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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 595 records · Page 33Linked to original sources

USGS2026

Scalable urban tree canopy modelling for Canadian cities

Urban tree cover (UTC) is a key indicator for monitoring climate adaptation, guiding policy goals, and designing equitable cities. However, consistent UTC estimates remain limited. This study proposes a transferable UTC modelling framework using global open-source data to map fractional UTC. The method involves satellite spectral products and high-resolution canopy height data to build city-specific machine learning models of 19 Canadian cities. Model accuracy, assessed through cross-validation, ranged from R² = 0.67–0.88 with RMSE values of 5.5–16.3%. Independent validation against airborne laser scanning in three cities demonstrated strong agreement (Pearson r = 0.82–0.92). Results suggest that UTC distributions are unevenly distributed, typically right skewed, with large parks and riparian corridors accounting for a disproportionate share of UTC. Greenness and moisture are the most influential predictors, while model residuals concentrate in areas with higher UTC. The resulting UTC maps and modelling framework provide a consistent and reproducible framework for UTC distribution assessments, benchmarking across diverse ecozones, and monitoring UTC change at urban scales over time.

Urban Forestry & Urban Greening↗

USGS2026

Tectonically driven integration of the 4.8 Ma Colorado River USA tracked with detrital sanidine and fish genetics

The development of the continental-scale Colorado River system, western USA, from 8 to 4.8 Ma, is revealed using 60-40 Ma detrital sanidine tracer grains and fish phylogeny. Here we show that precursor paleoriver segments became integrated north to south as traced by 60-40 Ma sand grains that were derived from the north and sequentially appeared in the 25-8 Ma Browns Park Formation of Utah, 7-6 Ma upper Bidahochi Formation of Arizona, and 4.8 Ma Bouse Formation of the lower Colorado River and proto Gulf of California. This timing is mimicked by molecular clock estimates of divergence times among fish lineages. River integration was a response to headwater uplifts in the Yellowstone hotspot track and Rocky Mountains. 40 Ar/ 39 Ar ages refine the timing for mantle-drips that caused subsidence, then uplift, of depositional basins that influenced the integration pathway and tempo. The ~ 3-million-year timescale suggests that multiscale mantle-driven uplift, rather than lake spillover, was the primary driver for integration of the proto-Colorado River through Grand Canyon.

Colorado River↗

USGS2026

Leveraging socioeconomic flows to inform shared, migratory species conservation

Migratory species, and the many cultural and economic values they provide, are declining worldwide. Previous research has quantified ecosystem service flows for single migratory species to provide valuable information on the dynamics of socio-ecological systems to inform cross-jurisdictional management. There are efficiencies in implementation to be gained from considering the dynamics of multiple species (e.g., ecological guilds) simultaneously. As proof of concept, this paper demonstrates how ecosystem service flows can be aggregated spatially for a group of three North American migratory species. We further present a flexible approach to estimating how conservation funding can be allocated equitably between regions of the migratory range. Results show that most benefits from these three migratory species are supported locally by habitat within each region, but net interregional flows exist, including a $33.1M annual subsidy from Mexico to the U.S. and Canada. Results also suggest that directing 18% of net conservation funding raised for these species in the U.S. and Canada toward conservation projects in Mexico would redress inequities in shared management responsibility. Considering the values provided by multiple species simultaneously has the potential to broaden coalitions and expedite negotiation of international agreements by providing a better shared understanding of the benefits to each party.

