Dissertations / Theses on the topic 'Groundwater'

This thesis concerns a groundwater modeling study south of Tucson, Arizona where 10,000 acre-feet of Central Arizona Project water may be annually recharged. South and west of the site are the Santa Cruz River and the Tohono O'odham Indian Nation. Well fields to the immediate east, west and south supply water to the City of Tucson and to farming and copper mining corporations. Operation of the corporate well fields has lead to a water table depression just west of the site. The purpose of the model is to understand of the most probable groundwater flow regime in light of aquifer recharging and groundwater mining. The model serves to compare groundwater conditions with previous investigations. Lack of data precluded the construction of a model capable of producing reliable predictive results. Hydrogeologic data gathered provide a foundation for future modeling studies. Insufficient data serve as indicators of present groundwater monitoring deficiencies.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1985.
MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.
Bibliography: leaves 94-97.
by Matthew Drake Reynolds.
M.S.

The Tjuntjuntjara Groundwater Desalination Thesis was conceived to solve the operational faults of a Vacuum-Multi-Effect-Membrane-Distillation (VMEMD) Pilot Plant. The National Centre for Excellence in Desalination (NCED), Murdoch University and other contributing parties intend to power the plant with renewable energies in order to supply the Tjuntjuntjara indigenous community with water. The thesis involved research into VMEMD technology and an assessment of the control system and instrumentation that operated it. During the assessment process, operational faults as well as potential improvements in the operation of the plant were recorded. It was found that the control system had a number of software based faults. The design and implementation of a new Programmable Logic Controller (PLC) operating code was undertaken to correct these faults. In parallel to this work, the design and implementation of systems to improve the operation of the plant was also undertaken. When all upgrades to the plant were complete, the vigorous process of validating the new additions commenced. As well as testing the new code and system improvements, a series of continuous trial periods was conducted. These proved that the plant can now operate continuously and at varying system temperatures for over 100 hours. During the trial periods, operating point data was collected and methods for increasing distillate output were found. The plant has been brought up to a stable operating standard and the additional systems installed to improve the plant have further increased its reliability. A number of recommendations have been provided to stimulate further development of the VMEMD pilot plant.

Thesis (M.A.)--University of Missouri-Columbia, 2006.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (February 23, 2007) Includes bibliographical references.

This Licentiate Thesis presents a new approach of understanding leakage in agricultural land. Former studies concentrate on long term measurement of different pollutants in nearby watercourses and streams. The new approach is so far only numerically performed, but will soon be complemented by laboratory tests and field measurements. Our hypothesis is that nutrient leakage into groundwater is caused by thermally driven groundwater convection. The maximum density of water occurs at a temperature of near 4oC. Thus, a density increase of the groundwater occurs by heating from about 0oC in the north of Sweden (springtime) and by cooling from about 10oC in the south (autumn). The depth of the convection (leakage) depends on the size of the thermal gradient. This hypothesis consequently explains both why the nutrient leakage occurs during different seasons in the north and south of Sweden and also why the leakage reaches greater depths in the south. The numerical results show that convection is induced by a small horizontal groundwater flow. In the south of Sweden the lowest required permeability for convection to occur was K=6.7∙10-10m2. In this soil the convection cells reached to a maximum depth of 6 meters. The Rayleigh number (Ra) could be as low as 19 for convection to occur, the general critical Ra is 40 in porous media. In northern Sweden a permeability of K=6.1∙10-92 was required. In this soil and climate convection occurred to depths from 0.2 to 0.9 meters. Transient solutions showed that the required time for the convection pattern to fully develop was 22 days. The effect of frost lenses on the groundwater convection was also studied. Small lenses changed the convection rolls slightly, while large obstacles forced the convection rolls to change size and shape. The simulations showed that the required grain size for convection to occur was considerably greater than the grain size in typical agricultural soils. Still vertical groundwater movements exist. Other possible explanations to groundwater convection in agricultural soil in northern Sweden are to be investigated. Unstable groundwater convection or oscillating convection cells, infiltration of rain and melt water, pressure induced convection and the possibility that Coriolis force due to Earth´s rotation could cause secondary currents in groundwater flow.
Godkänd; 2005; 20070102 (haneit)

The modular three-dimensional finite-difference groundwater flow model (MODFLOW) was used to study the hydrology of Upper Cienega Creek. The geological and hydrological characteristics of the basin indicate that the groundwater is contained in an unconfined aquifer. The study focuses on the interaction between groundwater and surface water in Upper Cienega Creek Basin and the surrounding basins (Sonoita and Bobocamari). The steady state analysis simulated the predevelopment conditions of the aquifer, and the transient state analysis, conducted between 1989 and 2002, predicted the response of the aquifer to future stresses. The location of pumpage and the volume of water pumped during the entire transient period resulted in a minimum reduction (1%) of the Cienega Creek stream flow. However, a drawdown of 200 ft located in Sonoita and Elgin area was predicted in the transient simulation. Capture calculations show that the reduction in evapotranspiratiou partially balanced the volume of water lost as result of pumping.

