Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--Michigan State University. Dept. of Geological Sciences, 2008. / David Hyndman, dissertation advisor--From acknowledgments. Title from PDF t.p. (viewed on Aug. 20, 2009) Includes bibliographical references (p. 148-150). Also issued in print.

Thesis (M.S.)--Brigham Young University. Dept. of Geological Sciences, 2007. / Includes bibliographical references (p. 38-41).

Doctor of Philosophy / Department of Civil Engineering / David Steward / Western Kansas has a semi-arid climate where the demand for water resources is greater than the natural supply. To meet the demand for irrigated agriculture, the groundwater has been extracted at a rate greater than the natural recharge rate, resulting in declining water table in the aquifer and reduced streamflow in the rivers and streams in the region. An assessment of the rivers in western Kansas was conducted to determine the fluxes between the river, groundwater, and the atmosphere. Riverbeds were instrumented to determine the conductivity of the riverbed sediments, the transmission losses of the Arkansas River were modeled to determine the interactions between the surface water and groundwater, and the evapotranspiration of the Arkansas River corridor was estimated using satellite remote sensing to quantify of water lost to the atmosphere. The Arkansas River and Cimarron River are shown to have a high hydraulic conductivity and a large infiltration capacity at the surface of the riverbed. However, the large surface infiltration capacity does not translate into large transmission losses, which are a fraction of the rate of the surface infiltration capacity of the riverbed. Thus, surface infiltration is only one factor of what controls the transmission losses. It is shown that transmission losses for a connected river-aquifer system are driven by induced infiltration by riparian vegetation. The interactions between the surface, groundwater and atmosphere were assessed over time, revealing that the flux to the atmosphere can be decoupled from the Arkansas River discharge and the groundwater recharge. While the declining discharge in the Arkansas River can be attributed to the extraction of groundwater resources and the management of surface water resource, the atmospheric fluxes are independent of the surface water and groundwater at an annual scale. When the river ecosystem is water stressed, the trees continue to draw water. This points to both the reliable store of water from the alluvial aquifer and the ability of the tree community to respond to water stress. While the water in the alluvial deposits are currently being lost from the system through evapotranspiration, this provides a potential store for consideration in future water management decisions.

abstract: A new loop configuration capable of reducing power radiation magnitudes lower than conventional loops has been developed. This configuration is demonstrated for the case of two coaxial loops of 0.1 meter radius coupled via the magnetic reactive field. Utilizing electromagnetism theory, techniques from antenna design and a new near field design initiative, the ability to design a magnetic field has been investigated by using a full wave simulation tool. The method for realization is initiated from first order physics model, ADS and onto a full wave situation tool for the case of a non-radiating helical loop. The exploration into the design of a magnetic near field while mitigating radiation power is demonstrated using an real number of twists to form a helical wire loop while biasing the integer twisted loop in a non-conventional moebius termination. The helix loop setup as a moebius loop convention can also be expressed as a shorted antenna scheme. The 0.1 meter radius helix antenna is biased with a 1MHz frequency that categorized the antenna loop as electrically small. It is then demonstrated that helical configuration reduces the electric field and mitigates power radiation into the far field. In order to compare the radiated power reduction performance of the helical loop a shielded loop is used as a baseline for comparison. The shielded loop system of the same geometric size and frequency is shown to have power radiation expressed as -46.1 dBm. The power radiated mitigation method of the helix loop reduces the power radiated from the two loop system down to -98.72 dBm. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2015

Aquifer recharge and recovery (ARR) is a low-cost and environmentally-friendly treatment technology which uses conventionally treated wastewater effluent for groundwater recharge and subsequent recovery for agricultural, industrial or drinking water uses. This study investigated the effect of different dissolved organic carbon (DOC) composition in wastewater effluent on the fate of trace organic chemicals (TOrCs) during ARR. Four biologically active columns were setup receiving synthetic wastewater effluent with varying DOC compositions. The difference in DOC composition triggered variations in the microbial community’s diversity and hence its ability to degrade TOrCs. It was found that the presence of protein-like DOC enhances the removal of DOC in comparison with the presence of humic-like DOC. On the other hand, the presence of humic-like DOC, which is more difficult to degrade, improved the removal of several degradable TOrCs. Other column experiments were also carried out to investigate the role of previous and continuous exposure to TOrCs in their removal. The use of soil pre-exposed to low concentrations of TOrCs and DOC provided better removal of both DOC and TOrCs. The findings of this study suggest that the presence of more humic-like DOC in the effluent enhances the biotransformation of TOrCs during ARR. In addition, long exposure to both DOC and TOrCs increases the degree of their removal over time

