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Research about Grand Canyon

Source-linked reports with geographic coverage including Grand Canyon.

At least 19 recordsLinked to original sources
USGS2026

Resurvey of the Marble Canyon and Bridge Canyon dam sites in Grand Canyon National Park—Changes in sediment storage and evidence supporting the occurrence of bedrock incision through the mid-20th century

The Bureau of Reclamation developed an extensive plan for a network of dams, water tunnels, and hydropower plants in and around Grand Canyon, Arizona, in the 1940s through 1960s. The two largest of these planned dams were the Marble Canyon and Bridge Canyon Dams on the Colorado River. Though these dams were ultimately never built, Reclamation conducted extensive topographic, bathymetric, and subsurface exploration work at the sites proposed for these dams in the 1940s and 1950s. Resurveys of these dam sites were conducted between 1998 and 2021 to determine the changes in sediment storage at these dam sites caused by the upstream construction and operation of Glen Canyon Dam and by the recession of Lake Mead, the reservoir impounded by Hoover Dam. The resurveys of the Marble Canyon dam sites indicate that the post-1950s changes in sediment storage at these dam sites are broadly consistent with flux-based estimates of voluminous sand erosion from Marble Canyon since the 1963 closure of Glen Canyon Dam. These resurveys also suggest that the pre-dam longitudinal variation in sediment thickness over bedrock played a key role in determining the locations of the sand erosion induced by Glen Canyon Dam; more sand eroded from locations where more sand was present in the 1950s. The resurvey of the Bridge Canyon dam sites indicates that the Colorado River’s incision of the Lake Mead delta is regulated both by bed-sediment grain size and downstream hydraulic controls. Finally, analyses of bed-sediment thickness and sedimentological data at the dam sites, and observations of bed scour and gravel transport, suggest that sufficient bedrock was exposed to allow bedrock incision during commonly recurring pre-dam snowmelt floods that entrained small boulders into transport.

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USGS2025

Genetic structure of an expanding population of Humpback Chub in Grand Canyon

Objective Humpback Chub (HBC) Gila cypha in Grand Canyon declined in abundance and distribution over the latter part of the 20th century but have substantially increased in abundance and distribution over the past two decades. Although previous genetic work suggested that HBC in Grand Canyon belong to one genetic group, here we evaluate the genetic structure of HBC in Grand Canyon to determine whether relic populations in western Grand Canyon may have contributed unique variation to the recent population expansion or whether differences in behavior linked to migration in eastern Grand Canyon may promote assortative mating and heretofore unrecognized population structure. Methods Using fin clips collected from 167 individual HBC representing four sampling sites within Grand Canyon, we extracted DNA and developed data sets consisting of approximately 20,000 anonymous genomic loci. We quantified patterns of genetic diversity, and we accounted for outlier single-nucleotide polymorphisms to ensure that our interpretations of genetic patterns were not misled by adaptive processes and did not mask adaptively important genetic variation. Results Despite behavioral variation and the possibility that individuals with unique genetic variation survived in isolated warmwater sites within western Grand Canyon, HBC were not differentiated by sampling site or by differences in migratory behavior. Heterozygosity and nucleotide diversity were consistently high among sampling sites, and inbreeding coefficients were close to zero. Conclusions The HBC in Grand Canyon constitute a single genetic population. Our results do not preclude a genetic basis to migratory behavior, but our data suggest that this trait does not lead to assortative mating. Furthermore, while HBC may have survived in discontiguous warmwater refugia in western Grand Canyon during decades when the main stem was too cold for spawning, our data did not reveal any noticeable spatial variability in HBC genetics in the main stem after the recent HBC population expansion.

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USGS2024

Population and spatial dynamics of desert bighorn sheep in Grand Canyon during an outbreak of respiratory pneumonia

