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Research about Arizona

Source-linked reports with geographic coverage including Arizona.

At least 91 records · Page 5Linked to original sources
USGS2024

The feasibility of using national-scale datasets for classifying wetlands in Arizona with machine learning

The advent of machine learning techniques has led to a proliferation of landscape classification products. These approaches can fill gaps in wetland inventories across the United States (U.S.) provided that large reference datasets are available to develop accurate models. In this study, we tested the feasibility of expediting the classification process by sourcing requisite training and testing data from existing national-scale land cover maps instead of customized sample sets. We created a single map of water and wetland presence by intersecting water and wetland classes from available land cover products (National Wetland Inventory, Gap Analysis Project, National Land Cover Database and Dynamic Surface Water Extent) across the U.S. state of Arizona, which has fewer wetland-specific mapping products than other parts of the U.S. We derived classified samples for four wetland classes from the combined map: open water, herbaceous wetlands, wooded wetlands and non-wetland cover. In Google Earth Engine, we developed a random forest model that combined the training data with spatial predictor variables, including vegetation greenness indices, wetness indices, seasonal index variation, topographic parameters and vegetation height metrics. Results show that the final model separates the four classes with an overall accuracy of 86.2%. The accuracy suggests that existing datasets can be effectively used to compile machine learning training samples to map wetlands in arid landscapes in the U.S. These methods hold promise for the generation of wetland inventories at more frequent intervals, which could allow more nuanced investigations of wetland change over time in response to anthropogenic and climatic drivers.

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USGS2024

Landscape-scale modeling to forecast fluvial-aeolian sediment connectivity in river valleys

Sedimentary landforms on Earth and other planetary bodies are built through scour, transport, and deposition of sediment. Sediment connectivity refers to the hypothesis that pathways of sediment transport do not occur in isolation, but rather are mechanistically linked. In dryland river systems, one such example of sediment connectivity is the transport of fluvially deposited sediment by wind. However, predictive tools that can forecast fluvial-aeolian sediment connectivity at meaningful scales are rare. Here we develop a suite of models for quantifying the availability of river-sourced sediment for aeolian transport as a function of river flow, wind regime, and land cover across 168 km of the Colorado River in Grand Canyon, USA. We compare and validate these models using topographic changes observed over 10 years in a coupled river sandbar-aeolian dunefield setting. The models provide a path forward for directly linking fluvial hydrology with the management and understanding of aeolian landscapes.

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USGS2024

A literature review and hypsometric analysis to support decisions on trout management flows on the Colorado River downstream from Glen Canyon Dam

Executive Summary Fish stranding has been studied in select rivers worldwide, often with the purpose of determining how to mitigate adverse effects of dam operations on highly valued salmon and trout populations. However, where a reduction in trout population size is desired by resource managers, as is the case downstream of the Glen Canyon Dam on the Colorado River, flow manipulations termed trout management flows (TMFs) may be used to optimize fish stranding and mortality. To inform the design and implementation of potential future TMFs, we reviewed relevant literature to identify key factors that influence fish stranding. We found that key factors were highly interdependent and site-specific, but general trends suggest that down-ramping (decreasing flow) at rapid rates in daytime during the late spring to summer emergence period would lead to stranding of age-0 rainbow trout in shallow shoreline habitat. A hypsometric analysis was then used to predict stranding risk for age-0 rainbow trout in Glen Canyon for a range of TMFs, which incorporated existing bathymetric data and flow and habitat suitability models. Our results indicate that a TMF with a steady high flow ranging from 12,000 to 16,000 cubic feet per second (ft 3 /s) combined with a minimum flow ranging from 3,000 to 5,000 ft 3 /s may effectively strand age-0 fish while also minimizing risk to water storage in Lake Powell and other resources. This strategy implemented under normal hydropeaking operations was predicted to lead to a substantive stranding risk when paired with low flows of 5,000 ft 3 /s, and especially 3,000 ft 3 /s. However, there remains uncertainty associated with elements of implementing an effective TMF downstream from Glen Canyon Dam. The main uncertainties include (1) the down-ramp rate that maximizes stranding of age-0 trout, (2) the duration of drawdown to maximize stranding mortality while minimizing impact to downstream resources, (3) duration of high flows required for age-0 fish to colonize newly created shoreline habitat (this is only for certain TMF hydrographs), (4) number of repetitions of TMF cycles to minimize compensatory survival response, and (5) recruitment threshold of both rainbow and brown trout populations to trigger TMF implementation.

