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USGS2017

Weather radar data correlate to hail-induced mortality in grassland birds

Small-bodied terrestrial animals such as songbirds (Order Passeriformes) are especially vulnerable to hail-induced mortality; yet, hail events are challenging to predict, and they often occur in locations where populations are not being studied. Focusing on nesting grassland songbirds, we demonstrate a novel approach to estimate hail-induced mortality. We quantify the relationship between the probability of nests destroyed by hail and measured Level-III Next Generation Radar (NEXRAD) data, including atmospheric base reflectivity, maximum estimated size of hail and maximum estimated azimuthal wind shear. On 22 June 2014, a hailstorm in northern Colorado destroyed 102 out of 203 known nests within our research site. Lark bunting ( Calamospiza melanocorys ) nests comprised most of the sample ( n = 186). Destroyed nests were more likely to be found in areas of higher storm intensity, and distributions of NEXRAD variables differed between failed and surviving nests. For 133 ground nests where nest-site vegetation was measured, we examined the ameliorative influence of woody vegetation, nest cover and vegetation density by comparing results for 13 different logistic regression models incorporating the independent and additive effects of weather and vegetation variables. The most parsimonious model used only the interactive effect of hail size and wind shear to predict the probability of nest survival, and the data provided no support for any of the models without this predictor. We conclude that vegetation structure may not mitigate mortality from severe hailstorms and that weather radar products can be used remotely to estimate potential for hail mortality of nesting grassland birds. These insights will improve the efficacy of grassland bird population models under predicted climate change scenarios.

Remote Sensing in Ecology and Conservation↗

USGS2025

Assessing risk for enhanced cyanobacteria, phytoplankton, and pathogens with changes in water level regime with potential application to Lake Powell and Lake Mead: A mixed methods literature review

Water levels in freshwater reservoirs worldwide are changing due to altered climate, management practices, and increasing human demand for water. In the desert southwestern USA, managers are considering significant changes to reservoir operation strategies and water management in response to consumptive use and ongoing drought. To inform reservoir management decision-making, we reviewed current peer-reviewed literature to identify the effects of decreasing or increasing water level on phytoplankton, cyanobacteria, Escherichia coli , and Naegleria spp. We identified 34 studies containing 42 individual waterbodies that investigated the effects of water level increases or decreases on phytoplankton or cyanobacteria. We found that water level decreases resulted in a higher likelihood of increased cyanobacteria, and that phytoplankton were more likely to decrease in response to water level increases. Most of the waterbodies included in the literature review were eutrophic or hypereutrophic, underscoring the need to explore the effects of water level fluctuations on oligotrophic systems. We only identified five studies on E. coli through our review, and no studies on Naegleria spp. We supplemented our review with regional white papers and case studies within the Colorado River Basin and the Rio Grande River Basin to highlight relevant research. Prior and ongoing research highlights the need to explore impacts of water level fluctuations on phytoplankton and cyanobacteria to guide future management decision-making.

Arizona, Utah, Nevada↗

USGS2018

Divergent effects of land-use, propagule pressure, and climate on woody riparian invasion

Landscape-scale analyses of biological invasion are needed to understand the relative importance of environmental drivers that vary at larger scales, such as climate, propagule pressure, resource availability, and human disturbance. One poorly understood landscape-scale question is, how does human land-use influence riparian plant invasion? To evaluate the relative importance of land-use, climate, propagule pressure, and water availability in riparian invasion, we examined tamarisk ( Tamarix ramosissima, T. chinensis , hybrids), Russian olive ( Elaeagnus angustifolia ), and Siberian elm ( Ulmus pumila ) occurrence, abundance, and dominance in 238 riparian sites in developed, cultivated, and undeveloped areas of four western USA river basins (281,946 km 2 ). Temperature and propagule pressure from individuals planted nearby largely drove invasive species occurrence, whereas factors likely to affect resource availability (e.g., land-use, precipitation, streamflow intermittency) were more important to abundance and dominance, supporting the argument that species distribution models based on occurrence alone may fail to identify conditions where invasive species have the greatest impact. The role of land-use varied among taxa: urban and suburban land-use increased Siberian elm occurrence, abundance, and dominance, and urban land-use increased Russian olive occurrence, whereas suburban land-use reduced tamarisk dominance. Surprisingly, Siberian elm, which has received scant prior scientific and management attention, occurred as or more frequently than tamarisk and Russian olive (except in undeveloped areas of the Colorado River headwaters) and had higher density and dominance than tamarisk and Russian olive in developed areas. More research is needed to understand the impacts of this largely unrecognized invader on riparian ecosystem services, particularly in urban and suburban areas.

