Thesis (Ph. D.)--Ohio State University, 2003. / Title from first page of PDF file. Document formatted into pages; contains xvi, 378 p.; also includes graphics (some col.). Includes bibliographical references (p. 229-252). Available online via OhioLINK's ETD Center

Thesis (Ph. D.)--University of Wisconsin--Madison, 1959. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 129-130).

Thesis (Ph. D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-11, Section: B, page: 6659. Adviser: Craig M. Bethke. Includes bibliographical references (leaves 58-65). Available on microfilm from Pro Quest Information and Learning.

Thesis (M.S.)--Western Kentucky University, 2008. / Includes bibliographical references (leaves 148-154).

The impact of various land-use changes on the hydrology of the Raisin River in Eastern Ontario was studied using simulation with the physically based semi-distributed hydrological model HYDROTEL. First, we have simulated the impact of the real land-use change which happened on the watershed between 1964 and 1978, on daily flow and soil water content. The increasing importance of cash crop in the agricultural landscape, in particular corn, and the increase in the forested area resulted in a decrease in the variability of hydrological conditions. Second, we have simulated a series of theoretical land-use scenarios, such as a totally forested watershed, a watershed entirely covered by cash crops, and a forested watershed with wetlands, in order to discriminate between the influence of particular land uses found on the watershed in the last thirty years. Cash crop is the land use which produced the most extreme conditions of all land uses tested, with spring flood happening earlier and with more intensity and low flow being the lowest. Following the two simulation exercises, it appears that from 1964 to 1978, the increasing forested area compensated for the drying effect of cash crop on soil. Land-use parameterisation is gaining importance in global-scale models but in this watershed-scale study, the parameters which have the most effect quantitatively on flow, are the snow melt factors and snow melt thresholds associated with forested or open field environments. Bioclimatic calendars of root depth, leaf area index and albedo associated with the various land uses were secondary. On the other hand, they are important for baseflow and for fall high flows and on soil water content at the end of the summer. Regarding the studied time period, meteorological fluctuations have more important impact on hydrology at the watershed scale than do land-use changes. On the other hand, land use plays a role of tempering, dampening, climatic effects and it is necessary to take that impact into account, because it is the only one for now on which it is possible to have some control.

The transport and partitioning of 129I has been examined for a shallow groundwater flow system at Sturgeon Falls in northeastern Ontario. Recharge into a sandy surficial postglacial deltaic aquifer occurs in the vicinity of a seasonally-wet boreal forest. Concentrations of stable iodine, 129I, tritium, radiocarbon, stable isotopes and major ions were measured on samples of groundwater and precipitation. The present-day tritium profile delineates the position of the early 1960's thermonuclear bomb-pulse at a depth of approximately 12 m. The concentrations of stable iodine for groundwaters above, near and below the present-day bomb pulse range from 0.07 to 1.7 ppb. The groundwater in the lower aquifer is practically tritium-free (<2 TU) and is considered to be pre-bomb in age. The lesser concentrations of 129I in Sturgeon Falls groundwaters, compared with those from other studies in central Canada, suggest that the levels of 129I in these groundwaters may have been attenuated by complexation or ion exchange with organic materials in the near-surface soil horizons. Additionally, the concentrations of 129I in the mine waters of the Con Mine, in Yellowknife, NWT were examined. (Abstract shortened by UMI.)

