Search
Search Results
-
291. [Article] Assessing Disaster Preparedness among Latino Migrant and Seasonal Farmworkers in Eastern North Carolina
This is the publisher’s final pdf. The published article is copyrighted by MDPI AG (Basel, Switzerland) and can be found at: http://www.mdpi.com/journal/ijerph. To the best of our knowledge, one or more ...Citation Citation
- Title:
- Assessing Disaster Preparedness among Latino Migrant and Seasonal Farmworkers in Eastern North Carolina
- Author:
- Bethel, Jeffrey W., Burke, Sloane, Britt, Amber Foreman
This is the publisher’s final pdf. The published article is copyrighted by MDPI AG (Basel, Switzerland) and can be found at: http://www.mdpi.com/journal/ijerph. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work.
-
For the last fifty years, meadow foxtail (Alopecurus pratensis L.) has been invading native flood meadows throughout the Harney Basin in southeastern Oregon. The expansion of this grass species has been ...
Citation Citation
- Title:
- The effect of grazing interval on forage quality and production of meadow foxtail
- Author:
- Wenick, Jess J.
For the last fifty years, meadow foxtail (Alopecurus pratensis L.) has been invading native flood meadows throughout the Harney Basin in southeastern Oregon. The expansion of this grass species has been the result of its broad climatic requirements and ability to withstand drought while thriving in saturated soil conditions for a large part of the growing season. Meadow foxtail starts growth as soon as adequate soil moisture exists. Managing this early maturing hay species can prove to be a challenge because soil saturation and elevated water tables make it difficult to harvest hay when forage quality and yield are maximized. The purpose of this study was to evaluate whether planned grazing would retard maturation and thus prolong forage quality. Treatments included a non-grazed control and grazing durations of 2, 4, 6, and 8 weeks. Grazing was initiated in May of 1998 and 1999 on six replications of each treatment arranged in a randomized block design. Within each treatment/replicate combination, ten 0.2 m² plots were clipped to ground level at about two week intervals from May to August. The samples were weighed and dried for standing crop estimation and 4 of the 10 samples were selected at random and analyzed for acid detergent fiber (ADF), neutral detergent fiber (NDF), and crude protein (CP). Analyses of variance, least significant differences, and regression analyses were calculated to determine whether or not there were statistical differences of P≤0.05. We found that early spring grazing decreased forage yield significantly. An increase in CP with duration of defoliation was expected and obtained. The results of grazing on the fiber components of forage, however, were inconclusive. Grazing had minimal effect on fiber fractions, but did delay the decline in CP. However, there was a fairly severe decline in hay production, even with the shortest duration of grazing.
-
The Juniper Ridge volcanic complex is located in the High Lava Plains Province of southeastern Oregon, a wide zone of bimodal volcanism and faulting that marks the northern limit of widespread Basin and ...
Citation Citation
- Title:
- Geology and geochemistry of Juniper Ridge, Horsehead Mountain and Burns Butte : implications for the petrogenesis of silicic magma on the High Lava Plains, southeastern Oregon
- Author:
- MacLean, James W.
The Juniper Ridge volcanic complex is located in the High Lava Plains Province of southeastern Oregon, a wide zone of bimodal volcanism and faulting that marks the northern limit of widespread Basin and Range-style faulting in the northern Great Basin Province. Rhyolite dome complexes are progressively younger to the northwest along the High Lava Plains, providing a mirror-image to age-progressive silicic volcanism on the Snake River Plain in southern Idaho. 40Ar-39Ar dating of rocks from western and eastern Juniper Ridge (5.70 ± 0.02 Ma and 6.87 ± 0.02 Ma, respectively) and Burns Butte (7.75 ± 0.06 Ma) confirms the overall age progression, and shows that age relations within the Juniper Ridge complex are consistent with the trend. Horsehead Mountain (15.54 ± 0.03 Ma) predates the age progression altogether. Rocks at both eastern Juniper Ridge and western Juniper Ridge are overlain by diktytaxitic olivine basalt flows similar to regional high-alumina olivine tholeiites (HAOTs). At western Juniper Ridge, high-silica rhyolite flows overlie lower-silica rhyolite and hybrid andesite flows. At eastern Juniper Ridge, a suite of intermediate rocks ranging from basaltic andesite to dacite overlies a series of rhyolite flows. Rocks at Burns Butte consist of high-silica rhyolite, porphyritic dacite and rhyodacite, and andesite. Field and petrographic observations, including mixing textures, inclusions, and xenocrysts, along with straight-line relationships on chemical diagrams, show that the intermediate rocks at western Juniper Ridge formed by mixing between high-silica rhyolite magma and slightly evolved HAOT, probably at the base of a large silicic magma chamber. In contrast, curvilinear geochemical trends and an internally consistent four-stage major and trace element model suggest that intermediate rocks at eastern Juniper Ridge evolved in small, unconnected magma chambers by removal of olivine, plagioclase, clinopyroxene, and magnetite from a primitive HAOT parent, accompanied by contamination by up to 22 percent rhyolite. Unusually elevated concentrations of incompatible trace elements in the Squaw Butte basaltic andesite were produced by either zone refining or combined fractionation and recharge. The least-evolved rhyolites at eastern and western Juniper Ridge have lower rare-earth element concentrations than the intermediate fractionates at eastern Juniper Ridge, thus precluding an origin by crystal fractionation from the observed intermediate rocks, but have major element compositions close to those of experimental dehydration melts of amphibolite. The rhyolites probably originated as dehydration melts of an amphibolite lower crust, which were subsequently modified by removal of quartz, sanidine, plagioclase, clinopyroxene and zircon. At western Juniper Ridge, the fractionating assemblage probably included trace allanite. Rhyolites from dome complexes and ash-flow tufts of the 5- to 10-Ma portion