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At least 775 records · Page 43Linked to original sources

USGS2016

Supersize me: Remains of three white-tailed deer ( Odocoileus virginianus ) in an invasive Burmese python ( Python molurus bivittatus ) in Florida

Snakes have become successful invaders in a wide variety of ecosystems worldwide. In southern Florida, USA, the Burmese python (Python molurus bivittatus) has become established across thousands of square kilometers including all of Everglades National Park (ENP). Both experimental and correlative data have supported a relationship between Burmese python predation and declines or extirpations of mid- to large-sized mammals in ENP. In June 2013 a large python (4.32 m snout-vent length, 48.3 kg) was captured and removed from the park. Subsequent necropsy revealed a massive amount of fecal matter (79 cm in length, 6.5 kg) within the snake’s large intestine. A comparative examination of bone, teeth, and hooves extracted from the fecal contents revealed that this snake consumed three white-tailed deer (Odocoileus virginianus). This is the first report of an invasive Burmese python containing the remains of multiple white-tailed deer in its gut. Because the largest snakes native to southern Florida are not capable of consuming even mid-sized mammals, pythons likely represent a novel predatory threat to white-tailed deer in these habitats. This work highlights the potential impact of this large-bodied invasive snake and supports the need for more work on invasive predator-native prey relationships.

BioInvasions Records↗

USGS2015

Geographic distribution: Boiga irregularis (Brown treesnake)

Rota: Rota Seaport (14.136502°N, 145.135351°E; WGS84). 3 September 2014. Shelwyn Taisacan, Robert Ulloa. Verified by G. Zug. USNM 581745. Snake (42 g, 810 mm SVL, 1020 mm total length) captured in a mouse-baited trap hung on the fence perimeter of the Rota Seaport. Because the Northern Marianas Islands are historically snake-free, these traps are used around ports and airports for early detection of snakes that may stow away in vessels or aircraft from Guam (60 km to the south), possibly evading quarantine detections. Necropsy revealed no prey items in stomach or gas- trointestinal tract. Dissection at USNM confirmed the snake was female. To our knowledge, this is the first incursion of a live Boiga irregularis on Rota. Brown Treesnakes previously observed on the island (N = 3) arrived in cargo already dead. The USGS Brown Treesnake Rapid Response Team mobilized 4 September–20 Oc- tober 2014 to search the focal and surrounding areas for evidence of a possible incipient population; no additional snakes were found during this search effort.

Herpetological Review↗

USGS2011

Genetic identity of Thamnophis sp. using microsatellite genetic markers

Butler’s gartersnake (Thamnophis butleri) was previously listed by the Wisconsin Department of Natural Resources as a state threatened species. Several key questions associated with species identity, integrity, and hybridization with other gartersnake species needed to be addressed to further refi ne the management plan for this species. The objectives of this research were: 1) to determine if genetic markers developed in the initial phase of research could identify discrete genetic groups of Wisconsin gartersnakes, 2) to determine if any or all genetic groups delineated in objective one were consistent with Butler’s gartersnake, plains gartersnake (T. radix), and/or common gartersnake (T. sirtalis), and 3) to determine if any of the genetic data were consistent with hybridization occurring between gartersnakes in Wisconsin. Snakes were sampled from various Midwestern locations with a focus on sites in Wisconsin. All snakes were photo-vouchered, morphological landmarks were taken, and a tail snip was collected for genetic analysis. Genetic data from previously developed microsatellite markers discriminated three genetic groups from a composite 13-locus dataset (N=815) using the Bayesian admixture analysis in STRUCTURE v2.3.3. These units were highly consistent with species-groups based on the membership of a small number of known snakes from areas where the species are not thought to co-occur. Using a threshold q-value (proportional genotype) of ≥80%, 498 Butler’s gartersnakes, 93 plains gartersnakes, and 107 common gartersnakes were identifi ed in Wisconsin samples; putative hybrid snakes of Butler’s gartersnake x plain gartersnake (34), Butler’s gartersnake x common gartersnake (8), and a single ambiguous snake were also identifi ed in Wisconsin samples. Levels of divergence among the species groups from Wisconsin were lower than between species groups from other states consistent with either larger than expected Wisconsin population sizes or signifi cant gene fl ow (introgressive hybridization) having occurred among species. Regardless, levels of divergence and overall integrity of the three groups were such that the presence of three species of gartersnakes in Wisconsin was supported and hybridization, at a minimum between Butler’s gartersnakes and the two other species, was shown to occur.

