Publications
Changes in sand storage in the Colorado River in Grand Canyon National Park from July 2017 through June 2020
Between July 2017 and June 2020, the Colorado River in Grand Canyon National Park experienced significant fluctuations in sand storage. Notably, Marble Canyon saw a decrease in sand mass during sediment years 2018 and 2020, coinciding with below-average Paria River sand inputs. Conversely, Grand Canyon exhibited indeterminate sand mass balance in 2020 but accumulated sand in 2019, a period marked by high sand contributions from both the Paria and Little Colorado Rivers alongside reduced Glen Canyon Dam discharge. The study utilized gaging stations to measure sand transport, enabling calculations of sand storage changes across six river segments. These findings underscore the dynamic relationship between tributary sand inputs, dam operations, and sediment dynamics in the Grand Canyon ecosystem.
Historical and projected climate change for Grand Canyon National Park and surrounding areas
Grand Canyon National Park has experienced significant warming since 1895, with temperatures rising at nearly twice the historical rate (6.31°F/century) from 1970 to 2020. This accelerated warming, observed across all elevations and seasons, is linked to anthropogenic climate change and has triggered cascading ecological disruptions, including reduced soil moisture, altered Colorado River flow, increased wildfire activity, shifts in vegetation zones, and declines in bird and pollinator species. Projections for mid- to late-century suggest continued warming, more extreme precipitation events, earlier runoff, and heightened drought risk, with varying scenarios for winter precipitation, annual rainfall, and fire conditions. These changes pose threats to the park's physical, ecological, and cultural resources, including increased erosion, invasive species expansion, and stress on native ecosystems. The study aims to inform adaptive management strategies by providing a range of plausible climate futures to guide proactive conservation efforts.
Anthropogenic influence on groundwater geochemistry in Horn Creek Watershed near the Orphan Mine in Grand Canyon National Park, Arizona, USA
Groundwater near the Orphan Mine in Grand Canyon National Park shows significant uranium concentration reductions, suggesting interaction with mineralized breccia pipe deposits. Uranium levels drop by an order of magnitude from bedrock to alluvial material, supported by low sulfur and uranium isotopic ratios. Per- and polyfluoroalkyl substances were detected at low concentrations, hinting at possible mining-related contamination. PHREEQC modeling indicates mixing of uranium-rich groundwater with other sources, including modern water influenced by Orphan Mine workings, as evidenced by elevated tritium levels. This study provides evidence of anthropogenic influence on groundwater geochemistry in the Horn Creek Watershed.
Comparison of in-person and virtual Grand Canyon undergraduate field trip learning outcomes
High-quality virtual field trips (iVFTs) can lead to greater learning gains than traditional in-person field trips (ipFTs), according to a study comparing undergraduate geoscience education experiences at Grand Canyon National Park. The research, which employed mixed-methods assessment of cognitive and affective outcomes, found that students engaging with an iVFT—anchored by 360° spherical images and adaptive feedback—demonstrated significantly higher learning gains than those participating in a guided ipFT along the Trail of Time. While ipFT students exhibited greater pre-trip excitement, virtual experiences proved equally or more effective for content mastery, suggesting their potential to expand access to high-impact geoscience education without compromising quality.
Deep-karst aquifer spring-flow trends in a water-limited system, Grand Canyon National Park, USA
A multi-year analysis of five springs in Grand Canyon National Park reveals no significant differences in snowmelt response timing or recession coefficients, indicating consistent flow regimes across a 50 km horizontal and 1,000 m vertical distance within the Redwall-Muav aquifer system. However, mean water volumes during snowmelt and annual discharges vary significantly among the springs, with Tapeats Spring showing more stable baseflow between recessions. Linear regression analyses detected no annual trends in most aquifer characteristics, except for the aforementioned stability at Tapeats Spring. Water budgets for Roaring Springs suggest missing outflow components or inaccuracies in precipitation/evapotranspiration data, highlighting the need for refined modeling and dye trace studies to improve groundwater understanding. This research provides critical insights for managing water supply and forecasting climate change impacts on spring-dependent species.
Predicting climate-change induced heat-related illness risk in Grand Canyon National Park visitors
Climate change is significantly increasing the risk of heat-related illnesses (HRIs) among visitors to Grand Canyon National Park, with projections indicating a 29%-137% rise by 2100 compared to 2004-2009 levels. The study found that HRI incidence is strongly linked to maximum daily temperature and minimum relative humidity, particularly during shoulder season months when visitors are more susceptible due to physical exertion and lack of adaptation. Researchers developed a model using historical data on HRIs, visitation rates, and weather conditions, then applied future climate projections to assess potential risks. These findings highlight the urgent need for land management agencies to update risk mitigation strategies, such as enhancing search-and-rescue operations and public education, to address the growing threat of extreme heat in iconic public lands.