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USGS2024

Control of introduced American bullfrogs and support of Chiricahua leopard frog conservation in southeast Arizona

1. This report summaries field surveys conducted during July 2023 through April 2024 to control introduced American bullfrogs ( Lithobates [ Rana ] catesbeianus ; hereafter bullfrog) and support Chiricahua leopard frog ( Lithobates [ Rana ] chiricahuensis ) conservation in southeast Arizona. We conducted 394 field surveys across 141 sites in Chiricahua leopard frog Recovery Units 1 and 2 during this survey period. 2. During these surveys, we detected bullfrogs at 36 sites and removed a total of 452 bullfrogs. Bullfrog reproduction was only observed during this survey period at sites on private property where we did not have landowner permission to remove bullfrogs. We found bullfrogs and Chiricahua leopard frogs co-occurring at only a single site (Chulo Tank). Only a single bullfrog was present at this site, and it was removed. 3. Within the Cobre Ridge/Recovery Unit 1 region, we detected Chiricahua leopard frogs at 15 sites, with reproductive activity confirmed at two sites. We performed or assisted with Chiricahua leopard frog translocations at five sites. We detected Chiricahua leopard frog overwinter survival at two sites in this region although moribund and dead frogs were observed at one of these two sites. 4. We did not detect Chiricahua leopard frog within our Canelo Hills Buffer Zone or stock tanks along the foothills of the San Rafael Valley. We detected Chiricahua leopard frogs at four sites on the Appleton-Whittell Research Ranch with reproduction documented at two sites. We also removed two adult bullfrogs from a single site. 5. We detected Chiricahua leopard frogs at 17 sites on the Las Cienegas National Conservation Area (LCNCA). While Chiricahua leopard frog reproduction was not confirmed during July–November of 2023, as of 24 April 2025 we detected Chiricahua leopard frog reproduction at three sites. We did detect a moribund Chiricahua leopard frog at Lower Empire Gulch in March 2024. No bullfrogs were detected on the LCNCA and a single adult bullfrog was removed from one site in the Elgin Buffer Zone. 6. We began bullfrog removal efforts at a new eradication site along the Babocomari River on the Babacomari Ranch. This planned four-year eradication project will remove a significant non-urban bullfrog source population that threatens existing Chiricahua leopard frog metapopulations.

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USGS2024

Using integrated step selection to determine effects of predation risk on bison habitat selection and movement

Animal movement is a fundamental mechanism that shapes communities and ecosystems. Ungulates alter the ecosystems they inhabit and understanding their movements and distribution is critical for linking habitat with population dynamics. Predation risk has been shown to strongly influence ungulate movement patterns, such that ungulates may select habitat where predation risk is lower (refugia), adjust movement rates, temporal patterns, or selection of cover variables in areas with greater predation risk. We evaluated potential predation avoidance behavior in a population of plains bison inhabiting the north rim of Grand Canyon National Park (GRCA) and adjacent Kaibab National Forest (KNF). The KNF has year-round hunting managed by Arizona Game and Fish Department, whereas hunting is not allowed in GRCA. Human-maintained water sources on the KNF are particularly important resources for bison wherein they may be exposed to higher predation risk to access these resources. We used 2-h GPS locations for three years from 31 bison ( n = 9 males; n = 22 females), and integrative step selection analysis to test four hypotheses about the potential for bison to reduce their risk from human predation by avoiding areas of high predation risk; moving faster in areas with high predation risk; entering high-risk areas at night when risk is reduced; and entering high-risk areas in habitats that provide cover (coniferous forest). The highest performing model indicated bison movement was 1.3 times faster per 2-h step interval than in areas with no hunting across all vegetation classes (coniferous forest, shrub, quaking aspen, grass-forb meadow) and across all topography classes (valley, slope, ridge). Bison moved more slowly in grass-forb meadows than all other vegetation types, and in valleys relative to slopes and ridges. Several radio-collared individuals had no GPS locations in KNF for the duration of the study. Bison avoided predation risk using two strategies: moving faster while in the KNF, and fully avoiding high-risk areas by remaining within GRCA. Management that manipulates or reduces timing of hunting seasons may reduce perceived predation risk and encourage bison to distribute into the KNF and across a broader range of available habitat.