Wisconsin DNR Research Report↗

USGS2018

Cytonuclear discordance in the Florida Everglades invasive Burmese python (Python bivittatus) population reveals possible hybridization with the Indian python (P. molurus)

The invasive Burmese python ( Python bivittatus ) has been reproducing in the Florida Everglades since the 1980s. These giant constrictor snakes have caused a precipitous decline in small mammal populations in southern Florida following escapes or releases from the commercial pet trade. To better understand the invasion pathway and genetic composition of the population, two mitochondrial (mtDNA) loci across 1,398 base pairs were sequenced on 426 snakes and 22 microsatellites were assessed on 389 snakes. Concatenated mtDNA sequences produced six haplotypes with an average nucleotide and haplotype diversity of π = 0.002 and h = 0.097, respectively. Samples collected in Florida from morphologically identified P. bivittatus snakes were similar to published cytochrome oxidase 1 and cytochrome b sequences from both P. bivittatus and Python molurus and were highly divergent (genetic distances of 5.4% and 4.3%, respectively). The average number of microsatellite alleles and expected heterozygosity were N A = 5.50 and H E = 0.60, respectively. Nuclear Bayesian assignment tests supported two genetically distinct groups and an admixed group, not geographically differentiated. The effective population size ( N E = 315.1) was lower than expected for a population this large, but reflected the low genetic diversity overall. The patterns of genetic diversity between mtDNA and microsatellites were disparate, indicating nuclear introgression of separate mtDNA lineages corresponding to cytonuclear discordance. The introgression likely occurred prior to the invasion, but genetic information on the native range and commercial trade is needed for verification. Our finding that the Florida python population is comprised of distinct lineages suggests greater standing variation for adaptation and the potential for broader areas of suitable habitat in the invaded range.

Florida↗

USGS2016

Large reptiles and cold temperatures: Do extreme cold spells set distributional limits for tropical reptiles in Florida?

Distributional limits of many tropical species in Florida are ultimately determined by tolerance to low temperature. An unprecedented cold spell during 2–11 January 2010, in South Florida provided an opportunity to compare the responses of tropical American crocodiles with warm-temperate American alligators and to compare the responses of nonnative Burmese pythons with native warm-temperate snakes exposed to prolonged cold temperatures. After the January 2010 cold spell, a record number of American crocodiles ( n = 151) and Burmese pythons ( n = 36) were found dead. In contrast, no American alligators and no native snakes were found dead. American alligators and American crocodiles behaved differently during the cold spell. American alligators stopped basking and retreated to warmer water. American crocodiles apparently continued to bask during extreme cold temperatures resulting in lethal body temperatures. The mortality of Burmese pythons compared to the absence of mortality for native snakes suggests that the current population of Burmese pythons in the Everglades is less tolerant of cold temperatures than native snakes. Burmese pythons introduced from other parts of their native range may be more tolerant of cold temperatures. We documented the direct effects of cold temperatures on crocodiles and pythons; however, evidence of long-term effects of cold temperature on their populations within their established ranges remains lacking. Mortality of crocodiles and pythons outside of their current established range may be more important in setting distributional limits.

Ecosphere↗

USGS2018

Evaluating airsoft electric guns for control of invasive brown treesnakes

Firearms are often used in lethal control of invasive vertebrates, but safety and regulatory aspects limit the circumstances under which they can be used. During August 2016 at the Brown Treesnake Project laboratory on Guam, we evaluated hobby‐grade Airsoft Electric Guns (AEGs)—a lower powered, less‐hazardous, and less‐regulated alternative to firearms—for capture and control of small animals, with specific emphasis on invasive brown treesnakes ( Boiga irregularis ). Tests of AEGs differing in power with ammunition (plastic pellets) masses ranging from 0.20 to 0.39 g, fired at gelatin blocks from distances of 4, 8, and 12 m, showed that heavy ammunition is of overriding importance for maximizing lethality: 0.39‐g pellets penetrated more deeply at 12 m than did 0.20‐g pellets at 4 m. Inspection of tissue damage in brown treesnake carcasses subjected to fire with the 0.39‐g ammunition from the same distances suggested that injuries sustained by a direct hit from 12 m would often be lethal, and snakes would be unlikely to survive multiple hits from automatic fire discharged at approximately 17/s. Limited trials with live snakes helped us to understand behavioral responses in a snake hit by ≥1 pellets, including distance traveled over time. Based on these factors, we assessed the risk that a snake injured by pellet fire might evade subsequent capture by rapid responders in the proximity. We also discuss ethical considerations and regulatory advantages of using AEGs. Published 2018. This article is a U.S. Government work and is in the public domain in the USA.