of the ageprogressive trend show systematic trace element variations with position along the trend. Dome complexes include Burns Butte, Palomino Butte, eastern and western Juniper Ridge and Glass Buttes; ash-flow tufts include the Devine Canyon Tuft, the Prater Creek Tuft, the Rattlesnake Tuff and the tuft of Buckaroo Lake. From east to west, Y/Nb and Yb/Ta increase, and Ce/Yb decreases in the least-evolved rhyolite in each suite. These variations can be accounted for by a systematic increase in degree of garnet-residual partial melting of amphibolite crust from east to west, correlating either with degree of extension with time along the Brothers fault zone, or with distance from the main axis of faulting. Porphyritic, calc-alkaline andesites and dacites erupted from at least six vents at Horsehead Mountain. Field relationships indicate a general decrease in age from southwest to northeast within the complex. At 15 Ma, calc-alkaline volcanism at Horsehead Mountain predates the age-progressive rhyolftes, and is instead part of an earlier phase of volcanism that produced the Steens and Columbia River flood basalts, along with several other caic-alkaline intermediate centers that are unrelated to subduction. Overlapping rare-earth element patterns of Horsehead Mountain intermediate rocks with those of Steens basalts precludes their derivation by fractionation from the broadly contemporaneous flood basalts.
-
Debris flow initiation is controlled by a complex interaction of geology, geomorphology, climate, and weather. In the Cascade Range of Pacific Northwest and mountainous areas globally, patterns of temperature ...
Citation Citation
- Title:
- Recent periglacial debris flows from Mount Rainier, Washington
- Author:
- Copeland, Elizabeth A. (Elizabeth Anne)
Debris flow initiation is controlled by a complex interaction of geology, geomorphology, climate, and weather. In the Cascade Range of Pacific Northwest and mountainous areas globally, patterns of temperature and precipitation are being altered by climate change, which may in turn impact debris flow initiation. Temperature has increased and patterns of precipitation have changed, potentially impacting the timing, geography, and triggering mechanisms of debris flows. Glacier retreat since the end of the Little Ice Age has exposed volumes of unstable sediment on steep slopes prone to debris flow initiation. Earlier spring snowmelt extends the snow-free window when rainstorms may mobilize sediment, resulting in debris flows. To ascertain the presence of a climate change signal we examined the timing, geography, and initiation mechanisms of recent (2001 to 2006) non-volcanic debris flows from Mount Rainier, Washington, the highest volcano in the Cascade Range with the largest ice-volume in the conterminous United States. Debris flows damage infrastructure, requiring costly repairs. Debris flows also deposit volumes of sediment in streams, potentially exacerbating future flood hazards. To characterize recent debris flows, field reconnaissance was conducted summer 2008 along suspected debris flow paths from initiation to deposition. Results from summer fieldwork were used in conjunction with analysis of aerial photography, Light Detection and Ranging (LiDAR), and other data to determine characteristics of debris flow initiation sites, such as elevation, slope, orientation, upslope contributing area, and proximity to glaciers. Recent debris flow initiation sites were also examined in reference to glacier characteristics, such as elevation of glacier termini, glacier retreat, orientation, area, and volume, for the years 1913, 1971, and 1994 from past work by Nylen (2004). Characterization of debris flow initiation sites and definition of the locations of longitudinal transitions in debris flow behavior allows estimation of future debris flow hazards also allows inferences to be drawn regarding initiation mechanisms to be inferred and suggests a trajectory for changing debris flow hazards due to climate change. Debris flows at Mt. Rainier occur in late summer through fall and recent events were no exception, occurring from August through November. A total of twelve debris flows occurred in six stream channels during the period of 2001 to 2006. Three channels not previously known to have experienced debris flows, two south-facing and one north-facing, were impacted. Debris flows tracks led up to glacier meltwater fed, steep-walled channels or gullies in unvegetated, unconsolidated Quaternary-age material immediately downslope of glacier margins. Debris flows initiated at an average elevation of 2181 m and an average channel gradient of 39°. While glaciers appear to play a key role in debris flow initiation, simple glacier metrics could not be used to distinguish glaciers near debris flow heads from those without proximal debris flows heads. All but one of the twelve debris flows initiated during rainfall. The single debris flow that occurred during dry-weather is described by Vallance et al. (2002). Rainfall induced debris flows in 2003, 2005, and 2006 were not associated with landslide scarps, rockfalls, or other indications of large slope failures. Rather, debris flows initiated in steep-walled gullies fed by glacier meltwater that were visible on aerial photography prior to the first known debris flow initiation in a particular channel. The steep flanks of Mt. Rainier contain many similar gullies that have not previously been associated with debris flows, but debris flow producing gullies are at higher elevations than gullies not associated with debris flows. The small population of recent debris flows and incomplete historic record of debris flows for the periods 1926 to 1985 and 1993 to 2001 limits analysis of changes in debris flow timing, geography, or triggering mechanism. The magnitude of recent events may have initially appeared greater than historic events as the 2005 and 2006 storms are the only ones known to have produced multiple debris flows in the recorded history of Mt. Rainier National Park. Yet much of the damage initially attributed to debris flows was due to widespread, severe flooding. Ongoing, detailed record keeping and possibly reconstruction of past events through paired geomorphic reconnaissance and dendrochronology is needed before conclusions regarding the impacts of climate change on debris flow initiation can be reached.