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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

Groundwater, surface-water, and water-chemistry data, Black Mesa area, northeastern Arizona—2019–2021

The Navajo (N) aquifer is an extensive aquifer and the primary source of groundwater in the 5,400-square-mile Black Mesa area in northeastern Arizona. Water availability is an important issue in the Black Mesa area because of the arid climate, past industrial water use, and continued water requirements for municipal use by a growing population. Precipitation in the area typically ranges from less than 6 to more than 16 inches per year, depending on location. The U.S. Geological Survey water-monitoring program in the Black Mesa area began in 1971 and provides information about the long-term effects of groundwater withdrawals from the N aquifer for industrial and municipal uses. This report presents the results of data collected as part of the monitoring program in the Black Mesa area from calendar years 2020–2021 and, additionally, uses streamflow statistics from November and December 2019. The monitoring program includes measurements of (1) groundwater withdrawals (pumping), (2) groundwater levels, (3) spring discharge, (4) surface-water discharge, and (5) groundwater chemistry. In calendar year 2020, total groundwater withdrawals were estimated to be 2,680 acre-feet (acre-ft), and, in 2021, total withdrawals were estimated to be 2,570 acre-ft. Total withdrawals during 2021 were about 65 percent less than total withdrawals in 2005 because the Peabody Western Coal Company discontinued its use of water to transport coal in a coal slurry pipeline after 2005 and ceased mining operations in 2019. Owing to Navajo Nation and Hopi Reservation access restrictions during the Coronavirus pandemic, water levels were not collected from municipal wells in 2020 or 2021. Water levels measured in 2021 from wells completed in the unconfined areas of the N aquifer within the Black Mesa area showed a decline in 7 of 13 wells when compared with water levels from the prestress period (prior to 1965). The changes in water levels across all 13 wells ranged from +8.4 feet (ft) to −42.4 ft, and the median change was −0.4 ft. Water levels also showed decline in 11 of 12 wells measured in the confined area of the aquifer when compared to the prestress period. The median change for the confined area of the aquifer was −25.9 ft, with changes across all 12 wells ranging from +17.3 ft to −133.7 ft. Spring flow was measured at four springs between 2020 and 2021. Flow fluctuated during the period of record for Burro Spring and Pasture Canyon Spring, but a decreasing trend was statistically significant (p<0.05) at Moenkopi School Spring and Unnamed Spring near Dennehotso, Arizona. Discharge at Burro Spring has remained relatively constant since it was first measured in the 1980s, and discharge at Pasture Canyon Spring has fluctuated for the period of record. Continuous records of surface-water discharge in the Black Mesa area were collected from streamflow-gaging stations at the following sites: Moenkopi Wash at Moenkopi 09401260 (1976–2021), Dinnebito Wash near Sand Springs 09401110 (1993–2020), Polacca Wash near Second Mesa 09400568 (1994–2020), and Pasture Canyon Springs 09401265 (2004–2021). Median winter flows (November through February) of each winter were used as an estimate of the amount of groundwater discharge at the above-named sites. For the period of record, the median winter flows have generally remained constant at Polacca Wash and Pasture Canyon Springs, whereas a decreasing trend was observed at Moenkopi Wash and Dinnebito Wash. In 2020 and 2021, water samples were collected from a total of four springs in the Black Mesa area and analyzed for selected chemical constituents. Results from the four springs were compared with previous analyses from the same springs. Dissolved solids, chloride, and sulfate concentrations increased at Moenkopi School Spring during the more than 30 years of record at that site. Concentrations of dissolved solids and sulfate at Pasture Canyon Spring have not varied significantly (p>0.05) since the early 1980s, and there is no increasing or decreasing trend in those data. However, concentrations of chloride from Pasture Canyon Spring show a diminishing trend. Concentrations of dissolved solids, chloride, and sulfate at Unnamed Spring near Dennehotso have varied for the period of record, but there is no statistical trend in the data. Concentrations of dissolved solids at Burro Spring have varied for the period of record, but there is no statistical trend in the data. However, concentrations of chloride and sulfate from Burro Spring show a trend towards lower concentrations.