Wildlife Society Bulletin↗

USGS2021

Locally abundant, endangered Mariana swiftlets impact the abundance, behavior, and body condition of an invasive predator

Invasive predators are known to have negative consumptive and non-consumptive effects on native species, but few examples show how the abundance of native prey may influence an established invasive predator. We compared invasive brown treesnakes ( Boiga irregularis ; BTS) found in caves occupied by endangered Mariana swiftlets ( Aerodramus bartschi ) to snakes found in nearby forests and caves without birds to quantify how the abundance of native avian prey impacts BTS abundance and behavior on Guam. From 2011 to 2017 we removed 151 BTS in caves occupied by swiftlets and never observed BTS in caves without birds. Notable locations included snakes foraging near swiftlets and in holes that allowed cave access and escape from capture. Of 43 BTS with gut contents, 27 (63%) contained swiftlets. BTS in swiftlet-occupied caves had greater fat mass compared to forests, indicating access to swiftlets may increase body condition and promote reproduction. Number of ovarian follicles was significantly greater in female snakes from swiftlet-occupied caves compared to those from ravine, but not limestone forests; evidence of male BTS being more capable of reproduction was limited (i.e., fewer non-discernible but not significantly larger testes in snakes from caves). Assuming other limiting factors are considered, altering the functional response of predators through the modification of caves or interdiction lures to exclude or hinder the largest BTS could bolster swiftlet populations by increasing nesting refugia in currently-occupied caves and facilitate recolonization of historical caves.

Oecologia↗

USGS2024

Mercury bioaccumulation and Hepatozoon spp. infections in two syntopic watersnakes in South Carolina

Mercury (Hg) is a ubiquitous environmental contaminant known to bioaccumulate in biota and biomagnify in food webs. Parasites occur in nearly every ecosystem and often interact in complex ways with other stressors that their hosts experience. Hepatozoon spp. are intraerythrocytic parasites common in snakes. The Florida green watersnake ( Nerodia floridana ) and the banded watersnake ( Nerodia fasciata ) occur syntopically in certain aquatic habitats in the Southeastern United States. The purpose of this study was to investigate relationships among total mercury (THg) concentrations, body size, species, habitat type and prevalence and parasitemia of Hepatozoon spp. infections in snakes. In the present study, we sampled N. floridana and N. fasciata from former nuclear cooling reservoirs and isolated wetlands of the Savannah River Site in South Carolina. We used snake tail clips to quantify THg and collected blood samples for hemoparasite counts. Our results indicate a significant, positive relationship between THg and snake body size in N. floridana and N. fasciata in both habitats. Average THg was significantly higher for N. fasciata compared to N. floridana in bays (0.22 ± 0.02 and 0.08 ± 0.006 mg/kg, respectively; p < 0.01), but not in reservoirs (0.17 ± 0.02 and 0.17 ± 0.03 mg/kg, respectively; p = 0.29). Sex did not appear to be related to THg concentration or Hepatozoon spp. infections in either species. We found no association between Hg and Hepatozoon spp. prevalence or parasitemia; however, our results suggest that species and habitat type play a role in susceptibility to Hepatozoon spp. infection.

South Carolina↗

USGS2006

Environmental contaminants and biomarker responses in fish from the Columbia River and its tributaries: spatial and temporal trends

