Thesis (M.S.)--Oregon State University, 1976. / Typescript (photocopy). Includes bibliographical references. Also available via the World Wide Web.

Thesis (M.S.)--Oregon State University, 1976. / Typescript (photocopy). Some maps folded in pocket. Includes bibliographical references. Also available via the World Wide Web.

Thesis (M.S.)--Oregon State University, 1975. / Typescript (photocopy). Includes bibliographical references. Also available via the World Wide Web.

Thesis (M.S.)--Oregon State University, 1974. / Typescript (photocopy). Maps folded in pocket. Includes bibliographical references. Also available via the World Wide Web.

Agricultural land and water use has modified natural flow regimes in the western US. Understanding the effect of agricultural water use on streamflow is critical to effective water management and is often limited by the available data record. This investigation evaluates agricultural water use and streamflow in the Smith River watershed (SRW), a semi-arid agricultural watershed located on the eastern slope of the northern Rocky Mountains in west-central Montana. Questions motivating this study include: (1) Has agricultural water use modified streamflow on the Smith River? (2) What aspect of agricultural activity in the Smith River watershed is having the greatest effect on streamflow? (3) What hydrologic properties of the watershed determine streamflow sensitivity to agricultural land and water use? Three approaches are employed to address these questions: (1) construction of an annual water budget, (2) comparison of streamflow to current and historic agricultural water use intensity, and (3) simulation of watershed processes using a precipitation-runoff model. Based on the mean-annual water budget estimate of the SRW, 12 percent of mean-annual streamflow in the Smith River is consumed by irrigation water use. The hydrologic effects of increased irrigated area detected with linear regression analyses of streamflow and agricultural water use include decreased seasonal flows in April, May, and June; increased late-summer flows in August and September; and increased low-flow volumes. Numerical hydrologic model simulations demonstrate that dominant precipitation-runoff processes in the watershed cannot be adequately represented without including agricultural water use.

Soil moisture processes in the top soil is a pivotal element in the terrestrial phase of the hydrologic cycle over a wide range of scales. At the plot scale, soil moisture exerts a strong control on runoff, evapotranspiration, and the transfer of water to deeper soil levels and aquifers. It affects the heat capacity of the soil and determines important ecological and geochemical processes such as the distribution of soil microbial communities, mineralization rates or soil respiration. The mechanisms that control soil moisture dynamics are controversial, varying for different regions and scales. Most understanding comes from research on water-limited systems that may not be applicable in snow-driven systems. This study presents a field investigation on the dynamics that control the distribution of soil moisture at the plot scale in a snow-dominated sub-alpine catchment. The research experimentally validates previous modeling studies and determines whether evapotranspiration (extractive, energy-driven controls) is the main generator of soil moisture heterogeneity vs. differential snowmelt (additive control). The field study site, located in the Bitterroot Mountains, Montana, is instrumented with soil moisture/temperature sensors, meteorological station, and sap flux system monitoring an Engelmann Spruce. Results show that the highest heterogeneity in moisture occurs at intermediate water contents resulting from the spring snowmelt driven wetting process while the lowest heterogeneity occurs at the early fall conclusion of the drying season. The presence of the tree canopy alters the spatial distribution of precipitation and snowmelt and results in a dampening of weather induced soil moisture variability under canopies in comparison to open areas. We show that spatial distribution of precipitation and snowmelt (additive processes) are a stronger control on the generation of heterogeneity in soil moisture than evapotranspiration (extractive processes) in a snow dominated environment.

The Lewis and Clark line experienced sinistral transpressive shear during the Late Cretaceous-late Paleocene Laramide orogeny along the boundary between the massive Lewis-Eldorado-Hoadley thrust slab to the NE and the Sapphire and Lombard thrust slabs to the SW. The transpression extruded SE trending, en echelon flower structures along a 40 km-wide shear zone. Late Cretaceous satellite stocks of the Boulder batholith intruded the shear zone and interfered with folding and faulting. One of these, the 83-Ma Garnet stock, invaded a narrow NE-trending fracture zone that straddled the shear zone at deeper levels in the Proterozoic Belt Supergroup but mushroomed in a SE-trending, SW-verging syncline in the Paleozoic section, imprinting a compressional fabric in its aureole of E-W striking cleavage planes and top-to-the-SW rotated porphyroblasts. The stock and its family of sills did not cross the axial plane of the neighboring anticline, and the contact aureole was generally confined to the syncline and the steep limb of the anticline-syncline pair. Maximum pressure and temperature of contact metamorphism is estimated at 2.8 kbar and 650°C from thermodynamic modeling of andalusite-sillimanite bearing hornfels. Magmatic stoping led to downward shear being applied to rock of the contact aureole, creating a down-dip stretching lineation and layer-parallel boudins. Stratigraphic units thin to ~1/2 of their normal thickness within the aureole due to metamorphism as well as shear associated with stoping. Emplacement was followed by a second phase of transpression that began after 76 Ma and ended during the early Cenozoic, when the Lewis and Clark Line underwent dextral transtensile shear evidenced by a newly-mapped right-lateral extensional accommodation zone within the field area.