Environmental tracers can provide information on groundwater age, recharge conditions and flow processes. This information is useful for evaluating groundwater sustainability and vulnerability by identifying groundwater provenance and information for water budgets. Gibsons, British Columbia is a growing coastal community relying on groundwater to supply drinking water to two thirds of its 4,300 residents. The Town of Gibsons is proud of its untreated groundwater resource and proactive about keeping it protected and sustainable for future generations. Samples of noble gases, tritium, and stable isotopes of oxygen and hydrogen were collected from the aquifer. Tracer results improved the site conceptual model by identifying a previously unknown contribution of mountain block recharge (MBR) and by providing recharge elevation estimates using noble gas thermometry. The updated conceptual model including the mountain block was integrated into a regional three-dimensional numerical groundwater flow model calibrated to both hydraulic heads and to recharge elevation, a non-traditional approach to model calibration. This is the first study to use recharge elevation as a calibration target, which proved to be imperative for constraining bedrock geometry and minimizing model non-uniqueness. Tracer and modeling results indicate that groundwater in the Gibsons aquifer contains a mixture of approximately 45% MBR and 55% bench recharge. The MBR component is pre-modern (> 50 years) groundwater that recharged at elevation and cold temperatures (~5°C) and has evolved hydrogeochemistry and high concentrations of excess air (EA; >0.005 ccSTP/g) and ⁴Heterr (>10-⁹ ccSTP/g). Bench recharge is modern (< 10 years) groundwater recharged at low elevations and warm temperatures (~9°C), and has non-evolved hydrogeochemistry and low concentrations of EA (0.001-0.003 ccSTP/g) and ⁴Heterr (<10-⁹ ccSTP/g). Effects of increased pumping due to population growth and decreased recharge rates caused by climate change were assessed by conducting a sensitivity analysis of groundwater flow. Based on the study results, it is recommended to carry out long-term groundwater monitoring; sustainable groundwater use and community involvement are required to ensure groundwater sustainability.

Surface-water and groundwater are two resources both requiring careful management and protection. Computer modelling of both has long been used as an aid to their management. Historically they have been modelled separately, as their behaviour is represented by different mathematical equations. However, in reality, they are a linked resource each affects the other. DIVAST is a two-dimensional hydrodynamic and water quality numerical model developed for estuarine and coastal modelling. The original model enables the simulation of problems such as pollution and flooding in surface waters. In this study the existing model is extended to allow the modelling of groundwater as well as surface water in the same model. Chapters 1-5 introduce the problem, review some existing models, and then derive, discretise, and implement the equations for surface water and groundwater flow into the new model. Chapters 6-10 test the new model against analytical solutions, laboratory data, field data, and an existing groundwater model (MODFLOW). The outcome is a new version of the DIVAST model, known as DIVAST-SG (Depth Integrated Velocities And Solute Transport in Surface water and Groundwater). It simulates interactions between two-dimensional surface water and groundwater, in addition to the facilities of the original code. The equations are solved within one model, avoiding coupling problems. It is successfully tested against analytical solutions, laboratory studies and field data, and compared to an existing groundwater code, where it successfully models a gravel aquifer adjacent to tidal surface water. A framework is laid for continuing this work to produce a pseudo 3-D surface- water / groundwater code. In addition, novel techniques are pioneered in the laboratory, where open cell foam is used in a tidal flume to represent a porous aquifer adjacent to a river, and a highly detailed dataset of groundwater field data is compiled in the course of the work.

The Lost River Groundwater Drainage Basin in Warren County, Kentucky, is a karst drainage system encompassing 55 square miles (143 square kilometers) developed within the Mississippian St. Louis and Ste. Genevieve Limestones. Near the contact between these two formations are two bedded chert units, the Lost River Chert Bed (Elrod, 1899) within the Ste. Genevieve and the Corydon Chert Member (Woodson, 1983) of the St. Louis, which appear to be perching layers to shallow karst groundwater flow. Groundwater may be seen flowing on top of these beds in various cave streams and at swallets and springs throughout the basin. In order to compare the vertical positions of these layers to shallow karst groundwater flow, geologic structure maps of the Lost River Chert Bed and the Corydon Chert Member were prepared for the basin, along with a contour map of the water table (at or near which shallow karst groundwater flow is assumed to take place) over the same area. These surfaces were digitized, then contoured and compared using SURFACE II and DISSPLA computer graphics systems. Correlation was accepted for points where the water table is either 20 feet (6.1 meters above or below the top of the two chert layers. The water table (at baseflow conditions) was found to correlate with the Lost River Chert Bed over 42.6% of the basin, as well as 40.7% for the Corydon Member. Shallow karst groundwater flow is found to correlated with bedded chert layers over 83.3% of the study area, and therefore it is concluded that chert layers have a dominant effect on the vertical position of groundwater flow within the Lost River Groundwater Drainage Basin.

This thesis examines the history of groundwater management through the development of groundwater conservation districts in Texas. Political, economic, ideological, and scientific understandings of groundwater and its regulation varied across the state, as did the natural resource types and quantities, which created a diverse and complicated position for lawmakers and landowners. Groundwater was consistently interpreted as a private property right and case law protected unrestricted use for the majority of the twentieth-century even as groundwater resources crossed property and political boundaries, and water tables declined particularly during the second-half of the century. The case study of the Brazos Valley Groundwater Conservation District describes the complicated history of groundwater in Texas as the state attempted to balance natural resource legislation and private property rights and illuminate groundwater’s importance for the future.