Introduction: Terrestrial species in riverine ecosystems face unique constraints leading to diverging patterns of population structure, connectivity, and disease dynamics. Desert bighorn sheep ( Ovis canadensis nelsoni ) in Grand Canyon National Park, a large native population in the southwestern USA, offer a unique opportunity to evaluate population patterns and processes in a remote riverine system with ongoing anthropogenic impacts. We integrated non-invasive, invasive, and citizen-science methods to address questions on abundance, distribution, disease status, genetic structure, and habitat fragmentation. Methods: We compiled bighorn sightings collected during river trips by park staff, commercial guides, and private citizens from 2000–2018 and captured bighorn in 2010–2016 to deploy GPS collars and test for disease. From 2011–2015, we non-invasively collected fecal samples and genotyped them at 9–16 microsatellite loci for individual identification and genetic structure. We used assignment tests to evaluate genetic structure and identify subpopulations, then estimated gene flow and recent migration to evaluate fragmentation. We used spatial capture-recapture to estimate annual population size, distribution, and trends after accounting for spatial variation in detection with a resource selection function model. Results and discussion: From 2010–2018, 3,176 sightings of bighorn were reported, with sightings of 56–145 bighorn annually on formal surveys. From 2012–2016, bighorn exhibiting signs of respiratory disease were observed along the river throughout the park. Of 25 captured individuals, 56% were infected by Mycoplasma ovipneumoniae , a key respiratory pathogen, and 81% were recently exposed. Pellet sampling for population estimation from 2011–2015 yielded 1,250 genotypes and 453 individuals. We detected 6 genetic clusters that exhibited mild to moderate genetic structure ( F ST 0.022–0.126). The river, distance, and likely topography restricted recent gene flow, but we detected cross-river movements in one section via genetic recaptures, no subpopulation appeared completely isolated, and genetic diversity was among the highest reported. Recolonization of one large stretch of currently empty habitat appears limited by the constrained topology of this system. Annual population estimates ranged 536–552 (95% CrI range 451–647), lamb:ewe ratios varied, and no significant population decline was detected. We provide a multi-method sampling framework useful for sampling other wildlife in remote riverine systems.

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USGS2024

Grand Canyon River Alerts: An emergency alert system designed for satellite texting devices

The Grand Canyon River Alert system is now live! The U.S. Geological Survey, Grand Canyon Monitoring and Research Center (GCMRC), in collaboration with Coconino County Emergency Management (CCEM), the National Weather Service (NWS) and the National Park Service (NPS), have developed and implemented a framework for sending emergency alerts to boaters and hikers in Grand Canyon. The system is specifically designed to send alerts to satellite texting devices, such those sold by Garmin and SPOT, and is a first of its kind in the nation. Alert messaging will be provided by NPS, NWS, or the Bureau of Reclamation depending on the nature of the incident. CCEM will disseminate alert messaging to devices subscribed to the Grand Canyon River Alerts list. Boating hazards, missing persons, critical dam related events, and extreme weather and flash flood hazards will be included in alert messaging.

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USGS2023

Arsenic in groundwater in the Grand Canyon region and an evaluation of potential pathways for arsenic contamination of groundwater from breccia pipe uranium mining

The Grand Canyon in northern Arizona is an international tourist destination, a home or sacred place to many Native Americans, and hosts some of the highest-grade uranium deposits in the United States. Although potential contamination of water resources by uranium from mining activities is a concern, other elements commonly associated with these uranium deposits may pose a greater risk to human populations in the area. This study presents an assessment of arsenic in groundwater in the Grand Canyon area. First, sampling results for arsenic are presented and areas with elevated arsenic concentrations are discussed. Potential pathways of groundwater contamination by arsenic from uranium mines are then discussed to elucidate situations and conditions under which elevated concentrations of arsenic might be expected to become mobilized from breccia-pipe uranium mining activities. Results for arsenic in groundwater in the study area were available for 652 samples collected from 230 sites. Arsenic concentrations in groundwater ranged from less than reporting limits in 60 samples to a maximum concentration of 875 μg/L at Pumpkin Spring. About 88% (202) of the sites sampled had a maximum arsenic concentration below the drinking water standard of 10 μg/L. Available data from near former or current breccia-pipe uranium mines in the area indicate limited evidence to-date of mining effects on elevated arsenic in groundwater, although slow groundwater flow paths in the region may result in extended times of decades or more for groundwater to reach discharge locations. Post-mining entry of groundwater into the shaft and underground mine workings, with subsequent transport of metal-enriched groundwater offsite, may be a potential pathway of groundwater arsenic contamination from mining, although concentrations would likely be attenuated by contact with sedimentary rock units and dilution with native groundwater along flow paths. Monitoring of perched groundwater at reclaimed mine sites post-reclamation could provide data on the effectiveness of clean-closure practices on protecting groundwater quality in the area.

