Arizona River Research Articles

Warfare and big game hunting: flaked-stone projectile points along the middle Gila River in Arizona

Abstract

Research resource review: Requiem for the Santa Cruz. An Environmental History of an Arizona River

Research resource review: Requiem for the Santa Cruz. An Environmental History of an Arizona River

Spring migrant use of native and saltcedar-dominated riparian areas along the lower Colorado River in Arizona

Riparian systems in the western United States provide essential stopover habitat to en-route migrant birds, and there is concern that the invasion and dominance of saltcedar (Tamarix) in many areas may inhibit use by some species. However, evidence from recent studies is challenging the widely held belief that invasive plants universally reduce habitat quality. Moreover, where many studies have compared avian use of riparian habitats dominated by saltcedar with those comprised primarily of native trees, few have investigated how birds use shrub communities, which are becoming more prevalent in western riparian zones because of widespread hydrologic modifications. We compared spring migrant use of 125-m sections of riparian habitat dominated by five different habitat types in southwestern Arizona in 2006 and 2007. We found that migrant abundance, species richness, and community assemblages were all influenced by the composition of riparian vegetation. Habitats completely dominated by saltcedar supported fewer migrants and migrant species than any other habitat type, but the presence of small amounts of native vegetation as a part of the overall riparian plant community greatly bolstered habitat use. Habitats dominated by native shrubs tended to support the greatest total migrant abundance, total species richness, and abundance of many individual species. Our findings suggest that riparian areas dominated by saltcedar are avoided by many western migrant species and have relatively low value as stopover habitat. In places where this species is a predominant component of the riparian plant community, restoration of at least a portion of native riparian vegetation may be effective for encouraging use by stopover migrants.

Thirty Years of Hybridization between Toads along the Agua Fria River in Arizona: I. Evidence from Morphology and mtDNA

Abstract The Arizona Toad (Bufo [ = Anaxyrus] microscaphus) occupied the entire Agua Fria River drainage in central Arizona until relatively recently. By the 1980s, a close relative, Woodhouse's Toad (Bufo woodhousii), colonized the lower reaches of the Agua Fria and replaced B. microscaphus at some sites. We tested the hypothesis that habitat disturbance drives replacement of B. microscaphus by B. woodhousii, via hybridization, by examining shifts in the distribution of these toads following the expansion of the Waddell Dam on the lower Agua Fria River in the early 1990s. As of 2010, the high elevation headwaters of the Agua Fria River were still occupied by B. microscaphus, the lower reaches near the confluence with the Gila River were occupied by B. woodhousii, and along the middle reaches, hybridization between these two anurans occurred at the same three sites as documented in the early 1990s. Contrary to expectations, evidence of hybridization along middle reaches of the river is largely unchanged: ...

Requiem for the Santa Cruz: an environmental history of an Arizona river

Requiem for the Santa Cruz: an environmental history of an Arizona river

Anomalous droughts, not invasion, decrease persistence of native fishes in a desert river.

Changing climate extremes and invasion by non-native species are two of the most prominent threats to native faunas. Predicting the relationships between global change and native faunas requires a quantitative toolkit that effectively links the timing and magnitude of extreme events to variation in species abundances. Here, we examine how discharge anomalies--unexpected floods and droughts--determine covariation in abundance of native and non-native fish species in a highly variable desert river in Arizona. We quantified stochastic variation in discharge using Fourier analyses on >15,000 daily observations. We subsequently coupled maximum annual spectral anomalies with a 15-year time series of fish abundances (1994-2008), using Multivariate Autoregressive State-Space (MARSS) models. Abiotic drivers (discharge anomalies) were paramount in determining long-term fish abundances, whereas biotic drivers (species interactions) played only a secondary role. As predicted, anomalous droughts reduced the abundances of native species, while floods increased them. However, in contrast to previous studies, we observed that the non-native assemblage was surprisingly unresponsive to extreme events. Biological trait analyses showed that functional uniqueness was higher in native than in non-native fishes. We also found that discharge anomalies influenced diversity patterns at the meta-community level, with nestedness increasing after anomalous droughts due to the differential impairment of native species. Overall, our results advance the notion that discharge variation is key in determining community trajectories in the long term, predicting the persistence of native fauna even in the face of invasion. We suggest this variation, rather than biotic interactions, may commonly underlie covariation between native and non-native faunas, especially in highly variable environments. If droughts become increasingly severe due to climate change, and floods increasingly muted due to regulation, fish assemblages in desert rivers may become taxonomically and functionally impoverished and dominated by non-native taxa.

