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USGS2024

Temperature

The “National Field Manual for the Collection of Water-Quality Data” (NFM) provides guidelines and procedures for U.S. Geological Survey (USGS) personnel who collect data used to assess the quality of the Nation’s surface-water and groundwater resources. This chapter, NFM A6.1, provides guidance and protocols for the measurement of temperature of air, of a surface-water body or in groundwater, which include the scientific basis of the measurement, selection and maintenance of equipment, calibration verification, troubleshooting, and procedures for measurement and reporting. It updates and supersedes USGS Techniques of Water-Resources Investigations, book 9, chapter A6.1, version 2.0, by Franceska D. Wilde. Temperature of air and water is routinely measured when water samples are collected, is often measured continually at USGS streamgages, and is a parameter regularly measured during laboratory and field experiments. The field method for measuring temperature described in this chapter is applicable to air and most natural waters. Before 2017, the NFM chapters were released in the USGS Techniques of Water-Resources Investigations series. Effective in 2018, new and revised NFM chapters are being released in the USGS Techniques and Methods series; this series change does not affect the content and format of the NFM. More information is in the general introduction to the NFM (USGS Techniques and Methods, book 9, chapter A0) at https://doi.org/10.3133/tm9A0 . The authoritative current versions of NFM chapters are available in the USGS Publications Warehouse at https://pubs.usgs.gov/ . Comments, questions, and suggestions related to the NFM can be addressed to nfm@usgs.gov .

Techniques and Methods↗

USGS2024

Characteristics of the fault damage zone From high-resolution seismic imaging along the Palos Verdes Fault, California

The distribution and intensity of fault damage zones provides insight into fault activity and its relationship to fluid flow in the crust. Presently, measures of the in-situ distribution of fault damage remain limited and along-strike studies are rare. This study focuses on an offshore section Palos Verdes Fault damage zone that spans 28 km, near Los Angeles, California. To investigate the previously unresolved shallow (∼400 m below the seafloor) fault damage zone we use densely spaced (∼500 m line separation) newly collected sparker multichannel seismic lines and sub-bottom profiles. The combination of high-resolution acquisition methods and specialized seismic processing workflows provide improved imaging of shallow faulting. We apply a multi-trace similarity technique to identify discontinuities in the seismic data that may be attributed to faults and fractures. This fault detection approach reveals diverse fault damage patterns on adjacent seismic profiles. However, a discernible damage zone pattern emerges by stacking multiple damage detection profiles along strike. We find that peak damage identified in this way corresponds to the active main fault strand, confirmed in this study, and thus the technique may be useful for identifying active fault strands elsewhere. Additionally, we observe that the variable width of the damage zone along strike is controlled by fault obliquity. Furthermore, our observations reveal a correlation between fault damage and seafloor fluid seeps visible in the water column, suggesting that damage plays a role in controlling fluid flow around the fault.

California↗

USGS2026

Perspectives and insights gained from applying landscape ecological approaches to the Upper Mississippi riverscape

Advances in remote sensing, spatial data collection, hydraulic and geospatial models, and the maturation of landscape ecology during the early 2000s spurred the concept of rivers as landscapes or ‘riverscapes’. Since that time, the Upper Mississippi River Restoration (UMRR) Program - one of the world’s longest running large-river ecosystem restoration and monitoring programs - has applied landscape ecological principles to the Upper Mississippi River System (UMRS). I examine spatial patterns of aquatic nutrient concentrations, submersed aquatic vegetation, and fish and mussel communities, finding that within-river patterns are often patchy in nature, likely resulting from how nutrient processes and community traits interact with spatial variability in hydraulic exchange patterns. Local-scale patchy spatial patterns in the UMRS are embedded in system-scale longitudinal gradients and a hierarchical view of the river has provided a foundation for strategic river restoration planning. Key Words: Aquatic Habitat, hydraulic connectivity, patch, restoration, riverscape

BioScience↗

USGS2000

Suspended-sediment characteristics in the Housatonic River Basin, western Massachusetts and parts of eastern New York and northwestern Connecticut, 1994-96