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USGS2023

Vital rates of a burgeoning population of Humpback Chub in western Grand Canyon

The Colorado River ecosystem has experienced habitat alterations and non-native species invasions, and as a result, many of its native species have experienced extirpations, abundance declines, and range constrictions. Despite these pitfalls, Humpback Chub, Gila cypha , have persisted and, in the last 10-15 years, expanded their range to become abundant in western Grand Canyon, a river segment in which it had been rare for the prior three decades. Here we analyze a 6-year mark-recapture study from a fixed monitoring reach in western Grand Canyon and provide the first estimates of survival and growth (vital rates) for this relatively ‘new’ group of Humpback Chub. We compare vital rates in western Grand Canyon to two life history forms (residents and migrants, which represent fast and slow life history trajectories, respectively) from the more established Little Colorado River (LCR) aggregation in eastern Grand Canyon. Compared to LCR-migrants and LCR-residents, Humpback Chub in western Grand Canyon had intermediate values for apparent survival, growth, and asymptotic length. Relatively high survival of subadults coupled with fast growth allows for rapid population growth in western Grand Canyon. However, a large cohort in 2017 failed to lead to noticeable increases in adults. Seasonal survival patterns were distinct in all three groups, and apparent survival was lowest in western Grand Canyon during spring months. Adult Humpback Chub in western Grand Canyon were mobile and had a high probability of transience (i.e., just passing through the reach) and temporary emigration, demonstrating the need for future movement studies in western Grand Canyon to better distinguish emigration from survival. We discuss how observations are related to disparate temperature regimes experienced by the three groups, and if(how) the relationship between metabolism and temperature influences vital rates within the river network.

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USGS2022

Laboratory simulation of groundwater along uranium-mining-affected flow paths near the Grand Canyon, Arizona, USA

Mining of volumetrically small, but relatively enriched (average 0.6% U 3 O 8 ) breccia pipe uranium (BPU) deposits near the Grand Canyon, Arizona, USA has the potential to affect groundwater and springs in the area. Such deposits also contain base metal sulfides that can oxidize to generate acid mine drainage and release trace metals. In this study, sequential batch experiments were conducted to simulate the geochemistry of local shallow groundwater that contacts BPU ore and then moves downgradient through sedimentary strata. The experiments simulated shallow groundwater in a carbonate aquifer followed by contact with BPU ore. The experiments subsequently simulated contact with sedimentary rocks and changing oxygen availability. Concentrations of several contaminants of potential concern became substantially elevated in the waters exposed to BPU ore, including As, Co, Ni, U, and Zn, and to a lesser extent, Mo. Of these, Co, Mo, Ni, and U were minimally attenuated by downgradient processes, whereas Zn was partially attenuated. Sb and Tl concentrations were more moderately elevated but also generally minimally attenuated. Although the mixture of elements is particular to these BPU ore deposits, sulfide oxidation in the ore and carbonate buffering of pH by sedimentary rocks generates patterns of water chemistry common in acid mine drainage settings. Ultimately, downgradient concentrations of elements sourced from BPU ore will also be strongly influenced by non-geochemical factors such as the quantities of water contacting BPU materials, heterogeneity of materials along flow paths, and mixing with waters that have not contacted BPU materials.

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USGS2022

Fault-influenced incision in western Grand Canyon, Arizona U.S.A.

Preliminary interpretation of new and updated incision rates in western Grand Canyon shows the effects of Quaternary faulting, which dampens river incision rates in the footwalls and amplifies them in the hanging walls of normal faults. In the reach between Lava Falls and Diamond Creek in western Grand Canyon, about 178 to 225 river miles downstream from Lees Ferry, the river crosses the neotectonically active Hurricane and Toroweap faults. For this reach, we offer a preliminary analysis of 23 new and updated incision rates determined from new U-Th dating of travertine associated with perched river gravel and previously published 40Ar/39Ar ages on intracanyon basalt flows that overlie river gravel. Results reveal diminished incision rates downstream of both the Hurricane and Toroweap faults, indicating the presence and geometry of hanging-wall anticlines with wavelengths of about 10 km. Upstream of the faults, increased incision rates are interpreted to represent localized footwall uplifts and/or regional block uplift, which could contribute to the overall uplift of the Colorado Plateau.

