Geology topics

Research about Montana

Source-linked reports with geographic coverage including Montana.

At least 289 records · Page 16Linked to original sources

USGS2013

Population-level thermal performance of a cold-water ectotherm is linked to ontogeny and local environmental heterogeneity

Negative effects of global warming are predicted to be most severe for species that occupy a narrow range of temperatures, have limited dispersal abilities or have long generation times. These are characteristics typical of many species that occupy small, cold streams. Habitat use, vulnerabilities and mechanisms for coping with local conditions can differ among populations and ontogenetically within populations, potentially affecting species‐level responses to climate change. However, we still have little knowledge of mean thermal performance for many vertebrates, let alone variation in performance among populations. Assessment of these sources of variation in thermal performance is critical for projecting the effects of climate change on species and for identifying management strategies to ameliorate its effects. To gauge how populations of the Rocky Mountain tailed frog ( Ascaphus montanus ) might respond to long‐term effects of climate change, we measured the ability of tadpoles from six populations in Glacier National Park (Montana, U.S.A.) to acclimate to a range of temperatures. We compared survival among populations according to tadpole age (1 year or 2 years) and according to the mean and variance of late‐summer temperatures in natal streams. The ability of tadpoles to acclimate to warm temperatures increased with age and with variance in late‐summer temperature of natal streams. Moreover, performance differed among populations from the same catchment. Our experiments with a cold‐water species show that population‐level performance varies across small geographic scales and is linked to local environmental heterogeneity. This variation could influence the rate and mode of species‐level responses to climate change, both by facilitating local persistence in the face of changes in thermal conditions and by providing thermally tolerant colonists to neighbouring populations.

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USGS2013

Estimating occupancy and predicting numbers of gray wolf packs in Montana using hunter surveys

Reliable knowledge of the status and trend of carnivore populations is critical to their conservation and management. Methods for monitoring carnivores, however, are challenging to conduct across large spatial scales. In the Northern Rocky Mountains, wildlife managers need a time- and cost-efficient method for monitoring gray wolf (Canis lupus) populations. Montana Fish, Wildlife and Parks (MFWP) conducts annual telephone surveys of >50,000 deer and elk hunters. We explored how survey data on hunters' sightings of wolves could be used to estimate the occupancy and distribution of wolf packs and predict their abundance in Montana for 2007–2009. We assessed model utility by comparing our predictions to MFWP minimum known number of wolf packs. We minimized false positive detections by identifying a patch as occupied if 2–25 wolves were detected by ≥3 hunters. Overall, estimates of the occupancy and distribution of wolf packs were generally consistent with known distributions. Our predictions of the total area occupied increased from 2007 to 2009 and predicted numbers of wolf packs were approximately 1.34–1.46 times the MFWP minimum counts for each year of the survey. Our results indicate that multi-season occupancy models based on public sightings can be used to monitor populations and changes in the spatial distribution of territorial carnivores across large areas where alternative methods may be limited by personnel, time, accessibility, and budget constraints.

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USGS2013

Variations in surface water-ground water interactions along a headwater mountain stream : comparisons between transient storage and water balance analyses

The accumulation of discharge along a stream valley is frequently assumed to be the primary control on solute transport processes. Relationships of both increasing and decreasing transient storage, and decreased gross losses of stream water have been reported with increasing discharge; however, we have yet to validate these relationships with extensive ﬁeld study. We conducted transient storage and mass recovery analyses of artiﬁcial tracer studies completed for 28 contiguous 100 m reaches along a stream valley, repeated under four base-ﬂow conditions. We calculated net and gross gains and losses, temporal moments of tracer breakthrough curves, and best ﬁt transient storage model parameters (with uncertainty estimates) for 106 individual tracer injections. Results supported predictions that gross loss of channel water would decrease with increased discharge. However, results showed no clear relationship between discharge and transient storage, and further analysis of solute tracer methods demonstrated that the lack of this relation may be explained by uncertainty and equiﬁnality in the transient storage model framework. Furthermore, comparison of water balance and transient storage approaches reveals complications in clear interpretation of either method due to changes in advective transport time, which sets a the temporal boundary separating transient storage and channel water balance. We have little ability to parse this limitation of solute tracer methods from the physical processes we seek to study. We suggest the combined analysis of both transient storage and channel water balance more completely characterizes transport of solutes in stream networks than can be inferred from either method alone.