-
MIKE SHE is a fully distributed, physically-based hydrologic model that can simulate water movement over and under the Earth's surface. Evapotranspiration (ET) is one of the components of this model. MIKE ...
Citation Citation
- Title:
- Use of MIKE SHE for estimation of evapotranspiration in the Sprague River Basin
- Author:
- Shakya, Suva R.
MIKE SHE is a fully distributed, physically-based hydrologic model that can simulate water movement over and under the Earth's surface. Evapotranspiration (ET) is one of the components of this model. MIKE SHE uses a modification of the Kristensen -Jensen (1975) method to calculate actual ET. This method is based on addition of the three evapotranspiration components – interception storage, transpiration by the plant and evaporation from the soil surface, to compute total actual evapotranspiration. The validity of the Kristensen-Jensen method has been tested on an arid region within the Sprague River subbasin of the Upper Klamath basin in southern Oregon. The model was setup on a 1,000 m by 1,000 m flat surface as a one-dimensional grid cell. There are sixteen computation layers which make three soil profile layers with varying soil properties. Meteorological data from the Pacific Northwest Cooperative Agricultural Weather Network (AgriMet) were used to setup the model. Soil physical properties were taken from the Soil Survey Geographic (SSURGO) database of the Natural Resources Conservation Service (NRCS). Values of the van Genuchten parameters for soil water retention and hydraulic conductivity as a function of soil texture from Carsel and Parrish (1988) were applied. Wetland vegetation such as duckweed and cattail, natural vegetation such as big sagebrush, ponderosa pine and juniper, and agricultural crops such as grass pasture and maize were used to test MIKE SHE evapotranspiration simulation. The length of growth stage, crop coefficient, leaf area index (LAI) and root depth values were taken from the literature. Actual crop ET rates were calculated based on AgriMet reference ET which uses the Kimberly Penman (Wright, 1982) method. The alfalfa reference ET was converted to a grass reference by multiplying by a factor of 0.833 (Jensen et al., 1990). The single crop coefficient method was used and soil stress was accounted for using the FAO 56 method (Allen et al, 1998). Simulated irrigation was applied to maize and grass to keep the root zone soil moisture close to field capacity. Crop ET rates from the MIKE SHE simulation were then compared to the AgriMet based ET rates, resulting in a comparison of Kristensen-Jensen method against the Kimberly Penman method. Both the Kristensen-Jensen and AgriMet simulation scenarios were driven by the same reference ET and the same FAO 56 basal crop coefficient. Differences are therefore a function of different methods for dealing with soil moisture stress. Results indicate that the MIKE SHE simulated evapotranspiration corresponds to the Kimberly Penman method for the duckweed and cattail wetlands species with resulting Nash and Sutcliffe (NS) efficiencies of 0.97 and 1.00, respectively. The big sagebrush, juniper, and ponderosa pine species required a soil stress correction factor for the crop coefficients and the results yielded NS efficiency values of 0.14, 0.59 and 0.68, respectively. Irrigation was automatically turned on for maize at a 20 percent soil moisture deficit to minimize the effects of water stress and the resulting NS efficiency was 0.85. For pasture, an irrigation based on average monthly water deficit for pasture in Klamath was used (Cuenca et al.,1992). This resulted in a NS efficiency of 0.77. Each crop requires unique treatment within the model. Required vegetation parameters such as crop coefficient and LAI, climatic factors such as reference ET, and soil hydraulic properties need to be based on local conditions to the extent possible. It should be noted that the MIKE SHE simulations were run in a one-dimensional mode which precluded accounting for spatial variability or lateral flow of surface or groundwater. The simulation results indicate that converting the study area into a well irrigated pasture would require application of substantial amounts of irrigation water by sprinkler or flooding. Wetlands would require even more water to flood the land, but would be well suited for development of regional habitat. Big sagebrush, juniper and ponderosa pine survive under natural conditions but experience considerable plant stress brought on by soil water deficits which limit plant production below the maximum possible growth.