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USGS2021

An assessment of uranium in groundwater in the Grand Canyon region

The Grand Canyon region in northern Arizona is a home or sacred place of origin for many Native Americans and is visited by over 6 million tourists each year. Most communities in the area depend upon groundwater for all water uses. Some of the highest-grade uranium ore in the United States also is found in the Grand Canyon region. A withdrawal of over 1 million acres of Federal land in the Grand Canyon region from new uranium mining activities for 20 years was instituted in 2012, owing in part to a lack of scientific data on potential effects from uranium mining on water resources in the area. The USGS collects groundwater chemistry samples in the Grand Canyon region to understand the current state of groundwater quality, to monitor for changes in groundwater quality that may be the result of mining activities, and to identify "hot spots" with elevated metal concentrations and investigate the causes. This manuscript presents results for the assessment of uranium in groundwater in the Grand Canyon region. Analytical results for uranium in groundwater in the Grand Canyon region were available for 573 samples collected from 180 spring sites and 26 wells from September 1, 1981 to October 7, 2020. Samples were collected from springs issuing from stratigraphic units above, within, and below the Permian strata that hosts uranium ore in breccia pipes in the area. Maximum uranium concentrations at groundwater sites in the region ranged from less than 1 µg/L at 23 sites (11%) to 100 µg/L or more at 4 sites (2%). Of the 206 groundwater sites sampled, 195 sites (95%) had maximum observed uranium concentrations less than the USEPA Maximum Contaminant Level of 30 µg/L and 177 sites (86%) had uranium concentrations less than the 15 µg/L Canadian benchmark for protection of aquatic life in freshwater. The establishment of baseline groundwater quality is an important first step in monitoring for change in water chemistry throughout mining lifecycles and beyond to ensure the health of these critical groundwater resources.

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USGS2021

A morphodynamic model to evaluate long-term sandbar rebuilding using controlled floods in the Grand Canyon

Controlled floods released from dams have become a common restoration strategy in river systems worldwide. Here we present a morphodynamic model of sandbar volume change for a subset of sandbars of the Colorado River in Grand Canyon National Park, where controlled floods are part of a management strategy focused on sandbar maintenance. We simulate sandbars as a triangular wedge, where deposition and erosion are modeled using physically based approaches that are driven by nearly continuous observations of flow and suspended sand concentration. We optimize an eddy exchange coefficient and erosion rate parameter by comparing model predictions to measured bar volumes. The model captures most of the variability in observed volume changes, and demonstrates the importance of flood frequency and sand concentration on average bar size. The model is easily implemented and adaptable, providing a means for predicting the future behavior of sandbars under a variety of streamflow and sediment supply scenarios.

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USGS2021

Terrestrial ecological risk analysis via dietary exposure at uranium mine sites in the Grand Canyon watershed (Arizona, USA)

The U.S. Department of the Interior recently included uranium (U) on a list of mineral commodities that are considered critical to economic and national security. The uses of U for commercial and residential energy production, defense applications, medical device technologies, and energy generation for space vehicles and satellites are known, but the environmental impacts of uranium extraction are not always well quantified. We conducted a screening-level ecological risk analysis based on exposure to mining-related elements via diets and incidental soil ingestion for terrestrial biota to provide context to chemical characterization and exposures at breccia pipe U mines in northern Arizona. Relative risks, calculated as hazard quotients (HQs), were generally low for all biological receptor models. Our models screened for risk to omnivores and insectivores (HQs>1) but not herbivores and carnivores. Uranium was not the driver of ecological risk; arsenic, cadmium, copper, and zinc were of concern for biota consuming ground-dwelling invertebrates. Invertebrate species composition should be considered when applying these models to other mining locations or future sampling at the breccia pipe mine sites. Dietary concentration thresholds (DCTs) were also calculated to understand food concentrations that may lead to ecological risk. The DCTs indicated that critical concentrations were not approached in our model scenarios, as evident in the very low HQs for most models. The DCTs may be used by natural resource and land managers as well as mine operators to screen or monitor for potential risk to terrestrial receptors as mine sites are developed and remediated in the future.