Colorado, New Mexico↗

USGS2006

Flood pattern and weather determine Populus leaf litter breakdown and nitrogen dynamics on a cold desert floodplain

Patterns and processes involved in litter breakdown on desert river floodplains are not well understood. We used leafpacks containing Fremont cottonwood ( Populus deltoides subsp. wislizenii ) leaf litter to investigate the roles of weather and microclimate, flooding (immersion), and macroinvertebrates on litter organic matter (OM) and nitrogen (N) loss on a floodplain in a cool-temperate semi-arid environment (Yampa River, northwestern Colorado, USA). Total mass of N in fresh autumn litter fell by ∼20% over winter and spring, but in most cases there was no further N loss prior to termination of the study after 653 days exposure, including up to 20 days immersion during the spring flood pulse. Final OM mass was 10–40% of initial values. The pattern of OM and N losses suggested most N would be released outside the flood season, when retention within the floodplain would be likely. The exclusion of macroinvertebrates modestly reduced the rate of OM loss (by about 10%) but had no effect on N dynamics over nine months. Immersion in floodwater accelerated OM loss, but modest variation in litter quality did not affect the breakdown rate. These results are consistent with the concept that decomposition on desert floodplains progresses much as does litter processing in desert uplands, but with periodic bouts of processing typical of aquatic environments when litter is inundated by floodwaters. The strong dependence of litter breakdown rate on weather and floods means that climate change or river flow management can easily disrupt floodplain nutrient dynamics.

Journal of Arid Environments↗

USGS2021

Groundwater and surface-water data from the C-aquifer monitoring program, Northeastern Arizona, 2012–2019

The Coconino aquifer (C aquifer) is a regionally extensive multiple-aquifer system supplying water for municipal, agricultural, and industrial use in northeastern Arizona, northwestern New Mexico, and southeastern Utah. This report focuses on the C aquifer in the arid to semi-arid area between St. Johns, Ariz., and Flagstaff, Ariz., along the Interstate-40 corridor where an increase in groundwater withdrawals coupled with ongoing drought conditions increase the potential for substantial water-level decline within the aquifer. The U.S. Geological Survey (USGS) C-aquifer Monitoring Program began in 2005 to establish baseline groundwater and surface-water conditions and to quantify physical and water-chemistry responses to pumping stresses and climate. This report presents data previously reported in Brown and Macy (2012) that extend back as far as the 1950s, along with new data collected from the USGS C-aquifer Monitoring Program since that publication, from water years 2012 to 2019. Water levels in 17 wells are measured quarterly as part of the C-aquifer Monitoring Program, and five of those are continuously monitored at 15-minute intervals. Water levels in an additional 18 wells in the study area are measured periodically by the USGS or other agencies. The largest historical change in water level in the study area was a decrease of 81.20 feet in Lake Mary 1 Well near Flagstaff between 1962 and 2018. Changes in water levels were greatest around major pumping centers and in the eastern extent of the study area. Surface-water water-quality parameters (pH, water temperature, specific conductance, and dissolved oxygen) and streamflow discharge measurements were collected and analyzed along perennial, groundwater-fed reaches of Clear Creek, Chevelon Creek, and the Little Colorado River during nine baseflow investigations of varying extent between 2005 and 2019. Both Clear Creek and Chevelon Creek gain in flow from the beginning of their perennial reaches to their outflow into the Little Colorado River. The Little Colorado River has relatively steady streamflow in the reach between where the two tributaries enter the river. Chevelon Creek showed an increase in median specific conductance during all baseflow investigations of nearly 4,000 microsiemens per centimeter (μS/cm) from near the headwaters to the confluence with the Little Colorado River; Clear Creek also showed an increase in median specific conductance of almost 5,000 μS/cm from headwaters to confluence. Water temperature, dissolved oxygen, and pH do not show substantial trends along the reaches of Clear Creek, Chevelon Creek, or the Little Colorado River.