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USGS2013

Nitrogen cycling responses to mountain pine beetle disturbance in a high elevation whitebark pine ecosystem

Ecological disturbances can significantly affect biogeochemical cycles in terrestrial ecosystems, but the biogeochemical consequences of the extensive mountain pine beetle outbreak in high elevation whitebark pine (WbP) (Pinus albicaulis) ecosystems of western North America have not been previously investigated. Mountain pine beetle attack has driven widespread WbP mortality, which could drive shifts in both the pools and fluxes of nitrogen (N) within these ecosystems. Because N availability can limit forest regrowth, understanding how beetle-induced mortality affects N cycling in WbP stands may be critical to understanding the trajectory of ecosystem recovery. Thus, we measured above- and belowground N pools and fluxes for trees representing three different times since beetle attack, including unattacked trees. Litterfall N inputs were more than ten times higher under recently attacked trees compared to unattacked trees. Soil inorganic N concentrations also increased following beetle attack, potentially driven by a more than two-fold increase in ammonium (NH4+) concentrations in the surface soil organic horizon. However, there were no significant differences in mineral soil inorganic N or soil microbial biomass N concentrations between attacked and unattacked trees, implying that short-term changes in N cycling in response to the initial stages of WbP attack were restricted to the organic horizon. Our results suggest that while mountain pine beetle attack drives a pulse of N from the canopy to the forest floor, changes in litterfall quality and quantity do not have profound effects on soil biogeochemical cycling, at least in the short-term. However, continuous observation of these important ecosystems will be crucial to determining the long-term biogeochemical effects of mountain pine beetle outbreaks.

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USGS2013

Feedback-driven response to multidecadal climatic variability at an alpine treeline

The Pacific Decadal Oscillation (PDO) has significant climatological and ecological effects in northwestern North America. Its possible effects and their modification by feedbacks are examined in the forest-tundra ecotone in Glacier National Park, Montana, USA. Tree ring samples were collected to estimate establishment dates in 10 quadrats. Age-diameter regressions were used to estimate the ages of uncored trees. The temporal pattern of establishment and survival was compared to the pattern of the PDO. A wave of establishment began in the mid-1940s, rose to a peak rate in the mid-1970s, and dropped precipitously beginning ca. 1980 to near zero for the 1990s. The period of establishment primarily coincided with the negative phase of the PDO, but the establishment and survival pattern is not correlated with the PDO index. The pattern indicates a period during which establishment was possible and was augmented by positive feedback from surviving trees. Snow may be the most important factor in the feedback, but studies indicate that its effects vary locally. Spatially differentiated analyses of decadal or longer periodicity may elucidate responses to climatic variation.

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USGS2013

Sediment accretion rates and sediment composition in Prairie Pothole wetlands under varying land use practices, Montana, United States