Suspended-sediment concentrations, discharges, loads, and yields were determined for eight subbasins in the Housatonic River Basin in western Massachusetts, eastern New York, and northwestern Connecticut from April 1994 through March 1996. Suspended-sediment samples were collected at three continuous-record sediment stations and at four partial-record sediment stations. Suspended-sediment concentrations in samples collected during the period of study ranged from less than 0.5 to 3,400 milligrams per liter, and concurrent streamflows ranged from 0.03 to 126 cubic feet per second per square mile at the seven stations. Median suspended-sediment concentrations in samples collected at each station ranged from 7 to 61 milligrams per liter. Median streamflows during suspended-sediment sampling ranged from 1.86 to 5.88 cubic feet per second per square mile. Instantaneous suspended-sediment yields ranged from less than 0.005 to 185 tons per day per square mile, and medians ranged from 0.03 to 1.12 tons per day per square mile at the seven stations. Total suspended-sediment loads (mass) from April 1994 through March 1996 at the continuous-record sediment stations were 11,603 tons at Housatonic River near Great Barrington, 7,929 tons at Green River, and 54,347 tons at Housatonic River near Ashley Falls. Suspended-sediment load during January 1996 at the Green River station accounted for about 54 percent of the total suspended-sediment load for the Green River during the 2-year study. Suspended-sediment load on January 19 and 20, 1996, at the Green River station accounted for about 50 percent of the January 1996 suspended-sediment load, or about 27 percent of the total suspended-sediment load during the 2-year study. This large suspended-sediment transport was the result of rainfall and snowmelt on January 19 and 20, 1996--the equivalent of a 5- to 6-inch rain storm in the Green River subbasin. Total suspended-sediment loads during the 2-year study at the partial-record sediment stations were 3,052 tons at Williams River, 1,758 tons at Ironworks Brook, and 17,927 tons at Konkapot River. Suspended-sediment yields from April 1994 through March 1996 at the continuous-record sediment stations were 21 (tons/yr)/mi 2 at Housatonic River near Great Barrington, 78 (tons/yr)/mi 2 at Green River, and 58 (tons/yr)/mi 2 at Housatonic River near Ashley Falls. Suspended-sediment yields during the 2- year study at the partial-record sediment stations were 35 (tons/yr)/mi 2 at Williams River, 78 (tons/yr)/mi 2 at Ironworks Brook, and 147 (tons/yr)/mi 2 at Konkapot River. Suspended-sediment yields were estimated for two subbasins in the Housatonic River Basin--Schenob Brook at Sheffield, a partial-record sediment station, and the area adjacent to the Housatonic River between Great Barrington and Ashley Falls. The estimate of suspended-sediment yield at Schenob Brook at Sheffield of 82 (tons/yr)/mi 2 is comparable to the yield determined for the Green River and Ironworks Brook. The estimate of suspended-sediment yield for the area adjacent to the Housatonic River between Great Barrington and Ashley Falls was 395 (tons/yr)/mi 2 . This estimated suspended-sediment yield was 2.7 to 18.8 times greater than that estimated for any of the other subbasins. Several basin and land-use characteristics thought to affect suspended-sediment transport in the subbasins were compared to the suspended-sediment yields. The characteristics that seemed to affect suspended-sediment discharge were dams, which contributes to decreased yields; Hadley, Limerick, Linlithgo, Saco, and Winooski silt loam soils (high erodibility soils), which contributes to increased yields; stratified-drift deposits, which contributes to increased yields; and agricultural and open land, which contributes to increased yields. The effect of stratified-drift deposits on suspended-sediment discharge is thought to be greater when those deposits are of glaciolacustrine (generally clay, silt, and fine sand), rather than glaciofluvial (clay, silt, sand, gravel, and cobbles) origin. The silt loam soils, glaciolacustrine deposits, and agricultural and open land are interrelated, inasmuch as the silt loam soils generally are associated with glaciolacustrine deposits and agricultural activities.

