Theses and Dissertations at Montana State University (MSU)
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Item Forecasting the response of invasive plant-infested communities to management(Montana State University - Bozeman, College of Agriculture, 2003) Rinella, Matthew James; Chairperson, Graduate Committee: Roger L. Sheley.Item Conceptual hydrologic modeling : insights into Bayesian analysis, model development, and predictions in ungauged basins(Montana State University - Bozeman, College of Agriculture, 2012) Smith, Tyler Jon; Chairperson, Graduate Committee: Lucy Marshall.; Ashish Sharma, Lucy Marshall, Raj Mehrotra and Scott Sisson were co-authors of the article, 'Development of a formal likelihood function for improved Bayesian inference of ephemeral catchments' in the journal 'Water resources research' which is contained within this thesis.; Lucy Marshall and Ashish Sharma were co-authors of the article, 'A Bayesian likelihood function specification methodology for conceptual hydrologic modeling' in the journal 'Water resources research' which is contained within this thesis.; Lucy Marshall and Brian McGlynn were co-authors of the article, 'Improving hydrologic model calibration using a flow-corrected time transformation' in the journal 'Water resources research' which is contained within this thesis.; Lucy Marshall, Brian McGlynn and Kelsey Jencso were co-authors of the article, 'Using field data to inform and evaluate a new model of catchment hydrologic connectivity' in the journal 'Water resources research' which is contained with this thesis.; Lucy Marshall, Brian McGlynn and Kelsey Jencso were co-authors of the article, 'A cross-catchment comparison and sensitivity analysis of the catchment connectivity model' in the journal 'Water resources research' which is contained within this thesis.; Lucy Marshall and Ashish Sharma were co-authors of the article, 'Predicting hydrologic response through a pooled catchment knowledgebase' in the journal 'Water resources research' which is contained within this thesis.Water is a fundamental resource, essential for human activities and underpinning economic and environmental sustainability. As such, management of water resources is a critical task, even more so in this time of climate uncertainty and change. Though hydrologic models have long been used to address water resource management, there is a growing desire to develop more reliable, transferable, and physically meaningful hydrologic models in light of data scarcity and uncertainty. In this dissertation, the three primary topics of (1) statistical implementation of models under uncertainty, (2) hydrologic model development, and (3) model applicability/transferability under data scarcity are considered. As a result of this research, we have: (1) developed methods for improved statistical implementation of hydrologic models through the development of a formal likelihood function for ephemeral catchments, the creation of a framework for identifying adequate likelihood functions across catchment conditions, and the introduction of a time domain transformation that was not previously used in hydrologic modeling; (2) developed a new model of catchment hydrologic connectivity based on extensive empirical observations that was shown to be consistent with both external and internal hydrologic variables, as well as transferable; and (3) introduced a new hierarchical Bayesian approach that was shown to accurately quantify uncertainty at an ungauged catchment based on pooled information from similar gauged catchments. This dissertation is divided into six key chapters/manuscripts that each address various aspects involved in improving hydrologic model performance, whose cumulative contribution results in a better understanding of how to construct, implement, and apply hydrologic models to lead to improved water resource management and planning problems of societal importance.Item Spatial and seasonal variability of watershed response to anthropogenic nitrogen loading in a mountainous watershed(Montana State University - Bozeman, College of Agriculture, 2010) Gardner, Kristin Kiara; Chairperson, Graduate Committee: Brian L. McGlynn.; Brian L. McGlynn was a co-author of the article, 'Seasonality in spatial variability and influence of land use/land cover and watershed characteristics on streamwater nitrogen export in a developing watershed in the Rocky Mountain West ' in the journal 'Water resources research' which is contained within this thesis.; Brian L. McGlynn was a co-author of the article, 'A multi-analysis approach to assess the spatio-temporal patterns of watershed response to localized inputs of nitrogen' in the journal 'Water resources research' which is contained within this thesis.; Brian L. McGlynn, and Lucy A. Marshall were co-authors of the article, 'Quantifying watershed sensitivity to spatially variable nitrogen loading and the relative importance of nitrogen retention mechanisms' in the journal 'Water resources research' which is contained within this thesis.Anthropogenic activity has greatly increased watershed export of bioavailable nitrogen. Escalating levels of bioavailable nitrogen can deteriorate aquatic ecosystems by promoting nuisance algae growth, depleting dissolved oxygen levels, altering biotic communities, and expediting eutrophication. Despite these potential detrimental impacts, there is notable lack of understanding of the linkages between anthropogenic nitrogen inputs and the spatial and seasonal heterogeneity of stream network concentrations and watershed nitrogen export. This dissertation research seeks to more accurately define these linkages by investigating the roles of landscape position and spatial distribution of anthropogenic nitrogen inputs on the magnitude and speciation of watershed nitrogen export and retention and how these roles vary seasonally across contrasting landscapes in a 212 km ² mountainous watershed in southwest Montana. Results indicate localized inputs of anthropogenic nitrogen occurring in watershed areas with quick transport times to streams had disproportionate effects on watershed nitrogen export compared to spatially distributed or localized inputs of nitrogen to areas with longer transport times. In lower elevation alluvial streams, these effects varied seasonally and were most evident during the dormant winter season by amplified nitrate peaks, elevated dissolved organic nitrogen:dissolved organic nitrogen (DIN:DON) ratios and lower dissolved organic carbon (DOC):total dissolved nitrogen (DOC:TDN). During the summer growing season, biologic uptake of nitrogen masked anthropogenic influences on watershed nitrogen export; however, endmember mixing analysis of nitrate isotopes revealed significant anthropogenic influence during the growing season, despite low nitrate concentrations and DIN:DON ratios. In contrast, streams draining alpine environments consisting of poorly developed, shallow soils and small riparian areas exhibited yearlong elevated nitrate concentrations compared to other sites, suggesting these areas were highly nitrogen enriched. Watershed modeling revealed the majority of watershed nitrogen retention occurred in the upland environment, most likely from biological uptake or lack of hydrologic connectivity. This work has critical implications for watershed management, which include: 1) developing flexible strategies that address varying landscape characteristics and nitrogen loading patterns across a watershed, 2) avoiding clustering nitrogen loading in areas with quick travel times to surface waters, 3) seasonal monitoring to accurately gauge watershed nitrogen saturation status, and 4) incorporating spatial relationships into streamwater nitrogen models.