Arizona↗

USGS1987

Comparison of estimates of evapotranspiration and consumptive use in Palo Verde Valley, California

Estimates of evapotranspiration and consumptive use by vegetation in Palo Verde Valley, California, were compared for calendar years 1981 to 1984. Vegetation types were classified, and the areas covered by each type were computed from Landsat satellite digital-image analysis. Evapotranspiration was calculated by multiplying the area of each vegetation type by a corresponding water use rate adjusted for year-to-year variations in climate. The vegetation classification slightly underestimates the total vegetated area when compared to crop reports, because not all multiple cropping could be identified. The accuracy of evapotranspiration calculated from vegetation classification depends primarily on the correct classification of alfalfa and cotton because alfalfa and cotton have larger acreages and use more water/acre than the other crops in the valley. Consumptive use was calculated using a water budget for each of the 4 years. Estimates of evapotranspiration and consumptive use by vegetation, respectively, were: (1) 439,400 and 483,500 acre-ft in 1981, (2) 430,700 and 452,700 acre-ft in 1982, (3) 402,000 and 364,400 acre-ft in 1983, and (4) 406,700 and 373,800 acre-ft in 1984. Evapotranspiration estimates were lower than consumptive use estimates in 1981 and 1982 and higher in 1983 and 1984. Both estimates were lower in 1983 and 1984 than in 1981 and 1982. Yearly differences in estimates correspond most closely to significant changes in stage of the lower Colorado River caused by flood control releases in 1983 and 1984 and to changes in cropping practices. (Author 's abstract)

Water-Resources Investigations Report↗

USGS2019

An introduced breeding population of Chrysemys picta marginata in the Kaibab National Forest, northern Arizona

The painted turtle ( Chrysemys picta ) is widely distributed from coast to coast in North America with each of four subspecies generally occupying different regions. In the southwestern USA and northern Mexico, where C. p. bellii is the expected native race, populations are small and widelyscattered. Introduced populations of other painted turtle subspecies are reported from various locations in the USA. We discovered a small but dense introduced population of C. p. marginata on the Colorado Plateau in northern Arizona, a region with few, if any, turtles due to aridity and an elevated topography with little surface water. The turtles were in a remote pond constructed to provide cattle with water. Chrysemys p. marginata occur naturally east of the Mississippi River, over 2,000 km away. The nearest native population of C. p. bellii in Arizona is over 160 km away. We observed nesting females, juveniles, and the presence of shelled eggs in females via Xradiography confirming a self-sustaining population. The body sizes and nesting season we observed were consistent with data for those variables from native populations of the taxon. It is unknown exactly how the turtles came to be established in such a remote location, but it is unlikely that they will spread due to the scarcity of perennial water sources in the semi-arid region. Due to increasing drought frequency and duration in the region, small populations like this one, introduced into a novel environment, may be bellwethers for monitoring the effects of climate change.

Arizona↗

USGS2005

Grassland bird use of Conservation Reserve Program fields in the Great Plains

An enormous area in the Great Plains is currently enrolled in the Conservation Reserve Program (CRP): 19.5 million acres (nearly 8 million ha) in Montana, North Dakota, South Dakota, Wyoming, Nebraska, Colorado, Kansas, Oklahoma, and Texas. This change in land use from cropland to grassland since 1985 has markedly influenced grassland bird populations. Many, but certainly not all, grassland species do well in CRP fields. The responses by birds to the program differ not only by species but also by region, year, the vegetation composition in a field, and whether or not a field has been hayed or grazed. The large scale and extent of the program has allowed researchers to address important conservation questions, such as the effect of the size of habitat patch and the influence of landscape features on bird use. However, most studies on nongame bird use of CRP in or near the Great Plains have been short-lived; 83% lasted only 1-3 years. Further, attention to the topic seems to have waned in recent years; the number of active studies peaked in the early 1990s and dramatically declined after 1995. Because breeding-bird use of CRP fields varies dramatically in response both to vegetational succession and to climatic variation, long-term studies are important. What was learned about CRP in its early stages may no longer be applicable. Finally, although the CRP provisions of the Farm Bill have been beneficial to many grassland birds, it is critical that gains in grassland habitat produced by the program not be off set by losses of native prairie.