-
Contiential margins on plate boundaries are complex systems with morphologies and characteristics dictated by the interplay of sediment deposition and erosion, tectonic faulting, folding, and strong ground ...
Citation Citation
- Title:
- Investigating Plate Boundaries through New High-Resolution Bathymetry and Seismic Data; 2 Case Studies from the Cascadia Subduction Zone and San Andreas Fault
- Author:
- Beeson, Jeffrey Watson
Contiential margins on plate boundaries are complex systems with morphologies and characteristics dictated by the interplay of sediment deposition and erosion, tectonic faulting, folding, and strong ground motion generating mass wasting events. With ever increasing advances in high-resolution remote sensing techniques these systems are increasingly becoming illuminated. A ~120 km offshore portion of the northern San Andreas Fault (SAF) between Point Arena and Point Delgada was mapped using closely spaced seismic-reflection profiles, high-resolution multibeam bathymetry and marine magnetics data. This new dataset documents SAF location and continuity, associated tectonic geomorphology, shallow stratigraphy and deformation. Variable deformation patterns in the generally narrow (~1-km-wide) fault zone are largely associated with fault trend, and with transtensional and transpressional fault bends. We divide this unique transtensional portion of the offshore SAF into six sections along and adjacent to the SAF based on fault trend, deformation styles, seismic stratigraphy, and seafloor bathymetry. This southern region of the SAF includes a 10-km-long zone characterized by two active, parallel fault strands in which the SAF is evolving into a straighter orientation via migrating fault releasing and restraining bends. The SAF in the northern region of the survey area passes through two acute fault bends (~9° (right), and ~8° (left)), resulting in both an asymmetric “Lazy Z” sedimentary basin (“Noyo Basin”) and an uplifted rocky shoal (“Tolo Bank”). Noyo Basin subsidence and tilt rates, as well as SAF lateral slip rates, were determined based on seismic-stratigraphic sequences and unconformities correlated with the previous 4 major Quaternary sea-level lowstands. Progressively steeper erosional surfaces record basin tilting of ~0.6° per 100,000 years. Migration of the basin depocenter indicates a lateral slip rate on the San Andreas Fault of 10 to 19 mm/yr for the past 350,000 years. Data collected west of the SAF on the south flank of Cape Mendocino rule out the previously postulated presence of an offshore fault strand that connects the SAF with the Mendocino Triple Junction. Instead, the SAF passes on land at Point Delgada, where the SAF plate boundary transitions to the Kings Range thrust. Utilizing new high resolution multibeam bathymetric data, chirp sub-bottom and multichannel seismic reflection profiles, we identify and describe submarine channels, submarine landslides, and three “new” erosional features on the toe of the Cascadia accretionary wedge near Willapa Canyon, offshore Washington, USA. Bathymetric data was compiled from the Cascadia Open-Access Seismic Transects (COAST) cruise and from the site survey cruise for the Cascadia Initiative. This new high-resolution dataset has illuminated geomorphic features that suggest this section of the margin underwent radical erosion in the latest-Pleistocene. Three “new” and peculiar features were imaged that superficially resemble slope failures of the frontal thrust, but are distinguished from such failures by 1) incision of the crest of the frontal thrust and anticlinal ridge, and piggyback basin; 2) they have floors below the level of the abyssal plain, and have excavated deeply into the frontal anticline 3) The features are connected to the main Willapa Channel by inactive paleo channels. The features were likely formed during the latest Pleistocene based on post event deposition, cross-cutting by the modern Juan de Fuca and Willapa Channel levees, and post- event slip on the frontal thrust of the Cascadia accretionary prism. Based on morphology, dissimilarity with other submarine features on the Cascadia and other margins, and available age constraints, we infer that these features were most likely formed by massive turbidity currents associated with the glacial lake outpourings in the Pacific Northwest known as the Missoula floods.