The Landfall and Inland Penetration of a Flood-Producing Atmospheric River in Arizona. Part II: Sensitivity of Modeled Precipitation to Terrain Height and Atmospheric River Orientation

AbstractThis manuscript documents numerical modeling experiments based on a January 2010 atmospheric river (AR) event that caused extreme precipitation in Arizona. The control experiment (CNTL), using the Weather Research and Forecasting (WRF) Model with 3-km grid spacing, agrees well with observations. Sensitivity experiments in which 1) model grid spacing decreases sequentially from 81 to 3 km and 2) upstream terrain is elevated are used to assess the sensitivity of interior precipitation amounts and horizontal water vapor fluxes to model grid resolution and height of Baja California terrain. The drying ratio, a measure of airmass drying after passage across terrain, increases with Baja’s terrain height and decreases with coarsened grid spacing. Subsequently, precipitation across Arizona decreases as the Baja terrain height increases, although it changes little with coarsened grid spacing. Northern Baja’s drying ratio is much larger than that of southern Baja. Thus, ARs with a southerly orientation, with water vapor transports that can pass south of the higher mountains of northern Baja and then cross the Gulf of California, can produce large precipitation amounts in Arizona. Further experiments are performed using a linear model (LM) of orographic precipitation for a central-Arizona-focused subdomain. The actual incidence angle of the AR (211°) is close to the optimum angle for large region-mean precipitation. Changes in region-mean precipitation amounts are small (~6%) owing to AR angle changes; however, much larger changes in basin-mean precipitation of up to 33% occur within the range of physically plausible AR angles tested. Larger LM precipitation sensitivity is seen with the Baja-terrain-modification experiments than with AR-angle modification.

Predicting the river's blue line for fish conservation.

River drying is increasing in frequency, duration, and extent in the United States, especially across the Sunbelt where drought has become the new norm (Fig. 1). Exceptional droughts and climate change are one cause of drying—surface water is scarcer and that trend is not changing (1⇓⇓–4). Increasing human appropriation of groundwater—especially during drought—is another cause (5, 6). River drying has clear implications for freshwater biodiversity, including mass mortality of commercially important fish if large reaches of a river dry completely (7). A much more subtle, but equally detrimental, impact of drying is habitat fragmentation, which can increase the risk of extinction from other causes (8, 9); however, data availability and a methodological void have left this critical issue unaddressed until now. In PNAS, Jaeger et al. (10) fill this void by integrating cutting edge and empirically grounded ecology with a tried-and-true surface water model that is in turn forced with forecasted and downscaled climate data. The authors use this intriguing model mashup to forecast network connectivity of flowing reaches in a desert river in Arizona at fine spatial scales. They then use this set of “blue lines” to forecast the persistence of the river's native fish populations. Their conclusions are dire: decreasing persistence of an endemic fauna. On the bright side, the mashup has real potential to be applied to address similar management problems in other basins. Fig. 1. ( Upper ) Mean (solid) and 95% CI (dashed) number of zero flow days for 23 stream gages across the US Sunbelt from the USGS National Water Information System (NWIS). Data cover a spatial extent that includes the states of Georgia, Florida, Kansas, Texas, New Mexico, and Arizona. ( Lower ) Mean (solid) and CI (dashed) number of days (per year) below the 40-y average (dotted black reference line) for 94 … [↵][1]1Email: john.l.sabo{at}asu.edu. [1]: #xref-corresp-1-1

Indirect effects of biocontrol of an invasive riparian plant (Tamarix) alters habitat and reduces herpetofauna abundance

