<p>In arid regions, springs are important in many aspects of society due to the scarcity of surface water features. In the Great Basin of the United States, desert springs support the majority of regional biodiversity and are critical for supporting rare, threatened, and endangered organisms. Despite their importance, there are numerous threats to desert springs, with the most ubiquitous being climate change. In contrast to many studies examining potential metrics to describe the vulnerability of streams, wetlands and other surface water features to the effects of climate change, springs are often overlooked. Part of the knowledge gap stems from the complexity of springflow generation and the rarely field-tested connection between groundwater response time and groundwater residence time.</p> <p> This dissertation tests, in a systematic way, different metrics that may help define criteria to evaluate whether a spring is likely to persist or desiccate with increasing regional hydrologic stress due to climate change. Field data was collected over a 4-year period from >80 springs across the topographically and geologically heterogeneous terrain of the southern Great Basin. </p> <p>Throughout this dissertation, I use a variety of different tools (e.g., remote sensing, environmental tracers, geospatial analysis) to “attack” this complicated problem from different angles. I begin by examining factors indicative of hydrogeologic resistance to major drought. After finding a connection between groundwater residence time and hydrogeologic resistance, I examine other factors (e.g., geochemical, topographic, ecological, variability) that are related to groundwater residence time and also identify where these relationships fail. </p>

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Thesis advisor: Alan Kafka / The stability of open-pit mine walls and other geotechnical infrastructure is a function of geometry, material properties and groundwater conditions (pore pressure distribution). A portion of failures are attributed to the effect of pore water pressures within the mine wall slopes. The objective of this research was to investigate the interaction between the increments/decrements of stresses that occur during the lithostatic unloading/excavation of the pit and the increments/decrements of pore water pressures. This interaction can be described by the theory of linear poroelasticity, which incorporates the coupling between changes in fluid pressure and changes in stress in porous media. The results of this thesis are displayed in the form of contour charts and graphs. / Thesis (MS) — Boston College, 2016. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

No passado, a disposição de resíduos sólidos sem nenhum tipo de tratamento e controle era algo normal e muito praticado. Em conseqüência, as áreas de disposição transformaram-se em um sério problema de caráter ambiental e de saúde pública. Uma solução encontrada foi reutilizar essas áreas como depósitos de resíduos sólidos, mas agora de forma segura em construções conhecidas como aterros sanitários. O objetivo do presente trabalho é analisar a água subterrânea sob uma célula de disposição de resíduo de origem municipal construída em um antigo terreno utilizado como depósito indiscriminado. Para isso, foram pesquisadas as características físicas da área (geomorfologia, geologia, hidrometeorologia e hidrogeologia). A partir da hidrometeorologia, foi estimada a quantidade de água meteórica sob a célula central e esta foi comparada com a produção de lixiviado produzido na célula central, a diferença entre o estimado (34.006m3) e o produzido (36.338m3) foi de 6,42% para o ano de 2005. Para obter a caracterização da qualidade da água subterrânea foram realizadas amostragens da água subterrânea e água superficial em torno da célula central ao longo dos anos de 2005 e 2006, com intervalos de três meses entre uma campanha e outra. Os parâmetros que apresentaram resultados acima dos valores orientadores para águas subterrâneas (CETESB, 2005 e Portaria 518, 2004) foram: alumínio total, arsênio total, bário total, chumbo total, cloreto total, coliformes totais, cor, ferro total, manganês total, mercúrio total, níquel total, sólidos dissolvidos totais, sulfato e turbidez. Já os parâmetros que apresentaram resultados acima dos valores de intervenção para águas superficiais classe III (CONAMA, 2005) foram: alumínio total, cor, fosfato total, fósforo total, manganês total, odor, óleos e graxas e sólidos totais. Os resultados dessas análises indicam que existe uma alteração das águas, provavelmente devido aos antigos resíduos que ainda são uma fonte de contaminação, mas não apresentaram evidências de que a célula central de disposição de resíduos esteja participando da alteração da água subterrânea e superficial. / In the past, the disposal of solid residue without any type of treatment and control was a common and widespread practice. As a result of that, the old areas used as dump have become a serious environmental and public health problem. Some of these areas are being reused in constructions now known as landfills, this time in a way that they arent a threat anymore. The objective of this research is to analyze the groundwater under a municipal area of residue disposal built on the land of an old irregular dump. For this purpose, the physical characteristics of the area (geomorphology, geology, hydrometeorology and hydrogeology) were studied. With the results from the hydrometeorology analyzes it was possible to estimate the quantity of meteoric water under the central cell which was compared to the production of leachate in the central cell; the difference between the estimated (34.006m3 ) and the produced (36.338m3) was 6,42% in 2005. To characterize the groundwater quality, samples from ground and superficial water were taken from the area surrounding the central cell every three months during 2005 and 2006. The parameters whose results are above reference values for groundwater (CETESB, 2005 e Portaria 518, 2004) were: aluminum, arsenic, barium, lead, chlorate, coliform total, color, iron, manganese, mercury, nickel, solids total dissolved, sulphate and turbidity. The parameters whose results were above intervention value for superficial water class III (CONAMA, 2005) were: aluminum, color phosphate, phosphor, manganese, odor, oils and grease and solids dissolved. The results of these analyzes indicate that theres an alteration in these waters, probably due to old residues disposed of that are still a source of contamination, but these results didnt provide any evidence as of to prove that the central cell is participating in this alteration of the ground and superficial water.