The thesis presents a two-dimensional Risk Assessment Method (RAM) where the assessment of risk to the groundwater resources incorporates both the quantification of the probability of the occurrence of contaminant source terms, as well as the assessment of the resultant impacts. The approach emphasizes the need for a greater dependency on the potential pollution sources, rather than the traditional approach where assessment is based mainly on the intrinsic geo-hydrologic parameters. The risk is calculated using Monte Carlo simulation methods whereby random pollution events were generated to the same distribution as historically occurring events or a priori potential probability distribution. Integrated mathematical models then simulate contaminant concentrations at the predefined monitoring points within the aquifer. The spatial and temporal distributions of the concentrations were calculated from repeated realisations, and the number of times when a user defined concentration magnitude was exceeded is quantified as a risk. The method was setup by integrating MODFLOW-2000, MT3DMS and a FORTRAN coded risk model, and automated, using a DOS batch processing file. GIS software was employed in producing the input files and for the presentation of the results. The functionalities of the method, as well as its sensitivities to the model grid sizes, contaminant loading rates, length of stress periods, and the historical frequencies of occurrence of pollution events were evaluated using hypothetical scenarios and a case study. Chloride-related pollution sources were compiled and used as indicative potential contaminant sources for the case study. At any active model cell, if a random generated number is less than the probability of pollution occurrence, then the risk model will generate synthetic contaminant source term as an input into the transport model. The results of the applications of the method are presented in the form of tables, graphs and spatial maps. Varying the model grid sizes indicates no significant effects on the simulated groundwater head. The simulated frequency of daily occurrence of pollution incidents is also independent of the model dimensions. However, the simulated total contaminant mass generated within the aquifer, and the associated volumetric numerical error appear to increase with the increasing grid sizes. Also, the migration of contaminant plume advances faster with the coarse grid sizes as compared to the finer grid sizes. The number of daily contaminant source terms generated and consequently the total mass of contaminant within the aquifer increases in a non linear proportion to the increasing frequency of occurrence of pollution events. The risk of pollution from a number of sources all occurring by chance together was evaluated, and quantitatively presented as risk maps. This capability to combine the risk to a groundwater feature from numerous potential sources of pollution proved to be a great asset to the method, and a large benefit over the contemporary risk and vulnerability methods.

Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2004.
Includes bibliographical references (leaves 203-227). Also available in electronic version. Access restricted to campus users.

Thesis (Ph. D.)--University of Texas at Austin, 2000.
Vita. Two folded maps in pocket. Includes bibliographical references (leaves 207-213). Available also in a digital version from Dissertation Abstracts.

Groundwater is used worldwide as a major source for agricultural irrigation, industrial processes, mining, and drinking water. An accurate understanding of groundwater levels and trends is essential for decision makers to effectively manage groundwater resources throughout an aquifer, ensuring its sustainable development and usage. Unfortunately, groundwater is one of the most challenging and expensive water resources to characterize, quantify, and monitor on a regional basis. Data, though present, are often limited or sporadic, and are generally not used to their full potential to aid decision makers in their groundwater management.This thesis presents a solution to this under-utilization of available data through the creation of an open-source, Python-based web application used to characterize, visualize, and quantify groundwater resources on a regional basis. This application includes tools to extrapolate and interpolate time series observations of groundwater levels in monitoring wells through multi-linear regression, using correlated data from other wells. It is also possible to extrapolate time series observations using machine learning techniques with Earth observations as inputs. The app also performs spatial interpolation using GSLIB Kriging code. Combining the results of spatial and temporal interpolation, the app enables the user to calculate changes in aquifer storage, and to produce and view aquifer-wide maps and animations of groundwater levels over time. This tool will provide decision makers with an easy to use and easy to understand method for tracking groundwater resources. Thus far, this tool has been used to map groundwater in Texas, Utah, South Africa, Colombia, and the Dominican Republic.

Nonpoint source pollution captured by urban stormwater runoff is the greatest challenge for surface water quality improvements. Computer-based design tools have been developed to help mediate this issue by guiding end users through the implementation of decentralized stormwater management. The majority of these tools focus on treatment via biofiltration, yet concern regarding this treatment regime is rising. Case studies from research past clearly indicate the susceptibility of groundwater to contamination from extensive anthropogenic activity at the surface. Contaminants, such as nitrates and pathogens, are not completely removed before runoff enters the underground watercourse. Additionally, national and state legislation, which explicitly lists where neglect for groundwater quality is permissible—exacerbate concerns. This research analyzes the efficiency the BMP Siting Tool developed by the US Environmental Protection Agency and the Grey-to-Green Decision Support Tool developed by the University of South Florida. The tools were used to obtain cartographic data illustrating suitable sites for bioswales and infiltration basins throughout northern portion of Hillsborough County, Florida. This data was then integrated with the Karst Aquifer Vulnerability Index (KAVI) groundwater vulnerability model. The area of bioswales and infiltration basins that intersected areas of the KAVI model listed as ‘highly vulnerable’ or ‘moderate-to-highly vulnerable’ was calculated. This permitted an assessment of which BMP facility had the greatest sitings atop vulnerable areas, respective of the tool. The BMP Siting Tool sited 2.80% of all bioswales and 27.89% of all infiltration basins above vulnerable areas. Likewise, the Grey-to-Green Decision Support Tool sited 21.66% of all bioswales and 9.62% of all infiltration basins above vulnerable areas. These results prompted the development of a supplemental groundwater vulnerability framework to be incorporated into both tools’ analytical process.

In the recent decades, therehave been frequent conflicts between groundwater waterresources and environmentally hazardous activities. Newmethodologies for aiding decision-making in groundwater impactassessment and protection areneeded and in which issues ofincreased awareness, better understanding of the groundwaterresources processes, and validation of predictive mathematicalmodels are addressed.

A framework fordecision–aid, based on predictive simulations that a)predicts the environmental impacts b) provides the totaleconomical value c) visualises the impacts and the groundwaterproperties and d) describes the uncertainties in the results isproposed herein. The framework can be applied in environmentalimpact assessments, strategic environmental assessments andprotection and management of water resources. The results ofthe model are used as feedback for determining new scenarios,depending on the required uncertainties, and if the plannedactivity is sustainable, and/or fulfils the legislative andpolicy measures. This framework is applied to a particular casestudy, Nybroåsen, in the south-eastern part of Sweden,where the highway E22 is constructed through the importantglaciofluvial esker aquifer, passing the protection zone of thewater supply for the Kalmar municipality.