North America↗

USGS2026

Polychlorinated biphenyl (PCB) exposure assessment of Carolina wren (Thryothorus ludovicianus) and barn swallow (Hirundo rustica) eggs and nestlings collected along Snow Creek and Choccolocco Creek watersheds near Anniston, Alabama, USA

Polychlorinated biphenyls (PCBs) persist for decades when released into the environment and bioaccumulate in aquatic and terrestrial environments, resulting in harmful concentrations of PCBs in fishes, birds, and humans. Approximately 310,000 metric tons of PCBs were produced at a facility in Anniston, Alabama from 1929–1971. Hundreds of metric tons of PCB-contaminated waste were suspected to have been released into local environments. This study was the first systematic exposure assessment of the degree and extent of PCBs and potential co-contaminants—polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, Pb, and Hg—in avian tissues downstream of the Anniston facility. We collected 122 egg and 36 nestling tissue samples from across four exposure areas downstream of the facility and a reference site. A total of seven bird species were collected, but samples were predominantly Carolina wren (resident, Thryothorus ludovicianus ) and barn swallow (migratory, Hirundo rustica ). Concentrations of Pb and Hg in bird tissues collected from the exposure areas were less than toxicity reference values, suggesting Pb or Hg exposures alone were unlikely to affect birds. Total PCB concentrations in avian eggs and nestlings collected from exposure areas were among the greatest ever recorded in birds collected in North America. The PCB congener profiles in this study, paired with results from previous soil and sediment sampling, suggest that PCB-contaminated sediment and soil were the likely source of elevated PCBs in the avian tissues. The PCB concentrations observed in birds downstream of the Anniston facility were at magnitudes that likely affect populations of both resident and migratory birds that utilize the area for foraging and reproduction.

Alabama↗

USGS2026

High and dry: The persistence of diverse coastal marsh communities depends on available upland area and connection to surrounding waters

Sea-level-rise and alterations to natural hydrology have contributed to coastal land loss. To combat coastal land loss and maintain the ecosystem services provided by marshes, marsh creation has been broadly implemented. Marsh creation projects can be performed in conjunction with the construction of elevated terrestrial ridges that seek to mimic historic delta-formed distributary ridges. Ridges and similar elevated structures, such as those surrounding created marshes, offer the opportunity to sample the ecotones between low marsh and upland areas within a small area. We sampled marsh assemblages on elevation gradients at eight sites in the Louisiana coastal zone. We identified nine marsh communities based on co-occurrence of taxa and abiotic conditions (soil salinity, percent time inundated, soil percent moisture, soil bulk density, and soil pH) with a two-step process of hierarchical clustering and random forest classification. Inundation time and salinity were identified as the most important conditions related to community composition. We used future estimates of coastal elevations based on local relative sea-level-rise estimates to make predictions of community change up to 50 years into the future. Our predictions, meant to serve as generalizations for the coastal region, indicate a near total loss of high-elevation salt marsh communities at the sites sampled. Elevation variation supports diverse marsh communities when water is allowed to flow as in a natural marsh. Hydrology regulates inundation, and by extension, salinity. Evaluating hydrologic exchange can be incorporated into decisions regarding future marsh creation to support marsh health and persistence.

Louisiana↗

USGS2026

High‐resolution surface deformation and slip distribution observations for the 2023 Kahramanmaraş, Türkiye, earthquake sequence help constrain the rupture process

Splay, or branch, faults are a common geometric feature of earthquake surface ruptures and may provide constraints on the rupture behavior of an earthquake. The 2023 M w 7.8 Pazarcık and M w 7.5 Elbistan, Türkiye, earthquakes are examples of ruptures with multiple small splays, and the Pazarcık earthquake nucleated on a splay fault, the Narlı fault, before rupturing bilaterally on the East Anatolian fault (EAF). Here, we present 3‐m‐resolution surface displacement from subpixel correlation of Planet Dove optical images for the entirety of both ruptures with corresponding surface slip distributions. For a 30‐km‐long study region spanning the Narlı‐EAF intersection, we compare surface slip derived from five data sets with different resolutions (on‐the‐ground, WorldView, Planet Dove, Sentinel‐2, and Sentinel‐1) to elucidate complementary information. In addition, we integrate information from the surface expression of faulting with published dynamic rupture simulations and rupture process studies to constrain a rupture evolution for the Pazarcık earthquake that is consistent across data sets. This work highlights the complementary nature of disparate surface slip data sets and the role that high‐resolution surface displacement information, including from fault splays, can play in constraining nonunique rupture models and refining understanding of the earthquake rupture process.