Wildlife Society Technical Review↗

USGS2019

Heterogeneity in hyporheic flow, pore water chemistry, and microbial community composition in an alpine streambed

The hyporheic zone, where surface water and groundwater mix, is an important microbial habitat where biogeochemical reactions influence water quality. We show that spatial variability in hyporheic flow in the East River near Crested Butte, Colorado, drives heterogeneity in streambed geochemical conditions and microbial community assemblages, but the diversity of assemblages remains nearly constant throughout the reach. In July 2018, we collected approximately 100 pore water samples at 20 cm depth and analyzed them for anions, cations, dissolved organic carbon, dissolved organic matter (DOM) quality, and basic water quality parameters. Vertical hydraulic head gradients were also measured to assess the potential for upward or downward flow, and heat tracing was used to quantify vertical flux rates at a subset of locations. We found that regions of the streambed that are more groundwater-dominated contain less dissolved oxygen, higher concentrations of reduced metals, and more microbially-processed, recalcitrant DOM, while more surface water-dominated locations contain higher dissolved oxygen concentrations and terrestrially-derived, labile DOM. 16S rRNA gene sequencing of extracted DNA revealed that microbial community composition varies with geochemical gradients related to hyporheic flow. These findings provide a better understanding of hyporheic controls on streambed biogeochemistry during the baseflow season, which is expected to lengthen with climate change in alpine watersheds due to earlier snowmelt onset and reduced snowpack.

Colorado↗

USGS2021

A case for multiscale habitat selection studies of small mammals

Habitat information for small mammals typically consists of anecdotal descriptions or infrequent analyses of habitat use, which often are reported erroneously as signifying habitat preference, requirements, or quality. Habitat preferences can be determined only by analysis of habitat selection, a behavioral process that results in the disproportionate use of one resource over other available resources and occurs in a hierarchical manner across different environmental scales. North American chipmunks ( Neotamias and Tamias ) are a prime example of the lack of studies on habitat selection for small mammal species. We used the Organ Mountains Colorado chipmunk ( N. quadrivittatus australis ) as a case study to determine whether previous descriptions of habitat in the literature were upheld in a multiscale habitat selection context. We tracked VHF radiocollared chipmunks and collected habitat information at used and available locations to analyze habitat selection at three scales: second order (i.e., home range), third order (i.e., within home range), and microhabitat scales. Mean home range was 2.55 ha ± 1.55 SD and did not differ between sexes. At the second and third order, N. q. australis avoided a coniferous forest land cover type and favored particular areas of arroyos (gullies) that were relatively steep-sided and greener and contained montane scrub land cover type. At the microhabitat scale, chipmunks selected areas that had greater woody plant diversity, rock ground cover, and ground cover of coarse woody debris. We concluded that habitat selection by N. q. australis fundamentally was different from descriptions of habitat in the literature that described N. quadrivittatus as primarily associated with coniferous forests. We suggest that arroyos, which are unique and rare on the landscape, function as climate refugia for these chipmunks because they create a cool, wet microclimate. Our findings demonstrate the importance of conducting multiscale habitat selection studies for small mammals to ensure that defensible and enduring habitat information is available to support appropriate conservation and management actions.

New Mexico↗

USGS1985

Sequentially and alternatively developed heights for two representative bench marks: near Palmdale, California and along the Bill Williams River, Arizona