Connecticut, Massachusetts, New York↗

USGS2024

Estimation of reservoir storage capacity and geomorphic change detection analysis from a multibeam bathymetric survey of Randy Poynter Lake, Rockdale County, Georgia

Rockdale County Department of Water Resources has a directive to update estimates of the reservoir storage capacity of Randy Poynter Lake, located in northern Georgia, and to assess recent sedimentation and associated storage capacity loss. In 2022, the U.S. Geological Survey completed a multibeam bathymetric survey of Randy Poynter Lake to update storage capacity estimates and to quantify storage capacity change since the first multibeam bathymetric survey in 2012 in consideration of estimated errors inherent to bathymetric surveys. Data from the 2022 survey were used to generate contours of the reservoir as well as compute storage capacity at regular increments of water-surface elevation. Storage capacity comparisons between 2012 and 2022 at Randy Poynter Lake show minimal changes that are within the estimated uncertainties, with consistent or slightly increased storage capacities observed at most water-surface elevations and reductions observed at the remaining few elevations. Comparison of the multibeam bathymetric data collected in 2012 with data collected in 2022 further allowed for a formal geomorphic change detection analysis to map, quantify, and infer causation of morphological change over time with respect to a level of detectable change. The volume change in Randy Poynter Lake for the decade between 2012 and 2022 was slightly net-depositional and within the estimated uncertainty. The spatial distribution of sediment deposition was primarily concentrated in the northern portion of the lake, where the principal tributary flows into Randy Poynter Lake. The results of the geomorphic change analysis were used to further understand the future implications to storage capacity change. Despite the challenges of confirming systematic biases because of uncertainties exceeding the observed changes, insights from the study help predict long-term reservoir sediment accumulation, indicating a reservoir half-life extending about 650 years from 2022 on the basis of the current sediment yield estimates.

Georgia↗

USGS2026

Tephra from Kīlauea’s 2008–2018 lava lake eruption—Proximal deposits and dispersal characteristics

A network of ten buckets was established early in the 2008–2018 summit eruption at Kīlauea to collect proximal tephra ejected from the new, informally named the “Overlook crater”; the buckets were emptied on most days of the eruption thereafter. This report summarizes the results of more than 2,400 different sampling intervals (most 1–3 days long) during the eruption, focusing on the physical and dispersal characteristics of the tephra deposits. The network was within about 300 meters south of the vent to capture tephra dispersed by the dominant northeast trade wind. The juvenile tephra mainly reflected spattering at the southeast (SE) sink, a downwelling area in the southeastern part of the lava lake in the Overlook crater that remained in the same area throughout the eruption, with admixtures of solid rock and secondary minerals derived from the wall of the crater. The proportion of juvenile material to lithic material ranged widely early in the eruption but was generally greater than 90 percent for the last 6 years of the eruption as lake level rose and the crater walls decreased in height and became more stable. The accumulation rate of tephra at each bucket was strongly dependent on the location of the bucket and reflects the interplay between lava lake level and wind direction and speed. The mass per unit area (m/a) of collected tephra was a maximum of about 97 kilograms per square meter for the entire eruption, equivalent to a thickness of about 75 millimeters. Thirty-two explosive events with a volcanic explosivity index of −2 to −4 deposited much of the tephra in the network. Fifteen of these rock-fall-induced events occurred within 6 days of one another. Pele’s hair, a volcanic glass predominantly associated with quieter activity at the vent in the final half of the eruption, was dispersed more than 60 kilometers downwind from the lava lake and formed a nearly continuous deposit near the Overlook crater. This eruption was probably the most frequently sampled long-lasting eruption in history, but most of the deposits are ephemeral. The collected samples, although generally of small mass, are retained by the Hawaiian Volcano Observatory and are available for detailed study.