Bulletin of the Seismological Society of America↗

USGS2026

The digital archivist: Automating legacy macroseismic data processing using large language models

Macroseismic data are a key resource to investigate shaking and damage from preinstrumental and early instrumental eras. However, data are often stored as inconsistently formatted reports describing observed shaking and damage, making manually parsing and interpreting accounts labor‐intensive. We introduce a novel workflow using Google’s Gemini 2.5 Pro large language model (LLM) to automate the extraction and structuring of macroseismic observations from summary reports. We apply this workflow to the 22 March 1957 M 5.3 Daly City, California, earthquake as a case study. We used Gemini to extract addresses, originally assigned modified Mercalli intensity values, and descriptions from each report. To address coordinate precision limits, addresses were geocoded via Google’s Geocoding application programming interface. This workflow yielded over 2300 geocoded intensity reports for the Daly City earthquake. We use the geocoded accounts, with the original report intensity assignments, to develop a shaking intensity map that in some respects rivals modern Did You Feel It? Maps. We also extract and present data for the 9 February 1971 M L 6.7 Sylmar, California, earthquake. Our results demonstrate the potential of LLMs for reliably extracting and analyzing large, unstructured macroseismic datasets. LLMs offer a scalable solution for rapidly digitizing macroseismic archives, enabling their broader use to constrain ground‐motion models in modern seismic hazard analysis and to improve our understanding of site effects in urban areas. The concepts explored here may also be applied to the handling of other legacy seismological and earth science data.

Seismological Research Letters↗

USGS2026

3D Elevation Program—Conterminous United States

Using 3D Elevation Program data, a modern illustration of the conterminous United States’ landscape showcases its elevation differences in vivid detail. This map has been consistently adjusted and colorized according to the highest and lowest elevations, accentuating differences across the conterminous United States. To further emphasize landforms, shaded relief has been added on top of the elevation colors.

Conterminous United States↗

USGS2026

Determination of baseline water-quality conditions using continuous specific conductance and discrete measurements of total dissolved solids and selected major ions, Arkansas River Basin, Colorado

From 2022 through 2024, the U.S. Geological Survey (USGS) in cooperation with the Regional Resources Planning Group (Southeastern Colorado Water Conservancy District, Colorado Springs Utilities, Pueblo Water, Lower Arkansas Valley Water Conservancy District, Aurora Water, and Upper Arkansas Water Conservancy District) established a basinwide water-quality monitoring network in the Arkansas River Basin in Colorado. The study leveraged ongoing continuous measurements of streamflow and specific conductance (SC) at 13 sites along the main stem Arkansas River and Fountain Creek from the USGS 07108600 Arkansas River at Granite, Colo., (Ark Granite) site to the USGS 07137500 Arkansas River near Coolidge, Kansas, (Ark Coolidge) site. Baseline water-quality conditions were established using data from October 1989 through September 2022 to help identify changes in water quality that could result from changes in land and water use. Total dissolved solids (TDS) concentration was the main indicator of general water quality in this study because it can be accurately estimated from SC and is sensitive to changes in streamflow, water operations, and source contributions. Median TDS concentrations in Arkansas River samples (October 1989 through December 2023) ranged from 75 milligrams per liter (mg/L) at Ark Granite near the headwaters to 3,660 mg/L at Ark Coolidge near the Colorado–Kansas State line. Distinct seasonal differences in median streamflow and TDS were apparent during the winter and summer months. Seasonal Kendall tests showed no significant trends in monthly mean streamflow (October 1995 through September 2022) at Arkansas River sites upstream from Pueblo Reservoir. Upward trends in TDS concentrations and loads occurred only at Ark Granite. Downward trends in streamflow, TDS concentrations, and TDS loads occurred at Arkansas River sites from USGS 07109500 Arkansas River near Avondale, Colo., to Ark Coolidge. Downward trends in streamflow and SC (surrogate for TDS) were more prevalent during winter base flow months and may indicate changes in groundwater quantity, and possibly groundwater quality, potentially affecting the river water-quality condition.