Increased sedimentation and nutrient cycle changes in Prairie Pothole Region wetlands associated with agriculture threaten the permanence and ecological functionality of these important resources. To determine the effects of land use on sedimentation and nutrient cycling, soil cores were analyzed for cesium-137 ( 137 Cs), lead-210 ( 210 Pb), and potassium-40 ( 40 K) activities; textural composition; organic and inorganic carbon (C); and total nitrogen (N) from twelve wetlands surrounded by cropland, Conservation Reserve Program (CRP) lands, or native prairie uplands. Separate soil cores from nine of these wetlands were also analyzed for phosphorus (P), nitrate (NO 3 ), and ammonium (NH 4 ) concentrations. Wetlands surrounded by cropland had significantly greater linear sediment accretion rates than wetlands surrounded by CRP or native prairie. Linear sediment accretion rates from wetlands surrounded by cropland were 2.7 and 6 times greater than wetlands surrounded by native prairie when calculated from the initial and peak occurrence of 137 Cs, respectively, and 0.15 cm y−1 (0.06 in yr−1) greater when calculated from 210 Pb. Relative to wetlands surrounded by CRP, linear sediment accretion rates for wetlands surrounded by cropland were 4.4 times greater when calculated from the peak occurrence of 137 Cs. No significant differences existed between the linear sediment accretion rates between wetlands surrounded by native prairie or CRP uplands. Wetlands surrounded by cropland had increased clay, P, NO 3 , and NH 4 , and decreased total C and N concentrations compared to wetlands surrounded by native prairie. Wetlands surrounded by CRP had the lowest P and NO 3 concentrations and had clay, NH 4 , C, and N concentrations between those of cropland and native prairie wetlands. We documented increased linear sediment accretion rates and changes in the textural and chemical properties of sediments in wetlands with cultivated uplands relative to wetlands with native prairie uplands. These findings demonstrate the value of the CRP at protecting wetland catchments to reduce sedimentation.

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USGS2013

Food availability and foraging near human developments by black bears

Understanding the relationship between foraging ecology and the presence of human-dominated landscapes is important, particularly for American black bears ( Ursus americanus ), which sometimes move between wildlands and urban areas to forage. The food-related factors influencing this movement have not been explored, but can be important for understanding the benefits and costs to black bear foraging behavior and the fundamental origins of bear conflicts. We tested whether the scarcity of wildland foods or the availability of urban foods can explain when black bears forage near houses, examined the extent to which male bears use urban areas in comparison to females, and identified the most important food items influencing bear movement into urban areas. We monitored 16 collared black bears in and around Missoula, Montana, during 2009 and 2010, while quantifying the rate of change in green vegetation and the availability of 5 native berry-producing species outside the urban area, the rate of change in green vegetation, and the availability of apples and garbage inside the urban area. We used parametric time-to-event models in which an event was a bear location collected within 100 m of a house. We also visited feeding sites located near houses and quantified food items bears had eaten. The probability of a bear being located near a house was 1.6 times higher for males, and increased during apple season and the urban green-up. Fruit trees accounted for most of the forage items at urban feeding sites (49%), whereas wildland foods composed <10%. Black bears foraged on human foods near houses even when wildland foods were available, suggesting that the absence of wildland foods may not influence the probability of bears foraging near houses. Additionally, other attractants, in this case fruit trees, appear to be more important than the availability of garbage in influencing when bears forage near houses.

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USGS2013

Disease in a dynamic landscape: host behavior and wildfire reduce amphibian chytrid infection

Disturbances are often expected to magnify effects of disease, but these effects may depend on the ecology, behavior, and life history of both hosts and pathogens. In many ecosystems, wildfire is the dominant natural disturbance and thus could directly or indirectly affect dynamics of many diseases. To determine how probability of infection by the aquatic fungus Batrachochytrium dendrobatidis (Bd) varies relative to habitat use by individuals, wildfire, and host characteristics, we sampled 404 boreal toads ( Anaxyrus boreas boreas ) across Glacier National Park, Montana (USA). Bd causes chytridiomycosis, an emerging infectious disease linked with widespread amphibian declines, including the boreal toad. Probability of infection was similar for females and the combined group of males and juveniles. However, only 9% of terrestrial toads were infected compared to >30% of aquatic toads, and toads captured in recently burned areas were half as likely to be infected as toads in unburned areas. We suspect these large differences in infection reflect habitat choices by individuals that affect pathogen exposure and persistence, especially in burned forests where warm, arid conditions could limit Bd growth. Our results show that natural disturbances such as wildfire and the resulting diverse habitats can influence infection across large landscapes, potentially maintaining local refuges and host behaviors that facilitate evolution of disease resistance.