The biological control agent (tamarisk leaf beetle, Diorhabda spp.) is actively being used to defoliate exotic saltcedar or tamarisk (Tamarix spp.) in riparian ecosystems in western USA. The Virgin River in Arizona and Nevada is a system where tamarisk leaf beetle populations are spreading. Saltcedar biocontrol, like other control methods, has the potential to affect non-target species. Because amphibians and reptiles respond to vegetation changes in habitat and forage in areas where beetles are active, herpetofauna are model taxa to investigate potential impacts of biocontrol defoliation. Our objectives related herpetofauna abundance to vegetation cover and indices (normalized difference vegetation index, NDVI; enhanced vegetation index, EVI) and timing of biocontrol defoliation. We captured herpetofauna and ground-dwelling arthropods in trap arrays and measured vegetation using remotely sensed images and on-the-ground measurements at 16–21 sites 2 years before (2009–2010) and 2 years following (2011–2012) biocontrol defoliation. Following defoliation, riparian stands (including stands mixed with native and exotic trees and stands of monotypic exotic saltcedar) had significantly lower NDVI and EVI values and fewer captures of marked lizards. Total captures of herpetofauna (toads, lizards, and snakes) were related to higher vegetation cover and sites with a lower proportion of saltcedar. Our results suggest that effects of biocontrol defoliation are likely to be site-specific and depend upon the proportion of native riparian trees established prior to biocontrol introduction and defoliation. The mechanisms by which habitat structure, microclimate, and ultimately vertebrate species are affected by exotic plant biocontrol riparian areas should be a focus of natural-resource managers.

Diel Cover use and Local Site Fidelity of a Large Southwestern Cyprinid, BonytailGila elegans, in a Lower Colorado River Backwater

Sonic transmitters were affixed to 10 large (40.4–51.4 cm TL) adult bonytail Gila elegans in 2003 from Cibola High Levee Pond, a small, isolated backwater adjacent to the lower Colorado River in Arizona and California, Point and paired directional observations showed that all marked adult bonytail occupied interstices of large riprap during daytime and used open water areas during darkness, presumably to feed. There were 2 spatial patterns of nighttime distribution by adult fish; 70% of fish exhibited mesohabitat site fidelity to a particular area of the pond, while others appeared to move about at random. Selection or design of bonytail management areas including grow-out and refuge sites should consider cover requirements for larger fish, as this may be a limiting factor if lack of cover subjects some individuals to higher predation risk.

Measurement Error in Fish Lengths: Evaluation and Management Implications

ABSTRACTA fundamental aspect of fisheries science is measuring body length. Humans are inherently prone to error despite systems and provisions made to reduce it. We evaluated length measurement error (herein, referred to as “error”) and digit preference from fish studies conducted on the Colorado River and Little Colorado River in Arizona. Empirical error estimates varied among fish species and generally increased with fish size. We identified a digit preference for numbers ending in zero and five, which was exacerbated with larger sizes. Error effects on growth estimates were largest for fish recaptured after a short time, and we suggest guarding against the error phenomenon by removing data from fish captured and recaptured within a minimum of 30 days. Human, situation, and specimen induced error factors are described. Fisheries professionals should be cognizant of error factors, especially in situations when high precision and accuracy are required and results have important management implications.

Framing Scenarios of Binational Water Policy with a Tool to Visualize, Quantify and Valuate Changes in Ecosystem Services

In the Santa Cruz Watershed, located on the Arizona-Sonora portion of the U.S.-Mexico border, an international wastewater treatment plant treats wastewater from cities on both sides of the border, before discharging it into the river in Arizona. These artificial flows often subsidize important perennial surface water ecosystems in the region. An explicit understanding of the benefits of maintaining instream flow for present and future generations requires the ability to assess and understand the important trade-offs implicit in water-resource management decisions. In this paper, we outline an approach for modeling and visualizing impacts of management decisions in terms of rare terrestrial and aquatic wildlife, vegetation, surface water, groundwater recharge, real-estate values and socio-environmental vulnerable communities. We identify and quantify ecosystem services and model the potential reduction in effluent discharge to the U.S. that is under scrutiny by binational water policy makers and of concern to stakeholders. Results of service provisioning are presented, and implications for policy makers and resource managers are discussed. This paper presents a robust ecosystem services assessment of multiple scenarios of watershed management as a means to discern eco-hydrological responses and consider their potential values for future generations living in the borderlands.