Fish were collected from 16 sites on rivers in the Columbia River Basin (CRB) from September 1997 to April 1998 to document temporal and spatial trends in the concentrations of accumulative contaminants and to assess contaminant effects on the fish. Sites were located on the mainstem of the Columbia River and on the Snake, Willamette, Yakima, Salmon, and Flathead Rivers. Common carp (Cyprinus carpio), black bass (Micropterus sp.), and largescale sucker (Catostomus macrocheilus) were the targeted species. Fish were field-examined for external and internal lesions, selected organs were weighed to compute somatic indices, and tissue and fluid samples were preserved for fish health and reproductive biomarker analyses. Composite samples of whole fish, grouped by species and gender, from each site were analyzed for organochlorine and elemental contaminants using instrumental methods and for 2,3,7,8-tetrachloro dibenzo-p-dioxin-like activity (TCDD-EQ) using the H4IIE rat hepatoma cell bioassay. Overall, pesticide concentrations were greatest in fish from lower CRB sites and elemental concentrations were greatest in fish from upper CRB sites. These patterns reflected land uses. Lead (Pb) concentrations in fish from the Columbia River at Northport and Grand Coulee, Washington (WA) exceeded fish and wildlife toxicity thresholds (> 0.4 ??g/g). Selenium (Se) concentrations in fish from the Salmon River at Riggins, Idaho (ID), the Columbia River at Vernita Bridge, WA, and the Yakima River at Granger, WA exceeded toxicity thresholds for piscivorous wildlife (> 0.6 ??g/g). Mercury (Hg) concentrations in fish were elevated throughout the basin but were greatest (> 0.4 ??g/g) in predatory fish from the Salmon River at Riggins, ID, the Yakima River at Granger, WA, and the Columbia River at Warrendale, Oregon (OR). Residues of p,p???-DDE were greatest (> 0.8 ??g/g) in fish from agricultural areas of the Snake, Yakima, and Columbia River basins but were not detected in upper CRB fish. Other organochlorine pesticides did not exceed toxicity thresholds in fish or were detected infrequently. Total polychlorinated biphenyls (PCBs; > 0.11 ??g/g) and TCDD-EQs (> 5 pg/g) exceeded wildlife guidelines in fish from the middle and lower CRB, and ethoxyresorufin O-deethylase (EROD) activity was also elevated at many of the same sites. Temporal trend analysis indicated decreasing or stable concentrations of Pb, Se, Hg, p,p???-DDE, and PCBs at most sites where historical data were available. Altered biomarkers were noted in fish throughout the CRB. Fish from some stations had responded to chronic contaminant exposure as indicated by fish health and reproductive biomarker results. Although most fish from some sites had grossly visible external or internal lesions, histopathological analysis determined these to be inflammatory responses associated with helminth or myxosporidian parasites. Many largescale sucker from the Columbia River at Northport and Grand Coulee, WA had external lesions and enlarged spleens, which were likely associated with infections. Intersex male smallmouth bass (Micropterus dolomieu) were found in the Snake River at Lewiston, ID and the Columbia River at Warrendale, OR. Male bass, carp, and largescale sucker containing low concentrations of vitellogenin were common in the CRB, and comparatively high concentrations (> 0.3 mg/mL) were measured in male fish from the Flathead River at Creston, Montana, the Snake River at Ice Harbor Dam, WA, and the Columbia River at Vernita Bridge, WA and Warrendale, OR. Results from our study and other investigations indicate that continued monitoring in the CRB is warranted to identify consistently degraded sites and those with emerging problems. ?? 2005 Elsevier B.V. All rights reserved.

Columbia River Basin↗

USGS2021

Recent recovery and expansion of Guam’s locally endangered Såli (Micronesian Starling) Aplonis opaca population in the presence of the invasive brown treesnake

Assessing the impacts of invasive predators on the demography and distribution of native species is critical for understanding mechanisms of species persistence and informing the design of recovery programmes. On the oceanic island of Guam, the introduction of the predatory brown treesnake Boiga irregularis after World War II caused the near-total loss of the native forest avifauna. Localised snake control measures have been implemented since the early 1990s, yet it remains poorly understood how they have impacted Guam’s remaining native bird populations. To address this question, we combined intensive area searches of Andersen Air Force Base (AAFB) with island-wide transect surveys and opportunistic sightings to provide a comprehensive update on the distribution and abundance of Såli (Micronesian Starling, Aplonis opaca ) – one of Guam’s last extant native bird species. Area searches of AAFB, where the largest remnant of the Såli population persists, revealed a 15-fold population increase since the last survey in the early 1990s, and transect surveys and opportunistic sightings indicate incipient recolonisation of other urbanised areas of northern and central Guam. We estimate the current island-wide population size at ~1,400 individuals. The population increase can likely be attributed to a combination of snake control measures and the Såli’s ability to exploit urban refugia for nesting and roosting. Although these trends demonstrate some population recovery, a skewed age ratio (>90% adults and subadults) at AAFB and a highly urbanised distribution and low abundance outside AAFB indicate that snake predation continues to strongly impact the population. More intensive snake suppression efforts, particularly in forested areas, may allow for the Såli population to attain its former distribution and abundance on Guam. More broadly, our findings reinforce the importance of urban areas as refugia for some threatened species.