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USGS2013

Breeding site heterogeneity reduces variability in frog recruitment and population dynamics

Environmental stochasticity can have profound effects on the dynamics and viability of wild populations, and habitat heterogeneity provides one mechanism by which populations may be buffered against the negative effects of environmental fluctuations. Heterogeneity in breeding pond hydroperiod across the landscape may allow amphibian populations to persist despite variable interannual precipitation. We examined recruitment dynamics over 10 yr in a high-elevation Columbia spotted frog ( Rana luteiventris ) population that breeds in ponds with a variety of hydroperiods. We combined these data with matrix population models to quantify the consequences of heterogeneity in pond hydroperiod on net recruitment (i.e. number of metamorphs produced) and population growth rates. We compared our heterogeneous system to hypothetical homogeneous environments with only ephemeral ponds, only semi-permanent ponds, and only permanent ponds. We also examined the effects of breeding pond habitat loss on population growth rates. Most eggs were laid in permanent ponds each year, but survival to metamorphosis was highest in the semi-permanent ponds. Recruitment success varied by both year and pond type. Net recruitment and stochastic population growth rate were highest under a scenario with homogeneous semi-permanent ponds, but variability in recruitment was lowest in the scenario with the observed heterogeneity in hydroperiods. Loss of pond habitat decreased population growth rate, with greater decreases associated with loss of permanent and semi-permanent habitat. The presence of a diversity of pond hydroperiods on the landscape will influence population dynamics, including reducing variability in recruitment in an uncertain climatic future.

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USGS2013

Interactive effects of wildfire, forest management, and isolation on amphibian and parasite abundance

Projected increases in wildfire and other climate-driven disturbances will affect populations and communities worldwide, including host–parasite relationships. Research in temperate forests has shown that wildfire can negatively affect amphibians, but this research has occurred primarily outside of managed landscapes where interactions with human disturbances could result in additive or synergistic effects. Furthermore, parasites represent a large component of biodiversity and can affect host fitness and population dynamics, yet they are rarely included in studies of how vertebrate hosts respond to disturbance. To determine how wildfire affects amphibians and their parasites, and whether effects differ between protected and managed landscapes, we compared abundance of two amphibians and two nematodes relative to wildfire extent and severity around wetlands in neighboring protected and managed forests (Montana, USA). Population sizes of adult, male long-toed salamanders ( Ambystoma macrodactylum ) decreased with increased burn severity, with stronger negative effects on isolated populations and in managed forests. In contrast, breeding population sizes of Columbia spotted frogs ( Rana luteiventris ) increased with burn extent in both protected and managed protected forests. Path analysis showed that the effects of wildfire on the two species of nematodes were consistent with differences in their life history and transmission strategies and the responses of their hosts. Burn severity indirectly reduced abundance of soil-transmitted Cosmocercoides variabilis through reductions in salamander abundance. Burn severity also directly reduced C. variabilis abundance, possibly though changes in soil conditions. For the aquatically transmitted nematode Gyrinicola batrachiensis , the positive effect of burn extent on density of Columbia spotted frog larvae indirectly increased parasite abundance. Our results show that effects of wildfire on amphibians depend upon burn extent and severity, isolation, and prior land use. Through subsequent effects on the parasites, our results also reveal how changes in disturbance regimes can affect communities across trophic levels.

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USGS2013

Thermal tolerance of meltwater stonefly Lednia tumana nymphs from an alpine stream in Waterton–Glacier International Peace Park, Montana, USA