This report consists chiefly of 41 tables that both describe and fully document the reconstructions of a series of alternately developed heights based on levelings leading into two representative bench marks in the southwestern United States. One of these marks, 3219, Vincent, California (fig. 1), lies within the area of the Pacific-North American plate boundary; the other, 22Q, Bill Williams River, Arizona (fig. 1), falls within what is believed to be a singularly stable section of southwestern Arizona. Because the levelings that produced these heights were characterized by especially disparate routes with respect to both terrain and climate, the resulting heights provide a test for the existence and magnitude of path-dependent error in geodetic leveling. These two marks were chosen both because of their relative stability with respect to adjacent marks and because their tectonic stability (or instability) can be inferred from the geologic record. Specifically, we can reasonably speculate that 3219 may have sustained measurably significant tectonic displacements during the 20th century, whereas 22Q probably has remained virtually invariant with respect to any fixed datum during the same period. Bench mark 3219 is a standard Geological Survey iron post stamped "3219" near the Southern Pacific Railroad station at Vincent (U.S. Geological Survey, 1898, p. 392); 22Q is a brass cap stamped "22Q (MWD)" set in a concrete post located in a gully immediately north of the Bill Williams River, Arizona (USC&GS Quad. 34114). 3219 was established by the Geological Survey no later than 1897 (Gannett and Baldwin, 1907, p. 365); 22Q was established by the Metropolitan Water District of southern California in advance of the 1931 control surveys along the projected route of the Colorado River Aqueduct.

Arizona, California↗

USGS1989

Significance of loessite in the Maroon Formation (Middle Pennsylvanian to Lower Permian), Eagle Basin, northwest Colorado

Quaternary loess deposits are widespread on the earth's surface, yet pre-Quaternary loess deposits have rarely been reported. The Maroon Formation (Middle Pennsylvanian to Lower Permian) of the Eagle Basin, northwest Colorado, includes a siltstone-dominated facies interpreted as loessite (lithified loess) along its downwind basin margin. The section of inferred loessite in the Maroon Formation is locally at least 490 m thick and consists in large part of structureless and nearly structureless beds of homogeneous sandy siltstone. Bed contacts are generally planar to undulatory and are either horizontal or are characterized by gentle relief. Loessite beds are separated by common claystone drapes and weakly developed paleosols, and by rare pond deposits, channel deposits, and eolian-ripple-laminated deposits. The loess interpretation is based on 1) the homogeneity and dominance of the sandy silt grain-size; 2) the relative lack of primary sedimentary structures; 3) the gentle character of most bedding contacts and the common mantling of irregular depositional topography; 4) the inferred paleogeographic setting; and 5) the absence of suitable alternative interpretations. The loessite grades laterally into mixed fluvial-eolian deposits of the Maroon Formation in the main part of Eagle Basin, which served as the loessite sediment source. Deposition of the Maroon Formation was probably strongly affected by cyclic climatic changes synchronous with fluctuations in late Paleozoic continental ice sheets. The paleogeography and paleoclimatology of the Maroon Formation depositional system are not unique, suggesting that there are probably many other ancient loessites that have gone unrecognized.

Journal of Sedimentary Petrology↗

USGS2008

Hydrologic droughts in Kansas— Are they becoming worse?

Multi-year droughts have been a recurrent feature of the climate and hydrology of Kansas since at least the 1930s. Streamflow records collected by the U.S. Geological Survey (USGS) indicate that water years 2000 to 2006 (October 1, 1999, through September 30, 2006) represent the sixth hydrologic drought during the past eight decades, and that corresponding streamflow levels in some parts of Kansas were lower than those during historic droughts of the 1930s and 1950s, even though the precipitation deficit was not as severe. Record-low streamflows in water year 2006 were recorded at USGS streamgages on the Republican, Smoky Hill, Solomon, Saline, upper Kansas, middle Arkansas, and Little Arkansas Rivers, as well as many tributary sites, and one tributary site of the Neosho River (fig. 1, table 1). Low streamflows during the hydrologic drought also resulted in record low levels at three Federal reservoirs in Kansas (fig. 1, table 2). An unprecedented number of administrative decisions were made by the Division of Water Resources, Kansas Department of Agriculture to curtail water diversions from rivers to maintain minimum desirable streamflows, and low flows on the lower Republican River in Kansas created concerns that Colorado and Nebraska were not complying with the terms of the 1943 Republican River Compact.

