Thesis (Ph. D. - Geology)--University of Arizona. / Includes bibliographical references (leaves 115-119).

Thesis (M.S.)--West Virginia University, 2010. / Title from document title page. Document formatted into pages; contains ix, 157, [1] p. : ill. (some col.), col. maps. Vita. Includes abstract. Includes bibliographical references (p. 116-120).

Thesis (Ph.D.)--Indiana University, Dept. of Geological Sciences, 2009. / Title from PDF t.p. (viewed on Jul 19, 2010). Source: Dissertation Abstracts International, Volume: 70-12, Section: B, page: 7445. Advisers: Mark A. Person; Enrique Merino.

The Lake C2 watershed at Taconite Inlet (82$\sp\circ$50$\sp\prime$N; 78$\sp\circ$00$\sp\prime$W) was the site of a three year project (1990-92), to investigate hydrological processes in the context of contemporary climate. The watershed is 21 km$\sp2$ in area, and 9 percent glacierized. This study was done in conjunction with a larger research effort, aiming to reconstruct paleoclimate using laminated lake sediments. A continuous record of discharge, determined by stage-discharge relations, and short-interval sampling of suspended sediment concentration (SSC), permitted the production of hourly time series. In addition, two weather stations logged hourly temperature, humidity, wind and complete radiation data at 7 m and 520 m a.s.l. The upper station was located close to the median watershed elevation. Mean daily air temperatures were rarely higher than 5$\sp\circ$C during the study periods, and the two weather stations revealed frequent temperature inversions. Precipitation events were small in magnitude ($<$13 mm d$\sp{-1})$, and primarily in the form of snowfall. Streamflow began June 9, 4 and 22 for the three years, respectively. Discharge followed a pronounced diurnal rhythm, especially during the brief nival flood. Maximum discharge was 4.0 m$\sp3$ s$\sp{-1}$. SSC fluctuated in close correspondence with discharge, and the highest measured concentration was 555 mg L$\sp{-1}$. Each year, approximately 50 percent of the suspended sediment discharge (SSQ) occurred during only 10 percent of the field season. Daily SSQ was strongly associated with air temperature at the median watershed elevation (r = 0.70, 0.92; entire field seasons 1991, 1992). These results demonstrate that sediment transfer to Lake C2 is a response to snowmelt. Among meteorological variables measured at weather station Alert (ca. 225 km east), rawinsonde sounding temperatures at 600 m were most closely associated with daily SSQ into Lake C2. Accordingly, an exponential equation, based on pooled 1990 and 1992 data, was used to predict daily watershed SSQ for the period of record (1951-89). The series of annual predicted sediment loads were found to be in excellent agreement with a normalized varve thickness series. This study indicates that laminated sediments in Lake C2 contain a high-resolution record of regional summer temperature.

<p> Researchers using Darcy's law to model flow in porous media must satisfy the requirement for sufficient scale separation between the pore scale and the model scale. This requirement is analogous to that for any continuum model, where application is restricted to scales larger than the underlying discrete structure. In the case of Darcy's law when the model scale becomes too small, the measurement of the permeability&mdash;the material property required to close the relationship&mdash;becomes polluted by the boundary conditions, either physical or numerical. The requirements for adequate scale separation to obtain permeability measurements (also known as satisfying the conditions for a <i>representative elementary volume, </i> or REV, for permeability) have not been previously reported. Likewise, the behavior of Darcy models when applied at sub-REV length scales has not been reported.</p><p> Here, the results of Stokes simulations of transverse flow in 90,000 sequential random packings of monodisperse cylinders at a variety of liquid fractions and averaging-volume sizes show that approximately 200 cylinders must be present in an averaging volume before the effects of periodic boundary conditions on the Stokes simulations (the conventional choice for permeability measurements using Stokes flow) are no longer evident in the measured permeability. Direct comparisons between flow predictions from a two-dimensional, tensor-based Darcy model and a Stokes model for additional 10,000 domains show that the Darcy model is an unbiased predictor of the flow distribution in the system, even when the permeability is expected to contain boundary-condition artifacts. Though unbiased, the Darcy models do show considerable reduction in accuracy as the model scale shrinks toward the pore scale, with significant declines observed after the side length of a square averaging volume reaches 10 times the cylinder diameter. Finally, a novel approach for visualizing flows using the linear properties of the Stokes equations shows how the periodic boundary conditions affect the flow, and motivates the development of a generalized approach for obtaining permeability that does not require periodic boundary conditions. Modest improvements in the Darcy model relative to the actual Stokes flow result when the new approach is used to obtain permeability at small averaging volumes.</p>

Thesis (Ph. D. in geology)--Washington State University, May 2008. / Includes bibliographical references.