Global climate change threatens to affect negatively the structure, function, and diversity of aquatic ecosystems worldwide. In alpine systems, the thermal tolerances of stream invertebrates can be assessed to understand better the potential effects of rising ambient temperatures and continued loss of glaciers and snowpack on alpine stream ecosystems. We measured the critical thermal maximum (CTM) and lethal temperature maximum (LTM) of the meltwater stonefly ( Lednia tumana ), a species limited to glacial and snowmelt-driven alpine streams in the Waterton–Glacier International Peace Park area and a candidate for listing under the US Endangered Species Act. We collected L. tumana nymphs from Lunch Creek in Glacier National Park, Montana (USA) and transported them to a laboratory at the University of Montana Flathead Lake Biological Station, Polson, Montana. We placed nymphs in a controlled water bath at 1 of 2 acclimation temperatures, 8.5 and 15°C. We increased water temperature at a constant rate of 0.3°C/min. We calculated the average CTM and LTM (± SD) for each acclimation temperature and compared them with Student’s t-tests. Predicted chronic temperature maxima were determined using the ⅓ rule. Mean LTMs were 32.3 ± 0.28°C and 31.05 ± 0.78°C in the 8.5 and 15°C acclimation treatments, respectively. CTM and LTM metrics were lower in the 15 than in the 8.5°C acclimation treatment, but these differences were not statistically significant (p > 0.05). The predicted chronic temperature maxima were 20.6 and 20.2°C for the 8.5 and 15°C acclimation treatments, respectively. More research is needed on the effects of chronic exposures to rising stream temperatures, but our results can be used to assess the potential effects of warming water temperatures on L. tumana and other aquatic macroinvertebrates in alpine ecosystems.

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USGS2013

Regional economic impacts of current and proposed management alternatives for Charles M. Russell National Wildlife Refuge

The National Wildlife Refuge System Improvement Act of 1997 requires all units of the National Wildlife Refuge System to be managed under a Comprehensive Conservation Plan (CCP). The CCP must describe the desired future conditions of a refuge and provide long-range guidance and management direction to achieve refuge purposes. Charles M. Russell (CMR) National Wildlife Refuge, located in north-central Montana, is in the process of developing a range of management goals, objectives, and strategies for the CCP. The CCP for the Refuge must contain an analysis of expected effects associated with current and proposed refuge-management strategies. For refuge CCP planning, an economic analysis provides a means of estimating how current management (No Action Alternative) and proposed management activities (Alternatives) affect the local economy. This type of analysis provides two critical pieces of information: (1) it illustrates a refuge’s contribution to the local community; and (2) it can help in determining whether economic effects are or are not a real concern in choosing among management alternatives. It is important to note that the economic value of a refuge encompasses more than just the impacts on the regional economy. Refuges also provide substantial nonmarket values (values for items not exchanged in established markets) such as maintaining endangered species, preserving wetlands, educating future generations, and adding stability to the ecosystem (Carver and Caudill, 2007). However, quantifying these types of nonmarket values is beyond the scope of this study. This report first presents a description of the local community and economy near the Refuge. Next, the methods used to conduct a regional economic impact analysis are described. An analysis of the final CCP management strategies that could affect stakeholders and residents and the local economy is then presented. The refuge management activities of economic concern in this analysis are: • Refuge purchases of goods and services within the local community; • Refuge personnel salary spending; • Grazing operations; • Spending in the local community by refuge visitors; and • Revenues generated from Refuge Revenue Sharing.