Kansas↗

USGS2016

Characterization of mean transit time at large springs in the Upper Colorado River Basin, USA: A tool for assessing groundwater discharge vulnerability

Environmental tracers (noble gases, tritium, industrial gases, stable isotopes, and radio-carbon) and hydrogeology were interpreted to determine groundwater transit-time distribution and calculate mean transit time (MTT) with lumped parameter modeling at 19 large springs distributed throughout the Upper Colorado River Basin (UCRB), USA. The predictive value of the MTT to evaluate the pattern and timing of groundwater response to hydraulic stress (i.e., vulnerability) is examined by a statistical analysis of MTT, historical spring discharge records, and the Palmer Hydrological Drought Index. MTTs of the springs range from 10 to 15,000 years and 90 % of the cumulative discharge-weighted travel-time distribution falls within the range of 2−10,000 years. Historical variability in discharge was assessed as the ratio of 10–90 % flow-exceedance ( R 10/90% ) and ranged from 2.8 to 1.1 for select springs with available discharge data. The lag-time (i.e., delay in discharge response to drought conditions) was determined by cross-correlation analysis and ranged from 0.5 to 6 years for the same select springs. Springs with shorter MTTs (<80 years) statistically correlate with larger discharge variations and faster responses to drought, indicating MTT can be used for estimating the relative magnitude and timing of groundwater response. Results indicate that groundwater discharge to streams in the UCRB will likely respond on the order of years to climate variation and increasing groundwater withdrawals.

Upper Colorado River Basin↗

USGS2000

Using new video mapping technology in landscape ecology

Biological and ecological monitoring continues to play an important role in the conservation of species, natural communities, and landscapes ( Spellerberg 1991 ). Although resource-monitoring programs have advanced knowledge about natural ecosystems, weaknesses persist in our ability to rapidly transfer landscape-scale information to the public. Ecologists continue to search for new technologies to address this problem and to communicate natural resource information quickly and effectively. New video mapping technology may provide much-needed help. Ecologists realize that only a small portion of large nature reserves can be monitored because of cost and logistical constraints. However, plant and animal populations are usually patchily distributed in subpopulations scattered throughout heterogeneous landscapes, and they are often associated with rare habitats. These subpopulations and rare habitats may respond differently to climate change, land use, and management practices such as grazing, fire suppression, prescribed burning, or invasion of exotic species ( Stohlgren et al. 1997b ). In many national parks, monuments, and wildlife reserves, a few long-term monitoring plots are used to infer the status and trends of natural resources in much larger areas. To make defensible inferences about populations, habitats, and landscapes, it is necessary to extrapolate from a few monitoring plots (local scale) to the larger, unsampled landscape with known levels of accuracy and precision. Recent technological developments have given population biologists and landscape ecologists a unique tool for bridging the data gap between small, intensively sampled monitoring plots and the greater landscape and for transferring this information quickly to resource managers and the public. In this article, we briefly describe this tool, a hand-held video mapping system linked to a geographic information system (GIS). We provide examples of its use in quantifying patterns of native and exotic plant species and cryptobiotic crusts in the new Grand Staircase–Escalante National Monument, Utah, and in surveying aspen clones and regeneration in Rocky Mountain National Park, Colorado.

BioScience↗

USGS2016

Wood decay in desert riverine environments

Floodplain forests and the woody debris they produce are major components of riverine ecosystems in many arid and semiarid regions (drylands). We monitored breakdown and nitrogen dynamics in wood and bark from a native riparian tree, Fremont cottonwood ( Populus deltoides subsp. wislizeni ), along four North American desert streams. We placed locally-obtained, fresh, coarse material [disks or cylinders (&sim;500–2000 cm 3 )] along two cold-desert and two warm-desert rivers in the Colorado River Basin. Material was placed in both floodplain and aquatic environments, and left in situ for up to 12 years. We tested the hypothesis that breakdown would be fastest in relatively warm and moist aerobic environments by comparing the time required for 50% loss of initial ash-free dry matter ( T 50 ) calculated using exponential decay models incorporating a lag term. In cold-desert sites (Green and Yampa rivers, Colorado), disks of wood with bark attached exposed for up to 12 years in locations rarely inundated lost mass at a slower rate ( T 50 = 34 yr) than in locations inundated during most spring floods ( T 50 = 12 yr). At the latter locations, bark alone loss mass at a rate initially similar to whole disks ( T 50 = 13 yr), but which subsequently slowed. In warm-desert sites monitored for 3 years, cylinders of wood with bark removed lost mass very slowly ( T 50 = 60 yr) at a location never inundated (Bill Williams River, Arizona), whereas decay rate varied among aquatic locations ( T 50 = 20 yr in Bill Williams River; T 50 = 3 yr in Las Vegas Wash, an effluent-dominated stream warmed by treated wastewater inflows). Invertebrates had a minor role in wood breakdown except at in-stream locations in Las Vegas Wash. The presence and form of change in nitrogen content during exposure varied among riverine environments. Our results suggest woody debris breakdown in desert riverine ecosystems is primarily a microbial process with rates determined by landscape position, local weather, and especially the regional climate through its effect on the flow regime. The increased warmth and aridity expected to accompany climate change in the North American southwest will likely retard the already slow wood decay process on naturally functioning desert river floodplains. Our results have implications for designing environmental flows to manage floodplain forest wood budgets, carbon storage, and nutrient cycling along regulated dryland rivers.