Hawaii↗

USGS2024

Perspectives on transportable array Alaska background noise levels

Background seismic noise fundamentally sets a lower bound on our ability to record signals arising from earthquakes. The background noise spectrum at a station is a combination of cultural noise, ocean-generated microseism noise, intrinsic instrument self-noise, and the sensitivity of the instrument to nonseismic noise sources. The USArray-Transportable Array Alaska deployed 195 stations across Alaska and parts of Canada (Yukon, British Columbia, and Northwest Territories). These stations were all installed using similar techniques and made use of instruments with similar self-noise levels. As such, this network provides an opportunity to look at how geographic location influences seismic background. Using these broadband stations, we report background noise levels from 0.2 to 75 s period in six discrete bands. By constructing “noise maps,” we depict both spatial and temporal changes in the background noise field. Using these maps, combined with targeted analysis, we infer sources and contributing factors to noise levels in these different period bands. These include cultural noise, the formation of sea ice, seasonal changes in permafrost and wave activity in the Gulf of Alaska, and magnetic field variability. We use this study as an opportunity to review several previous studies examining seismic noise in Arctic regions.

Book chapter↗

USGS1992

Nonpoint-source pollutant discharges of the three major tributaries to Reelfoot Lake, west Tennessee, October 1987-September 1989

An investigation of the concentration and loads of nitrogen, phosphorus, and suspended sediment in storm runoff to Reelfoot Lake, in western Tennessee, was conducted from October 1987 through September 1989. Concentrations of selected herbicides also were defined. Reelfoot Lake, with a surface area of about 15,500 acres, is the largest natural lake in Tennessee and an important recreation and fisheries resource. Previous studies showed that the lake is hypereutrophic, a condition caused by high concentrations of nutrients in water and sediments discharged from the three principal tributaries (South Reelfoot Creek, North Reelfoot Creek, and Running Slough) to the lake. Pesticides, including herbicides, have been detected in the lake's bottom sediments. Storm runoff contributed about 87percent of the total water discharge of the three main tributaries to Reelfoot Lake. South Reelfoot Creek contributed about 4.7 tons per acre per year of suspended sediment, while North Reelfoot Creek contributed about 1.9 tons per acre per year. Running Slough contributed only about 0.31 ton per acre per year of suspended sediment. Most of the suspended sediment was transported by storm runoff between October and March. About 80 percent of the annual streamflow of the three tributaries occurs during these months. The North Reelfoot Creek basin contributed 8.2 pounds per acre per year of total nitrogen and 2.4 pounds per acre per year of total phosphorus. South Reelfoot Creek basin contributed about 6.5 and 1.3 pounds per acre per year of total nitrogen and phosphorus, respectively, while Running Slough basin contributions were 3.4 and 0.86 pounds per acre per year, respectively. The differences in nutrient yields appear to result from more row-crop agriculture and the relatively steeply sloping agricultural land in the North Reelfoot Creek basin. Ninety-one percent of the total nitrogen load and 95 percent of the total phosphorus load in the three streams was transported by storm runoff. Significant differences in the mean concentrations of nutrients in runoff were defined between the active agricultural months (April through September) and the inactive months (October through March). Storm-runoff samples were analyzed for II selected triazine herbicides. Alachlor and atrazine were the most commonly detected herbicides. Thirty-two percent of the samples contained detectable levels of alachlor and 93 percent of the samples contained detectable levels of atrazine. Ninety percent of the samples collected during the active agricultural months contained detectable leveki of alachlor and all 29 samples contained detectable levels of atrazine. Sixteen samples exceeded lifetime health-advisory levels for atrazine in drinking water (3 micrograms per liter); two samples collected from the April IS, 1988, storm at North Reelfoot Creek and South Reelfoot Creek contained 42 and 57 micrograms per liter of atrazine, respectively. Concentrations of the other nine triazine herbicides were generally less than the level of detection (0.1 microgram per liter).