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USGS2013

Quaternary geologic map of the Shelby 1° x 2° quadrangle, Montana

The Shelby quadrangle encompasses approximately 16,084 km 2 (6,210 mi 2 ). The northern boundary is the Montana/Saskatchewan (U.S./Canada) boundary. The quadrangle is in the Northern Plains physiographic province and it includes the Sweet Grass Hills. The primary river is the Marias River. The ancestral Missouri River was diverted south of the Bearpaw Mountains by a Laurentide ice sheet. The fill in the buried ancestral valleys of the Missouri River and Marias River in the southeast quarter of the quadrangle contains a complex stratigraphy of fluvial, glaciofluvial, ice-contact, glacial, lacustrine, and eolian deposits. The map units are surficial deposits and materials, not landforms. Deposits that comprise some constructional landforms (for example, ground-moraine deposits, end-moraine deposits, stagnation-moraine deposits, all composed of till) are distinguished for purposes of reconstruction of glacial history. Surficial deposits and materials are assigned to 21 map units on the basis of genesis, age, lithology or composition, texture or particle size, and other physical, chemical, and engineering characteristics. It is not a map of soils that are recognized in pedology or agronomy. Rather, it is a generalized map of soils recognized in engineering geology, or of substrata or parent materials in which pedologic or agronomic soils are formed. Glaciotectonic (ice-thrust) structures and deposits are mapped separately, represented by a symbol. On the glaciated plains, the surficial deposits are glacial, ice-contact, glaciofluvial, alluvial, lacustrine, eolian, colluvial, and mass-movement deposits. In the Sweet Grass Hills, beyond the limit of Quaternary glaciation they are fluvial, colluvial, and mass-movement deposits. Till of late Wisconsin age is represented by three map units. Tills of Illinoian and pre-Illinoian glaciations are not mapped, but are widespread in the subsurface. Linear ice-molded landforms (primarily drumlins) indicate directions of ice flow during late Wisconsin glaciation.

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USGS2013

Water-quality, bed-sediment, and biological data (October 2010 through September 2011) and statistical summaries of data for streams in the Clark Fork basin, Montana

Water, bed sediment, and biota were sampled in streams from Butte to near Missoula, Montana, as part of a monitoring program in the upper Clark Fork basin of western Montana; additional water samples were collected from near Galen to near Missoula at select sites as part of a supplemental sampling program. The sampling program was conducted by the U.S. Geological Survey in cooperation with the U.S. Environmental Protection Agency to characterize aquatic resources in the Clark Fork basin, with emphasis on trace elements associated with historic mining and smelting activities. Sampling sites were located on the Clark Fork and selected tributaries. Water samples were collected periodically at 20 sites from October 2010 through September 2011. Bed-sediment and biota samples were collected once at 14 sites during August 2011. This report presents the analytical results and quality-assurance data for water-quality, bed-sediment, and biota samples collected at sites from October 2010 through September 2011. Water-quality data include concentrations of selected major ions, trace elements, and suspended sediment. Turbidity was analyzed for water samples collected at the four sites where seasonal daily values of turbidity were being determined. Daily values of suspended-sediment concentration and suspended-sediment discharge were determined for four sites. Bed-sediment data include trace-element concentrations in the fine-grained fraction. Biological data include trace-element concentrations in whole-body tissue of aquatic benthic insects. Statistical summaries of water-quality, bed-sediment, and biological data for sites in the upper Clark Fork basin are provided for the period of record since 1985.

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USGS2013

Estimates of the volume of water in five coal aquifers, Northern Cheyenne Indian Reservation, southeastern Montana

The Tongue River Member of the Tertiary Fort Union Formation is the primary source of groundwater in the Northern Cheyenne Indian Reservation in southeastern Montana. Coal beds within this formation generally contain the most laterally extensive aquifers in much of the reservation. The U.S. Geological Survey, in cooperation with the Northern Cheyenne Tribe, conducted a study to estimate the volume of water in five coal aquifers. This report presents estimates of the volume of water in five coal aquifers in the eastern and southern parts of the Northern Cheyenne Indian Reservation: the Canyon, Wall, Pawnee, Knobloch, and Flowers-Goodale coal beds in the Tongue River Member of the Tertiary Fort Union Formation. Only conservative estimates of the volume of water in these coal aquifers are presented. The volume of water in the Canyon coal was estimated to range from about 10,400 acre-feet (75 percent saturated) to 3,450 acre-feet (25 percent saturated). The volume of water in the Wall coal was estimated to range from about 14,200 acre-feet (100 percent saturated) to 3,560 acre-feet (25 percent saturated). The volume of water in the Pawnee coal was estimated to range from about 9,440 acre-feet (100 percent saturated) to 2,360 acre-feet (25 percent saturated). The volume of water in the Knobloch coal was estimated to range from about 38,700 acre-feet (100 percent saturated) to 9,680 acre-feet (25 percent saturated). The volume of water in the Flowers-Goodale coal was estimated to be about 35,800 acre-feet (100 percent saturated). Sufficient data are needed to accurately characterize coal-bed horizontal and vertical variability, which is highly complex both locally and regionally. Where data points are widely spaced, the reliability of estimates of the volume of coal beds is decreased. Additionally, reliable estimates of the volume of water in coal aquifers depend heavily on data about water levels and data about coal-aquifer characteristics. Because the data needed to define the volume of water were sparse, only conservative estimates of the volume of water in the five coal aquifers are presented in this report. These estimates need to be used with caution and mindfulness of the uncertainty associated with them.