Bird Conservation International↗

USGS1986

Contrasting magma types and steady-state, volume-predictable, basaltic volcanism along the Great Rift, Idaho

The Great Rift is an 85-km-long, 2- to 8-km-wide volcanic rift zone in the Snake River Plain, Idaho. Three latest Pleistocene to Holocene basaltic lava fields, Craters of the Moon, Kings Bowl, and Wapi, are located along the Great Rift. The Craters of the Moon lava field is a composite of more than 60 lava flows, 25 cinder cones, and at least 8 eruptive fissure systems. It covers 1,600 km 2 and contains ∼30 km 3 of lava flows and associated pyroclastic deposits. Field, radiocarbon, and paleomagnetic data show that the Craters of the Moon lava field formed in eight eruptive periods, each of which was typically several hundred years or less in duration and was separated from others before and after by intervals of several hundred to several thousand years. The first eruptive period began ∼15,000 yr B.P., and the latest eruptive period ended ∼2100 yr B.P. The small Kings Bowl lava field (3.3 km 2 , 0.01 km 3 ) and the larger Wapi lava field (330 km 2 , 6 km 3 ) both formed ∼2250 yr B.P. Three magma types have fed flows along the Great Rift. The types are (1) a contaminated type that has a SiO 2 range of ∼49%–64% and commonly shows petrographic evidence of contamination, (2) a fractionated type that has a SiO 2 range of ∼44%–54% and shows no evidence of contamination and whose chemical and mineralogical variation can be accounted for mainly by crystal fractionation, and (3) a Snake River Plain type that has a SiO 2 range of ∼45%–48%, shows little evidence of fractionation, and is represented by Kings Bowl–Wapi flows and olivine basalts of the Snake River Plain. The contaminated and fractionated magma types were erupted at the Craters of the Moon lava field, and the Snake River Plain magma type was erupted at the Kings Bowl and Wapi lava fields. These relations imply that the magma reservoirs are spatially isolated. The magma output rate for the Craters of the Moon segment of the Great Rift was constant at ∼1.5 km 3 /1,000 yr for the period from 15,000 to 7000 yr B.P. The rate increased to ∼2.8 km 3 /1,000 yr from 7000 to 2000 yr B.P., mainly as a result of the addition of contaminated magma to the nearly constant output rate of fractionated magma. The Craters of the Moon segment of the Great Rift has experienced quasi-steady-state, volume-predictable volcanism for the last 15,000 yr. The recurrence interval of eruptive activity for the Craters of the Moon lava field ranges from several hundred to ∼3,000 yr. Because the present interval has lasted ∼2,100 yr, another eruptive period seems likely to occur within the next 1,000 yr. The steady-state, volume-predictable relationship suggests that 5–6 km 3 of lava will be erupted in the next eruptive period.

Idaho↗

USGS2023

Development and application of a qPCR-based genotyping assay for Ophidiomyces ophidiicola to investigate the epidemiology of ophidiomycosis

Ophidiomycosis (snake fungal disease) is an infectious disease caused by the fungus Ophidiomyces ophidiicola to which all snake species appear to be susceptible. Significant variation has been observed in clinical presentation, progression of disease, and response to treatment, which may be due to genetic variation in the causative agent. Recent phylogenetic analysis based on whole-genome sequencing identified that O . ophidiicola strains from the United States formed a clade distinct from European strains, and that multiple clonal lineages of the clade are present in the United States. The purpose of this study was to design a qPCR-based genotyping assay for O . ophidiicola , then apply that assay to swab-extracted DNA samples to investigate whether the multiple O . ophidiicola clades and clonal lineages in the United States have specific geographic, taxonomic, or temporal predilections. To this end, six full genome sequences of O . ophidiicola representing different clades and clonal lineages were aligned to identify genomic areas shared between subsets of the isolates. Eleven hydrolysis-based Taqman primer-probe sets were designed to amplify selected gene segments and produce unique amplification patterns for each isolate, each with a limit of detection of 10 or fewer copies of the target sequence and an amplification efficiency of 90–110%. The qPCR-based approach was validated using samples from strains known to belong to specific clades and applied to swab-extracted O . ophidiicola DNA samples from multiple snake species, states, and years. When compared to full-genome sequencing, the qPCR-based genotyping assay assigned 75% of samples to the same major clade (Cohen’s kappa = 0.360, 95% Confidence Interval = 0.154–0.567) with 67–77% sensitivity and 88–100% specificity, depending on clade/clonal lineage. Swab-extracted O . ophidiicola DNA samples from across the United States were assigned to six different clonal lineages, including four of the six established lineages and two newly defined groups, which likely represent recombinant strains of O . ophidiicola . Using multinomial logistic regression modeling to predict clade based on snake taxonomic group, state of origin, and year of collection, state was the most significant predictor of clonal lineage. Furthermore, clonal lineage was not associated with disease severity in the most intensely sampled species, the Lake Erie watersnake ( Nerodia sipedon insularum ). Overall, this assay represents a rapid, cost-effective genotyping method for O . ophidiicola that can be used to better understand the epidemiology of ophidiomycosis.