The impacts from the new highwayand the existing road have been predicted by two-dimensionalphysically based time-variant flow and solute groundwatermodelling. The results, breakthrough curves of contaminantconcentration in wells and maps of concentration distributions,as well as travel times, flow paths, and capture zones forwells determined by particle tracking have been presented.

The constructed model of theNybroåsen study area was calibrated by comparing observedand simulated groundwater levels for 15 observation wells forten years of measurements. The model has been evaluated bothgraphically and numerically and the calibration target wasfulfilled for 13 of the 15 observation wells. The model workincludes investigations of the catchment information, a waterbalance study, simulation of the groundwater recharge,consideration of the unsaturated zone by a numerical columnsimulation, and sensitivity analysis.

From the sensitivity analysis ofthe flow and transport parameters, it has been shown that theuncertainties are mainly due to the hydraulic conductivity.Comparison of the derived conductivity from the steady-stateautomatic calibration and the time-variant calibration showedthat there are major differences in the derived parameters,which illustrates the importance of a time dependentcalibration over both wet and dry periods and in more than onepoint in the area of interest of the model predictions.

In addition, a multi-criteriadecision analysis has been carried out for four roadalternatives (including the new highway E22) and the existingroad in the case study concerned. The multi-criteria decisionaid is applied as an illustration of how it can be used in thestudy area to identify a) interest groups of actors and theirconcerns b) ranking of alternative road scenarios according toactors’preferences and c) coalition groups of actorsi.e.groups that have similar views with regard to theroad alternatives.

Keywords:Physically-based groundwater modelling,contamination, flow and solute transport, glaciofluvialdeposits, Nybroåsen, Sweden, and multi-criteriadecision-aid.

Gravity is the main driving force for groundwater flow, and both landscape topography and geology distribute the effects of gravity on groundwater flow.  The groundwater table defines the distribution of the potential energy of the water. In humid regions where the bedrock permeability is relatively low and the soil depth is sufficiently shallow, the groundwater table closely follows the landscape topography and, thus, the topography controls the groundwater circulation in these regions. In this thesis, I investigate multi-scale topography-controlled groundwater flow, with the goal of systematizing the spatial distribution of groundwater flow and assessing geological parameters of importance for groundwater circulation.  Both exact solutions and numerical models are utilized for analyzing topography-controlled groundwater flow. The more complex numerical models are used to explore the importance of various simplifications of the exact solutions. The exact solutions are based on spectral representation of the topography and superpositioning of unit solutions to the groundwater flow field. This approach is an efficient way to analyze multi-scaled topography-controlled groundwater flow because the impact of individual topographic scales on the groundwater flow can be analyzed separately.  The results presented here indicate that topography is fractal and affects groundwater flow cells at wide range of spatial scales. We show that the fractal nature of the land surface produces fractal distributions of the subsurface flow patterns. This underlying similarity in hydrological processes also yields a single scale-independent distribution of subsurface water residence times which have been found in distributions of solute efflux from watersheds. Geological trends modify the topographic control of the groundwater circulation pattern and this thesis presents exact solutions explaining the impact of geological layering, depth-decaying and anisotropic hydraulic conductivity on the groundwater flow field. For instance, layers of Quaternary deposits and decaying permeability with depth both increase the importance of smaller topographic scales and creates groundwater flow fields where a larger portion of the water occupies smaller and shallower circulation cells, in comparison to homogeneous systems.
Gravitationen är den mest betydelsefulla drivkraften för grundvattenströmning. Topografin och geologin fördelar vattnets potentiella energi i landskapet. Grundvattenytans läge definierar vattnets potentiella energi, vilket är ett randvillkor för grundvattnets strömningsfält. I humida områden med en relativt tät berggrund och tillräckligt tunna jordlager, följer grundvattenytan landskapets topografi. Därav följer att grundvattenströmningen är styrd av topografin i dessa områden. I denna avhandling belyser jag den flerskaliga topografistyrda grundvattenströmningen. Min målsättning har varit att kvantitativt bestämma grundvattenströmningens rumsliga fördelning samt att undersöka hur olika geologiska parametrar påverkar grundvattencirkulationen. Jag har använt såväl numeriska modeller som analytiska lösningar, för att undersöka hur topografin styr grundvattenströmningen. De numeriska modellerna är mer komplexa än de analytiska lösningarna och kan därför användas för att undersöka betydelserna av olika förenklingar som finns i de analytiska lösningarna. De analytiska lösningarna är baserade på spektralanalys av topografin, samt superponering av enhetslösningar, där varje enhetslösning beskriver hur en specifik topografisk skala påverkar grundvattnets strömningsfält. Detta är ett effektivt tillvägagångssätt för att undersöka flerskaliga effekter av topografin, eftersom påverkan av varje enskild topografisk skala kan studeras separat. Resultaten som presenteras indikerar att topografin är fraktal och att den ger upphov till cirkulationsceller av varierande storlek som även dessa är av en fraktal natur. Denna grundläggande fördelning i grundvattnets strömningsfält ger upphov till att grundvattnets uppehållstid i marken följer ett självlikformigt mönster och kan förklara uppmätta tidsvariationer av lösta ämnens koncentrationer i vattendrag efter regn. Geologiska trender påverkar hur grundvattenströmningen styrs av topografin. De exakta lösningar som presenteras här, beskriver hur geologiska lager samt djupavtagande och anisotropisk hydraulisk konduktivitet påvekar grundvattnets strömning. Exempelvis är betydelsen av mindre topografiska skalor viktigare i områden med kvartära avlagringar och en berggrund med djupavtagande konduktivitet, än i områden med homogen bergrund utan kvartära avlagringar. Dessutom är en större andel strömmande vatten belägen närmare markytan i de förstnämnda områdena.
QC 20100802