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USGS2013

Erosional and depositional changes wrought by the flood of May 1978 in the channels of Powder River, southeastern Montana

Powder River’s second largest flood of record (1919–2012) moved through northeastern Wyoming and southeastern Montana during May 1978. Within a ninety-kilometer reach of the channel in southeastern Montana, the most prominent planform effects of the flood were the growth of meander bends by bank erosion (this was most intense just downriver of bend apexes, causing 1–2 channel widths of lateral displacement) and the erosion of new cutoff channels through the necks of two large and two small meanders. Surveys of cross sections, made before and after the flood, show the responses of the channel to the flood waters, which ranged from minimal (bedrock control) to large (maximum channel curvature in unconsolidated bank and terrace deposits). Geomorphic work done during two weeks of extreme flooding in May 1978, as measured by cross-channel erosion and new sediment deposition, was approximately equal in magnitude to the work done during the two decades (1978–1998) that followed the flood.

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USGS2013

Groundwater and surface-water interaction within the upper Smith River Watershed, Montana 2006-2010

The 125-mile long Smith River, a tributary of the Missouri River, is highly valued as an agricultural resource and for its many recreational uses. During a drought starting in about 1999, streamflow was insufficient to meet all of the irrigation demands, much less maintain streamflow needed for boating and viable fish habitat. In 2006, the U.S. Geological Survey, in cooperation with the Meagher County Conservation District, initiated a multi-year hydrologic investigation of the Smith River watershed. This investigation was designed to increase understanding of the water resources of the upper Smith River watershed and develop a detailed description of groundwater and surface-water interactions. A combination of methods, including miscellaneous and continuous groundwater-level, stream-stage, water-temperature, and streamflow monitoring was used to assess the hydrologic system and the spatial and temporal variability of groundwater and surface-water interactions. Collectively, data are in agreement and show: (1) the hydraulic connectedness of groundwater and surface water, (2) the presence of both losing and gaining stream reaches, (3) dynamic changes in direction and magnitude of water flow between the stream and groundwater with time, (4) the effects of local flood irrigation on groundwater levels and gradients in the watershed, and (5) evidence and timing of irrigation return flows to area streams. Groundwater flow within the alluvium and older (Tertiary) basin-fill sediments generally followed land-surface topography from the uplands to the axis of alluvial valleys of the Smith River and its tributaries. Groundwater levels were typically highest in the monitoring wells located within and adjacent to streams in late spring or early summer, likely affected by recharge from snowmelt and local precipitation, leakage from losing streams and canals, and recharge from local flood irrigation. The effects of flood irrigation resulted in increased hydraulic gradients (increased groundwater levels relative to stream stage) or even reversed gradient direction at several monitoring sites coincident with the onset of nearby flood irrigation. Groundwater-level declines in mid-summer were due to groundwater withdrawals and reduced recharge from decreased precipitation, increased evapotranspiration, and reduced leakage in some area streams during periods of low flow. Groundwater levels typically rebounded in late summer, a result of decreased evapotranspiration, decreased groundwater use for irrigation, increased flow in losing streams, and the onset of late-season flood irrigation at some sites. The effect of groundwater and surface-water interactions is most apparent along the North and South Forks of the Smith River where the magnitude of streamflow losses and gains can be greater than the magnitude of flow within the stream. Net gains consistently occurred over the lower 15 miles of the South Fork Smith River. A monitoring site near the mouth of the South Fork Smith River gained (flow from the groundwater to the stream) during all seasons, with head gradients towards the stream. Two upstream sites on the South Fork Smith River exhibited variable conditions that ranged from gaining during the spring, losing (flowing from the stream to the groundwater) during most of the summer as groundwater levels