Floods, drought, and seed mass of riparian plant species

Plant communities in dryland riparian ecosystems are influenced by flood disturbance and water availability. As global climate change alters stream flow regimes, there is increasing need to understand which traits allow plant species to persist under increased stress and disturbance. Small seed mass is part of a strategy that adapts for disturbance, but the role of seed mass as an adaptation for drought is less well documented. For dryland riparian plant communities, we asked, does seed mass vary with water availability and flood frequency? We compared community seed mass between sites that vary in flow permanence (longitudinal water gradient) and between hydrogeomorphic surfaces within sites (lateral gradients of moisture and disturbance). Using data from four rivers in Arizona, we contrasted seed mass between plant groups. We found community seed mass to be greater at sites with ephemeral than perennial flow, and to increase laterally from wet, frequently-flooded channel edges to dry, less disturbed terraces. Seed mass varied by moisture group (smallest for hydroriparian species) and by disturbance group (smallest for disturbance species), and showed a trend for being greater in introduced species. We conclude that small seed mass is independently associated with wet and disturbed conditions in dryland riparian ecosystems.

The Landfall and Inland Penetration of a Flood-Producing Atmospheric River in Arizona. Part I: Observed Synoptic-Scale, Orographic, and Hydrometeorological Characteristics

AbstractAtmospheric rivers (ARs) are a dominant mechanism for generating intense wintertime precipitation along the U.S. West Coast. While studies over the past 10 years have explored the impact of ARs in, and west of, California’s Sierra Nevada and the Pacific Northwest’s Cascade Mountains, their influence on the weather across the intermountain west remains an open question. This study utilizes gridded atmospheric datasets, satellite imagery, rawinsonde soundings, a 449-MHz wind profiler and global positioning system (GPS) receiver, and operational hydrometeorological observing networks to explore the dynamics and inland impacts of a landfalling, flood-producing AR across Arizona in January 2010. Plan-view, cross-section, and back-trajectory analyses quantify the synoptic and mesoscale forcing that led to widespread precipitation across the state. The analyses show that a strong AR formed in the lower midlatitudes over the northeastern Pacific Ocean via frontogenetic processes and sea surface latent-heat fluxes but without tapping into the adjacent tropical water vapor reservoir to the south. The wind profiler, GPS, and rawinsonde observations document strong orographic forcing in a moist neutral environment within the AR that led to extreme, orographically enhanced precipitation. The AR was oriented nearly orthogonal to the Mogollon Rim, a major escarpment crossing much of central Arizona, and was positioned between the high mountain ranges of northern Mexico. High melting levels during the heaviest precipitation contributed to region-wide flooding, while the high-altitude snowpack increased substantially. The characteristics of the AR that impacted Arizona in January 2010, and the resulting heavy orographic precipitation, are comparable to those of landfalling ARs and their impacts along the west coasts of midlatitude continents.

Detrital zircons indicate no drainage link between southern California rivers and the Colorado Plateau from mid-Cretaceous through Pliocene

Central to debate about the age, origin, and evolution of Grand Canyon (southwestern United States) is the history of the Colorado River and its precursors. Reversal of dextral slip along the San Andreas fault system since the early Pliocene restores southern California to the downstream end of the Colorado River. If the Colorado River flowed to the Pacific Ocean prior to 6 Ma, then its sand would have the distinctive detrital-zircon age distributions of upper Paleozoic and Mesozoic strata of the Colorado Plateau, which contain 30%–46% 300–1100 Ma zircon originally transported from orogenic belts of southeastern Laurentia. In contrast, age distributions of 6662 detrital zircons from 167 Upper Cretaceous–Pliocene sandstone samples from southern California average 44%–88% Cretaceous, with only 0.4%–1.3% 300–1100 Ma grains, most of which can be attributed to local recycling from older deposits. No individual Upper Cretaceous to Pliocene sandstone sample from southern California contains >3% 300–1100 Ma zircon. Although Paleogene headwaters of southern California rivers extended into the eastern Mojave Desert, Sonoran Desert, and Mogollon Highlands, our results indicate that these headwaters did not extend as far as the Colorado Plateau. This conclusion conflicts with the hypothesis of a Paleogene southwest-flowing Arizona River, but supports late Miocene–Pliocene drainage reorganization and integration of the Colorado River coincident with development of the Salton Trough and Gulf of California.