Bromate (BrO3") is a by-product formed at concentrations of 0.4 - 60 µg L'' during potable water ozonation. Following World Health Organisation designation as a 'possible human' carcinogen, a 10 pg L" drinking water limit was introduced in England and Wales. Discovery of bromate contamination within a UK aquifer highlighted a knowledge gap, addressed by this project, relating to environmental behaviour and groundwater remediation. Following selection of an anion analysis strategy utilising Ion Chromatography (IC), bromate behaviour in wastewater was investigated as contaminated groundwater ingress to treatment processes was deemed possible. Respiration of wastewater biomass was unaffected by spiking of < 200 mg Ul bromate or bromide, with pilot-scale process dosing trials (S 100 mg L') using a Membrane Bioreactor (MBR) also exhibiting little negative effect following biomass acclimation. Bromate reduction to bromide was observed in a continuous-flow suspended growth chemostat bioreactor at retention times of 20 - 80 hours. A biological mechanism was confirmed in this system, with reduction mediated by indigenous groundwater bacteria following glucose addition. Bromate reduction rates were initially low (5 27.8 pg U' hr 1), but acclimation increased rates to > 1000 pg L" hr t. An alteration in microbial composition was noted over this period, from a denitrifying 'co-metabolic' culture to predomination of 'high-rate' specific bromate degraders. Operational parameters including pH, temperature, carbon source, influent bromate and glucose, and retention times were investigated, with all parameters apart from pH shown to affect bromate reduction rates. For example increased bromate influent enhanced reduction rate, although potentially toxic effects were noted with an influent > 75 - 80 mg L"'. Batch studies suggested glucose was rapidly fermented (< 48 hours) by the microbial consortium. Nitrate was also rapidly removed (< 4 hours), with sulphate reduction only following removal of bromate. A fixed-film pilot-scale bioreactor system, seeded with biomass from the chemostat culture, reduced > 90% of a 1.1 mg L"1 bromate influent within unspiked contaminated groundwater. Plating studies were successful in producing a range of isolates from the mixed chemostat culture. Overall the project demonstrated, for the first time, continuous remediation of bromate groundwater contamination within a bioreactor system.

Groundwater Visibility: The Missing Link published within Column Theme: Groundwater Management Directions—Stewardship to Sustain Our Water Resources, edited by Vicki Kretsinger Grabert and Dawn Samara Kaback.