Tennessee↗

USGS2024

Framework for mapping liquefaction hazard–Targeted design ground motions

Liquefaction-induced ground failure poses substantial challenges to geotechnical earthquake engineering design. Current approaches for designing against liquefaction hazards, as specified in most seismic provisions, focus on estimating a liquefaction factor of safety ( 𝐹⁢𝑆𝐿 ) and typically characterize earthquake loading using design parameters based on probabilistic or deterministic ground motion levels. Because 𝐹⁢𝑆𝐿 is estimated deterministically, this basis of design neglects considerable uncertainties for estimating liquefaction triggering and its consequences and results in a lack of liquefaction-specific design criteria, particularly as structural design has advanced toward risk-targeted performance objectives. This study presents a framework for developing liquefaction-targeted design criteria based on a minimum acceptable return period of liquefaction, informed by probabilistic liquefaction hazard analysis (PLHA). PLHA quantifies annualized rates of liquefaction by considering contributions from (1) the full ground-motion probability space, and (2) uncertainties in liquefaction triggering using probabilistic models. PLHA is used in this study to characterize the current, effective return periods of 𝐹⁢𝑆𝐿 ( 𝑇𝑅,𝐹⁢𝑆 ) obtained from conventional liquefaction hazard analysis (CLHA) using uniform-hazard ground motions. 𝑇𝑅,𝐹⁢𝑆 is evaluated in a parametric study of nearly 100 sites throughout the conterminous United States. The results indicate large geographic variations in acceptable liquefaction hazard levels, with implied 𝑇𝑅,𝐹⁢𝑆 ranging between approximately 1,000 to 3,000 years. To address these inconsistencies without the computational demands of full PLHA, a framework is proposed for developing a liquefaction-targeted design peak ground acceleration, 𝑃⁢𝐺⁢𝐴𝐿 , for use in liquefaction models that result in consistent liquefaction design levels across all geographic locations. The mapped 𝑃⁢𝐺⁢𝐴𝐿 is shown to be somewhat sensitive to site-specific properties, and adjustment factors are developed and presented. The proposed 𝑃⁢𝐺⁢𝐴𝐿 mapping procedure produces 𝐹⁢𝑆𝐿 estimates that are consistent with those obtained from full PLHA at a target 𝑇𝑅,𝐹⁢𝑆 , providing a promising roadmap to incorporating PLHA concepts into current liquefaction design methods.

Journal of Geotechnical and Geoenvironmental Engin↗

USGS2025

Disparate groundwater responses to wildfire

Post-wildfire investigations of groundwater response reveal a range of outcomes, varying from substantial increases to notable decreases in recharge and baseflow, with some studies indicating negligible or short-lived effects. This review assesses these varied responses within five critical categories: climate, vegetation, hydrogeology, fire characteristics, and the cryosphere, examining both short-term (within 2 years) and intermediate (2–10 years post-fire) effects. Despite considerable variability, some consistent patterns emerge. For instance, in hydroclimatic settings where water input and evaporative demand cycles are out of sync, post-wildfire groundwater responses tend to be positive (i.e., increased flux or storage), whereas under low fire severity conditions or in vegetation types that quickly recover, groundwater responses tend to be negative (i.e., decreased flux or storage). We synthesize relevant findings into a compendium of testable hypotheses aimed at explaining the spatiotemporal variability in observed post-wildfire groundwater responses. A recurring theme is the critical influence of the pre-wildfire groundwater regime on expected response and recovery. We identify opportunities for specific improvements in post-wildfire monitoring and modeling that would further advance capabilities to predict groundwater response. A key area for further research is understanding how wildfire effects on snow dynamics and other cryospheric processes translate to changes in groundwater.