Utilizing anthropogenic compounds and geochemical tracers to identify preferential structurally controlled groundwater pathways influencing springs in Grand Canyon National Park, Arizona, USA
A groundbreaking study reveals that treated wastewater from Grand Canyon Village influences both Garden Springs and Monument Spring, challenging long-held assumptions about discharge locations. Using anthropogenic tracers—including pharmaceuticals, PFAS, and nitrate—the research identifies preferential groundwater pathways within the complex fault network of the Grand Canyon, distinguishing conduits from barriers to flow. Stable isotopic measurements further confirm the wastewater's contribution at Monument Spring, providing critical insights into subsurface hydrology. This approach offers a novel method for studying fracture flow and karst systems, with broader implications for water resource management in similar geological settings.
Outbreak of Acute Gastroenteritis Among Rafters and Backpackers in the Backcountry of Grand Canyon National Park, April–June 2022
A significant outbreak of acute gastroenteritis, primarily caused by norovirus, affected 222 backcountry visitors—including rafters and backpackers—in Grand Canyon National Park between April and June 2022. The highly transmissible nature of the virus, particularly in settings with close contact and limited hygiene access, was confirmed through testing of portable toilet specimens from nine rafting groups. Public health agencies recommended enhanced infection prevention measures, such as regular disinfection of water spigots, promotion of handwashing, and separation of ill individuals to mitigate future outbreaks. The study underscores the need for rapid illness reporting, adherence to IPC guidelines by commercial outfitters, and minimizing interactions among groups to prevent such incidents in protected backcountry environments.
Residents’ Perceptions toward Tourism Development: A Case Study from Grand Canyon National Park, USA
A significant gap exists between the desires of residents in gateway communities near Grand Canyon National Park for tourism development and the current state of affairs, highlighting the need for targeted management strategies to mitigate tourism impacts. The study identified five key drivers of local support for national park tourism: community participation, living environment, trust in tourism institutions, tourism benefits, and community satisfaction, while perceived tourism cost was not a significant factor. Researchers used importance–performance analysis (IPA) and structural equation modeling (SEM) to assess these factors across five gateway communities, providing insights that could guide sustainable tourism planning and policy-making.
Terrestrial lidar monitoring of the effects of Glen Canyon Dam operations on the geomorphic condition of archaeological sites in Grand Canyon National Park, 2010–2020
Between 2010 and 2020, 21 out of 30 monitored archaeological sites along the Colorado River in Grand Canyon National Park transitioned to a more degraded geomorphic condition due to Glen Canyon Dam operations. The study used high-resolution terrestrial lidar surveys to quantitatively assess changes in site morphology, focusing on 23 locations classified using established geomorphic frameworks. While controlled flood releases can mitigate erosion, most sites showed worsening degradation, providing critical benchmarks for cultural resource management and risk assessment. This research offers a methodologically robust foundation for future monitoring efforts in similar river valleys.
Comparison of Aerial Thermal Infrared Imagery and Helicopter Surveys of Bison (Bison bison) in Grand Canyon National Park, USA
Helicopter surveys outperform aerial thermal infrared (TIR) imagery for estimating bison populations in dense canopy cover areas, offering more accurate results at a fraction of the cost. A study comparing TIR and helicopter surveys on the Powell Plateau in Grand Canyon National Park found that TIR surveys detected fewer bison (101 to 127 individuals) and were 367% more expensive than helicopter surveys. The TIR estimate was also 18.8% lower than a larger dataset of helicopter detections, while the helicopter survey was only 9.3% lower. Despite limitations, this research suggests that current methods for bison abundance estimation in such environments favor helicopters due to their balance of accuracy and cost-effectiveness. Further investigation is needed to assess these techniques in more open landscapes.
Monitoring Tamarix Changes Using WorldView-2 Satellite Imagery in Grand Canyon National Park, Arizona
A significant decline in tamarisk canopy cover, amounting to 29.5% between 2009 and 2019, was detected in Grand Canyon National Park using high-resolution WorldView-2 satellite imagery. This study employed a Spectral Angle Mapper (SAM) supervised classification method with images from May and August 2019, achieving overall accuracies of 80.0% and 83.1%, respectively. Seasonal change detection revealed that 47.5% of healthy tamarisk detected in May had been defoliated by August within the study area. These findings suggest that the impacts of the introduced northern tamarisk beetle, a biocontrol agent for tamarisk, continue to accumulate despite its presence since 2012, highlighting the ongoing ecological changes in this UNESCO World Heritage Site.
Strandlines from large floods on the Colorado River in Grand Canyon National Park, Arizona
Seven distinct strandlines from large floods on the Colorado River in Grand Canyon National Park, Arizona, provide critical data for understanding flood dynamics. These strandlines, marked by driftwood logs, woody debris, and trash, were deposited during floods with peak discharges ranging from 45,000 to 210,000 cubic feet per second (ft³/s) between 1884 and 2012. The study used multiple lines of evidence—including strandline vertical position, weathering of indicators, datable trash, and map-view location—to determine the year of each flood event. Stage-discharge relations developed from these strandlines revealed that river width significantly influences stage changes, with narrower bedrock-dominated reaches experiencing greater stage variability than wider alluvial reaches. This comprehensive dataset validates model-predicted flood stages along the Colorado River, offering insights into historical flood events and improving future modeling accuracy.