MESHWR / Department of Hydrology and Water Resources / This study was focused on determining groundwater recharge and groundwater potential for Mhinga area in South Africa, which is a rural area that depends mainly on groundwater for domestic water supply. Numerical modelling was used to simulate the groundwater behaviour in the aquifer and estimate groundwater recharge. MIKE SHE and MIKE 11 models were coupled and used to estimate groundwater recharge within calibration and validation periods of 2007/07/01 to 2009/12/31 and 2010/01/01 to 2013/05/21, respectively. Due to limited data availability for Mhinga, modelling was carried out at quaternary scale and then localised to Mhinga area. Remotely sensed data (satellite images, shapefiles and maps) was used to produce the groundwater potential map for Mhinga. The data were assigned with weights using Saaty’s Analytical Hierarchy Process and overlain on ArcGIS platform. Borehole drilling statistics of the boreholes in A91H quaternary catchment were used to validate the groundwater potential map. In streamflow modelling using MIKE 11, values of Nash-Sutcliffe efficiency (NSE), correlation coefficient (R), root mean square error (RMSE) and mean absolute error (MAE) were 0.51-0.89, 0.73-0.97, 3.61-7.96 and 1.13-2.75, respectively. In integrated groundwater modelling using MIKE SHE, values of NSE, R, RMSE and MAE were 0.72-0.84, 0.87-0.93, 0.18-0.32 and 0.13-0.26, respectively. These values showed that MIKE SHE and MIKE 11 models had satisfactory performances. Groundwater recharge estimates were generally very low ranging from 0 to 2.75 mm/year, which constituted 0 – 0.42 % of Mean Annual Precipitation (MAP) for the A91H quaternary catchment. This was associated with high evapotranspiration (mean of approximately 4 mm/day) compared to the low precipitation levels (MAP of 656 mm/year). Moreover, in the low lying areas, with gentle slopes, low recharge between 0.2 – 0.4 mm was observed. The groundwater potential (GWP) map produced revealed that Mhinga is predominantly covered by regions of very low and low groundwater potential, which was associated with the type of geology. Area coverages of 34.47 % had very low, 51.39 % had low, 7.66 % had moderate and 6.48 % had high groundwater potential. Moderate to high groundwater potential zones were located along the geologic fault zones. In A91H, 112 unsuccessful boreholes were drilled, 69 (61.6 %) fell in the very low GWP zones, 16 (14.3 %) fell in the low GWP zones, 17 (15.2 %) fell in moderate GWP zones and 10 (8.9 %) fell in the high GWP zones. In the Mhinga, 19 unsuccessful boreholes were drilled of which, 11 (57.9%) fell in the very low GWP zones, while 6 (31.6%) fell in the low GWP zones and 2 (10.5%) fell in the moderate GWP zone. Hence 89.5% of all the unsuccessful boreholes drilled occurred in the very low to low GWP zones. It is concluded that the study area is mainly dominated by of areas with low recharge and very low to low groundwater potential. It is recommended that the MIKE SHE – MIKE 11 model and the GIS models should be developed further and improved as more data is collected to refine the conceptualisation of the aquifer.