WIREs Water↗

USGS2026

Detecting snow avalanche activity using infrasound: Hooker Valley, New Zealand

Snow avalanches pose considerable hazards to people and infrastructure in alpine environments. Traditional avalanche monitoring relies on meteorological data and visual observations, which can be limited in scope and timeliness. Infrasound offers a promising complementary monitoring tool by detecting the low-frequency sound waves generated by avalanches. Here, we present infrasound and camera observations during a 50-day field campaign in the Hooker Valley of Aoraki/Mount Cook National Park, New Zealand. Our study detected seven avalanches with the cameras, whereas the infrasound system identified only one of these events, which was the largest and occurred under conditions that likely favoured infrasound propagation. The infrasound system recorded numerous other events not captured by the cameras, indicating the benefit of further investigation to determine their sources. These findings highlight the potential of infrasound technology for detecting avalanches and providing broad spatial coverage, capturing events in areas not monitored by cameras, while also showcasing limitations in infrasound capabilities. The limited detection of smaller avalanches underscores the opportunity for further research to enhance detection capabilities and understand environmental influences such as snow cover and wind noise. Overall, this study emphasises the utility of multidisciplinary monitoring techniques to improve avalanche detection in alpine environments.

Hooker Valley↗

USGS2025

Laboratory assessment for recovery of porcine circovirus 2 and porcine reproductive and respiratory syndrome virus using two types of commercially available hollow-fiber ultrafilters

Groundwater near swine farms is an uninvestigated reservoir for porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circoviruses (PCVs). Enteric microorganisms are often collected from groundwater via dead-end ultrafiltration, but recovery of PRRSV and PCV with this method has not been assessed. We recovered PRRSV2 and PCV2 by dead-end ultrafiltration followed by polyethylene glycol (PEG) precipitation, nucleic acid extraction, and reverse-transcription quantitative real-time PCR. We also compared 2 commercial hemodialysis ultrafilters (Asahi Kasei Rexeed-25A, Nipro Elisio-25H) and compared PRRSV2 recovery in these filters to other waterborne microorganisms. On average, 8 ± 1% of PRRSV2 was recovered by dead-end ultrafiltration and PEG precipitation, compared to 25 ± 6% for adenovirus 41. Full-process recovery of bacteria in the same filters was 5–15%; Cryptosporidium parvum recovery was 42 ± 12%. PCV2 was detected in 4 of 12 replicate filters, but low stock concentrations precluded quantitative recovery estimates. Elisio-25H ultrafilters performed similarly to Rexeed-25A filters for all organisms tested and is an effective replacement for the Rexeed-25A, which is no longer available in the United States. Our recovery of PRRSV2 and PCV2 by dead-end ultrafiltration in the laboratory suggests that PRRSV2 detection limits are as low as 3–50 genomic copies/L in sample volumes of 100–1,500 L. Based on quantitative microbial risk assessment, these concentrations are relevant to PRRSV2 infection rates in the U.S. swine herd.

Journal of Veterinary Diagnostic Investigation↗

USGS2024

Subducting plate structure and megathrust morphology from deep seismic imaging linked to earthquake rupture segmentation at Cascadia

The origin of rupture segmentation along subduction zone megathrusts and linkages to the structural evolution of the subduction zone are poorly understood. Here, regional-scale seismic imaging of the Cascadia margin is used to characterize the megathrust spanning ~900 km from Vancouver Island to the California border, across the seismogenic zone to a few tens of kilometers from the coast. Discrete domains in lower plate geometry and sediment underthrusting are identified, not evident in prior regional plate models, which align with changes in lithology and structure of the upper plate and interpreted paleo-rupture patches. Strike-slip faults in the lower plate associated with oblique subduction mark boundaries between regions of distinct lower plate geometry. Their formation may be linked to changes in upper plate structure across long-lived upper plate faults. The Juan de Fuca plate is fragmenting within the seismogenic zone at Cascadia as the young plate bends beneath the heterogeneous upper plate resulting in structural domains that coincide with paleo-rupture segmentation.