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USGS2024

Bees of the Buenos Aires National Wildlife Refuge—A preliminary report on a bee survey in a vulnerable semi-desert grassland of the Sonoran Desert

Pollinators are vital to the continued existence and seed production of about 87.5 percent of all flowering plants (Ollerton and others, 2011). In the semi-desert grasslands of Buenos Aires National Wildlife Refuge, in the Sonoran Desert of the United States, flowering forbs provide seed vital to the food base of wildlife, including the 136 species of resident and migratory birds using the Refuge’s grasslands and, notably, the endangered Colinus virginianus ridgwayi (masked bobwhite quail) for which the Refuge was established. The Sonoran Desert is known for its high diversity of native bees, but these pollinators have not been extensively described at the Refuge. We conducted a survey of native bees at the Refuge from late May 2019 through early February 2020. Of all bees collected, we subsampled, curated, and identified over 3,300 bees representing 39 genera within four families (Andrenidae, Apidae, Halictidae, Megachilidae). For about 8 percent of the sampled bees, we further identified 36 species and several potentially new, undescribed species using either visual or deoxyribonucleic acid (DNA) barcoding methods. Sampling was done using bee bowls and blue-vane traps. Our initial results suggest the Refuge is species rich in native bees and supports diverse bee faunas across subtle differences in plant composition and location within the Refuge. Continued survey, inventory, and focused monitoring of the bee populations of the Refuge will be valuable in understanding the relationship of bee populations with the health and productivity of seed-bearing plants, effect of prescribed fire on bee fauna, the ongoing dynamics of bee-plant interactions, and how the bee pollinator community of the Refuge is responding to stressors, such as invasive species proliferation and changing climate conditions.

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USGS2024

Balancing natural resource use and extraction of uranium and other elements in the Grand Canyon region

The Grand Canyon region is an important natural, cultural, and archeological resource known worldwide. The region contains uranium resources that could be used to generate electricity. The U.S. Geological Survey (USGS), in cooperation with the National Park Service, Bureau of Land Management, and U.S. Department of Agriculture Forest Service, is conducting studies to answer questions about the environmental effects of mining uranium and other associated elements in the region.

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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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USGS2024

Estimating age and growth of Largemouth Bass in southwestern reservoirs using otoliths and scales

Age and growth data are frequently used to monitor and manage important North American sport fishes such as Largemouth Bass Micropterus salmoides . Continental and regional growth standards have been developed for this species to assess fish growth over time and across space. However, Largemouth Bass age and growth data are infrequently collected in Arizona and the reliability of age estimates derived from typical structures (e.g., scales, otoliths) in the Southwest is uncertain. Our objectives were to 1) compare precision and bias of age estimates from scales with those from otoliths and 2) estimate Largemouth Bass growth in several southwestern warmwater reservoirs by using otoliths. We collected Largemouth Bass from three Arizona reservoirs—Alamo, Peña Blanca, and Roosevelt—by boat electrofishing in spring 2021. We removed scales and sagittal otoliths from fish and then prepared and independently aged them three times. We compared differences in precision and bias between scales and otoliths using reader agreement percentages, confidence ratings, average coefficients of variation, and age-bias plots. We used age estimates from Largemouth Bass otoliths to calculate mean lengths-at-age at capture and relative growth indices based on published growth standards in each reservoir. Largemouth Bass scale age estimates were less precise, overestimated ages of younger fish, and underestimated age of older fish compared with those of otoliths. Growth was lower in Peña Blanca Lake than in the other two reservoirs according to mean length-at-age estimates, and relative growth indices suggested that Largemouth Bass growth in all three reservoirs was above average at younger ages, but less so at older ages. The results from this study add to a growing body of literature supporting the use of otoliths for estimating age and growth of Largemouth Bass.