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USGS2021

Seasonal activity and diets of bats at uranium mines and adjacent areas near the Grand Canyon

Little information exists on the habitat use and feeding ecology of insectivorous bats in arid ecosystems, especially at and near uranium mines in northern Arizona, within the Grand Canyon watershed. In 2015–2016, we conducted mist-netting, nightly acoustic monitoring (>1 year), and diet analyses of bats, as well as insect sampling, at 2 uranium mines (Pinenut and Arizona 1) with water containment ponds. Because of physical barriers and limited general access to areas within the mine yard, mist-netting was limited to outside of the perimeter fence and away from the containment ponds. Mist-netting also occurred at 2 nearby sites that served as proxies to the mines. Bats captured directly at the mines included one pregnant Antrozous pallidus and 3 adult male Parastrellus hesperus . At the proxy sites, we captured 45 individuals identified as A. pallidus , Corynorhinus townsendii , Eptesicus fuscus , Euderma maculatum , Lasionycteris noctivagans , Myotis californicus , Myotis ciliolabrum , P. hesperus , and Tadarida brasiliensis . The nightly and seasonal presence of bats, as shown through acoustic recordings at each mine, coincided with the seasonal migratory and hibernation behaviors of the bat species. Statistical comparisons of acoustic recordings with precipitation data collected over one year show that seasonal monsoon rains generally had a negative effect on the nightly activity and presence of bats. Diets of P. hesperus from both mines were comprised mostly of coleopterans but also included smaller volumes of Hymenoptera, Hemiptera, Lepidoptera, Diptera, and Neuroptera. The diet of A. pallidus was comprised solely of Coleoptera. Diets of bat species from the proxy sites were characteristic of their known feeding ecology, which ranged from the consumption of soft-bodied insects (e.g., moths) by C. townsendii to the consumption of hard-bodied insects (e.g., beetles) by E. fuscus . Ultimately, the increased knowledge of the natural history of bats through multiple methods of data collection allows for a better understanding of complex arid ecosystems. It also provides resources needed for the management of habitat associated with alternative energy, such as uranium mining.

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USGS2020

Geochemical characterization of groundwater evolution south of Grand Canyon, Arizona (USA)

Better characterization of the geochemical evolution of groundwater south of Grand Canyon, Arizona (USA), is needed to understand natural conditions and assess potential effects from breccia-pipe uranium mining in the region. Geochemical signatures of groundwater at 28 sampling locations were evaluated; baseline concentrations for select trace elements (As, B, Ba, Cr, Li, Mo, Rb, Se, Sr, Th, Tl, U, V) were established, and anomalous chemistry characteristics were identified. Concentrations at some groundwater sites exceeded the USEPA drinking water standard for As of 10 μg/L (Red Canyon, Miners, JT, Havasu, and Warm Springs) and U of 30 μg/L (Salt Creek Spring). Four springs from the study area (Blue, Havasu, Fern, and Warm Springs) had unique chemistry, which may indicate a deep flow path or potential contribution of fluids from lower in the crust. Other springs in the study area were distinguished by major anion water type: sulfate, bicarbonate, and a mixture of the two. Water type distinctions were somewhat spatially segregated, with sulfate type present on the western side of the study area, bicarbonate type on the eastern side, and a mixture of the two interspersed between the endmember sites. Sulfate-type water from this study area had low strontium isotopic ratio (87Sr/86Sr) values. The location of spring discharge within single drainages of the Grand Canyon may influence chemistry, as groundwater discharging from bedrock was altered after flowing through alluvial material. Geochemical analysis of groundwater in Grand Canyon indicates the importance of continued monitoring and better understanding of short-term chemical fluctuations.

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USGS2020

A primer of fishery studies in Grand Canyon: The nonnative fish removal story

Globally, rivers have become the most altered of ecosystems, chiefly due to pollution, water withdrawals, and dams that have modified their former function, and led to large and unforeseen impacts, particularly for fish populations. Extensive research is directed at studying impacts of dams because they sever migration routes and change the physical template (flow, temperature, and sediment and organic loads), and by extension, influence vital rates of fish populations such as growth, survival, movement and recruitment. Prior to introduction of nonnative fishes and network of dams, the humpback chub (Gila cypha, chub) was broadly distributed throughout the Colorado River (mainstem). Since then, chub have declined over their entire historical range and are now restricted to six populations, a factor that led to it being Federally listed as an endangered species. The largest of these chub populations is found in Grand Canyon and is isolated from other upstream populations by Glen Canyon Dam (Dam). Over 90% of this population resides within the Little Colorado River (LCR) and mainstem in regions adjacent to the confluence. The remainder is broadly distributed in small aggregations throughout the ecosystem. Cold water temperatures from the Dam has largely impeded the growth and spawning of chub in the mainstem. Luckily, chub spawn and rear young successfully in the seasonally warm and saline waters of the LCR, though survival of some juveniles (< 200 mm total length) that disperse into the mainstem varies among years.

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