Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 47 for “"Unsaturated Zone"”.
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Finite element analysis of nitrogen species transport and transformation in the unsaturated zone
A two-dimensional finite element model was developed to predict water flow and nitrogen species transport and transformation in variably saturated soil. In the finite element analysis various numerical algorithms were examined to evaluate methods of improving the efficiency of the traditional …
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Ground-penetrating radar images of a dye tracer test within the unsaturated zone at the Susquehanna-Shale Hills CZO
… to image preferential flow paths in the shallow, unsaturated zone on hillslopes in two adjacent watersheds within the Susquehanna-Shale Hills Critical Zone Observatory (CZO). At each site we injected about 50 L of water mixed with brilliant blue dye (4 g/L) into a trench cut perpendicular to the …
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Tritium Plume Dynamics in the Shallow Unsaturated Zone Adjacent to an Arid Waste-Disposal Facility, Amargosa Desert Research Site, Nevada
… movement of tritiated water from sub-root-zone gravel into the root-zone contributes to atmospheric release via evapotranspiration. Estimates of lateral and vertical tritium fluxes during the study period indicate (1) vertical tritiated water fluxes were dominated by diffusive-vapor fluxes …
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Characterisation of sedimentary structure and hydraulic behaviour within the unsaturated zone of the Triassic Sherwood Sandstone aquifer in North East England
… of moisture migration in the vadose zone at a single field site. Sedimentary structure and likely permeability variations were studied by use of laboratory grainsize analysis, logging of nearby outcrops, borehole geophysics and Ground Penetrating Radar (GPR). GPR is ideal for vadose …
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MONITORING INFILTRATION FROM NATURAL STORMS USING TIME-LAPSE ELECTRICAL RESISTIVITY TOMOGRAPHY
… of the heterogeneity of flow through the unsaturated zone especially when compared to point measurements taken within the same survey area. The most powerful tool for understanding the unsaturated zone is a combination of several techniques. Many models of unsaturated zone flow assume a …
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Valutazione dei meccanismi di degradazione dei nitrati durante il processo di infiltrazione e trasporto nelle acque sotterranee come verifica della efficacia delle misure di mitigazione della contaminazione nelle Zone Vulnerabili da Nitrati
… has been observed in many Nitrates Vulnerable Zones. The study area, the plain of Arborea (Sardinia), has been identified as a NVZ since 2005, and this phenomenon is clearly observable there. The unsaturated zone is a fundamental part of the hydrological cycle, capable of storing water, …
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The Hydrogeologic effects of fly ash utilization in concrete at Coal Creek Station, Underwood, North Dakota
… monitoring network encompassing surface water, unsaturated zone water, and saturated zone water was designed for the site. Surface water quality was documented using a runoff collector and precipitation collector. soil moisture and ground water occurrence and quality were monitored using …
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Numerical methods for optimization problems in water flow and reactive solute transport processes of xenobiotics in soils
… water flow and reactive solute transport in the unsaturated zone to determine unknown parameters, e.g. degradation rates. In this thesis new contributions are made to the following fields: 1. Modeling of parameter estimation problems and optimal experimental design problems: Mathematical modeling …
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The effect of oil-and-gas well drilling fluids on shallow groundwater in western North Dakota
… all of the study sites, Water obtained from the unsaturated zone beneath the buried drilling fluid at all of the four study sites exceeds some of the Recommended and Maximum Permissible Concentration Limits for trace elements and major ions (As, Cl-, Pb, Se and N03-). These values are greatly …
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Determination of coefficient of storage by use of gravity measurements.
… resulting from change of amounts of water in the unsaturated zone indicates that the coefficient of storage computed for field stations near Rillito Creek, the source of the unsaturated-zone water, are too low. Using data from stations least affected by gravity increases after stream recharge, a …
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Precipitation and Sea Level Rise Impacts on Groundwater Levels in Virginia Beach, Virginia
… and thereby decrease storage capacity of the unsaturated zone.</p> <p>This study investigates the spatial and temporal response of the groundwater table to SLR and precipitation. We choose a tidal watershed, West Neck Creek, in Hampton Roads was chosen to conduct a conceptual yet realistic …
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Flow and Distribution of Water in Fractional Wettability Unsaturated Porous Media
… interest in fluid flow and transport in the unsaturated zone has gained more attention, due to growing concerns that the quality of the subsurface environment is adversely affected by agricultural, industrial, and municipal activities. The wettability properties (e.g., water repellency) of …
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A continuous real-time interactive basin simulator (RIBS)
… moisture transfer in the ground water system. An unsaturated zone - ground water coupling mechanism is implemented to account for interdependences between the two systems. All these newly added features ensure the capability of the model in applications over longer periods of time under a broader …
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The use of radiorespirometry for evaluation of subsurface biodegradation
… in Pennsylvania and Virginia. Both saturated and unsaturated zone soils were used. The alcohols used were methanol and tertiary-butanol. Methanol was easily degraded under both aerobic and anoxic conditions up to approximately 3000 mg/L. Tertiary-butanol was degraded very slowly under both aerobic …
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Nitrate and Ammonium Transformation and Fate in Groundwater of an Agricultural Watershed: An Isotope and Geochemistry Approach
… nor were nitrate and ammonium consistent in the unsaturated zone and groundwater. Findings indicate the urea only site has possibly longer retention of NH 4 in soil water, low concentrations of NH4 but the presence of moderately higher NO3 concentrations (up to 20 ppm-N) in shallow groundwater. …
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Modernized Approach For Generating Micro-Layering And Macro-Heterogeneous Structures In Porous Media For Use In Transmitted-Light Method Flow Visualization Experiments
… Interactions of fluid flow between the vadose zone and permanent water table are of great interest to researchers because this zone is responsible for all recharge waters, pollutant transport and even irrigation efficiency for agriculture. Griffith, et al. (2011) developed an approach where …
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Assessing the use of exfiltration pervious pavements as a best management practice for storm water management for Lusaka urban
… to have been contributed to the immediate unsaturated zone below the pavement systems through infiltration during each observed rainfall events ranged from 140mm to 211.4mm in 1100mm depth of soil. The study concluded that full exfiltration pervious pavement systems as a best management …
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Transport of copiotrophic bacteria in oligotrophic coarse soils: a Monte Carlo analysis
… will not pass unaltered through an unsaturated zone located in the soil below each system. Studies have shown that 0.6 to 1.2 m of unsaturated soil below an on-site system drainfield is sufficient to remove most bacteria and viruses in most environments. Little is known of the …
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Representation of water table dynamics in a land surface scheme : observations, models, and analyses
… soil drainage flux). The total thickness of the unsaturated zone varies in response to the water table fluctuations, thereby interactively couples the aquifer model with the soil model. The second issue to be addressed in this thesis is the representation of the sub-grid variability of water …
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