Laramie Basin Research Articles

Climatic Impacts on Snowpack, Irrigation, and Small Reservoirs for Waterbird Nesting in a Semiarid Rocky Mountain Basin

In the semiarid western United States, annual variability of mountain snowmelt has long prompted construction of small reservoirs to sustain irrigation through the summer and among years. With relatively consistent, prolonged flooding, these small reservoirs commonly support tall emergent vegetation that is otherwise often limiting to diverse breeding waterbirds. However, increasing water shortages have promoted irrigation methods that apply less water, as well as water transfers from irrigation to urban uses or to mandated deliveries downstream. These initiatives generally overlook wildlife values of irrigation-related wetlands, and approaches to predicting water allocations needed by particular habitats have not been developed. This study examined multidecadal variations in water deliveries to small reservoirs suitable for overwater nesting in the Laramie Basin, Wyoming, and used that variability to project reductions in this habitat resulting from a range of water shortages. Analyses indicate that surrounding high elevations have so far remained cold enough to avoid declines in snowmelt deliveries seen elsewhere. Nevertheless, high snowpack variability and legal obligations to out-of-basin demands make future shortages an important concern. Estimates of the percentage of years when flows to representative wetlands would be inadequate to flood tall emergent vegetation increased from 13‒34% historically to 35‒47% and 70‒78% with decreased snowmelt of 25% and 50% projected by some published models, or by similar reallocations of flows. Given persistent calls for increased water storage for agricultural and municipal uses, further development of small reservoirs in this region may provide opportunities to offset habitat shortfalls in ways that serve multiple purposes.

Passive Source Reverse Time Migration Based on the Spectral Element Method

AbstractIncreasing deployment of dense arrays has facilitated detailed structure imaging for tectonic investigation, hazard assessment and resource exploration. Strong velocity heterogeneity and topographic changes have to be considered during passive source imaging. However, it is quite challenging for ray‐based methods, such as Kirchhoff migration or the widely used teleseismic receiver function, to handle these problems. In this study, we propose a 3‐D passive source reverse time migration strategy based on the spectral element method. It is realized by decomposing the time reversal full elastic wavefield into amplitude‐preserved vector P and S wavefields by solving the corresponding weak‐form solutions, followed by a dot‐product imaging condition to get images for the subsurface structures. It enables us to use regional 3‐D migration velocity models and take topographic variations into account, helping us to locate reflectors at more accurate positions than traditional 1‐D model‐based methods, like teleseismic receiver functions. Two synthetic tests are used to demonstrate the advantages of the proposed method to handle topographic variations and complex velocity heterogeneities. Furthermore, applications to the Laramie array data using both teleseismic P and S waves enable us to identify several south‐dipping structures beneath the Laramie basin in southeast Wyoming, which are interpreted as the Cheyenne Belt suture zone and agree with, and improve upon previous geological interpretations.

Size, age, and insights into establishment, dynamics and persistence of fairy rings in the Laramie Basin, Wyoming

Size, age, and insights into establishment, dynamics and persistence of fairy rings in the Laramie Basin, Wyoming

Fairy rings, associated fungi, and assessment of their distribution across environmental variables using GIS

Fairy rings, associated fungi, and assessment of their distribution across environmental variables using GIS

Analysis of Medicine Bow-Laramie River Drainage Divide Using Topographic Map Interpretation Techniques, Southeastern Wyoming, USA