Colorado↗

USGS2026

The surface elevation table and marker horizon technique: A protocol for measuring wetland elevation dynamics, narrative (Version 2.0)

The National Park Service (NPS), in response to the growing evidence and awareness of the effects of climate change on federal lands, determined that monitoring wetland elevation change is a top priority in North Atlantic Coastal parks (Stevens et al. 2010). As a result, the NPS Northeast Coastal and Barrier Network (NCBN) in collaboration with colleagues from the U.S. Geological Survey (USGS) and the National Oceanic and Atmospheric Administration (NOAA) have developed a protocol for monitoring wetland elevation change and other processes important for determining the viability of wetland communities. Although focused on North Atlantic Coastal parks, this document is applicable to all coastal and inland wetland regions. Wetlands exist within a narrow range of elevation that is influenced by local hydrologic conditions. For tidally influenced coastal wetlands, local hydrologic conditions may be changing as sea levels continue to rise. As sea level rises, coastal wetland systems may either a) build elevation to maintain favorable hydrologic conditions for their survival or b) become increasingly inundated beyond their physiological tolerance resulting in an eventual conversion to open water. A better understanding of these processes will help to determine the present and future viability of coastal wetlands managed by the NPS and can help address measures to ensure these communities exist into the future. This protocol provides the reader with instructions and guidelines on designing a monitoring plan or study to: Quantify elevation change in wetlands with the Surface Elevation Table (SET); understand the processes that influence elevation change, including vertical accretion (SET and Marker Horizon methods); survey the wetland surface and SET mark to a common reference datum to allow for comparing sample stations to each other and to local tidal datums; survey the SET mark to monitor its relative stability; and establish water level equipment to characterize the hydrology and tidal datums for a particular wetland site or sites. The protocol is divided into two documents: The narrative (this document) presents an overview of all aspects of monitoring wetland elevation dynamics, and a document of Standard Operating Procedures (SOPs) with detailed instructions on the design, installation, data collection, and data management in support of monitoring changes in wetland elevation.

Science Report↗

USGS2026

Avoiding common pitfalls in the implementation of adaptive forest wildlife management

Forest management planning requires the evaluation of tradeoffs in proposed management actions to meet multiple objectives, including providing the habitat required to sustain wildlife populations. However, various species-specific life history strategies and ecological uncertainties complicate our understanding of the responses of wildlife to disturbances, such as wildfires and forest management. We believe that adaptive management processes, applied through the close collaboration of researchers and managers (e.g., coproduction), will be valuable in this effort. Although adaptive management programs have been touted in the past, we stress that many of these programs have fallen short of the requisite steps to complete the learning cycles of this process (i.e., single- and double-loop learning). Thus, we provide guidance on what we believe to be the missing components of these efforts in hopes to guide future coordination of local and regional adaptive management programs for forest wildlife.

General Technical Report↗

USGS2026

A simplified two-station approach for modeling metabolism in dam tailwaters subject to diel flow variation

Tailwaters are ubiquitous and highly managed ecosystems whose food webs often rely disproportionately on autochthonous energy. In situ continuous dissolved oxygen data are increasingly being used to estimate gross primary productivity and ecosystem respiration in rivers, but this approach is complicated in tailwaters, where upriver discontinuities (i.e., dams) violate commonly employed one-station approaches. In such cases, two-station metabolism models can be applied, although substantial diel variation in flow (a common outcome of hydropower production) requires more complex treatment of water parcel travel times. Here, we present a new two-station metabolism model that allows estimation of reach-scale gross primary productivity and ecosystem respiration in streams and rivers that experience within-day variation in flow. Our approach simplifies two-station variable flow model implementation compared to previous efforts. We apply our model to a 6-yr dissolved oxygen time series and use Bayesian inference to estimate daily gross primary productivity, ecosystem respiration, and gas exchange velocity ( k 600 ) for a ~12-km reach of the Colorado River downriver of Glen Canyon Dam. We compare our model's performance to a more mechanistically detailed and computationally intensive Eulerian dynamic flow model and also to a widely-used one-station model that uses assumptions of reach uniformity that are often strongly violated in tailwaters. These comparisons show that our metabolism estimates conform with output from the more detailed dynamic flow model and that the one-station approach deviates substantially from both two-station approaches. Our new stream metabolism model can help resolve a fundamental analytical impediment in tailwater ecology.