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USGS2024

Monitoring aquifer-storage change from artificial recharge with repeat microgravity along Santa Cruz River, Tucson, Arizona, 2019–22

The City of Tucson water utility, Tucson Water, began releasing treated effluent into the Santa Cruz River channel near downtown Tucson in 2019. This recharge project—the Heritage Project—is intended to create a reach of consistent flow in the channel and recharge water to the aquifer. Tracking the dispersal of recharged water is important for management decisions because groundwater movement depends on spatially variable characteristics of the subsurface and cannot be fully predicted in advance. Groundwater-level measurements in wells are useful, but the relation between water storage and groundwater-level change depends on the unknown storage coefficient of the aquifer. To estimate storage changes caused by recharge of reclaimed effluent released into the channel for the Heritage Project, the U.S. Geological Survey (USGS) collected repeat microgravity data along the Santa Cruz River in Tucson, Arizona, from 2019 to 2022. This method augments groundwater-level monitoring by providing a direct quantitative measurement of changes in the quantity of water stored in the subsurface. Preliminary results of the monitoring through 2022 showed consistent storage increases only near and upstream from the Heritage Project outfall site. Initially high storage increases at some locations west of the channel and in line with Sentinel Peak reached roughly steady state in later times. North of Sentinel Peak, a storage increase from 2020 to 2021 was followed by a storage decrease from 2021 to 2022. Storage changes in the area north of Sentinel Peak appear to be related to the number of days flows in the channel were observed farther downstream from the outfall site (at USGS streamgage 09482500). This observation is likely due to the potential formation of a clogging layer that would allow surface water to disperse farther horizontally (downstream) before infiltrating. This phenomenon has been observed downstream of other recharged effluent projects and has been reduced by large flows in the channel, such as those occurring during large runoff events. There were no large or consistent storage increases near the Water Quality Assurance Revolving Fund (WQARF) sites included in this study area.

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USGS2024

Multiple stressors mediate the effects of warming on leaf decomposition in a large regulated river

Predicting how increasing temperatures interact with other global change drivers to influence the structure and dynamics of Earth's ecosystems is a primary challenge in ecology. Our study made use of multiple simultaneous “natural experiments” to examine how rapid warming, declining nutrients, invasive consumers, and riparian invasive species management interact to influence leaf decomposition in a large and regulated river. Specifically, we compared the breakdown of cottonwood ( Populus fremontii ), willow ( Salix exigua ), and saltcedar ( Tamarix sp.) leaf litter in 2022 to a previous experiment from 1998 that occurred under much cooler water temperatures, and had higher water phosphorus concentrations, low numbers of invasive New Zealand mudsnails ( Potamopyrgus antipodarum ), and unaltered litter chemistry from the herbivory of saltcedar leaf beetles ( Diorhabda carinulata ). We found that the effects of up to 10°C warmer temperatures on leaf decomposition were mediated by the establishment and management of invasive species and declining water nutrient concentrations arising from upstream reservoir lowering. Such interactions led to accelerated breakdown of saltcedar, but relatively minor effects of warming on the rate of cottonwood and willow decomposition. Additionally, our results demonstrate the potential for favorable invasive species management outcomes in the terrestrial environment to produce unintended responses in adjacent freshwater ecosystems. As temperatures continue to rise, it is critical that future studies consider how warming interacts with multiple stressors and environmental factors to influence processes such as decomposition in freshwater ecosystems.