Detailed topographic maps provide much of the information needed to understand how drainage divides like the southeast Wyoming Medicine Bow River-Laramie River drainage divide originated. Topographic map evidence for each Medicine Bow-Laramie River drainage divide segment is here described and analyzed first using a commonly published interpretation (accepted paradigm) in which drainage routes developed on a surface of now mostly absent Oligocene and Miocene sediments that previous investigators have hypothesized to have once filled the Laramie Basin and to have also buried (or partially buried) the surrounding Laramie and Medicine Bow Mountains. Second, the same map evidence is analyzed using a recently proposed interpretation (new paradigm) in which massive and prolonged floods flowed across Wyoming as the Laramie and Medicine Bow Mountains began to be uplifted and as the southeast-oriented North Platte River valley eroded headward along the rising Laramie Mountains northeast flank. Low points along the drainage divide (referred to as divide crossings) are interpreted to be places where water once flowed across the drainage divide with the drainage divide being formed when capture events diverted the water in other directions. Valleys leading away from divide crossings are used to determine the nature of observed capture events, many of which are difficult or impossible to explain from the accepted paradigm perspective, but which are consistent with the mountain uplift, headward erosion of deeper valleys, and/or draining of floodwaters trapped in the Laramie Basin as the new paradigm predicts. However, the new paradigm requires a North American continental ice sheet heavy enough to raise entire regions and mountain ranges as massive and prolonged meltwater floods flowed across them, something the accepted paradigm does not recognize.

Isolation and Characterization of 27 Novel Microsatellite Loci in Critically Endangered Wyoming Toad

Abstract Wyoming toad Anaxyrus baxteri is a federally endangered amphibian endemic to the Laramie basin in southwestern Wyoming, USA. A captive breeding program propagates A. baxteri, and the monitoring of genetic diversity in the captive stock can assist in guiding conservation measures of this species. Illumina paired-end sequencing lead to 27 species-specific polymorphic microsatellite genetic markers being developed. Across 24 samples, A. baxteri exhibited two to eight alleles per locus, and observed and expected heterozygosities per locus ranged from 0.292 to 0.958 and from 0.344 to 0.787, respectively. Tests for Hardy–Weinberg equilibrium were nonsignificant except for Abax_13 and Abax_39. These microsatellite markers will be useful for genetic monitoring to aid recovery efforts of A. baxteri captive and wild populations as well as other amphibians in the family Bufonidae.

Topographic Map Analysis of Laramie Range Bedrock-Walled Canyon Complex and the Goshen Hole Escarpment-Surrounded Basin, Albany and Platte Counties, Southeast Wyoming, USA

The Laramie River after flowing in a north direction through southeast Wyoming’s Laramie Basin abruptly turns in an east direction to flow across the north-to-south oriented Laramie Range in a bedrock-walled canyon and eventually reaches the lower elevation Great Plains and southeast-oriented North Platte River. The North Laramie River, Bluegrass Creek, and North Sybille/Sybille Creek also flow from the Laramie Basin in separate bedrock-walled valleys into the Laramie Range before eventually joining the Laramie River. Bedrock-walled through valleys link the various Laramie Range stream and river crossing valleys and detailed topographic maps were used to determine how this anastomosing bedrock-walled canyon complex and the large escarpment-surrounded Goshen Hole basin (located just to the east of the anastomosing canyon complex) originated. Map evidence shows multiple streams of water must have diverged in the Laramie Basin from the north-oriented Laramie River to enter the Laramie Range before converging in or east of the Laramie Range and also shows how present day through valleys enabled diverging and converging streams of water to cross the Laramie Range. The anastomosing bedrock-walled valley complex studied here extends from north of the North Laramie River valley to south of the North Sybille/Sybille Creek valley. Large volumes of water flowing from the Laramie Basin to the Great Plains are interpreted to have eroded the anastomosing canyon complex and the “downstream” Goshen Hole escarpment-surrounded basin. Headward erosion of the north-oriented Sybille and Chugwater Creek valleys across large sheets of east-oriented water are interpreted to have left the Goshen Hole escarpment-surrounded basin as a large abandoned headcut. A water source was not determined, although a continental ice sheet that deeply eroded and warped the North American continent is considered to be a possible source.