Access to surface water is limited in Australia and many regions rely on groundwater for all their water needs. Most of aquifers are already fully allocated and there is an increasing demand for more extraction. During drought, drop in rainfall can result in less recharge into groundwater system. Decrease in rainfall can cause direct and indirect impacts on groundwater. Drop in rainfall can result in less recharge into groundwater system. Moreover decreased rainfall can cause limited accessibility to surface water which results in increased demand for extraction. Understanding of groundwater recharge mechanism and quantifying how far climate change can influence groundwater, plays an important role for establishing sustainable extraction without causing any damage into environment. The CoupModel was selected as a tool to simulate groundwater behavior under different Scenarios. Model inputs are derived from actual observations, such as climatic data. Few assumptions were considered to conceptualize drainage system, such as soil hydraulic parameters, drainage system and evaporation procedure. The study period is 30 years between 1979 and 2008. Model was run for two 15-year periods to identify how far climate change can influence groundwater recharge in the study area. Eyre Peninsula area is highly dependent on groundwater for town water supply, Irrigation and industrial development. Therefore any science study would be definitely valuable for groundwater resource management of this area.

Karst aquifers are productive groundwater systems around the world, supplying approximately 25% of the world's drinking water. However, they are highly vulnerable to contamination due to rapid groundwater transit in the transmission zone (KWI 2006). The epikarst, also known as the subcutaneous zone, is an interface between the soil overburden and the transmission zone. The epikarst is considered a critical zone as it can control hydrologic and geochemical characteristics of recharge to the underlying karst aquifer.  The overall goal of this thesis is to utilize time series hydrologic and geochemical data collected at James Cave, Virginia, to examine the influence of epikarst on the quantity, quality, and rates of recharge to aquifers in Appalachian karst. Results of this study indicate a strong seasonality of both the hydrology and geochemistry of recharge. The conceptual model of the epikarst developed in this study identifies three hydrologic seasons: recharge, recession, and baseflow. Seasonality of recharge geochemistry coincides with these three hydrologic seasons.  These results have implications for management of karst aquifers.  First, recharge to Appalachian karst aquifers is seasonal, reaching a maximum during the winter-early spring; the onset of recharge depends on antecedent climatic conditions.  Second, water that infiltrates into the epikarst will have seasonally variable residence times due to changes in hydrologic storage; these variations in attenuation affect geochemical reactions in the epikarst, which can influence recharge quality. Overall, these results point to the complex influence of epikarst on karst recharge, which necessitates collection of long-term and high resolution datasets. / Master of Science

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in partial fulfillment of the requirements for the degree of Master of Science in Hydrogeology. July 2017. / Hydrogeological research was undertaken in the transboundary Ramotswa dolomitic aquifer to provide understanding and quantification of the processes governing recharge mechanism and rates, in order to promote efficient and sustainable groundwater resource utilization and development, as well as to improve the Ramotswa transboundary aquifer management. Hydrochemical and tracer approaches were utilized to evaluate the processes governing the recharge mechanism while the chloride mass balance approach was further applied to assess groundwater recharge rates. Results indicated that all groundwater samples contained detectable amounts of tritium highlighting the renewability of the transboundary Ramotswa aquifer resources. Two distinct water types were characterised: sub-modern waters approximately recharge prior to the 1950s and a mixture of modern and sub-modern waters of recently recharge rainfall indicative of active recharge in the area through intensive rainfall. Correlation between δ18O and δ2H, and soil Cl- indicated that groundwater recharge in the Ramotswa dolomitic aquifer takes place mainly by two flow mechanisms: a displacement of moisture through a diffuse or piston flow through permeable soils and from concentrated runoffs due to surface depressions, and a preferential flow component through fractures that outcrop at surface and riverbed infiltration along the ephemeral Notwane River. Annual groundwater recharge estimates varied from 0.4% MAP to 12% MAP and from 5% MAP to 14% MAP within the northern parts and the southern parts of the study area, respectively. Recharge estimates correlated well with the proposed mechanism of flow both in the southern and in the northern parts of the study area as well as with the previous studies conducted within the greater Ramotswa area. A way forward to ensure the long-term sustainability of the transboundary Ramotswa aquifer resources is recommended, such as to preserve and protect potential recharge areas through carefully controlled land use planning and development, and to equate abstraction rates to average recharge rates, which has to be subjected to the Limpopo Watercourse Commission. / MT2018