PLoS ONE↗

USGS2014

Movements and activity of juvenile Brown Treesnakes ( Boiga irregularis )

Understanding the spatial ecology and foraging strategy of invasive animals is essential for success in control or eradication. We studied movements and activity in juvenile Brown Treesnakes on Guam, as this population segment has proven particularly difficult to control. Distance between daytime refugia (from telemetry of 18 juveniles, 423-800 mm snout-vent length) ranged from 0-118 m ( n = 86), with a grand mean of 43 m. There were tendencies for shorter snake movements on nights directly following a full moon and on dry nights, but variation among snakes was of a larger magnitude and would greatly reduce chances to detect moon or rain effects unless corrected for. Snake activity was estimated from audio recordings of signals from “tipping” radio transmitters, analyzed for pulse period and amplitude. Activity was highest in the hours immediately after sunset, and gradually declined throughout the night before dropping abruptly in conjunction with sunrise. Snake activity was higher on rainy nights, and tended to be highest during waning moons and when the moon was below the horizon. We conclude that small Brown Treesnakes forage actively and appear to move far enough to regularly encounter the traps and bait used on Guam for control purposes, suggesting that alternative explanations are required for their low capture rates with these control tools.

Copeia↗

USGS2014

Invasive Brown Treesnake movements at road edges indicate road-crossing avoidance

Roads have significant impacts on the dispersal of wildlife. Although this poses a threat to the abundance and diversity of desirable flora and fauna, it also affords some opportunity for enhancing control of invasive species. Roads are the most common terrain features that may affect the rate of landscape-scale movements of invasive Brown Treesnakes (Boiga irregularis) throughout Guam. We radio tracked 45 free-ranging Brown Treesnakes in close proximity to two roads in Guam and recorded instances where daily relocations of snakes spanned roads. Then we reconstructed observed movement histories with randomized turning angles, which served as a useful null hypothesis for assessing the effect of roads or road edge habitat on Brown Treesnake movement patterns. Random walk simulations demonstrated that Brown Treesnakes crossed these roads at a rate far lower than would be expected if snake movement was random with respect to roads and road edge habitat. We discuss two alternative hypotheses for these results: 1) habitat gaps posed by roads physically or behaviorally restrict snake movement; or 2) road edges provide preferred foraging habitat from which snakes are reluctant to depart. Because roads often form the boundaries of jurisdictional and management units, the effects of roads on the movement of invasive Brown Treesnakes will influence the prospects for success of future landscape-level suppression efforts.

Journal of Herpetology↗

USGS1981

Hydrologic conditions at the Idaho National Engineering Laboratory, Idaho, emphasis: 1974-1978