Late Laramide tectonic fragmentation of the eastern greater Green River Basin, Wyoming

Today9s greater Green River Basin is limited to the southwestern quarter of Wyoming. From late in the Cretaceous into late Paleocene time, however, sedimentary accumulations within that basin continued uninterruptedly much farther to the east, connecting areas now occupied by the isolated Hanna, Carbon, Pass Creek, and Laramie basins. Field-based research resulted in three contiguous geologic maps that focus on modern basin margins and boundaries among those eastern elements. Analyses of derived cross sections and restored stratigraphic columns suggest that active subsidence and rapid sedimentary accumulation persisted with only minor interruptions until very late in the Laramide Orogeny. That led to a generally symmetrical north–south cross-sectional configuration of the original Hanna Basin, with its true depositional axis set well south of its apparent position of today. The Hanna Basin9s present strong asymmetry developed only secondarily. That basin9s modern configuration reflects Paleogene influences of: (1) late Laramide (early Eocene and probably younger) basement-involved contractional tectonics and associated uplifts; (2) out-of-the-basin thrusting passively responding to stratigraphic crowding; (3) prodigious syntectonic erosion; and (4) resulting basin fragmentation. North–south dimension of the late Paleocene (i.e., pre-fragmentation) greater Hanna Basin sedimentary sequence was roughly twice that of today, and near-sea-level topographic conditions persisted until late Eocene time. As expected, remnants of basin margins universally show major thinning of stratigraphic sequences. Principal thinning was from tectonic causes, however, exhibiting erosional angular unconformities only rarely. Out-of-the-basin, younger-on-older faulting (in which fault planes cut down-section) accompanied by massive erosion was the rule at all basin margins. Uplift of Simpson Ridge Anticline postdated deposition of upper Paleocene strata in direct continuity between what is now the separated Hanna and Carbon basins. The basement-involved fault system responsible for westward relative tectonic transport (and ca. 8 km of elevation) by Simpson Ridge also led to raising the attached Carbon Basin. Original Hanna Formation of the Carbon Basin was beveled away by erosion and soon thereafter became replaced by shallow-slope sliding of a long-runout allochthon, the Carbon Basin Klippe. The klippe9s original site of deposition probably was to the northeast, above what later became Flat Top Anticline. Uplift of Flat Top and Simpson Ridge anticlines was essentially synchronous (latest Paleocene or, more probably, early Eocene), establishing a lengthy, faulted-synclinal separation of the Hanna/Carbon Basin from the Laramie Basin. That syncline also bifurcated Simpson Ridge Anticline into western and eastern segments. A second allochthon, the Dana Klippe, rests upon southern parts of the Hanna Syncline (of Hanna Basin). That klippe9s site of deposition probably was above the area that later elevated as Elk Mountain, thus causing origin of Pass Creek Basin. Elk Mountain9s ca. 12 km uplift could not have occurred prior to the early Eocene, and that event contributed to tight folding of the Hanna Syncline. Coal Bank Basin is a giant footwall syncline ahead of the out-of-the-basin, thrust-faulted (with relative tectonic transport to the southwest) Dana Ridge Anticline. That fault–fold complex represents a common structural style seen at all scales across the Hanna Basin.

Isolation and characterization of eight novel microsatellite loci in endangered Wyoming toad, Bufo baxteri

Wyoming toad (Bufo baxteri) is an endangered amphibian native to the Laramie Basin, Wyoming, USA. A captive breeding program propagates B. baxteri, and the monitoring of genetic diversity in captive stock can assist in guiding restoration and recovery efforts. We developed eight species-specific polymorphic loci from an enriched microsatellite library. For 281 samples, B. baxteri exhibited 2–11 alleles per locus, and observed and expected heterozygosities per locus ranged from 0.411 to 0.943 and from 0.400 to 0.691, respectively. Four loci deviated significantly from Hardy–Weinberg equilibrium. The eight microsatellite markers may be useful for conservation, population, and quantitative genetics for B. baxteri and closely related species.

Sketch-based Identification of Bench and Terrace Slope Breaks in the Laramie Basin, Wyoming

This study presents a semi-automated approach to support the identification of fluvial landform slope breaks in the Laramie Basin, southeastern Wyoming. The landforms in question form the edges of terraces and benches and tend to be subtle and varied depending on where they appear in the landscape. Because of this variation combined with DEM error, conventional raster filtering methods were unable to readily identify the benches with any consistency. In an effort to automate the collection of benches, a two stage, sketch-based algorithm was designed to detect bench edges on a semi-automated basis and was integrated into a commercial GIS environment for testing and execution. The approach of tailoring an algorithm to detect a particular feature proved viable and, in fact, more consistent in many cases than heads-up digitizing. However, feature complexity appears to be a significant driver in the accuracy of the algorithmic approach with the unlikely finding that more complex features are more accurately identified than less complex features. This research demonstrates that user cognition, DEM resolution, algorithm functionality and landform characteristics are thus all important and interrelated factors requiring consideration when implementing approaches to topographic feature identification.