The dazed and confused identity of Agassiz's land tortoise, Gopherus agassizii (Testudines, Testudinidae) with the description of a new species, and its consequences for conservation.

We investigate a cornucopia of problems associated with the identity of the desert tortoise, Gopherus agassizii (Cooper). The date of publication is found to be 1861, rather than 1863. Only one of the three original cotypes exists, and it is designated as the lectotype of the species. Another cotype is found to have been destroyed in the 1906 San Francisco earthquake and subsequent fire. The third is lost. The lectotype is genetically confirmed to be from California, and not Arizona, USA as sometimes reported. Maternally, the holotype of Gopherus lepidocephalus (Ottley & Velázques Solis. 1989) from the Cape Region of Baja California Sur, Mexico is also from the Mojavian population of the desert tortoise, and not from Tiburon Island, Sonora, Mexico as previously proposed. A suite of characters serve to diagnose tortoises west and north of the Colorado River, the Mojavian population, from those east and south of the river in Arizona, USA, and Sonora and Sinaloa, Mexico, the Sonoran population. Species recognition is warranted and because Gopherus lepidocephalus is from the Mojavian population, no names are available for the Sonoran species. Thus, a new species, Gopherus morafkai sp. n., is named and this action reduces the distribution of Gopherus agassizii to only 30% of its former range. This reduction has important implications for the conservation and protection of Gopherus agassizii, which may deserve a higher level of protection.

THE INFLUENCE OF WASTEWATER SUBSIDY, FLOOD DISTURBANCE AND NEIGHBOURING LAND USE ON CURRENT AND HISTORICAL PATTERNS OF RIPARIAN VEGETATION IN A SEMI‐ARID WATERSHED

ABSTRACTRiparian systems are among the most diverse and most threatened ecosystems in the western USA and consequently the focus of much conservation and restoration effort. Detailed mapping of existing riparian vegetation and quantitative description of historical riparian dynamics can inform and direct ecosystem conservation and restoration efforts. Using historical aerial photography, satellite imagery and field methods, we examine and compare historical riparian vegetation dynamics within catchments of varying land‐use/water‐use intensity along a 51‐km stretch of the Santa Cruz River in Arizona, USA. We mapped current (2006–2007) vegetation to a formation class level (dominant life form) through aerial photo‐interpretation and refined the map to an alliance level (dominant species) with extensive field data. We mapped historical vegetation to the formation level using six dates of aerial photography (1936–2004) and quantified rates of land‐use and vegetation change over the 70‐year period with spatial analysis techniques. Our results indicate that the current amount, distribution and diversity of vegetation alliances are linked to effluent supply. Sites receiving effluent since 1972 experienced a rapid increase in area of riparian forest and woodland from 1984 to 2004, followed by retrogression to herbaceous‐dominated types from 2004 to 2006, the result of an extensive cottonwood tree die‐off. Sites with no effluent subsidy are currently dominated by a mixture of riparian shrub and non‐native herbaceous alliances but tend to have higher overall alliance diversity and exhibit more stability over time. These results suggest that the use of effluent for riparian restoration may have variable long‐term effects depending on catchment land‐use history. Copyright © 2011 John Wiley & Sons, Ltd.

Wet/Dry Mapping: Using Citizen Scientists to Monitor the Extent of Perennial Surface Flow in Dryland Regions

Wet/dry mapping provides a low-cost, comprehensive snapshot for monitoring flow conditions in rivers with interrupted perennial (spatially intermittent) surface flow. When used in conjunction with more traditional point-specific stream flow or groundwater measurements, it provides a better understanding of hydrologic systems at the broad landscape or watershed scale. Through use of trained volunteers, we mapped reaches with surface water during the driest time of year to track annual variation in length and location of perennial flow. Data from 12 years of wet/dry mapping on the San Pedro River in Arizona, USA, showed 62 reaches with surface flow in every year, totaling 32% of the river length through the San Pedro Riparian National Conservation Area. They also show areas with high year-to-year variation in flow length, which indicate changes in local groundwater conditions and may provide early warning of ecological changes. Data and maps from this project have been useful for a wide variety of conservation, management, and research efforts.