The Idaho National Engineering Laboratory (INEL) site covers about 890 square miles of the eastern Snake River Plain and overlies the Snake River Plain aquifer. Low concentrations of aqueous chemical and radio-active wastes have been discharged to shallow ponds and to shallow or deep wells on the site since 1952. The regional water table ranges from about 200 feet to more than 1,000 feet below land surface within the INEL boundaries. The gradient of the water table averages about 4 feet per mile to the south-southwest. During the latest period of record, 1974 through 1978, the position of the water table has shown a net decline that ranges from 0.2 foot near the northern boundary of the INEL to more than 10 feet in the central and southern parts of the site. Recharge from surface water has been minimal or non-existent during the latter part of this period. A large body of perched ground water has formed in the basalt underlying the waste disposal ponds in the Test Reactor Area. This perched zone contains tritium, chromium-51, cobalt-60, strontium-90, and several nonradioactive ions. Tritium is the only mappable waste constituent in that portion of the Snake River Plain aquifer directly underlying this perched zone. Low concentrations of chemical and low-level radioactive wastes enter directly into the Snake River Plain aquifer through the Idaho Chemical Processing Plant (ICPP) disposal well. From 1974 through 1978, this 600-foot well was used to discharge a total of 1,861 million gallons of waste water which contained 1,697 curies of radioactivity, ninety-five percent of which was tritium. Tritium has been discharged to the well since 1953 and has formed the largest waste plume, about 28 square miles in area, in the regional aquifer, and minute concentrations have migrated downgradient a horizontal distance of 7.5 miles. Other waste plumes south of the ICPP contain sodium, chloride, nitrate, and the resultant specific conductance. These plumes have similar configurations, flow southward, and the contaminants are in general laterally dispersed in that portion of the aquifer underlying the INEL. Other waste plumes, containing strontium-90 and iodine-129, cover small areas near their points of discharge because strontium-90 is sorbed from solution as it moves through the aquifer and iodine-129 is discharged in very low quantities. Cesium-137 is also discharged through the well but it is strongly sorbed from solution and has never been detected in a sample of ground water at the INEL. Radionuclide plume size and concentrations therein are controlled by aquifer flow conditions, the quantity discharged, radioactive decay, sorption, dilution by dispersion, and perhaps other chemical reactions. Distributions of non-radoactive chemical wastes are subject to the same processes except for radioactive decay.

Idaho↗

USGS2005

Baseline water-quality characteristics of the Alaska Army National Guard Stewart River Training Area near Nome, Alaska

The Alaska Army National Guard Stewart River Training Area is approximately 23 miles north of Nome on the Seward Peninsula in northwest Alaska. The Stewart River Training Area encompasses much of the Stewart River Basin and a small part of the Snake River Basin. Hydrologic, water-quality, and physical-habitat data were collected at seven surface-water sites within the Stewart River Training Area during the summer runoff months (late-May to early-September) in 2004. Two of the sampling sites selected for this study were on the main stem Stewart River, one at the upstream boundary and one at the downstream boundary of the training area. Continuous hydrologic, precipitation, and water temperature data were collected at these two sites throughout the summer of 2004. Three pond sites, along the upper, middle, and lower reaches of the Stewart River within the training area, were each sampled twice during the summer of 2004 for analysis of water-quality constituents. Two tributaries to the Snake River Basin, Goldbottom Creek and North Fork Snake River, within the Stewart River Training Area boundary, also were sampled twice during the summer of 2004. Water-quality data collected from the Stewart River at the upstream and downstream study sites indicate similar constituent concentrations. Concentrations of most water-quality constituents collected during the summer of 2004 did not exceed standards for drinking water or recreational contact. Analysis of trace-element concentrations in bed sediment samples indicate the threshold effect concentration (below which no adverse effects on organisms is expected) was exceeded for arsenic, chromium, and nickel concentrations at all sample sites within the Stewart River Training Area and cadmium, copper, zinc, and lead concentrations were found to exceed the threshold effect concentration in varying degrees at the sample sites. The probable effect concentration (above which toxic effects on organisms is likely) was exceeded by arsenic concentrations at all sites except the lower pond site. Chromium and nickel concentrations exceeded the probable effect concentration at the upstream Stewart River site and at the North Fork Snake River site.