Telling time at Grand Canyon National Park: 2020 update
Grand Canyon National Park's geological record, spanning billions of years, reveals distinct rock formations with precisely dated ages, updating previous stratigraphic nomenclature and numeric age determinations. The study identifies three primary rock sets: the Vishnu Basement Rocks (1,840–1,375 million years ago), the Grand Canyon Supergroup (729–1,255 million years ago), and the Layered Paleozoic Rocks (270–530 million years ago). These sets are separated by unconformities, including the Great Unconformity, which represents significant erosion periods. The research provides numeric ages for all groups and formations, incorporating recent scientific advancements to offer a comprehensive reference for geologic history.
Ecosystem management applications of resource objective wildfires in forests of the Grand Canyon National Park, USA
A study on the long-term effects of 'resource objective' (RO) wildfires in Grand Canyon National Park revealed that these fires were broadly successful in maintaining or creating open and heterogeneous forest conditions, promoting fire- and drought-tolerant species like ponderosa pine. Over 12 years, tree density rebounded to near pre-fire levels despite initial high mortality of smaller trees (46–68%). However, reductions in basal area and canopy cover, particularly in mixed-conifer and spruce-fir sites, raised concerns about the resilience of larger, older trees under future climate warming. The research involved remeasuring monitoring plots more than a decade after RO fires, providing critical insights into their effectiveness across diverse forest types.
Estimating the contribution of tributary sand inputs to controlled flood deposits for sandbar restoration using elemental tracers, Colorado River, Grand Canyon National Park, Arizona
Controlled floods in the Grand Canyon National Park effectively redistribute tributary-derived sediment, with 69% to 84% of flood deposits originating from the Paria River during the 2013 and 2014 releases. This finding suggests that sandbar restoration through dam-release floods remains viable if Paria River sand inputs are sustained. Researchers used multivariate mixing analysis of seven elemental tracers (Fe, Ca, K, Ti, Rb, Sr, Zr) in sediment samples to quantify tributary contributions. Bayesian modeling revealed substantial variation among sites but confirmed the predominance of Paria River-derived material under decreasing storage conditions since 1963. The study highlights the importance of maintaining sand inputs for long-term ecosystem management.
Isotopic and Geochemical Tracers of Groundwater Flow in the Shivwits Plateau, Grand Canyon National Park
A novel approach using isotopic and geochemical tracers has successfully characterized groundwater flow systems in the Shivwits Plateau, Grand Canyon National Park. The study identified four distinct groundwater groups based on carbon isotopes (δ13C of dissolved organic and inorganic carbon) and fluorescent dissolved organic matter (fDOM), revealing complex hydrogeological processes including epikarst flow, gypsiferous bed influence, canyon slope runoff, and deep mixing in the Redwall Limestone. These findings demonstrate that ambient geochemical tracers can provide a simple yet effective conceptual model for mixed-lithology aquifers, though higher-resolution data are needed to fully assess climate change impacts on groundwater resources.
Spring flow in a portion of Grand Canyon National Park, Arizona
Groundwater flow in four side canyons of Grand Canyon National Park—Hermit, Monument, Salt, and Horn Creeks—is structurally controlled by two major faults: the Hermit Fault near Hermit Creek and the Bright Angel Fault east of Horn Creek. These northeast-trending faults act as hydrologic collector structures, channeling water downward from the south rim through impermeable strata. The study found a dual groundwater system feeding the springs, with flow paths influenced by fracture zones. Lag times between precipitation on the rim and spring discharge (less than one month for Hermit Creek, 1–2 months for others) and water chemistry indicate distinct flow paths. This interconnected, fault-dominated system dominates the hydrology of the study area.
Water Temperature Controls for Regulated Canyon‐Bound Rivers
A study on the Colorado River within Grand Canyon National Park reveals that water temperature dynamics are primarily controlled by shortwave radiation and hydropeaking flow conditions, with significant variability due to topographic shading. The research adapted a dynamic river routing and temperature model to simulate temperatures over 18 years, achieving high accuracy (RMSE of 0.93°C). Findings indicate that reservoir release temperatures dominate upstream thermal regimes, while downstream influences shift toward discharge, shortwave radiation, and air temperature. This underscores the critical role of spatial and temporal shading patterns in predicting water temperatures in canyon-bound rivers.
Exertional Heat-Related Illnesses at the Grand Canyon National Park, 2004–2009
Heat-related illnesses (HRI) pose a significant public health risk to visitors of the Grand Canyon National Park, with nearly 500 nonfatal and six fatal cases reported between 2004 and 2009. The study, analyzing Ranger Emergency Medical Services data, found that 84% of cases involved U.S. residents, primarily hikers aged 43 years on average, with a notable prevalence of cardiovascular conditions (18%). Clinical assessments revealed dehydration (25%), heat exhaustion (23%), and suspected hyponatremia (19%), while 40% required helicopter evacuations. HRI rates peaked in May, underscoring the urgency for targeted prevention efforts, particularly during high-visitation periods.
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