-
297. [Article] Paleoclimate, paleoventilation, and paleomagnetism as recorded in a 17kyr marine sediment record from the SE Alaska margin
The deglacial behavior of the sub-Arctic North Pacific is poorly constrained, with many published records suffering from limited age control due to extensive post- depositional biogenic carbonate dissolution. ...Citation Citation
- Title:
- Paleoclimate, paleoventilation, and paleomagnetism as recorded in a 17kyr marine sediment record from the SE Alaska margin
- Author:
- Davies, Maureen Helen
The deglacial behavior of the sub-Arctic North Pacific is poorly constrained, with many published records suffering from limited age control due to extensive post- depositional biogenic carbonate dissolution. Potential alternative dating methods could include the correlation of stable-isotopic and/or paleomagnetic secular variation records to an independently-dated regional template, however no such template currently exists. Cores EW0408-85JC (59°33.32'N, 144°9.21'W, 682 m water depth) and EW0408-79JC (59°33.32'N, 144°9.21'W, 682 m water depth) are located above the carbonate compensation depth on the Gulf of Alaska margin, affording an opportunity to inter- compare stable-isotopic and paleomagnetic variability from a single location, as well as to place observations of Northeast Pacific paleoclimate and paleomagnetic secular variation in a global context via an independent radiocarbon-based chronology. We evaluate three possible age models for core EW0408-85JC and their implications for North Pacific stable isotopic and paleoventilation behavior. These include calibrated planktonic and benthic foraminiferal radiocarbon dates, assuming constant reservoir ages, as well as a correlation of planktonic δ¹⁸O in foraminifera to δ¹⁸O in a layer-counted Greenland ice core (NGRIP). We conclude that the calibrated planktonic dates provide the most accurate chronology. Benthic foraminiferal radiocarbon dates evaluated on this age model indicate that intermediate-depth ventilation ages at the site increased to >2,670 ± 180 during Termination 1, implying reduced ventilation relative to the Holocene average of 1,740 ± 210 yr. The shift to lower ventilation ages occurs at ~10,500 cal ybp, coeval with the flooding of Beringia and the opening of the Bering Strait, suggesting that flooded shelves and net export of low- salinity surface waters enhanced ventilation of the North Pacific. Oxygen isotope data from planktonic and benthic foraminifera, interpreted on this age model, document surface freshening by 16,650 ± 170 cal ybp, likely due to freshwater input from retreating regional glaciers. A sharp transition to laminated hemipelagic sedimentation at 14,790 ± 380 cal ybp is coincident with abrupt warming and/or freshening of the surface ocean (i.e. additional δ¹⁸O reduction of 0.9 ‰), essentially coincident with the Bolling Interstade of Northern Europe and Greenland. Cooling and/or higher salinities returned during the Allerod interval, coeval with the Antarctic Cold Reversal and continuing until 11,740 ± 200 cal ybp, when the onset of warming coincides with the end of the Younger Dryas. This may indicate convolved Northern and Southern drivers of climate variability in the North Pacific. Two laminated opal-rich intervals record episodes of high productivity are observed from 14,790 ± 380 to 12,990 ± 190 cal ybp, and from 11,160 ± 130 to 10,750 ± 220 cal ybp. These events likely correlate to similar observations elsewhere on the margins of the North Pacific, and may be driven my remobilization of iron from newly inundated continental shelves during episodes of rapid sea-level rise. High-resolution paleomagnetic secular variation (PSV) records from the Gulf of Alaska constrain regional field behavior and provide information on larger scale geomagnetic dynamics. Both cores studied (EW0408-79JC and 85JC) preserve a generally strong and relatively stable (MAD <5°) magnetization for the period of overlap, though the quality of the magnetization at 85JC deteriorates beyond 8,000 cal ybp, in association with deglacial and early Holocene shifts in magnetic mineralogy. Component inclinations from both sites are consistent with historical reconstructions and consistent with a geocentric axial dipole (GAD), supporting spherical-harmonic attempts to model the Holocene field. Comparison with regional reconstructions suggest that even the earlier component of 85JC captures PSV fairly accurately, providing new information on this part of the record. Normalized remanence is reconstructed using NRM/ARM, though variability in the magnetic remanence carrier precludes us from interpreting these records as robust reflections of North Pacific relative paleointensity. The independently-dated directional records, however, are consistent with other regional reconstructions as well as those derived further afield in North America, suggesting that the concept of coherent North American flux lobe behavior through the majority of the Holocene can now be extended to the Gulf of Alaska.
-
California's water resources vary throughout the state owing to the regions varying topography, diverse climate, and the distribution of precipitation. Most of the state's precipitation falls over the ...
Citation Citation
- Title:
- Identifying "at-risk" regions of snow accumulation within California's Sierra Nevada Mountains, and assessing implications on reservoir operations
- Author:
- Kalyan, Imtiaz-Ali M.