Arizona↗

USGS2026

Sedimentological reconstruction of hurricane storm surges from a carbonate reef coastline at Anegada, British Virgin Islands

Anegada is a small, low-lying carbonate island in the British Virgin Islands that is highly vulnerable to marine inundation from frequent hurricanes. A major challenge in forecasting the timing, intensity, and impacts of future hurricanes to islands such as Anegada is the limited short-term instrumental record that does not capture the full spectrum of inundation events from the frequent but low-magnitude to rare, but high-magnitude events. Washover deposits, which are transported onshore by hurricane-related storm surges and preserved within the onshore stratigraphy, can provide insight into the recurrence of these events. Here, we use grain size distributions, X-ray fluorescence (XRF) data, and an inverse sediment transport model to characterize a series of anomalous sand deposits from shallow hypersaline ponds to determine the variability in storm surges impacting Anegada over at least the last 70 years. The analyses were successfully applied to modern analogues of storms impacting Anegada's southern shoreline (Hurricanes Donna in 1960 at Category 3; Earl in 2010 at Category 4; and Irma in 2017 at Category 5). These deposits are identified by coarse-grained material and elevated marine geochemical signals (Ca, Sr, ln(Br/Ti)). Inverse modelled flow parameters (average flow depth = 0.89–1.46 m relative to the reef flat, average flow speed = 2.95–3.78 m/s) agree with observational data and eyewitness accounts, and the deposit associated with Hurricane Donna indicates the greatest impacts occurred along the southern shoreline (modelled flow depth = 1.24–1.46 m relative to the reef flat, flow speed = 3.49–3.78 m/s). Using the modern analogues as a basis for comparison, we infer the origin of an older sand deposit to be from Hurricane Dog in 1950, when it tracked by Anegada as a Category 3 storm. This methodology provides a transferable framework for interpreting storm recurrence in carbonate-dominated coastlines worldwide that could be used to inform hurricane hazard assessments and risk management efforts.

Anegada↗

USGS2026

Mercury biomagnification across food webs with varying non-native fish presence: Implications for native fish conservation in the upper Colorado River Basin

Environmental contaminants and non-native species introductions negatively affect aquatic ecosystem conservation. Mercury (Hg) accumulates within food webs where it can biomagnify to toxic concentrations, which can be affected by altered trophic relationships from non-native species. This study examined Hg concentrations (n samples = 655) and stable carbon and nitrogen isotope ( n = 746) compositions in native ( n = 313) and non-native ( n = 342) species among four river subbasins (Gunnison, Lower Green, Colorado-Dolores, and White-Yampa), in the Upper Colorado River Basin (UCRB) during 2016 and 2017 to inform the potential combined effects of Hg exposure and non-native species interactions on native fishes of conservation concern. We assessed Hg biomagnification at the fish assemblage level, compared concentrations to risk thresholds for fish and human health, and evaluated niche overlap among trophic levels across subbasins. The generalist-invertivores feeding guild had the lowest Hg concentrations (0.001–0.191 μg g −1 wet weight), and no individuals exceeded the U.S. Environmental Protection Agency aquatic life criterion (0.225 μg g −1 ). Piscivores had the highest concentrations (0.008–1.840 μg g −1 ), and 74% of individuals exceeded the criterion. Biomagnification across trophic levels was observed throughout the UCRB, yet varied by subbasin, with higher magnification factors in the Lower Green and White-Yampa subbasins which also had the highest proportion of non-native species. Stable isotope compositions revealed niche overlap among native and non-native species. Additionally, trophic position varied within species among the subbasins. The proliferation of non-native species has likely reshaped food webs and may have intensified the potential threat Hg poses to native fish recovery and conservation. This study documented increased Hg concentrations relative to past assessments, suggesting that continued monitoring could assist in evaluating trends in Hg accumulation. Particularly studies that focus on sources entering the food web, vectors for accumulation, and competitive interactions among native and non-native species.