Our ability to predict solute transport in groundwater is limited by our imperfect understanding of the physical processes governing the spreading of underground contaminant plumes beneath the surface. Inaccurate prediction of solute migration can in turn result in unreliable risk analyses, or higher costs for groundwater decontamination. It is generally accepted that spatial variations in the hydraulic conductivity of porous materials largely contributes to the spreading of solutes dissolved in groundwater. Unsteady hydraulic gradients can also enhance this dispersion by imposing an additional source of variability on the flow field. Most field and numerical studies assume steady state groundwater flow, despite compelling field evidence suggesting that flow transience may be ubiquitous. This study characterizes the effects of transient groundwater flow on contaminant migration in both homogeneous and heterogeneous porous media. The macroscopic dispersion of miscible solutes subjected to unsteady flow fields is assessed quantitatively through a series of laboratory experiments and numerical simulations. An innovative laboratory model is presented, which consists of a two-dimensional flow cell and coupled hydraulic control system that allow the construction of spatially homogeneous or heterogeneous porous media of prescribed statistical properties, and to impose deterministic flow transients on the system. A monitoring procedure combining image processing with spatial moment analysis is used to characterize with great spatial and temporal resolution the evolution of contaminant plumes, as measured from sequences of digital images acquired during the course of laboratory experiments. Results suggest that the influence of flow transience on solute dispersion compares well with results reported in the literature, based on theoretical or numerical investigations. Changes in the mean flow direction significantly increase transverse dispersion in proportion to the rotation angle; conversely, longitudinal dispersivity decreases in response to variations in the flow direction, but to a lesser extent. Reversing hydraulic gradients can cause a reduction in the plume extents, or plume "shrinking". Although both the spatial and temporal variability enhance solute spreading, heterogeneity of the porous medium can mask the temporal variations in the flow field. The increased complexity introduced by the spatial and temporal variability can lead to inconsistencies between experimental and numerical models.

Geochemical exploration methods are able to contribute significantly to the detection of concealed Au mineralization in glaciated terrains. Gold analyses of lake sediments from the glaciated Canadian Shield have been used since the mid-1980s to explore for Au mineralization. For lake sediments to be an effective indicator of Au mineralization, the element must migrate in solution or adsorbed on suspensates in the boreal forest zone where low relief and disorganized drainage restricts dispersal and concentration in clastic form. Organic-rich profundal lake sediments often contain anomalous Au contents near Au mineralization, suggesting that Au is entering the lake environment in mobile form. Confirmation of the processes by which Au is mobilized into lake sediments could thus contribute to improved exploration methodologies. This study investigated the nature of Au mobility and dispersion into lake sediments under alkaline and acid hydrological conditions in the southern Canadian Shield. The study makes recommendations for exploration strategies to be employed under these conditions. Three field areas were selected for detailed study: Napier Lake, Ontario; PAP Lake, Saskatchewan; and Foster Lake, Manitoba. (Abstract shortened by UMI.)

The objectives of the study were to investigate the hydraulic, geochemical and solute or contaminant transport properties of the upper fractured zone at four Leda clay deposits in Eastern Ontario. These four sites are known as NRC, Fallowfield, Renfrew and Casselman. Physical conditions and depth of fractures of the Leda subsoil was investigated with the use of boreholes and test pits. Piezometers were installed using a conventional auger method and the double-Shelby method developed at the University of Waterloo. Hydrogeological aspects of the upper twelve metres were analyzed using water level fluctuations and variation profiles, hydraulic head and conductivity profiles. A geochemistry analysis was made by measuring the major ions and tritium concentration distribution in groundwater samples obtained from piezometers. Laboratory tests were performed on five Leda clay samples to determine the effective diffusion coefficients and the retardation factors of the major ions. The results of the study indicated that the upper portion of Leda clay deposits within Eastern Ontario are fractured and hydraulically active. Fractured Leda clay deposits less than 12 metres in depth are highly questionable on their ability to protect any underlying aquifer from surficial or buried contaminants.

The Sandilands glaciofluvial complex is believed to be a region of significant groundwater recharge in southeastern Manitoba. Chlorofluorocarbon (CFC-11, CFC-12, and CFC-113), tritium (3H) and tritium/helium (3H/3He) groundwater age dating methods were used to estimate and characterize groundwater recharge in the surficial aquifer in the Sandilands. The multi-tracer technique was used to provide comparison between groundwater age estimates and to evaluate if subsurface processes affected groundwater ages. Five sites within the Sandilands were instrumented with shallow nests (11--28 m total depth) of three piezometers with vertical spacings of 2--7 meters to determine groundwater age profiles and to estimate vertical groundwater velocities and recharge rates. Groundwater recharge was estimated at different locations in the study area to assess the spatial variability of recharge rates and to identify possible controlling factors. Piezometric and geochemical data (major ions, delta 18O, delta13CDIC) were also collected to aid in the interpretation of groundwater ages. (Abstract shortened by UMI.)