California's water resources vary throughout the state owing to the regions varying topography, diverse climate, and the distribution of precipitation. Most of the state's precipitation falls over the northern coastal range and the western slopes of the Sierra Nevada Mountains. Winter snowpack that accumulates within these mountain basins serves as an efficient means of natural water storage. Moreover, the state's two massive water conveyance systems, the State Water Project (SWP) and the Central Valley Project (CVP), are integrally dependent upon winter snowpack accumulation, and subsequent spring snowmelt runoff. The SWP and CVP's extensive network of reservoirs, pipes, and aqueducts are engineered to collect and transport water from the snowcapped Sierra Nevada Mountains where it is plentiful, to farmland and urban communities where it is scarce but in greatest demand. However, increased warming within these mountain basins is causing a declined winter snowpack, altering the fraction of precipitation occurring as snow, and changing the timing of snowmelt derived streamflow. The loss of this immense amount of naturally occurring stored water, and its earlier arrival at the downstream reservoirs, has profound implications on the state's existing water management infrastructure. This work attempts to address these water management challenges that lie in the foreseeable future. Using a binary based deterministic approach, and a climatologically record of temperature and precipitation, "at-risk" snow dominated regions were identified throughout the Feather River Basin, and nested basins of the San Joaquin Watershed. These "at-risk" regions represent locations that would be the first to transition from a snow dominated, to a rain dominated precipitation regime under projected future warming scenarios. Future warming projections ranging from 1°C to 4°C were analyzed relative to the 1971-2000 base period. Results show that if warming trends considered by the IPCC 2007 report to be highly likely continue, nearly all snow dominated regions existing between 1500 and 2100 m in the San Joaquin Watershed would become rainfall dominated. Within the Feather River Basin, in the Sacramento Watershed, implications are even more alarming. A 3°C warming in February would result in approximately 87% of the regions previously snow covered area (SCA) becoming rainfall dominated; only 12% of the basin would remain snow covered. The decline of winter snowpack within all six study basins is closely correlated with elevation and average winter temperatures. Lower elevation, snow dominated regions near the rain to snow transition zone are highly sensitive to warmer temperatures relative to higher elevation, colder snow dominated regions. Furthermore, warming during high precipitation months, from December to February, would yield the largest reductions in loss of Snow Water Equivalent (or SWE). The loss of this immense amount of naturally occurring stored water, and its earlier arrival at the downstream reservoirs poses challenges and opportunities for California's water managers. For reservoir managers, adapting to a rapidly changing climate would require updating rigid flood control rule curves that were established based on hydrological trends during the first half of the twentieth century. Developing greater flexibility into flood-control rule curves could allow reservoir managers to store more water in the winter, thereby mitigating the consequences of snow loss from natural stored water sources. Faced with an expanding population and increased strains on water resources availability, sustaining future water demands hinges on developing adaptive water management strategies. By understanding basin and, at a finer scale, elevation specific vulnerability to snow loss due to warming, water managers can begin to guide effectual adaptation strategies.
-
A trial was conducted May 1 to September 4, 1989 at the Eastern Oregon Agricultural Research Center (EOARC) Burns, OR to examine the effects of strip or continuous grazing management on the diet and performance ...
Citation Citation
- Title:
- Effects of strip versus continuous grazing management on diet parameters and performance of yearling steers grazing native flood meadow vegetation in eastern Oregon
- Author:
- Blount, David Kenneth
A trial was conducted May 1 to September 4, 1989 at the Eastern Oregon Agricultural Research Center (EOARC) Burns, OR to examine the effects of strip or continuous grazing management on the diet and performance of steers grazing native flood meadows. The objective was to determine if strip grazing would be a more efficient means of grazing management than continuous grazing. The experiment was designed to test diet quality, botanical composition of the diet, daily dry matter (DM) intake and performance of yearling steers. Eighty yearling steers weighing 253±17 kg were selected from cattle at the Squaw Butte Experiment Station. The experimental design was a randomized complete block, with blocking based on past forage production. Treatments were continuous or strip grazing. A representative meadow of approximately 22.4 ha was divided into four equal pastures. Continuous grazing steers had access to 5.6 ha pastures for the duration of the study. Animals on strip grazing were confined to an area that was estimated to provide 5-7 days of forage using New Zealand portable electric fencing. Strip sizes were predetermined based on standing forage crop. Steers were not allowed to graze more than 7 days in any one strip. Diet quality was estimated from bi-weekly esophageal samples. Extrusa was collected from 4 esophageal fistulated steers per treatment on two consecutive days. Collections