Oregon, Washington↗

USGS2024

Deep syntectonic burial of the Anthracite belt, Eastern Pennsylvania

Fluid inclusion microthermometry and Raman spectroscopy of fluid inclusions in quartz veins from the Pennsylvanian rocks of the Anthracite belt, eastern Pennsylvania support a deep burial model of coalification in favor of focused orogenic hot fluid flow. High-temperature (250 to 255 °C) trapping of CH 4 ± CO 2 saturated aqueous fluids and CH 4 ± CO 2 inclusions indicate fluid trapping at depths of 11.5 to 13.4 km under a cover of Pennsylvanian to Permian(?) syntectonic load. In the folded rocks to the south of the Anthracite belt, CH 4 ± CO 2 fluid inclusions indicate a sediment load that was up to 16.3 km thick. Re -equilibrated aqueous fluid inclusions from veins in Silurian through Devonian rocks give the same range of trapping conditions but a wide range of fluid salinities suggesting that folding, fracturing, and meteoric recharge resulted in the intermixing of fluids from throughout the stratigraphic succession.

Pennsylvania↗

USGS2024

Shallow faulting and folding beneath south‐central Seattle, Washington State, from land‐based high‐resolution seismic‐reflection imaging

The geologic framework of the Seattle fault zone (SFZ) has been extensively studied, but the structure and fault strand locations in the central portion of the fault zone through the city of Seattle have remained controversial. Much of what is known about the SFZ has come from light detection and ranging (lidar)‐topographic surveys and paleoseismic investigations of fault scarps primarily west of Puget Sound, regional gravity and aeromagnetic modeling, and multiscale marine seismic imaging in waters both west and east of Seattle. We analyze ∼24 km of land‐based P ‐wave seismic‐reflection data that fill in a critical gap in our understanding of the SFZ beneath the urban areas of West Seattle, south‐central Seattle, and Mercer Island. These data image deformed strata in the upper 1 km, including upwarped Tertiary rock and younger sediments. Collectively, these data provide evidence for multiple Quaternary‐active thrust faults, back thrusts, and sub‐basins within the SFZ beneath the city of Seattle. The results indicate that multiple and potentially active back thrusts in the upper ∼500 m extend across the length of the SFZ and the entire urban corridor that may be analogous to those on Bainbridge Island west of Puget Sound.

Washington↗

USGS2026

Development of a hydrologic flow model of the Zuñi Salt Lake and surrounding areas, west-central New Mexico

The terminal Zuñi Salt Lake is in a maar in west-central New Mexico and contains hypersaline water that has long been used by Native Americans for religious purposes and the collection of salt. The U.S. Geological Survey (USGS), in cooperation with the Zuni Tribe of the Zuni Reservation, New Mexico, and Bureau of Reclamation, developed the Zuñi Salt Lake hydrologic flow model to simulate the steady-state conditions of the lake and surrounding groundwater-flow system. The model is a tool that can be used to analyze the potential hydrologic responses to resource development in the region under different water-use scenarios, which can support negotiations that could help protect future use of the lake. The USGS modular hydrologic model, MODFLOW 6, was used to simulate the hydrologic system of the lake and surrounding areas. To define the layering of the model, a three-dimensional hydrogeologic framework was constructed, which included seven informal hydrogeologic units and the locations of faults that truncate and offset the units. Calibration of the model was performed using the iterative ensemble smoother included in a parameter estimation software suite (PEST++). The iterative ensemble smoother approach resulted in a posterior parameter ensemble of model realizations with parameter and simulated values that show similar success in matching observations. Groundwater flux to the Zuñi Salt Lake simulated by using the posterior parameter distribution ranged from 26 to 730 acre-feet per year with a mean, median, and standard deviation of 530, 570, and 170 acre-feet per year, respectively. The relative contribution of groundwater discharge to the lake was simulated using a particle-tracking model for MODFLOW (MODPATH) to be from, in order of decreasing contribution, the Mesaverde, Cenozoic, Mancos, and Dakota hydrogeologic units. Simulations of future conditions using the ensemble of models can provide an empirical estimate of forecast uncertainty without substantial additional analysis.