Scientific Investigations Report↗

USGS2025

Hydrogeologic framework of the Mountain Home area, southern Idaho

In the arid western Snake River Plain around the City of Mountain Home, Idaho, declining groundwater levels concern agricultural, municipal, and other water users who rely on groundwater for sustenance because surface-water resources are limited. The U.S. Geological Survey developed this hydrogeologic framework to provide an updated characterization of groundwater resources in the western Snake River Plain around the City of Mountain Home. The hydrogeologic framework comprises: (1) a conceptual description of hydrogeologic units, (2) a three-dimensional hydrogeologic model and borehole database, (3) a map of groundwater levels and change, and (4) a discussion of groundwater occurrence and movement within the study area. Hydrogeologic units were defined based on existing literature and the borehole database compiled for this study; the five hydrogeologic units are granite, rhyolite, basalt, fine-grained sediments, and coarse-grained sediments. Each unit can bear water, but the main regional aquifer in the study area occurs in the basalt and fine-grained sediment units with depth to water ranging from 150 to 765 feet. A perched groundwater zone near the City of Mountain Home is primarily hosted in basalt and used domestically with most depths to water ranging from 30 to 100 feet. Interflow zones, scoria, and vertical fractures create heterogeneity within the basalt hydrogeologic unit that exerts strong control on groundwater movement, creating horizontal perching conditions and zones of enhanced vertical conductivity that facilitate downward groundwater percolation. In the fine- and coarse-grained sediments and rhyolite units, inferred faults both impede and enhance groundwater movement. The borehole database was constructed by digitizing 540 well-driller reports and was used to build a three-dimensional hydrogeologic framework model which reasonably represents the spatial distribution of hydrogeologic units in the study area. Generally, fine-grained sediments underlie much of the study area, with basalt concentrated in the central and western study area and rhyolite and granite in the uplands to the north. Groundwater levels were measured in 180 wells in March and November 2023; these data were used to develop water-table contour maps and describe groundwater-level change over an irrigation season. Groundwater generally flows south-southwest to the Snake River and groundwater levels declined across most of the study area (from 0.03 to 22.01 feet) between spring and autumn 2023, which is consistent with long-term declines in the Cinder Cone Butte Critical Groundwater Area and Mountain Home Groundwater Management Area. Groundwater levels rose (0.6 to 15.44 feet) over the irrigation season in most wells in the perched groundwater zone near the City of Mountain Home and near the Snake River, indicating the importance of surface-water recharge to groundwater in areas where surface water irrigation occurs. In aggregate, this hydrogeologic framework provides an updated characterization of and new insights into groundwater resources in the study area to help inform water resources management.

Idaho↗

USGS2026

Groundwater budget for the Mountain Home area, southern Idaho, 2022–23

The U.S. Geological Survey, with funding from the Idaho Department of Water Resources, developed a groundwater budget for the Mountain Home area in southern Idaho for irrigation year 2023 (November 1, 2022–October 31, 2023). This study focused on the water balance across the Cinder Cone Butte Critical Groundwater Area (CGWA), Mountain Home Groundwater Management Area (GWMA), and the rest of the study area (RoSA), compiling data from various sources, including precipitation records, groundwater level measurements, metered groundwater pumpage data, surface water diversions and evapotranspiration (ET) estimates derived from remote sensing satellite imagery, and ground-based reference data. Key inflow components included recharge from applied surface water irrigation (which incorporates incidental recharge from irrigation practices and conveyance losses), estimated tributary streamflow, and estimated mountain block recharge. The key outflow components were groundwater pumpage for irrigation, municipal, industrial, and domestic uses, and ET. Recharge from applied irrigation and mountain block recharge were the largest inflows, and groundwater pumpage for irrigation was the largest outflow. The CGWA had a positive groundwater budget residual of 2,170 acre-feet (acre-ft), which contrasts with observed long-term groundwater level declines and historical trends of storage depletion. This positive residual is likely associated with unquantified outflows, including lateral groundwater flow out of the subregion, or other complexities, such as overestimated tributary contributions relative to the actual recharge for the 2023 water budget. The GWMA exhibited a positive residual of 56,563 acre-ft, primarily owing to recharge from applied surface water irrigation and areal recharge during a wetter-than-average year, which allowed irrigation entities to deliver more water from in-basin and out-of-basin reservoirs. The RoSA showed a large positive residual of 124,933 acre-ft. The interpretation of these positive residuals must account for significant uncertainties, including estimations of areal recharge, tributary streamflow (particularly losses and diversions), ET, the volume of surface water loss to the Snake River, lateral groundwater flows between subregions and across study area boundaries, and the unquantified groundwater discharge to the Snake River. These uncertainties, in combination with the complex hydrogeologic controls on water movement and limitations of remotely sensed data, directly affect the accuracy of water availability assessments. Future data collection efforts would help reduce these uncertainties and support water resource management decisions in the Mountain Home area. Key efforts could include installing additional streamflow gaging stations (particularly to quantify tributary losses and gains and surface water losses to the Snake River), improving groundwater pumpage metering, and validating remotely sensed ET data with ground-based measurements. Furthermore, to better quantify unrepresented or highly uncertain fluxes, focused investigations on groundwater discharge to the Snake River, lateral groundwater flows between subregions and across study area boundaries, and a more robust determination of the actual influence and volume of mountain block recharge would help refine future water availability assessments for the Mountain Home area.

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