The California River and its role in carving Grand Canyon

Recently published thermochronological and paleoelevation studies in the Grand Canyon region, combined with sedimentary provenance data in both the coastal and interior portions of the North American Cordillera, place important new constraints on the paleohydrological evolution of the southwestern United States. Review and synthesis of these data lead to an interpretation where incision of a large canyon from a plain of low elevation and relief to a canyon of roughly the length and depth of modern Grand Canyon occurred primarily in Campanian time (80–70 Ma). Incision was accomplished by a main-stem, NE-flowing antecedent river with headwaters on the NE slope of the North American Cordillera in California, referred to herein after its source region as the California River. At this time, the river had cut to within a few hundred meters of its modern erosion level in western Grand Canyon, and to the level of Lower Mesozoic strata in eastern Grand Canyon. Subsequent collapse of the headwaters region into a continental borderland and coeval uplift of the Cordilleran foreland during the Laramide orogeny reversed the river's course by Paleogene time. After reversal, its terminus lay near its former source regions in what is now the Western Transverse Ranges and Salinian terrane. Its headwaters lay in the ancient Mojave/Mogollon Highlands region of Arizona and eastern California, apparently reaching as far northeast as the eastern Grand Canyon region. This system is herein referred to after its source region as the Arizona River. From Paleogene through late Miocene time, the interior of the Colorado Plateau was a closed basin separated from the Arizona River drainage by an asymmetrical divide in the Lees Ferry–Glen Canyon area, with a steep SW flank and gently sloping NE flank that drained into large interior lakes, fed primarily by Cordilleran/Rocky Mountain sources to the north and west, and by recycled California River detritus shed from Laramide uplifts on the plateau. By Oligocene time, the lakes had largely dried up and were replaced by ergs. By mid-Miocene time, a pulse of unroofing had lowered the erosion level of eastern Grand Canyon to within a few hundred meters of its present level, and the Arizona River drainage below modern Grand Canyon was deranged by extensional tectonism, cutting off the supply of interior detritus to the coast. Increasing moisture in the Rocky Mountains in late Miocene time reinvigorated fluviolacustrine aggradation NE of the asymmetrical divide, which was finally overtopped between 6 and 5 Ma, lowering base level in the interior of the plateau by 1500 m. This event reintegrated the former Arizona drainage system through a cascade of spillover events through Basin and Range valleys, for the first time connecting sediment sources in Colorado with the coast. This event, combined with the intensification of summer rainfall as the Gulf of California opened, increased the sediment yield through Grand Canyon by perhaps two orders of magnitude from its Miocene nadir, giving birth to the modern subcontinental-scale Colorado River drainage system. The Colorado River has thus played a major role in unroofing the interior of the Colorado Plateau, but was not an important factor in the excavation of Grand Canyon.

An Integrative Assessment of the Effects of Tamarisk on Stopover Ecology of a Long-Distance Migrant Along the San Pedro River, Arizona

ABSTRACT. The riparian habitats of the arid southwestern United States provide critical stopover habitat for avian migrants, but they have been severely altered by invasive tamarisk (Tamarix spp.). The responses of birds to such habitat alterations are not well understood. We combined ecological and physiological measurements to provide an integrative assessment of how tamarisk invasion affects the stopover ecology of vernally migrating Wilson's Warblers (Wilsonia pusilla) along the San Pedro River in Arizona. Despite higher arthropod biomass in native cottonwood—willow habitat, the refueling rate of Wilson's Warblers, as measured by plasma metabolite profiling, was higher in tamarisk. Density and detections of Wilson's Warblers did not differ between habitats, but both measurements were significantly higher in cottonwood—willow habitat for the other members of the Wilson's Warbler foraging guild. Our measurements of food resources and migrant densities suggest that cottonwood—willow may provide high-qual...