions, such as taste, odor, or color. A grid-based method was used to estimate the areal proportions of groundwater resources used for domestic drinking supply that have water-quality constituents present at high concentrations (greater than the benchmark), moderate concentrations (between one-half of the benchmark and the benchmark for inorganic constituents, or between one-tenth of the benchmark and the benchmark for organic constituents), and low concentrations (less than one-half or one-tenth of the benchmark for inorganic and organic constituents, respectively). This method provides statistically representative results at the study-area scale and permits comparisons to other California Groundwater Ambient Monitoring and Assessment Priority Basin Project study areas. In this study, inorganic constituents in groundwater were greater than regulatory benchmarks for public drinking-water quality in 30 percent of domestic groundwater resources. Inorganic constituents present at concentrations greater than MCLs for drinking water were hexavalent chromium, total chromium, and nitrate. Total dissolved solids, manganese, and iron were present at concentrations greater than their SMCL in 27 percent of domestic groundwater resources. 1,2,3-trichloropropane was present at concentrations greater than State of California MCLs for drinking water in 2.3 percent of domestic groundwater resources and was the only volatile organic compound detected at concentrations greater than a benchmark. Per-and polyfluoroalkyl substances were detected in 16 percent of domestic groundwater resources, and 2.3 percent had concentrations greater than U.S. Environmental Protection Agency MCLs. Total coliform bacteria and enterococci were detected in 9.1 and 2.3 percent of domestic groundwater resources, respectively. To understand groundwater quality in the study area, factors that affect groundwater quality were evaluated using results from statistical testing of associations between constituent concentrations and potential physical and chemical variables. Relevant factors include the oxidation-reduction conditions of groundwater, agricultural land use, and geologic sources of aquifer sediments. Manganese and iron concentrations were affected by oxidation-reduction state. Nitrate concentrations were affected by the interplay of agricultural practices and denitrification, where denitrification under anoxic redox conditions can mitigate some nitrate derived from fertilizer application. Ultramafic aquifer sediments in the western Central Valley provide a geogenic source for chromium and hexavalent chromium. Total dissolved solids primarily were derived from water-rock interactions with soils and aquifer materials, but agricultural practices may also contribute to these concentrations.

California↗