were timed to coincide with the mid point of the strip being currently grazed. Samples were pooled by collection dates and analyzed for CP and IVOMD. Dietary OM intake was estimated from biweekly, 24 hr total fecal collections starting the day following esophageal collections. Total DM fecal output from 6 fecal collection steers per treatment was corrected with the %IVOMD to predict actual DM intake. Diet botanical composition was estimated by microhistological examination of fecal sub-samples. Animal weight gains were recorded bi-weekly. Experimental animals grazed together at all times during the trial. Initial stocking densities were 2.0 AU/ha in each treatment pasture. Steers were counted as .56 AU with 20 steers grazing 5.6 ha pastures. The average strip size over the trial was .46 ha; and depending upon standing crop of forage, ranged from .23-1.15 ha. Record moisture from snowmelt and rainfall resulted in greater than expected standing crop of forage. This growth resulted in under stocking of both treatment pastures. A 1.08 ha block was removed as hay from the higher forage producing strip treatment block to adjust for over abundant forage. This resulted in a total mean strip grazed area of 4.37 ha or 22% less than continuous grazing. Actual grazing density means over the summer were 2.6 AU/ha for continuous and 3.15 AU/ha for the strip treatment. Available forage was determined from clipped plots on a DM basis and expressed as herbage allowance at a given point in time. Herbage allowance for steers in continuous grazed pastures ranged from 405-1153 kg/AU when measured at bi-weekly intervals and 68-186 kg/AU for strip grazed steers when estimated at the beginning of each strip. Grazing pressure was higher for strip grazed steers (.10 AU/kg) compared to continuous (.02 AU/kg). Diet quality declined significantly over the summer (P<.01). Analysis for CP in steer diets provided values of 13.9 vs 10.9% for continuous and strip treatments, respectively. However, this difference was not significant (P=.14). Digestibility analysis suggested that forage in continuous diets tended (P=.07) to have higher IVOMD than strip diets (64.6 vs 60.7%), respectively. Daily herbage intake was similar (P=.42) for both treatments when expressed as a percentage of body weight. Diet botanical composition was positively affected by the type of management system. The amount of the major grass species, meadow foxtail (Alopecurus pratensjs), was increased (P=.05) 39% in the diet of strip grazing steers. Differences were noted in the amounts of other, less frequently occurring grass species. The total amount of grass tended (P=.06) to be higher in strip diets (49% vs 35% for continuous). Rushes (Juncus spp.) and sedges (Carex spp.) contributed a similar percentage to the diets of both treatments. Forbs comprised less than .5% of the overall diet of both strip and continuous steers. Individual animal performance tended (P=.09) to be higher under continuous grazing management. The ADG was 1.16 and .77 kg for steers in continuous and strip grazing, respectively. However, total animal production per hectare grazed area (26.14 vs 22.13 kg/hd) was not considered different (P=.17).
-
Geologic mapping of the Longview-Kelso area and the measurement and description of a composite 650-meter thick stratigraphic section of the Cowlitz Formation (Tc) in Coal Creek using bio-, magneto-, litho-, ...
Citation Citation
- Title:
- Stratigraphy and sedimentology of the middle eocene Cowlitz Formation and adjacent sedimentary and volcanic units in the Longview-Kelso area, southwest Washington
- Author:
- McCutcheon, Mark S.
Geologic mapping of the Longview-Kelso area and the measurement and description of a composite 650-meter thick stratigraphic section of the Cowlitz Formation (Tc) in Coal Creek using bio-, magneto-, litho-, and sequence stratigraphy reveals a complex interplay of Cowlitz micaceous, lithic arkosic shelf to tidal/estuarine to delta plain facies associations, and Grays River basalt lava flows and interbedded basalt volcaniclastics from nearby Grays River eruptive centers (e.g., Mt. Solo and Rocky Point). The lower 100 meters of the Coal Creek section (informal unit 1, Chron 18r) consists of micaceous, lithic arkosic sandstone and siltstone and minor coals, was deposited as part of a highstand system tract (HST) at the base of 3rd order cycle number 3. This unit consists of four dominantly tidal shoaling-upward arkosic sandstone parasequences reflecting upper shoreface to delta plain depositional environments. The overlying unit 2 (Chron 18n) is defined by abundant Grays River basalt volcaniclastic interbeds that intertongue with Cowlitz lithic arkoses. This unit represents the latter part of 3rd order cycle 3, and consists of mostly fining- and thinning-upward parasequences of middle shoreface to delta plain successions of an aggradational to transgressive parasequence set. Near the top of unit 2 is a maximum marine flooding surface depositing lower shoreface lithic arkosic sandstone to shelf siltstones over upper shoreface micaceous lithic arkose. Unit 3 comprises 3rd order cycle 4 (Chron 17r), a lowstand system tract, and consists of 6 mostly fining- and thinning-upward parasequences of lower shoreface to delta plain facies associations. A parasequence or erosional boundary at the base of unit 5 (Chron 17r) consists of submarine channel-fill scoured into underlying micaceous siltstones, produced during a lowstand system tract (LST) of 3rd order cycle 5. This deep marine channel-fill sequence is overlain by thinlybedded to laminated overbank distal turbidites and hemipelagic siltstones that define the top of the Coal Creek section. These 5 informal units