New Mexico↗

USGS2025

Cooling perspectives on the risk of pathogenic viruses from thawing permafrost

Climate change is inducing wide-scale permafrost thaw in the Arctic and subarctic, triggering concerns that long-dormant pathogens could reemerge from the thawing ground and initiate epidemics or pandemics. Viruses, as opposed to bacterial pathogens, garner particular interest because outbreaks cannot be controlled with antibiotics, though the effects can be mitigated by vaccines and newer antiviral drugs. To evaluate the potential hazards posed by viral pathogens emerging from thawing permafrost, we review information from a diverse range of disciplines. This includes efforts to recover infectious virus from human remains, studies on disease occurrence in polar animal populations, investigations into viral persistence and infectivity in permafrost, and assessments of human exposure to the enormous viral diversity present in the environment. Based on currently available knowledge, we conclude that the risk posed by viruses from thawing permafrost is no greater than viruses in other environments such as temperate soils and aquatic systems.

mSystems↗

USGS2025

Salinas Valley integrated hydrologic and reservoir operations models, Monterey and San Luis Obispo Counties, California

The area surrounding the Salinas Valley groundwater basin in Monterey and San Luis Obispo Counties of California is a highly productive agricultural area, contributes significantly to the local economy, and provides a substantial portion of vegetables and other agricultural commodities to the Nation. This region of California provides about half of the Nation’s lettuce, celery, broccoli, and spinach each year. Thus, this agricultural area provides significant volumes of agricultural products not just for California but the entire United States. Changes in population and increased agricultural development, which includes a shift toward more water-intensive crops, and climate variability, have put increasing demand on both surface water and groundwater resources in the valley. This has resulted in water management challenges in the Salinas Valley that are predominantly related to distribution of water supply throughout the basin. Where and when the water is present in the surface and subsurface does not coincide with where and when the water is needed. To deal with the distribution issue, historically water has been used conjunctively in the valley. Conjunctive use is a water management strategy that coordinates surface water and groundwater use to maximize water availability. Groundwater is used throughout the Salinas Valley to meet water demands when surface water supplies are insufficient. Availability of surface water is constrained by climate. Precipitation and streamflow vary seasonally and year to year. Although there are two reservoirs in the Salinas Valley to capture and store water during wet periods, the only conveyance of reservoir water to coastal agricultural areas is the Salinas River. Increasing demand on groundwater and surface water resources throughout the Salinas Valley has resulted in undesirable effects of unsustainable water use, such as surface water depletion, groundwater level declines, storage depletion in the principal aquifers, and seawater intrusion. To address these escalating issues, local communities, water management agencies, and groundwater sustainability agencies are evaluating how to sustainably manage both their surface water and groundwater resources. To meet water demands and reduce undesirable effects of unsustainable water use, continued conjunctive management of surface water and groundwater would ideally incorporate strategies to deal with increases in demand and a variable climate. To evaluate the challenging water management issues in the Salinas Valley, the U.S. Geological Survey, Monterey County Water Resource Agency, and the Salinas Valley Basin Groundwater Sustainability Agency developed a comprehensive suite of models that represent the Salinas Valley Hydrogeologic system called the Salinas Valley System Model. The Salinas Valley Geologic Framework was developed to characterize the subsurface using various topographic and geologic data sources, including information on hydrogeologic units, their surfaces and extents, geologic structures, lithology, and elevations from borehole data and cross sections, as well as details on faults and existing models. The Salinas Valley Watershed Model simulates the entire Salinas River watershed. Monthly surface water inflows into the integrated hydrologic model domain were simulated using the Salinas Valley Watershed Model. The historical model uses historical climate data, water and land use data, and reservoir releases to simulate agricultural operations, including landscape water demands, diversions, and reclaimed wastewater. The operational model adds an embedded reservoir operations framework to the simulation of the historical model that allows specified operational rules to simulate reservoir releases and changes in reservoir storage. The operational model assumes current reservoir operations and constant land use, which differs from historical conditions. Thus, the operational model is a hypothetical baseline model that can be used by local water managers to evaluate and quantify potential benefits of water supply projects. Together, the geologic framework, watershed, historical, and operational models form a tool that can be used to simulate irrigated agriculture and associated reservoir operations of the integrated hydrologic system of the Salinas Valley.

EarthArXiv↗