The discharge of groundwater into surface water bodies is a hidden, but significant pathway for the input of water and matter into lakes, rivers, estuaries and the coastal sea. Since groundwater is most often characterized by higher levels of nutrients or heavy metals, its discharge has often a crucial effect on the surface water body´s chemistry and the ecosystem health as well as on the related ecosystem service supply. For instance, groundwater-derived nutrient inputs are essential to fuel primary productivity, but if critical thresholds are exceeded groundwater-derived nutrient inputs can cause eutrophication, which may trigger harmful algal blooms or the creation of oxygen minimum zones – a serious threat to aquatic life. This thesis focuses on quantifying submarine and lacustrine groundwater discharge by applying environmental tracer based methods with emphasis on radionuclide (radon and radium isotopes) and stable water isotope (δ18O, δ2H) techniques. These tracers are suitable for determining groundwater discharge as they show distinct concentration and isotope ratio gradients between groundwater and the receiving surface water. Four studies are presented in this thesis: (1) The quantification of the response delay of the mobile radon detector RAD7 applied for radon-in-water mapping. The response delay of the mobile radon-in-air detector RAD7 is determined for two detection set-ups (radon extraction via RADaqua and via a membrane module) as well as for a range of water flow rates. For the membrane module the response delay is less pronounced compared to the RADaqua. For instance, at a water flow rate of 1 l min-1 the peaks of the instruments recordings lag behind the radon-in-water concentrations by ~10 min for the membrane module and by ~18 min for the RADaqua. Further, it was demonstrated that faster water flow rates decrease the response delay. An algorithm is presented that allows the inverse calculation of radon-in-water concentrations from RAD7 records for the described detection set-ups and water flow rates. Thus, it allows a more precise localization of radon-in-water anomalies and, consequently a more precise localization of groundwater discharge areas. (2) Determination of submarine groundwater discharge into a large coastal bay (False Bay, South Africa) SGD consists generally of two components: (a) fresh terrestrial SGD (FSGD) driven by the inland hydraulic gradient and (b) seawater re-circulation (RSGD) through the coastal aquifer driven by seaward effects such as tidal pumping. A bay-wide radon mapping resulted in identification of a SGD site, where subsequently detailed investigations were conducted. At this SGD site a salt and a radon mass balance were applied consecutively for determining FSGD and total SGD, respectively. RSGD was inferred from the difference between FSGD and total SGD. For the radon mass balance, new approaches for calculating the radon degassing and mixing loss were proposed. The tracer mass balance revealed median FSGD of 2,300 m³ d-1 or 0.9 m³ d-1 per m coastline and median RSGD of 6,600 m³ d-1 or 2.7 m³ d-1 per m coastline. The FSGD rate was validated using (a) a hydrological model for calculating the groundwater recharge rate and (b) a groundwater flow model for delineating the subsurficial FSGD capture zone. This validation supported the tracer based findings. The relevance of this study is foremost the presentation of new methodological approaches regarding the radon mass balance as well as the validation of FSGD under consideration of hydrological and hydrogeological information. (3) Differentiation of fresh and re-circulated submarine groundwater discharge in an estuary (Knysna Estuary, South Africa) Knysna Estuary is a more complex system than False Bay since besides seawater, FSGD and RSGD also river water mixes within the estuary. Both FSGD and RSGD were differentiated by applying a mixing analysis of the estuary water. For this purpose, an end-member mixing analysis (EMMA) was conducted that simultaneously utilizes radon and salinity time series of estuary water to determine fractions of the end-members seawater, river water, FSGD and RSGD. End-member mixing ratio uncertainty was quantified by stochastic modelling (Monte Carlo simulation) under consideration of end-member characterization uncertainty. Results revealed highest FSGD and RSGD fractions in the estuary during peak low tide. Median fractions of FSGD and RSGD were 0.2 % and 0.8 % of the estuary water near the mouth over a 24 h time-series. In combi-nation with a radon mass balance median FSGD of 46,000 m³ d-1 and median RSGD of 150,000 m³ d-1 were determined. By comparison to other sources, this implies that the SGD is a significant source of dissolved inorganic nitrogen (DIN) fluxes into the estuary. This study demonstrates the ability of EMMA to determine end-member fractions in a four end-member system under consideration of end-member uncertainty. Further, the importance of SGD for the water and DIN budget of Knysna Estuary was shown. (4) Quantification of groundwater discharge and water residence time into a groundwa-ter-fed lake (Lake Ammelshainer See, Germany). The presented approach utilizes the stable isotopes of water (δ18O, δ2H) and radon for determining long-term average and short-term trends in groundwater discharge rates. The calculations were based on measurements of isotope inventories of lake and groundwater in combination with climatic and isotopic monitoring data (in precipita-tion). The results from steady-state annual isotope mass balances for both δ18O and δ2H are consistent and reveal an overall long-term average groundwater discharge that ranges from 2,800 to 3,350 m³ d-1. These findings were supported by the good agree-ment of the simulated annual cycles of δ18O and δ2H lake inventories utilizing the de-termined groundwater discharge rates with the observed lake isotope inventories. However, groundwater discharge rates derived from radon mass balances were signifi-cantly lower, which might indicate a distinct seasonal variability of the groundwater discharge rate. This application shows the benefits and limitations of combining δ18O/δ2H and radon isotope mass balances for the quantification of groundwater con-nectivity of lakes based on a relatively small amount of field data accompanied by good quality and comprehensive long-term meteorological and isotopic data (precipitation). This thesis presents important methodological achievements with respect to radon and stable water isotope mass balances, uncertainty quantification, geochemical differentia-tion between FSGD and RSGD and validation of FSGD. Further, first SGD estimates are reported for False Bay and Knysna Estuary in South Africa