Impact of Irrigation Cessation on Wetland Communities within the Elk Ranch, Grand Teton National Park, Moose, Wyoming

Riparian ecology research in Arizona and California has documented the likelihood of a subsurface linkage between irrigation, especially flood-irrigation, and riparian function (Smith et al. 1989; Stromberg et al. 1996). Initial groundwater monitoring results from rural New Mexico indicate water tables rose 1 to 2m after the onset of field irrigation and subsurface flow paths towards the Rio Grande River developed soon after (Fernald et al. 2008). Results from a study of wetlands in southeastern Wyoming suggest that declining flood-irrigation levels would lead to a reduction in the total area of wetlands and related areas of wetland vegetation types in the Laramie Basin (Peck and Lovvorm 2001). Stringham et al. (1998) have reported further evidence for a linkage between irrigation and riparian function. These Oregon researchers noted lower water temperatures in stream reaches receiving subsurface return flows from irrigated hayfields than similar reaches flowing through non-irrigated lands. This information is timely because Grand Teton National Park (GTNP) managers have begun an evaluation of historic irrigation operations within the Park and are endeavoring to learn how cessation of flood irrigation will affect Park wetlands. The historically irrigated hayfields at the Elk Ranch provide an opportunity to address the Park Service's informational needs through identification of vegetation composition, soil physical characteristics and groundwater patterns associated with irrigated and naturally occurring wetlands. Successful description of patterns unique to natural wetlands will provide an avenue for predicting which Park wetlands would remain functional should irrigation efforts be brought to a close. Development of criteria for identifying naturally occurring wetlands could also serve as a basis for identifying areas for wetland mitigation and rehabilitation elsewhere in GTNP and the mountain valleys of the Northern Rocky Mountains.

Patterns of macroinvertebrate abundance in inland saline wetlands: a trophic analysis

We used stable isotopes and gut-content analysis to compare trophic relations of macroinvertebrates between two types of saline wetlands in the Laramie Basin, Wyoming, USA. Amphipods (Hyallela azteca), chironomid larvae, and predatory insects (mainly Zygopteran larvae) occurred in both wetland types. However, in oligosaline wetlands (0.5–5‰ total dissolved solids) amphipods were dominant, whereas in mesosaline wetlands (5–18‰) amphipods were scarce and chironomid larvae and predatory insects were much more abundant. Salinity alone seemed inadequate to explain these differences, so we examined trophic interactions to address three main questions: (1) why are predatory insects more abundant in mesosaline wetlands, (2) why are chironomid larvae less abundant in oligosaline wetlands, and (3) why are amphipods uncommon in mesosaline wetlands? Zygopteran larvae ate mainly chironomid larvae and zooplankton, and did not eat amphipods; chironomid larvae were an average 93 dry mass of zygopteran intake. Guts of amphipods contained no animal parts and little vascular plant tissue, but rather mainly amorphous detritus. Chironomid larvae ate amorphous detritus as well as diatoms. There is potential for competition between amphipods and chironomids, but the nature of amorphous detritus in these wetlands needs further study. Because amphipods appear unavailable as prey for predatory insects, top-down impacts on chironomid larvae may be greater in oligosaline than in mesosaline wetlands. Our results suggest that (1) predatory zygopteran larvae and hemipterans are more abundant in mesosaline wetlands due to more abundant chironomid prey, (2) chironomids are less common in oligosaline wetlands because of both competition with amphipods and greater per capita consumption by predatory insects, and (3) amphipods are scarce in mesosaline wetlands because, lacking a resting stage and mode of direct dispersal, they do not cope well with extremes created by hydrologic instability in mesosaline wetlands. These mechanisms may apply to wetlands in other regions where similar patterns of invertebrate community structure have been reported.