Ranney radial collector wells consist of an array of horizontal lateral wells arranged radially around and connected to the base of a vertical well. They offer numerous advantages over traditional vertical wells with application in both the petroleum industry and hydrologic sciences. This study improved the understanding of the interaction of collector wells and the aquifers/reservoirs they tap by numerically modeling flux exchanges between a collector well and a river in an unconfined aquifer with regional background flow. Modeling demonstrated that flux along each horizontal lateral increased with distance from the vertical well stem following a third order polynomial function. Ultimately these models demonstrated that in the collector well/aquifer/river system, the pumping rate of the collector well was the dominant factor in controlling flux between the river and aquifer under various conditions. This study can be used to project the maximum allowable pumping rate without causing an initially gaining river to become a losing river.

The Ruttan Cu-Zn mine produced approximately 30 million tons of fine-grained tailings over 30 years. Since the closure of the mine in 2002, the tailings have been systematically dewatered through trenches which drain into Ruttan Lake and into the open pit and underground mine workings. This study evaluated the evolution of the tailings of Cell 3, which was underwater in 2002, and Cell 2, which was already dry and oxidized. Dewatering the submerged tailings in Cell 3 resulted in measureable changes in acidification in pore and shallow groundwater from rapid oxidation of very fine grained sulphides. Depth profiles of the concentration of metals in dissolved and solid fractions, when compared to other studies, suggest that the tailings in Cell 2 and Cell 3 are in an early stage of oxidation and that these tailings will produce low pH, metal laden water for years. / February 2009

Ranney radial collector wells consist of an array of horizontal lateral wells arranged radially around and connected to the base of a vertical well. They offer numerous advantages over traditional vertical wells with application in both the petroleum industry and hydrologic sciences. This study improved the understanding of the interaction of collector wells and the aquifers/reservoirs they tap by numerically modeling flux exchanges between a collector well and a river in an unconfined aquifer with regional background flow. Modeling demonstrated that flux along each horizontal lateral increased with distance from the vertical well stem following a third order polynomial function. Ultimately these models demonstrated that in the collector well/aquifer/river system, the pumping rate of the collector well was the dominant factor in controlling flux between the river and aquifer under various conditions. This study can be used to project the maximum allowable pumping rate without causing an initially gaining river to become a losing river.

Collector well designs are necessary to maximize groundwater uptake and riverbank filtration without negatively impacting an aquifer. Unfortunately, there is a lack of information and research regarding the implementation of collector well design parameters. In the past, collector well installation was too costly, but recent advances in well technology have made collector wells more cost effective. This research will contribute a set of guidelines to optimize riverbank filtration and groundwater remediation. This study models the hydrodynamics surrounding collector well configurations in riverbank filtration and groundwater remediation. Visual Modflow® was utilized to run a variety of numerical models to test four areas: flux along the laterals of a collector well, collector well interactions with a river, collector well yield, and collector well remediation capability. The two design parameters investigated were lateral length (25 m, 50 m, and 100 m) and number of laterals (3 and 4). The lateral flux tests confirm flux increases towards the terminal end of each lateral and pumping rate is the controlling factor in flux amount obtained along the laterals. The analysis of the flux-river interaction shows the main factor in determining flux amount is the initial river geometry, followed by the pumping rate, regional background flow, and collector well design, respectively. The models suggest that the 4-lateral collector well design is more effective than the 3-lateral design and in addition, 100 meter length laterals provide the highest amount of yield with the least amount of drawdown. The remediation tests investigate the application of vertical well equations to evaluate collector well designs in two areas: minimum pumping rate to capture line source of particles and first arrival time of particles. The remediation models show 100 meter length laterals provide both the lowest pumping rate and the highest residence time with the surrounding aquifer for maximum remediation. Ultimately, these models provide basic design guidelines and explain which designs are most effective, depending on the collector well purpose.

Thesis (M.S.)--Florida State University, 2004. / Advisor: Dr. William C. Burnett, Florida State University, College of Arts and Sciences, Department of Oceanography. Title and description from dissertation home page (viewed June 16, 2004). Includes bibliographical references.