Der Austritt von Grundwasser in Oberflächengewässer stellt einen unsichtbaren Ein-tragspfad von Wasser und Stoffen in Seen, Flüsse, Ästuare und das küstennahe Meer dar. Die Konzentrationen vieler Stoffe wie beispielsweise von Nährstoffen und Schwermetallen ist im Grundwasser im Allgemeinen signifikant höher als in Oberflächengewässern. Daher können selbst volumetrisch verhältnismäßig kleine Grundwasseraustritte entscheidenden Einfluss auf Wasserchemie und den Gesundheitszustand des aquatischen Ökosystems haben, womit Auswirkungen auf die Bereitstellung von Ökosystemleistungen verbunden sein können. Beispielsweise sind grundwasserbürtige Nährstoffeinträge eine entscheidende Steuergröße für die Primärproduktivität. Überschreiten diese grundwasserbürtigen Nährstoffeinträge jedoch einen Schwellenwert, kann es zur Eutrophierung des Oberflächengewässers kommen. Dies wiederum kann toxische Algenblüten oder die Entstehung von Sauerstoffminimumzonen zur Folge haben und das aquatische Leben bedrohen. Diese Dissertation beschäftigt sich mit Methoden zur Quantifizierung von Grundwas-sereinträgen in den küstennahen Ozean, Ästuare und in Seen. Dabei stützt sich diese Arbeit primär auf Umwelttracer, vor allem auf Radionuklide (Radon- und Radium-Isotope) sowie die stabilen Isotope des Wassers (δ18O, δ2H). Diese Umwelttracer sind für die untersuchten Systeme in besonderer Weise geeignet, da zwischen Grundwasser und Oberflächenwasser ein ausgeprägter Gradient hinsichtlich Konzentration bzw. Isotopensignatur besteht. Vier Einzelstudien stellen den Kern dieser Arbeit dar: (1) Die Quantifizierung der Antwortverzögerung des mobilen Radon-Detektors RAD7, an-gewendet für die Radon-in-Wasser-Kartierung. Die Antwortverzögerung des mobilen Radon-in-Luft-Detektors RAD7 wurde für zwei Messanordnungen (Radonextraktion via RADaqua und via Membranmodul) sowie für einen Bereich von Wasserdurchflussraten bestimmt. Für die Radonextraktion via RADaqua ist die Antwortverzögerung stärker ausgeprägt als für das Membranmodul. Bei einer Wasserdurchflussrate von 1 l min-1 treten die Peaks der aufgezeichneten Werte ~10 min nach den Radon-in-Wasser Peaks auf, während die Verzögerung bei Radonextraktion via RADaqua ~18 min beträgt. Weiterhin wurde eine Reduktion der Antwortverzögerung mit zunehmenden Wasserdurchflussraten beobachtet. Der vorgestellte Algorithmus ermöglicht in Kombination mit den berechneten Radontransfer-Koeffizienten die inverse Modellierung der Radon-in-Wasser-Konzentrationen, basierend auf den RAD7-Messwerten. Dies ermöglicht beispielsweise eine genauere Lokalisierung von räumlichen Radon-in-Wasser Anomalien und folglich eine präzisere Bestimmung von Grundwasseraustrittsstellen. (2) Quantifizierung untermeerischer Grundwasseraustritte in eine große Meeresbucht (False Bay, Südafrika) Untermeerische Grundwasseraustritte (“Submarine Groundwater Discharge” – SGD) bestehen aus zwei Komponenten: (a) Süßwasser-SGD (“Fresh SGD” – FSGD) angetrieben durch den meerwärtsgerichteten hydraulischen Gradienten, und (b) re-zirkuliertem SGD („re-circulated SGD“ – RSGD), verursacht durch Prozesse wie gezeitengesteuerte Infiltration von Meerwasser in den Aquifer. Eine Radon-Kartierung entlang der gesamten Küstenlinie der Bucht führte zur Lokalisierung von SGD, woraufhin dort vertiefende Untersuchungen durchgeführt wurden. In diesem Bilanzgebiet wurden eine Salz- und eine Radon-Massenbilanz durchgeführt, um FSGD bzw. Gesamt-SGD zu bestimmen. RSGD wurde aus der Differenz von FSGD und SGD abgleitet. Für die Radon-Massenbilanz wurden neue Ansätze für die Berechnung der Radon-Entgasung in die Atmosphäre und des Radon-Mischungsverlustes mit küstenfernerem Wasser präsentiert. Die Tracer-Massenbilanzen ergaben einen FSGD-Median von 2.300 m³ d-1 bzw. 0,9 m³ d-1 pro Meter Küstenlinie und einen RSGD-Median von 6.600 m³ d-1 bzw. 2,7 m³ d-1 pro Meter Küstenlinie. Die FSGD-Rate wurde mit Hilfe eines hydrologischen Modells zur Abschätzung der Grundwasserneubildungsrate und eines Grundwasserströmungsmodells zur Abgrenzung des unterirdischen Einzugsgebiets des Bilanzraums bestimmt. Diese unabhängige Methode bestätigte die Tracer-basierten Ergebnisse. Die Bedeutung dieser Studie besteht zuvorderst in der Vorstellung neuer methodischer Ansätze bei der Radon-Massenbilanzierung sowie in der Validierung von FSGD unter Berücksichtigung hydrologischer und hydrogeologischer Daten. (3) Unterscheidung von FSGD und RSGD in einem Ästuar (Knysna Ästuar, Südafrika). Das Knysna-Ästuar ist hinsichtlich der Bestimmung von SGD im Vergleich zur False Bay ein komplexeres System, da sich neben Meerwasser, FSGD und RSGD auch Flusswasser in signifikanten Mengen im Ästuar mischt. FSGD- und RSGD-Anteile wurden anhand der chemischen Zusammensetzung des Ästuarwassers unterschieden. Für diesen Zweck wurde eine End-Member-Mischungsanalyse (EMMA) auf Grundlage von Radon- und Salinitätszeitreihen des Ästuarwassers durchgeführt. Durch ein Optimierungsverfahren wurde die Mischung der End-member Meerwasser, Flusswasser, FSGD und RSGD für jeden Zeitschritt mit dem Ziel der bestmöglichen Übereinstimmung mit den gemessenen Radon- und Salinitätszeitreihen bestimmt. Die Unsicherheit in der Bestimmung der End-member-Anteile wurde durch stochastische Modellierung (Monte-Carlo-Simulation) quantifiziert. Die höchsten Anteile von FSGD und RSGD traten bei Niedrigwasser auf. Die mittleren Anteile von FSGD und RSGD betrugen in der Nähe der Ästuarmündung 0,2 % und 0,8 % während einer 24-stündigen Zeitreihenmessung. Diese Informationen führten in Kombination mit einer Radon-Massenbilanz zur Bestimmung eines mittleren FSGD von 46.000 m³ d-1 sowie eines mittleren RSGD von 150.000 m³ d-1. Diese Ergebnisse implizieren unter Einbeziehung weiterer Daten, dass SGD ein bedeutender Pfad für den Eintrag von gelöstem anorganischem Stickstoff (DIN) in das Knysna-Ästuar darstellt. Diese Studie zeigt das Potenzial einer EMMA für die Bestimmung der Anteile von vier End-membern unter Nutzung von zwei gemessenen Variablen und unter Berücksichtigung der End-member-Unsicherheit. Außerdem wurde die Bedeutung von SGD für das Wasser- und DIN-Budget des Knysna-Ästuars aufgezeigt. (4) Quantifizierung von Grundwasseraustrittsrate und Wasserverweilzeit eines grundwas-sergespeisten Sees (Ammelshainer See, Deutschland). Der vorgestellte Ansatz nutzt die stabilen Isotope des Wassers (δ18O, δ2H) und von Ra-don für die Bestimmung des mittleren langfristigen sowie der aktuellen Grundwas-seraustrittsrate. Die Berechnungen beruhen auf Abschätzungen des Isotopeninventars anhand von Feldmessungen, der Isotopensignatur des Grundwassers sowie ergänzen-den Klima- und Isotopen-Daten (Niederschlag). Die Ergebnisse einer stationären Isoto-pen-Massenbilanz für δ18O und δ2H sind übereinstimmend und ergaben einen langfristigen mittleren Grundwasseraustritt von 2.800 bis 3.350 m³ d-1. Dieses Ergebnis wurde für die Modellierung des jährlichen Zyklus des Isotopeninventars im See benutzt, welches mit den gemessenen Isotopenwerten konsistent ist. Die auf Grundlage einer Radon-Massenbilanz abgeleiteten aktuellen Grundwasserzutrittsraten lagen im Gegensatz dazu deutlich niedriger, was jedoch nicht notwendigerweise einen Widerspruch darstellen muss, sondern vielmehr ein Hinweis auf eine möglicherweise ausgeprägte saisonale Variabilität des Grundwasseraustritts darstellen kann. Diese Studie zeigt Möglichkeiten und Grenzen der Anwendung von einer Kombination aus δ18O/δ2H- und Radon-Massenbilanzen für die Bestimmung der Grundwasseranbindung von Seen mit einem vergleichsweise geringen Messaufwand unter Nutzung qualitativ hochwertiger und umfangreicher Klima-und Isotopen-Daten (Niederschlag). Diese Dissertation präsentiert wichtige methodische Fortschritte hinsichtlich der An-wendung von Radon- und stabilen Isotopen-Massenbilanzen, der Quantifizierung von Unsicherheit, der Unterscheidung von FSGD und RSGD anhand geochemischer Daten und der Validierung von FSGD. Außerdem wurden erstmals SGD-Raten für Standorte in Südafrika (False Bay und Knysna-Ästuar) vorgestellt