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USGS2024

Water resources inventory of the Las Cienegas National Conservation Area, southeastern Arizona

The Las Cienegas National Conservation Area was established by the Las Cienegas National Conservation Area Establishment Act of 1999 (Public Law 106–538) and is managed by the Bureau of Land Management. Located in southeastern Arizona, the conservation area contains more than 45,000 acres of rolling grassland, wetlands, and woodlands surrounded by isolated mountain ranges that are part of the Madrean archipelago. This report describes the surface-water and groundwater resources within, and hydrologically connected to, the conservation area. Two primary aquifers have been identified within the Las Cienegas National Conservation Area: a Quaternary alluvial aquifer and a Miocene to Pliocene basin-fill aquifer. The Quaternary alluvial aquifer consists of Quaternary saturated stream alluvium along Cienega Creek and its major tributaries. This aquifer provides the water necessary for base flow in the perennial stream reaches that support aquatic life and for wetland and riparian habitat along the stream courses. Wells and piezometers completed in the Quaternary alluvial aquifer show both seasonal and daily water-level fluctuation patterns, as well as responses to flood flows in Cienega Creek. The basin-fill aquifer, in contrast, consists chiefly of Miocene to Pliocene alluvium within a sedimentary basin that is at least 4,800 feet deep. This aquifer is developed for anthropogenic uses more often than the Quaternary alluvial aquifer is developed. Generally, water levels in wells completed in the basin-fill aquifer have gradually declined a few feet between 2011, when measurements began, and 2022, when this report was written. Most water-chemistry samples available from the basin-fill aquifer had either a sodium-bicarbonate or calcium-bicarbonate water type. Previous research has shown that most recharge to the basin-fill aquifer likely comes from mountain-front and mountain-block recharge. Research further shows that this aquifer likely provides most of the recharge to the Quaternary alluvial aquifer. Because no production wells completed in bedrock exist within the conservation area, little is known about the hydraulic properties of the bedrock therein, but usable quantities of water can likely be produced from places where the bedrock has highly developed joint or fracture systems. During 2006–2021, the average combined length of measured perennial stream reaches within the main part of the Las Cienegas National Conservation Area was 6.35 miles. The average annual base flow of Cienega Creek during 2002–2021, estimated with the Standard Base-Flow Index method using data from a streamgage within the conservation area, was 0.62 cubic feet per second. Monthly mean streamflow measured at this streamgage for the same period ranged from a low of 0.29 cubic feet per second (in June) to a high of 9.8 cubic feet per second (in July). The July average is heavily influenced by a flood that occurred in July 2021; the median July streamflow for 2002–2021 is just 0.84 cubic feet per second. Periods with no daily flow are not uncommon at this gage during late May and June.

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USGS2024

Abundance estimates of Gunnison’s prairie dogs compared to the number of active burrows

Reliable estimates of prairie dog ( Cynomys spp.) population size and distribution are critical for assessing the status of prairie dogs and for selecting sites to reintroduce black-footed ferrets ( Mustela nigripes ). The density of active prairie dog burrows has commonly been used as an index of prairie dog abundance. Indices derived from active burrow counts were developed for black-tailed ( C. ludovicianus ) and white-tailed ( C. leucurus ) prairie dogs, but their efficacy has not been evaluated for all prairie dog species and studies affirming their validity with robust abundance estimators are few. We indexed or estimated the abundance of Gunnison's prairie dogs ( C. gunnisoni ) in the Aubrey Valley, Arizona, USA, in 2006 at 2 different time periods using 4 different methods—maximum above ground counts (MAGC), minimum number known alive (MNKA), capture-mark-recapture (CMR), and mark-resight—and compared these estimates to active burrow counts in 2005 and 2006. We found no positive relationship between active burrow counts and any abundance estimators. Mark-resight estimates of abundance were greater than the MNKA and were positively correlated with both the MNKA ( r 2 = 0.30) and CMR estimates ( r 2 = 0.49). Both CMR estimates and MAGC were typically below the MNKA and therefore biased low. Our results indicated that more rigorous estimation methods may be necessary to accurately estimate prairie dog abundance and assess habitat quality for ferret conservation.