declined, and then approached or returned to gaining conditions in late summer. Parts of the South Fork Smith River became dry during periods of losing conditions, thus classifying this tributary as intermittent. The North Fork Smith River is highly managed at times through reservoir releases. The North Fork Smith River was perennial throughout the study period although irrigation diversions removed a large percentage of streamflow at times and losing conditions persisted along a lower reach. The lowermost reach of the North Fork Smith River near its mouth transitioned from a losing reach to a gaining reach throughout the study period. Groundwater and surface-water interactions occur downstream from the confluence of the North and South Fork Smith Rivers, but are less discernible compared to the overall magnitude of the main-stem streamflow. The Smith River was perennial throughout the study. Monitoring sites along the Smith River generally displayed small head gradients between the stream and the groundwater, while one site consistently showed strongly gaining conditions. Synoptic streamflow measurements during periods of limited irrigation diversion in 2007 and 2008 consistently showed gains over the upper 41.4 river miles of the main stem Smith River where net gains ranged from 13.0 to 28.9 cubic feet per second. Continuous streamflow data indicated net groundwater discharge and small-scale tributary inflow contributions of around 25 cubic feet per second along the upper 10-mile reach of the Smith River for most of the 2010 record. A period of intense irrigation withdrawal during the last two weeks in May was followed by a period (early June 2010 to mid-July 2010) with the largest net increase (an average of 71.1 cubic feet per second) in streamflow along this reach of the Smith River. This observation is likely due to increased groundwater discharge to the Smith River resulting from irrigation return flow. By late July, the apparent effects of return flows receded, and the net increase in streamflow returned to about 25 cubic feet per second. Two-dimensional heat and solute transport VS2DH models representing selected stream cross sections were used to constrain the hydraulic properties of the Quaternary alluvium and estimate temporal water-flux values through model boundaries. Hydraulic conductivity of the Quaternary alluvium of the modeled sections ranged from 3x10-6 to 4x10-5 feet per second. The models showed reasonable approximations of the streambed and shallow aquifer environment, and the dynamic changes in water flux between the stream and the groundwater through different model boundaries.

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USGS2013

Factors influencing the distribution of native bull trout and westslope cutthroat trout in western Glacier National Park, Montana

The widespread declines of native bull trout ( Salvelinus confluentus ) and westslope cutthroat trout ( Oncorhynchus clarkii lewisi ) populations prompted researchers to investigate factors influencing their distribution and status in western Glacier National Park, Montana. We evaluated the association of a suite of abiotic factors (stream width, elevation, gradient, large woody debris density, pool density, August mean stream temperature, reach surface area) with the occurrence (presence or absence) of bull trout and westslope cutthroat trout in 79 stream reaches in five sub-drainages containing glacial lakes. We modeled the occurrence of each species using logistic regression and evaluated competing models using an information theoretic approach. Westslope cutthroat trout were widely distributed (47 of 79 reaches), and there appeared to be no restrictions on their distribution other than physical barriers. Westslope cutthroat trout were most commonly found in relatively warm reaches downstream of lakes and in headwater reaches with large amounts of large woody debris and abundant pools. By contrast, bull trout were infrequently detected (10 of 79 reaches), with 7 of the 10 (70%) detections in sub-drainages that have not been compromised by non-native lake trout ( S. namaycush ). Bull trout were most often found in cold, low-gradient reaches upstream of glacial lakes. Our results indicate that complex stream habitats in sub-drainages free of non-native species are important to the persistence of native salmonids in western Glacier National Park. Results from this study may help managers monitor and protect important habitats and populations, inform conservation and recovery programs, and guide non-native species suppression efforts in Glacier National Park and elsewhere.

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