Sweden have faced decreasing groundwater storage with critical low groundwater levels for several years. Gotland is one example with issues of providing freshwater due to the low groundwater levels. These circumstances can be related to impacts caused by early agriculture development, an increased demand of freshwater and climate change. There is a need in this region to increase the groundwater storage to ensure enough freshwater. The aim of the study is to increase freshwater storage. Digital geographical information system (GIS) was chosen as a tool in this study in order to cover large geographical areas.  The study was divided into two parts, with focus to determine hydrological and hydrogeological conditions and to identify suitable areas where groundwater storage could be increased. The first part studied: specific capacity, groundwater storage, groundwater balance and topographic wetness index. The second part locked at four methods to increase freshwater storage: Lakes, controlled drainage, wetland and subsurface dam. The result tells us that lakes have the potential to provide freshwater for the municipal distribution network. The controlled drainage method has the ability reduce the outflow of surface water and to increase the groundwater infiltration. Earlier drained wetland areas was identified which could serve as freshwater storage. Suitable areas for subsurface dams were identified. They could work as a large groundwater storage as a decentralized system with the ability to provide groundwater for wells that are spread out. However the identified areas for each methods needs further investigations in more detail to determine the accuracy of the results.

Investigators who were closely associated with five groundwater monitoring programs were asked to critically examine their studies as a guide to others involved in similar projects. The particular question to be answered was, "What monitoring techniques should have or could have been implemented?" given that time and money were not constraints. The case studies involved contamination of aquifers from oil field brine disposal, plating waste disposal, landfill leachate, nitrate from multiple sources, and recharge from an oxidation pond. Among the general recommendations of the investigators, resulting from the process of critical evaluation of their associated projects, were the following: establish interdisciplinary committees to set up the monitoring program; maximize the density of well network; use alternative methods to wells; completely analyze the samples, including heavy metals; thoroughly examine the hydrogeology of the problem site; use tracers; develop predictive computer models of the flow system; monitor in the zone of aeration, where applicable; develop innovative methodologies; and continue monitoring until the problem is thoroughly quantified.

Dissertation (Ph.D.)--Auburn University, 2007.
Abstract. Vita. The research presented herein has resulted in the following publications: Radu, Tanja; Yang, Jae K.; Hilliard Jeremy H.; Barnett, Mark O.; "Transport of As (III) and As (V) in experimental subsurface systems", ACS Symposium Series 915, Advances in Arsenic Research, 2005, 91-103 Radu, Tanja; Subacz, Jonathan L.; Jonathan L.; Phillippi, John M.; Barnett, Mark O. "Effects of dissolved carbonate on arsenic adsorption and mobility" Environmental Science and Technology, 2005, 39(20), 7875-7882 Radu, Tanja; Kumar, Anjani; Clement, T. Prabhakar ; Jeppu, Gautham; Barnett, Mark O.; "Development of scalable model for predicting arsenic oxidation and adsorption at pyrolusite surfaces" Journal of Contaminant Hydrology, 2007, in press Includes bibliographic references (p.106-115).

Thesis (M.S. in computer science)--Washington State University, May 2009.
Title from PDF title page (viewed on June 11, 2009). "School of Electrical Engineering and Computer Science." Includes bibliographical references (p. 46-47).

The objective of the MSc thesis is to develop a systematic framework for groundwater pollution risk evaluation starting from the groundwater vulnerability maps of Wallonia developed through a GIS-based interface. The aim is rather to conduct a first assessment, that could trace the path for further application and be integrated in the existent Apsû methodology for vulnerability assessment. The first phase of the study consisted in undertaking a literature review on regional risk assessment procedures in the other countries and regions of the world, in order to identify the best approach to apply in Wallonia: the “European Approach” is selected. The probability that, following the occurrence of a hazardous event on the surface of the soil, the contamination could reach the water table and have a serious impact on the groundwater status is evaluated. To do so, data on potential pressures on soil is collected, to create an Hazard map. The risk assessment is carried out on a regional scale for groundwater body RWM040, combining the created Hazard Map, Intrinsic Vulnerability map and Consequences. The selected groundwater body has been subject of several studies, due to the peculiar features of the chalks aquifer (e.g. double porosity and dry valleys), that enhance the risk of groundwater pollution. Furthermore, the area, harshly affected by nitrates and pesticides pollution linked to the extensive agricultural practices, is a perfect site to test the strength of the developed method.