I investigated relationships between geomorphology, hydrogeology, and bull trout (Salvelinus confluentus) redd occurrence and density at multiple spatial scales in gravel-bed, pool-riffle, snowmelt dominated headwater streams of northwestern Montana. Subreach redd occurrence tended to be associated with the finest available textural facies. In subreach streambed sections hosting bull trout redds, redd density was significantly (at α=0.05) positively related to bankfull Shields stress (τ*bf, p=0.04) and bankfull Shields stress adjusted for grain stress only (τ**bf, p=0.02). In stream reaches hosting bull trout redds, reach-average redd density was significantly positively related to reach-average τ**bf (p=0.02) and reach-average streambed grain size (D16, p=0.01; D50, p=0.02, D84, p=0.02). Spawning reaches exhibited high streambed horizontal and vertical hydraulic conductivities, and streambed temperatures were dominated by stream water diurnal cycles to a depth of at least 25 cm. Groundwater provided substantial thermal moderation of stream water for multiple high density spawning reaches. At the valley-scale, redd occurrence tended to be associated with unconfined alluvial valleys. Many previous studies highlight the thermal sensitivity of bull trout. My spawning gravel competence results indicate that a shift in the timing of high flows could increase the likelihood of redd scour during the bull trout egg incubation period.

The Santonian-Campanian Eagle Formation in south-central Montana was deposited along the western margin of the Cretaceous Western Interior Seaway and is composed of a series of well preserved regressive and transgressive deposits. This study documents the depositional evolution of the informal lower member of the Eagle Formation exposed near Billings, MT. Detailed mapping and characterization of the internal stratigraphy, facies architecture, and bounding surfaces of the lower Eagle provide the basis for reconstruction of a paleodelta system that serves as a valuable reservoir analog within the Cretaceous Seaway and elsewhere. This study demonstrates that the informal lower member of the Eagle Formation in south-central Montana was deposited in a regressive to transgressive wave-dominated deltaic system. Within this deltaic succession the identification of five facies and four bounding surface types are used to establish a two-phase depositional history: 1) a regressive phase characterized by prograding pro-delta to distal delta front deposits emplaced below fair weather wave base but above storm wave base; and 2) a transgressive phase characterized by landward dipping proximal to distal shoal overwash fan deposits derived from combined-flow storm-generated turbidity currents. A maximum regressive surface (MRS) separates underlying prograding deltaic deposits from downlapping shoal overwash fan deposits above. Shoal overwash fan packages dip and stack en-echelon towards the paleoshoreline indicating landward migration of the shoal during delta transgression. A time-transgressive ravinement surface (TRS) developed on the basinward side of the transgressive shoal and migrated landward with the shoreline, truncating of shoal overwash fan deposits.

This research describes the alluvial deposits and Quaternary geomorphic evolution of the Upper Green River in Kentucky by documenting the nature of flood plain sediments at two sites along the valley bottom of the Upper Green River between Mammoth Cave National Park and Green River Lake. Field methods employed included stratigraphic descriptions of bank exposures and borings obtained in flood plain surfaces, along with textural and radiocarbon analysis of sediment samples. Sediment samples from boreholes and bank exposures in two study sites (Pitman Creek confluence, -PCC- and Upper Green River Biological Preserve -UGRBP-) were collected and sieved to determine grain size distributions and stratigraphic patterns. Deposits characterized in the study area are predominantly medium to coarse silt, reflecting vertical aggradation, underlain by sands and gravels representing channel deposits associated with lateral channel migration. In collaboration with the Kentucky Geological Survey, additional boreholes were drilled at both sites using a Giddings probe. Stratigraphic sections, radiocarbon dating of buried organic material, and geomorphic observations suggest the existence of three distinctive geomorphic surfaces at PCC study site: a Lower Holocene alluvium (LHA), an Early Holocene alluvium (EHA), and a Dissected Quaternary terraces (DQT). Equivalent LHA, EHA, and DQT units were recognized downstream at the UGRBP study site. During the Pleistocene and Early Holocene epochs the Upper Green River experienced periodic entrenchment as evidenced by terraces preserved in the valley (e.g. DQT unit) followed by a renewed period of incision and aggradation stages during the Holocene reflected by alluvial units (EHA) and (LHA). Based on radiocarbon analysis of in-situ organic material, overbank sedimentation rates on the LHA surfaces of 2.5 cm/yr at the PCC site and 1.7 cm/yr at UGRBP study site are estimated for the most recent (-1750-1950 AD) deposits. Radiocarbon analysis of leaves collected from a layer at the base of an island bank exposure at the UGRBP site returned a date of 2300 ± 40 yrs BP. This layer is interpreted as remnants of older deposits incorporated into the modern river alluvium. An increase in sediment deposition rates in the historical period is consistent with increasing sediment supply due to land clearance for agriculture. Since no major Quaternary tectonic activity is reported for the region, it is reasonable to conclude that climate variability is the primary driver of Quaternary river incision and aggradation that are responsible for the valley features. The absence of paleosols in the upper 10 m of the deposits suggests rapid and continuous accumulation of sediment and the lack of stable conditions for soil development. This alluvial chronology of the Upper Green River complements the previous work on the Quaternary environmental and geomorphic evolution of the region. The contribution of new information about the textural trends and geomorphic characteristics of the Upper Green River floodplain deposits is useful to understand present-day river bank stability and sediment loading related to bank erosion. The evidence of accelerated sedimentation over the last 250 years corroborates the importance of land surface disturbance during the settlement of the region by non-native peoples. Key words: Green River, floodplain deposits, radiocarbon, Quaternary.