Arizona, Colorado, Nevada↗

USGS2026

Comparative assessment of STIC sensors, streamflow and rain gauges for quantifying river connectivity in intermittent systems

In intermittent stream systems, including those occurring in Texas, USA, the severity of low-flow conditions, duration of seasonal disconnection, and frequency of no-flow events have been amplified by drought. Documentation of these no-flow events is necessary to evaluate ecosystem health. However, many intermittent reaches remain un-gauged given that perennial river sec-tions are often prioritized for gauge placement. Our objectives were to 1) document stream flow using Stream Temperature, Intermittency, and Conductivity (STIC) loggers to determine the frequency and duration of no-flow events in intermittent tributaries of the Colorado River, Texas and 2) compare logger data to publicly available data from streamflow discharge and precipitation gauge networks to understand differences among these data types for drying event characterization. We use these comparisons to summarize benefits and limitations of the application of in-stream data loggers. STIC loggers were deployed at 19 sites, one in each pool and riffle habitat of a stream reach. STIC loggers recorded a measurement of relative conductance every six hours from June 2022 to March 2024, which was used to determine the presence or absence of flow connectivity in a reach. No-flow duration among intermittent reaches varied between 37 and 270 days across tributaries during an ongoing drought in the study area. Overall, logger data was more precise than discharge data for characterizing no-flow events or precipitation data when documenting presence of water in the stream channel due to runoff. Lack of discharge gauges in intermittent tributaries left large sections of stream reaches undocumented and resulted in mischaracterization of flow patterns. Drought severity across the tributaries did not follow longitudinal patterns that would be expected by the climatic precipitation gradient of the study area. More research is needed to determine if factors such as population size affect severity. Likewise, precipitation data did not correlate well with logger water presence data, lacking consideration for groundwater recharge, soil hydrophobicity, and surface compaction. This study shows that to monitor no-flow events, detailed spatial datasets are necessary and that STIC loggers are useful tools that provide data to fill spatial information gaps and facilitate more accurate flow characterization and water presence data in intermittent systems.

Texas↗

USGS2006

Vegetation greenness impacts on maximum and minimum temperatures in northeast Colorado

The impact of vegetation on the microclimate has not been adequately considered in the analysis of temperature forecasting and modelling. To fill part of this gap, the following study was undertaken. A daily 850–700 mb layer mean temperature, computed from the National Center for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis, and satellite-derived greenness values, as defined by NDVI (Normalised Difference Vegetation Index), were correlated with surface maximum and minimum temperatures at six sites in northeast Colorado for the years 1989–98. The NDVI values, representing landscape greenness, act as a proxy for latent heat partitioning via transpiration. These sites encompass a wide array of environments, from irrigated-urban to short-grass prairie. The explained variance (r 2 value) of surface maximum and minimum temperature by only the 850–700 mb layer mean temperature was subtracted from the corresponding explained variance by the 850–700 mb layer mean temperature and NDVI values. The subtraction shows that by including NDVI values in the analysis, the r 2 values, and thus the degree of explanation of the surface temperatures, increase by a mean of 6% for the maxima and 8% for the minima over the period March–October. At most sites, there is a seasonal dependence in the explained variance of the maximum temperatures because of the seasonal cycle of plant growth and senescence. Between individual sites, the highest increase in explained variance occurred at the site with the least amount of anthropogenic influence. This work suggests the vegetation state needs to be included as a factor in surface temperature forecasting, numerical modeling, and climate change assessments.

Meteorological Applications↗