in Coal Creek lithologically and chronologically correlate to 5 similar informal units defined by Payne (1998) in the type section of Cowlitz Formation in Olequa Creek near Vader -30 km to the north. Middle Eocene Grays River Volcanics of the study area are mapped as two separate units: a lower unit over 150 meters thick in places, consisting of subaerial basaltic flows and invasive flows (Tgvl), intrusions (Tgvis and Tgvid), and volcaniclastics (Tgvsl); and an upper unit consisting of commonly mollusk-bearing, shallow marine basaltic sedimentary interbeds that intertongue with the Cowlitz Formation (Tgvs2), particularly Cowlitz unit 2 of the Coal Creek section. These volcaniclastic deposits are intrabasinal, derived from volcanic highlands to the west and northwest, and local phreatomagmatic tuff cones. The lower Grays River volcaniclastic unit typically overlies Grays River flows in the study area and is divided into 5 informal facies. Geochemically, Grays River flows in the study area fall within normal parameters (3 to 4% TiO2 and high iron tholeiitic basalts). However, basalt flows and bedded scoriaceous breccias near Rocky Point are anomalously low in TiO2 and are considered in this study to be a separate volcanic subunit (Rocky Point Basalts), time equivalent to and interfingering with Grays River lavas, but may represent mixing with shallower western Cascade calc-alkaline magma. Over 60 younger Grays River dikes intrude the Cowlitz Formation in Coal Creek. A dike low in the Coal Creek section is dated at 40 ± 0.36 Ma, and an invasive flow at Mt. Solo is dated at 36.98 ±.78 Ma. Volcanics capping the hills east of the Cowlitz River are chemically distinct as slightly younger western Cascade basaltic andesite flows, and two dikes east of the river are chemically distinct as western Cascade andesite. Overlying Grays River Volcanics and Cowlitz Formation in much of the study area, are clayey and commonly tuffaceous siltstones and silty sandstones, possibly of the late Eocene-early Oligocene Toutle Formation, a new unit to this area. The Toutle Formation is a mixture of wave and stream reworked micaceous and arkosic Cowlitz Formation and fresh silicic pyroclastic ash and pumice from the active western Cascade arc. An angular unconformity separates the Paleogene Grays River Volcanics, Cowlitz Formation, and Toutle Formation from the early to middle Miocene Columbia River Basalt Group. Based on lithology, geochemistry, stratigraphic relationships, and magnetic polarity, 6 individual Columbia River Basalt flows have been mapped in this study. The three lower Grande Ronde flows are of normal polarity and Ortley low MgO chemical composition. The lowermost flow (N2 Ortley #1) is absent in the Columbia Heights area, low MgO, about 10 meters thick and consists of pillow-palagonite sequences in the upper quarry on Mt. Solo. Aphyric N2 Ortley flow #2 is over 35 meters thick with well-developed upper and lower colonnade, and of intermediate MgO. N2 Ortley flow #3 is pillow-palagonite in the Storedahl Quarry and low MgO. A -4-meter thick tuffaceous overbank siltstone and basalt conglomeratic channel interbed separates the three low MgO Ortley flows from the overlying high MgO N2 Grande Ronde Sentinel Bluffs flow. A single exposure of well-developed large colonnade with sparse 1 cm labradorite laths, and reddish oxidized soil, defines the N Sand Hollow flow of the Frenchman Springs Member of the Wanapum Formation. The overlying Pomona Member is mapped based on previous work by other authors. Pliocene gravels and arkosic sand of the Troutdale Formation form upland terrace deposits up to 100 meters thick in southern parts of the study area, and represent the uplifted paleo-thalweg and overbank flood deposits of the downcutting, antecedent ancestral Columbia River. Well-rounded clasts are a mixture of extrabasinal granitic and metamorphic quartzite, and intrabasinal porphyritic basaltic andesite, dacite, and basalt from the western Cascades and Columbia River Basalts. Troutdale terrace gravels grade northward into contemporaneous volcanic pebble and cobble gravel terrace deposits produced along the ancestral Cowlitz River that are dominantly composed of porphyritic andesite gravel and volcanic sand from the western Cascades. Lower terraces along the Cowlitz River were deposited by the late Pleistocene Missoula Floods. All of these unconsolidated to semiconsolidated gravels and sands are prone to landslides, and the Aldercrest-Banyon landslide, the second worst landslide disaster in American history, occurred in the Troutdale Formation gravels. After eruption of the Grays River Volcanics and deposition of the Cowlitz Formation, the forearc underwent a period of transtension in the late-middle Eocene related to magmatic upwelling and reorganization of the subducting Farallon Plate. This event produced a northwest-trending set of oblique slip normal faults, along which Grays River dikes intruded. Starting in the early Miocene the region underwent a transpressional event, reactivating many of the northwest-trending faults, and producing the Columbia Heights Anticline, Hazel Dell Syncline, the Coal Creek Fault, and the Kelso Fault Zone. The paleotopography resulting from this event was stream eroded to a nearly flat plain before emplacement of the Columbia River Basalts, which are nearly horizontal today. Continued offset along the northwest-trending fault set has also offset the Columbia River Basalts. Continued oblique slip post-Miocene broad arching of the Coast Range and downcutting by the Columbia and Cowlitz Rivers has resulted in Pliocene and Pleistocene terraces, and produced an east-west fault set that offsets all earlier structural features.