With increasing demand and pressures on groundwater resources, accurate and reliable groundwater prediction models are essential for sustainable groundwater management. Groundwater models are merely approximations of reality, and we are unable to either fully characterize or mathematically describe the true complexity of the hydrologic system; therefore, inherent in all models are varying degree of uncertainty. A robust management policy should consider uncertainties in both the imprecise nature of conceptual/numerical models and their parameters. This study addresses the critical question of whether the use of multiple conceptual models to explicitly account for conceptual model uncertainty improves the ability of the models to assist in management decisions. Twelve unique conceptual models, characterized by three alternative geological interpretations, two recharge estimations, and two boundary condition implementations, were formulated to estimate sustainable extraction rates from Thailand’s Thaphra Area, where increasing groundwater withdrawals may result in water level declination and saline water upconing. The models were developed with MODFLOW and calibrated using PEST with the same set of observed hydraulic head data. All of the models were found to reasonably produce predictions of the available heads data. To select the best among the alternative models, multiple criteria have been defined and applied to evaluate the quality of individual models. It was found that models perform differently with respect to different evaluation criteria, and that it is unlikely that a single inter-model comparison criterion will ever be sufficient for general use. The chosen alternative models were applied both individually and jointly to quantify uncertainty in the groundwater management context. Different model-averaging methods were assessed in terms of their ability to assist in quantifying uncertainty in sustainable yield estimation. The twelve groundwater simulation models were additionally linked with optimization techniques to determine appropriate groundwater abstraction rates in the TPA Phu Thok aquifer. The management models aim to obtain maximal yields while protecting water level decline. Despite similar performances among the calibrated models, total sustainable yield estimates vary substantially depending on the conceptual model used and range widely, by a factor of 0.6 in total, and by as much as a factor of 4 in each management area. The comparison results demonstrate that simple averaging achieves a better performance than formal and sophisticated averaging methods such as Maximum Likelihood Bayesian Model Averaging, and produce a similar performance to GLUE and combined-multiple criteria averaging methods for both validation testing and management applications, but is much simpler to implement and use, and computationally much less demanding. The joint assessment of parameter and conceptual model uncertainty was performed by generating the multiple realizations of random parameters from the feasible space for each calibrated model using a simple Monte Carlo approach. The multi-model averaging methods produce a higher percentage of predictive coverage than do any individual models. Using model-averaging predictions, lower optimal rates were obtained to minimize head constraint violations, which do not ensue if a single best model is used with parameter uncertainty analysis. Although accounting for all sources of uncertainty is very important in predicting environmental and management problems, the available techniques used in the literature may be too computationally demanding and, in some cases, unnecessary complex, particularly in data-poor systems. The methods presented here to account for the main sources of uncertainty provide the required practical and comprehensive uncertainty analysis and can be applied to other case studies to provide reliable and accurate predictions for groundwater management applications.

The objective of this study was to determine the dominant biogeochemical controls on mercury partitioning in super-permafrost groundwater at Truelove Lowland, Devon Island, Nunavut. Mercury partitioning in snow, ephemeral standing water, and super-permafrost groundwater was investigated. <p>Results indicate that partitioning differs between matrices, and that particulate mercury is spatially and temporally dynamic in Truelove Lowland groundwater. Particulate mercury in groundwater was 73 % of total mercury, while snow had only 22 % particulate mercury. Particulate mercury in groundwater rose by over 20 % from Julian day 181 to 189, and decreased slightly on Julian day 191. No single geochemical parameter was a good predictor of particulate mercury concentrations. To expand upon the findings of the field study a laboratory microcosm study was conducted to determine whether certain biogeochemical processes influence mercury partitioning in super-permafrost groundwater. Particulate mercury in the dissimilatory iron reducing bacteria inhibited microcosm was 61 % of total mercury, approximately 18 % lower than in all other treatments. Iron (III) concentrations had a positive correlation with particulate mercury while chloride concentrations had a negative correlation with particulate mercury. Sulfate reducing bacteria were not found to influence mercury partitioning.

Since Texas contains less than 5% public land, private landowners are critical to the success of environmental management initiatives in the state. This has implications for resources that traverse property boundaries, such as wildlife and groundwater. Texas landowners are increasingly capitalizing on the income potential of fee-based hunting, and many have banded together to form Wildlife Management Associations (WMAs). Not only can such landowner associations enhance the coordination of resource management decisions, they also have the potential to increase social capital, which is reflected by interpersonal trust, reciprocity and civic participation. To improve the management of common-pool resources it is important to understand the relationship between social capital and coordinated resource management because long-term community stability and resource sustainability appear to be highly correlated. A 600-landowner mail survey (with 48.1% response) was conducted in the Edwards Plateau region of Texas to compare the land management characteristics and social capital of landowners who are members of WMAs with non-member landowners. The goal of this research was to determine how WMA membership, property size, and location affect levels of social capital and interest in cooperative resource management. It was hypothesized that members, large landowners, and northern landowners would be more interested in cooperative management and exhibit higher social capital. While WMA members and large-property owners were more involved in wildlife management than non-members and small-property owners, this interest in resource management did not carry over to groundwater. These groups were not more involved in groundwater management activities, and all survey groups were disinterested in joining private cooperatives for groundwater marketing. Social capital differences were more evident between large- and small-property owners than between WMA members and non-members. Members scored higher only on community involvement, while large owners scored higher on community involvement as well as trust. These results suggest that WMA membership per se does not significantly increase social capital among Edwards Plateau landowners, but do not necessarily refute the importance of social capital within WMAs. Differences in trust between members were positively correlated with increased communication and meeting frequency, suggesting ways WMAs can improve intra-association social capital.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves [135]-139). Also available on the Internet.

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 254-259). Available also in a digital version from Dissertation Abstracts.

Thesis (M.S.)--University of Nevada, Reno, 2008. / "Decmber 2008." Includes bibliographical references (leaves 60-62). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2009]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (M.S. in E.A.S.)--School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 2004. Directed by James Gaherty. / Includes bibliographical references (leaves 38-42).

Thesis (Ph.D.)--Murdoch University, 2006. / Thesis submitted to the Division of Science and Engineering. Includes bibliographical references (leaves 148-163)

Thesis (Ph. D.) in Food and Nutrition Sciences--University of Maine, 2002. / Includes vita. Includes bibliographical references (leaves 93-98).