Irrigation-Dependent Wetlands Versus Instream Flow Enhancement: Economics of Water Transfers from Agriculture to Wildlife Uses

Irrigated agriculture throughout western North America faces increasing pressure to transfer water to nonagricultural uses, including instream flows for fish and wildlife management. In an important case, increased instream flows are needed in Nebraska's Platte River for recovery of threatened and endangered fish and wildlife species. Irrigated agriculture in the Laramie Basin of southeast Wyoming is a potential water source for the effort to enhance instream flow. However, flood irrigation of hayfields in the Laramie Basin has created many wetlands, both ephemeral and permanent, over the last century. Attempting to increase Platte River instream flows by purchasing water rights or improving irrigation efficiency in the Laramie Basin would transform irrigated agriculture, causing a substantial fraction of the Laramie Basin's wetlands to be lost. A creative solution is needed to prevent the sacrifice of one ecosystem on behalf of another. A rotating short-term water-leasing program is proposed. The program allows Laramie Basin producers to contribute to instream flows while continuing to support local wetlands. Permanent wetland desiccation is prevented and regional environmental water needs are met without impairing local ecological resources. Budget analysis is used to provide an initial cost estimate for acquiring water from agriculture through the short-term leasing program. The proposed approach is more expensive than traditional programs but allows contribution to instream flows without major wetland loss. Short-term leasing is a more efficient approach if benefits from wetlands exceed the difference in cost between the short-term lease program and programs that do not conserve wetlands.

Strontium isotopic identification of water-rock interaction and ground water mixing.

87Sr/86Sr ratios of ground waters in the Bighorn and Laramie basins' carbonate and carbonate-cemented aquifer systems, Wyoming, United States, reflect the distinctive strontium isotope signatures of the minerals in their respective aquifers. Well water samples from the Madison Aquifer (Bighorn Basin) have strontium isotopic ratios that match their carbonate host rocks. Casper Aquifer ground waters (Laramie Basin) have strontium isotopic ratios that differ from the bulk host rock; however, stepwise leaching of Casper Sandstone indicates that most of the strontium in Casper Aquifer ground waters is acquired from preferential dissolution of carbonate cement. Strontium isotope data from both Bighorn and Laramie basins, along with dye tracing experiments in the Bighorn Basin and tritium data from the Laramie Basin, suggest that waters in carbonate or carbonate-cemented aquifers acquire their strontium isotope composition very quickly--on the order of decades. Strontium isotopes were also used successfully to verify previously identified mixed Redbeds-Casper ground waters in the Laramie Basin. The strontium isotopic compositions of ground waters near Precambrian outcrops also suggest previously unrecognized mixing between Casper and Precambrian aquifers. These results demonstrate the utility of strontium isotopic ratio data in identifying ground water sources and aquifer interactions.

Isotopic identification of natural vs. anthropogenic sources of Pb in Laramie basin groundwaters, Wyoming, USA

Water well samples, precipitation, and leachates of aquifer rock samples from the Laramie basin, Wyoming, were analyzed to test the suitability of Pb isotopes for tracing hydrologic processes in a basin where Sr isotopes had proven effective. Leachable Pb from host rocks to aquifers in this basin have isotopically distinct compositions and isotopic tracing would be effective in differentiating natural sources of Pb. However, in almost all cases, this natural signal is apparently swamped by anthropogenic Pb sources in drilled water wells. The isotopic compositions of these samples cannot be produced by any combination of Pb in precipitation and leached Pb from the aquifers alone, but are consistent with mixtures of anthropogenic Pb. Thorogenic (208Pb) vs. uranogenic (206Pb, 207Pb) Pb was especially useful for discriminating natural from anthropogenic sources for these samples. It is strongly recommended that all four Pb isotopes be reported in hydrologic and environmental studies that employ this approach.