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USGS2024

Forest fire, thinning, and flood in wildland-urban interface: UAV and lidar-based estimate of natural disaster impacts

Context Wildland-urban interface (WUI) areas are facing increased forest fire risks and extreme precipitation events due to climate change, which can lead to post-fire flood events. The city of Flagstaff in northern Arizona, USA experienced WUI forest thinning, fire, and record rainfall events, which collectively contributed to large floods and damages to the urban neighborhoods and city infrastructure. Objectives We demonstrate multi-temporal, high resolution image applications from an unoccupied aerial vehicle (UAV) and terrestrial lidar in estimating landscape disturbance impacts within the WUI. Changes in forest vegetation and bare ground cover in WUIs are particularly challenging to estimate with coarse-resolution satellite images due to fine-scale landscape processes and changes that often result in mixed pixels. Methods Using Sentinel-2 satellite images, we document forest fire impacts and burn severity. Using 2016 and 2021 UAV multispectral images and Structure-from-Motion data, we estimate post-thinning changes in forest canopy cover, patch sizes, canopy height distribution, and bare ground cover. Using repeat lidar data within a smaller area of the watershed, we quantify geomorphic effects in the WUI associated with the fire and subsequent flooding. Results We document that thinning significantly reduced forest canopy cover, patch size, tree density, and mean canopy height resulting in substantially reduced active crown fire risks in the future. However, the thinning equipment ignited a forest fire, which burned the WUI at varying severity at the top of the watershed that drains into the city. Moderate-high severity burns occurred within 3 km of downtown Flagstaff threatening the WUI neighborhoods and the city. The upstream burned area then experienced 100-year and 200–500-year rainfall events, which resulted in large runoff-driven floods and sedimentation in the city. Conclusion We demonstrate that UAV high resolution images and photogrammetry combined with terrestrial lidar data provide detailed and accurate estimates of forest thinning and post-fire flood impacts, which could not be estimated from coarser-resolution satellite images. Communities around the world may need to prepare their WUIs for catastrophic fires and increase capacity to manage sediment-laden stormwater since both fires and extreme weather events are projected to increase.

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USGS2024

Changes in sand storage in the Colorado River in Grand Canyon National Park from July 2017 through June 2020

Changes in the quantity of sand stored within river segments can affect aquatic and riparian habitat, archeological resources, and recreation. Since summer to fall of 2002, gaging stations on the Colorado River in Grand Canyon National Park and on its major tributaries and selected lesser tributaries have measured the mass of sand transported past each station, which allows for changes in the mass of sand stored between gaging stations to be calculated. Sand mass balances on six Colorado River segments are currently measured; the upstream two segments measure sand mass balance in Marble Canyon, the middle three segments measure sand mass balance within the majority of Grand Canyon, and the downstream-most segment—western Grand Canyon and the Lake Mead delta—measures the quantity of sand transported past Diamond Creek and ultimately deposited in Lake Mead. Between July 1, 2017, and June 30, 2020, the amount of sand stored in the Colorado River in Marble Canyon decreased, whereas the sand mass balance in Grand Canyon was indeterminate. Of the 3 years of study presented herein, sand was eroded from Marble Canyon during sediment year 2018 (July 1, 2017–June 30, 2018), a year with less than 40 percent of the 2003–2020 mean Paria River sand input, and sediment year 2020 (July 1, 2019–June 30, 2020), a year with negligible Paria River sand input. During sediment year 2018, when the Little Colorado River supplied negligible sand, sand was also eroded from Grand Canyon. The sand mass balance was indeterminate for Grand Canyon during sediment year 2020. During sediment year 2019 (July 1, 2018–June 30, 2019) sand accumulated in both Marble Canyon and Grand Canyon. This sediment year had sand inputs from both the Paria River and the Little Colorado River of more than 170 percent the 2003–2020 mean, coupled with below post-1964 mean discharge from Glen Canyon Dam.

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