Colorado, Utah, Wyoming↗

USGS2026

Growth of a threatened desert fish becomes resource dependent when released from temperature limitation in a regulated river

1. Growth of ectotherms typically positively correlates with increasing temperature towards an optimal temperature range, followed by a decline in growth when temperatures exceed the optimal temperature range for that organism. When temperature is within or close to the optimal range, food availability and other environmental factors can play important roles in modifying growth rates. River regulation often alters both environmental conditions (e.g., flow, turbidity and temperature) and aquatic food webs, modifying the quality and quantity of resources available to consumers. Here we aim to understand how food availability, water temperature and other environmental factors are associated with fish growth (defined here as a change in length) in a large, regulated desert river. 2. We measured growth of humpback chub (Gila cypha) at two river reaches located 240 km apart in the Colorado River within the Grand Canyon, Arizona, USA. We then fit Bayesian state-space models of growth that account for variable time at large to test environmental predictors such as water temperature, flow, turbidity (which increases during tributary flooding and can be a proxy for allochthonous inputs) and gross primary productivity (a proxy for autochthonous food) using an inclusion parameter approach. Both river reaches are located below Glen Canyon Dam, which regulates flow, alters seasonal water temperatures and traps sediment, nutrients, and organic carbon; however, merging tributaries and a greater distance from the dam lead to differences in environmental conditions. 3. In the upriver reach, where warm season water temperatures are below the optimal range for humpback chub most of the time, temperature was the primary driver of variation in growth according to inclusion parameter values and the strength of the standardised effect size. Turbidity was also included in the final model for the upper reach, but the inclusion parameter values and standardised effect size were smaller than for temperature. In the downriver, warmer reach, temperature still had the highest inclusion parameter value, but GPP had the highest standardised effect and nearly as high an inclusion parameter value. 4. We conclude that temperature is the primary limiting factor on growth of humpback chub in the Grand Canyon; however, as water temperatures increase, other factors, especially GPP, are associated with temporal variation in growth rates. Over the past two decades, declines in reservoir elevations and the volume of summer releases have increased downstream water temperatures. If warm temperatures persist into the future, other factors may have increasing roles in regulating interannual variability in chub growth. 5. Field studies of ectotherm growth often emphasise the role of water temperature; however, the role of resource availability is also increasingly recognised, especially in bioenergetics studies. Quantifying resource availability directly can be difficult, especially in large, remote rivers. Here, we show here that using proxies for resource availability (i.e., GPP as a proxy for autochthonous inputs) can yield useful insights regarding resource limitations with implications for management of federally listed fish species in a larger regulated river system.

Arizona↗

USGS2026

Flood-frequency estimates for Kentucky streamgages based on data through water year 2021 and results of updating the fundamental layers in Kentucky StreamStats