Interpreting stable isotopes from macroinvertebrate foodwebs in saline wetlands

We compared stable‐isotope (δ13C and δ15N) and gut‐content analyses of macroinvertebrate foodwebs in saline wetlands of the Laramie Basin, Wyoming, USA. Standard assumptions of stable‐isotope fractionation between trophic levels (<1‰ for δ13C, mean of 3.4‰ for δ15N) suggested that zygopteran (damselfly) larvae consumed mainly amphipods. However, the guts of zygopterans contained no amphipods but rather a mix of chironomid larvae and zooplankton. In all wetlands the gut contents of zygopterans indicated that they were secondary consumers (trophic level 3), but enrichment of δ15N between zygopterans and their prey (Δδ15N) varied from 1 to 3.4‰ between wetlands. In other studies, such variation in Δδ15N has been interpreted to mean that food‐chain length differed between aquatic systems. We review alternative interpretations of variable 15N enrichment, namely, varying C:N ratios in food, differential enrichment between consumer species, and habitat‐specific variation of δ15N at the base of foodwebs. We also suggest that variation in the timing and rates of nitrogen cycling can affect measured Δδ15N both within and between foodwebs. For aquatic macroinvertebrates, we urge that stable isotopes be supplemented with independent observations to avoid incorrect conclusions about trophic pathways, trophic levels, and food‐chain lengths in different ecosystems.

The importance of flood irrigation in water supply to wetlands in the Laramie Basin, Wyoming, USA

Abstract As in many areas of western North America, flood irrigation for hay production has created many wetlands in the Laramie Basin, Wyoming. Since the early 1900s, water from mountain snowmelt has reached wetlands via ditches and as interflow and ground water percolating from flooded fields and unlined ditches. Such systems are viewed as inefficient for irrigation and other human uses because they reduce the volume and increase the salinity of downstream flows. Increasing irrigation efficiency by lining ditches or installing sprinklers would decrease wetland habitat, but such effects are seldom considered. To assess potential impacts of increased irrigation efficiency, we determined how flood irrigation affects the hydrology and types of wetlands in the Laramie Basin. For 74 wetlands with 80 total inflows, just 14% of inflows were as surface flow from natural stream channels. In contrast, 65% of inflows were directly from irrigation: 30% as surface flow from ditches and 35% as interflow percolating fr...

Vegetation dynamics and primary production in saline, lacustrine wetlands of a Rocky Mountain basin

Vegetation dynamics and primary production in saline, lacustrine wetlands of a Rocky Mountain basin

STRATIGRAPHY, SOILS, AND AGE RELATIONSHIPS OF MIMA-LIKE MOUNDS, LARAMIE BASIN, WYOMING

Mima-like mounds in the Laramie Basin, Wyoming, are circular in plan view, lens or funnel-shaped in cross-section, and frequently have relief of 15 to 65 cm. They consist of churned materials derived from adjacent/subjacent soils and sediments. Strong intermound (premound) soils, or parts of them, usually collapse beneath the mounds or are sometimes truncated at mound edges. Both active and inactive mounds occur in areas of shallow, impermeable bedrock, thin alluvium overlying the bedrock, and strong premound soil development on terraces and benches. Radiocarbon dating, along with stratigraphic and soil relationships at various sites, indicates that the mounds are late Holocene (Neoglacial) in age. The premound soils and sediments beneath the mounds, in addition to those in intermound areas, appear to be affected chemically by salty groundwater related to mound formation or salt leached from overlying mound material into these units after the mounds formed. Accordingly, in response to the Hilgard reaction, the salts would lead to decomposition of calcium carbonate in Btk horizons and removal of clay, along with breakdown of calcium carbonate and clay removal from alluvium that formerly contained lower parts of the B horizons. As a result, where they appear to be affected directly by groundwater flow, the alluvial gravels and sands are clean, lack coherency, are devoid of much clay and silt, have cavernous openings, contain some secondary selenite crystals, and readily crumble under slight pressure. The degradation of the alluvium and soils, common to areas of mounded topography, conforms to the groundwater vortex hypothesis proposed for mound formation. Further research, however, is needed, including the gathering of additional data to support the hypothesis or change it. [Key words: groundwater, Holocene, mima-like mounds, soil stratigraphy, topography.]

A groundwater vortex hypothesis for mima-like mounds, Laramie Basin, Wyoming

A groundwater vortex hypothesis for mima-like mounds, Laramie Basin, Wyoming