Flight at high altitude is part of a migration strategy that maximises insect population displacement. This thesis represents the first substantial analysis of insect migration and layering in Europe. Vertical-looking entomological radar has revealed specific characteristics of high-altitude flight: in particular layering (where a large proportion of the migrating insects are concentrated in a narrow altitude band). The meteorological mechanisms underpinning the formation of these layers are the focus of this thesis. Aerial netting samples and radar data revealed four distinct periods of high-altitude insect migration: dawn, daytime, dusk, and night-time. The most frequently observed nocturnal profiles during the summertime were layers. It is hypothesised that nocturnal layers initiate at a critical altitude (200–500 m above ground level) and time (20:00–22:00 hours UTC). Case study analysis, statistical analysis, and a Lagrangian trajectory model showed that nocturnal insect layers probably result from the insects’ response to meteorological conditions. Temperature was the variable most correlated with nocturnal insect layer presence and intensity because insects are poikilothermic, and temperatures experienced during high-altitude migration in temperate climates are expected to be marginal for many insects’ flight. Hierarchical effects were detected such that other variables—specifically wind speed—were only correlated with insect layer presence and intensity once temperatures were warm. The trajectory model developed comprised: (i) insect flight characteristics; (ii) turbulent winds (which cause vertical spread of the layer); and (iii) mean wind speed, which normally leads to horizontal displacements of hundreds of kilometres in a single migratory flight. This thesis has revealed that there is considerable migratory activity over the UK in the summer months, and a range of fascinating phenomena can be observed (including layers). The UK has moved from one of the least studied to perhaps the best studied environments of aerial insect migration and layering in the world.

<p> Landscape-scale forest restoration treatments are planned for four national forests in Northern Arizona: the Coconino, Kaibab, Tonto, and Apache-Sitgreaves National Forests. The first analysis area comprises 900,000 acres on the Coconino and Kaibab National Forests where the U.S. Forest Service is proposing restoration activities on approximately 600,000 acres over a ten year period pending acceptance of an Environmental Impact Statement. These forest restoration treatments are intended to accomplish a number of objectives including reducing the threat of catastrophic wild fire and subsequent flooding and to restore forest health, function, and resiliency. Previous studies suggest that in semi-arid, ponderosa pine watersheds there was a possibility to increase surface water yields 15-40% when basal area was reduced by 30-100%. Because of these results, there is considerable interest in the amount of increased water yield that may recharge from these activities. </p><p> The objectives of this study were to 1) examine the state of knowledge of forest restoration thinning and its hydrological responses and to evaluate the quality and type of related references that exist within the literature and 2) simulate possible changes in recharge and aquifer response following forest restoration treatments and climate change. A systematic review process following the guidelines suggested by the Collaboration for Environmental Evidence was conducted to examine literature relevant to this topic. The Northern Arizona Regional Groundwater-Flow Model was used to simulate the changes expected from forest restoration treatments and climate change. </p><p> The systematic review returned 37 references that were used to answer questions regarding tree removal and the associated hydrological responses. Data from individual studies suggest that forest treatments that reduce tree density tend to increase surface water yield and groundwater recharge while reducing evapotranspiration. On average, there was a 0-50% increase in surface water yield when 5-100% of a watershed was treated. Groundwater results were less conclusive and there was no overall correlation for all studies between percent area treated and groundwater recharge. A majority of studies (33 of 37) reported statistically significant results, either as increases in water yield, decreases in evapotranspiration, or increases in groundwater table elevation. Results are highly variable, and diminish within five to ten years for water yield increases and even quicker (&lt; 4 years) for groundwater table heights. </p><p> Using a groundwater-flow model, it was estimated that over the ten-year period of forest restoration treatment there was a 2.8% increase in annual recharge to aquifers in the Verde Valley compared to conditions that existed in 2000-2005. However, these increases were assumed to quickly decline after treatment due to regrowth of vegetation and forest underbrush. Furthermore, estimated increases in groundwater recharge were masked by decreases in water levels, stream baseflow, and groundwater storage resulting from surface water diversions and groundwater pumping. These results should be used in conjunction with other data such as those recovered from paired-watershed studies to help guide decision-making with respect to groundwater supply and demand issues, operations, and balancing the needs of both natural and human communities. </p>

<p> Releases of perchloroethylene (PCE) from dry cleaners pose a threat to groundwater quality. An assessment was performed of the Niles Cone Groundwater Basin to determine its vulnerability to PCE contamination from both historic and more recently operating dry cleaners. Sensitivity assessments of the Basin's two subbasins were performed using a modification of the DRASTIC Index Method, whereby the hydrogeological variables of depth to water, aquifer media, vadose zone media, and soil drainage classification were represented by a range of sensitivity categories and ratings assigned to each range. A source assessment was performed by identifying the locations of historic and presently operating dry-cleaning plants and assigning a threat ranking to each based on the approximate years in which the four generations of dry-cleaning machinery were introduced. Using ArcGIS, the sensitivity assessments and the source assessment were mapped, and the source assessment was superimposed over the sensitivity maps to create vulnerability maps of the two subbasins. The most sensitive area of the Below Hayward Fault subbasin in the forebay area near the Hayward Fault is due to a higher proportion of coarse-grained aquifer and vadose zone media and a thinner to absent aquitard due to deposition from the Alameda Creek. The existence of dry cleaners of higher threat makes this an area that is vulnerable to PCE contamination.</p>

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-05, Section: B, page: 3154. Adviser: Marcelo H. Garcia. Includes bibliographical references (leaves 118-130) Available on microfilm from Pro Quest Information and Learning.