The U.S. Geological Survey, in cooperation with the Kentucky Transportation Cabinet, analyzed flood-frequency statistics for streamgages in Kentucky. Using annual peak-flow data through water year 2021, flood-frequency estimates were computed for 261 streamgages, including unregulated and regulated sites as well as sites with mixed regulation records. Methods followed those outlined in “Guidelines for Determining Flood Flow Frequency—Bulletin 17C” (U.S. Geological Survey Techniques and Methods 4–B5). These estimates included flows corresponding to annual exceedance probabilities of 50, 20, 10, 4, 2, 1, and 0.2 percent. Temporal trend analyses using the Mann-Kendall test indicated that 18 percent of unregulated streamgages with (1) at least 30 years of peak-flow record and (2) peak-flow record at least as recent as water year 2000 showed statistically significant trends, most of which were weak to moderate increases in peak flows. Concurrently, the fundamental geospatial datasets that support the Kentucky StreamStats application were updated by using high-resolution digital elevation models and hydrography datasets to derive flow direction, flow accumulation, and stream definition rasters. Comparisons of regression-based flood-frequency models using the old and new layers demonstrated consistent results, with a statewide root-mean-square error of 0.019, in the base-10 logarithm of cubic feet per second. Furthermore, to assess model performance, flood-frequency estimates made by using the updated layers and previously published regression-based models were compared to flood-frequency estimates newly computed by following Bulletin 17C. This analysis showed the models performed adequately for most Kentucky stream locations. The updated statistics and geospatial layers provide stakeholders with more accurate, current data for flood-risk assessment, infrastructure design, and water-resource management.

Kentucky↗

USGS2026

Mass mortality of avian migrants in New Mexico, USA, that coincided with an extreme weather event

Many birds are migratory, and this life history strategy allows for maximized access to seasonally abundant resources and favorable climates. However, migration exposes birds to threats and stressors, resulting in high mortality during migration. Anthropogenic landscape alterations and climate change have intensified threats, and mass mortality events linked to extreme weather are more common in recent decades. Documenting mass mortality is critical for predicting future occurrences and implementing effective conservation. Here, we describe a mortality event that occurred throughout New Mexico, USA in fall 2020. Carcasses began appearing in the region in mid-August, during a period of extreme heat and drought. Following an extreme cold weather event on September 8–9 th , the number of carcasses increased dramatically and expanded throughout the state. In total, we collected 628 carcasses comprising 58 species within Doña Ana and Otero Counties in New Mexico. Necropsy determined emaciation was the cause of death for 74.6% of carcasses. Live birds captured during the period of peak mortality (n = 223) were in similarly poor condition. This event provides a striking example of how multiple types of extreme stressors, in this case widespread drought and unseasonal cold, coincided with a mortality event, indicating a possible synergistic relationship between these factors and the mass mortality. Mortality events are likely to increase in frequency with intensifying climate change. Establishment of networks of biologists and researchers could improve our ability to identify and communicate developing mortality events, organize data collection, and improve understanding of the causes and consequences of mortality.

New Mexico↗

USGS2026

Seasonal estimates of nutrient loading, sources, and impacts on water availability in streams across the conterminous United States, 2000–2020

Excess riverine nutrients can limit water availability for humans and ecosystems. Nutrient monitoring on individual stream reaches provides important information about current and past conditions, yet most river reaches are unmonitored. Additionally, monitored data integrate effects of upstream sources, sinks, and pathways by which nutrients get into streams, making explicit planning for effective nutrient reduction strategies challenging. We developed and applied dynamic SPAtially Referenced Regression On Watershed attributes (SPARROW) models to quantify total nitrogen (TN) and total phosphorus (TP) delivery and source-specific loading in all stream reaches of the conterminous United States (CONUS) at a seasonal timestep from 2000 through 2020. Between one third and one half of non-point source nutrients lagged more than one season in their delivery to CONUS streams over the study period. The largest sources of nutrients that were applied and delivered to streams within a season were agricultural fertilizers, treated wastewater, atmospheric deposition, and manure. Increases in loads were widespread across the CONUS and predominantly associated with increased loading from lagged delivery of non-point source inputs and current season fertilizer application. Model results also identified extensive areas where predicted seasonal concentrations frequently exceeded the National Rivers and Streams Assessment “poor” criteria. Increased loading occurred in areas with high yields and delivery to downstream receiving waterbodies, particularly across the Midwest, raising the risk of negative impacts to downstream water availability. The modeling approach presented here provides a continental-scale framework for identifying when, where, and why nutrients are generated and how that may ultimately impact receiving waterbodies.

conterminous United States↗