High concentrations of sulfate in groundwater, up to ten times the amount recommended by the EPA, in Blanco and Hays Counties, Texas, are of concern as groundwater pumping and population increase. The goals of this study are to characterize the chemistry of groundwaters in Blanco and Hays Counties within the context of Texas Groundwater Management Area-9 and to determine chemically and hydrogeologically the explanation for the spatial distribution of sulfate between the Pedernales River, the Blanco River, and Onion Creek. Insights gained by examining sulfate distribution in Blanco and Hays Counties can be applied to the other counties on the Edwards-Trinity Plateau with similarly high concentrations of sulfate in groundwater. Hydrochemical data from the Cretaceous Edwards and Trinity Groups and water level measurements were used to analyze groundwater chemistry and flow. PHREEQC was used to examine whether phase changes in aquifer minerals could explain the observed geochemical patterns. COMSOL was used to develop a simplified groundwater flow model for a cross-sectional area between the Pedernales River and Onion Creek in Hays County. Water levels indicate that groundwater generally flows southeast in the study area and most streams are gaining. The groundwater flow model indicates a zone of slow-moving groundwater beneath the topographic high between the Pedernales River, the Blanco River, and Onion Creek. Chemical analyses of well data show the presence of four groundwater chemical endmembers in Groundwater Management Area-9; a Ca-Mg-HCO3 fresh endmember, a Ca-Mg-SO4 endmember, a Ca-Mg-SO4-Na-Cl endmember, and a Na-Cl endmember. High sulfate waters generally come from the Upper and Middle Trinity aquifers while fresher waters are from the Edwards aquifer. Physical and chemical analyses indicate that the zone of high sulfate in Blanco and Hays Counties may be the result of gypsum dissolution and dedolomitization in the Upper and Middle Trinity aquifers combined with low rates of groundwater flow beneath the topographic high. Groundwater flow analyses are consistent with those for the Groundwater Availability Models published for the region. Chemical analyses, specifically SO4 distributions and Ca/Mg ratios, are consistent with those found by Nance(2010) on the Edwards Plateau, farther west of the study area. / text

The mixing zone developed at freshwater-seawater interface is one of the most important features in complex coastal hydrogeologic systems, which controls subsurface flow and reactive transport dynamics. Freshwater-seawater mixing-zone development is influenced by many physical and chemical processes, such as characteristics of geologic formation, hydrodynamic fluctuations of groundwater and seawater levels, fluid-rock interactions, and others. Wide mixing zones have been found in many coastal aquifers all over the world. However, the mechanisms responsible for wide mixing zones are not well understood. In this thesis, two hypotheses were proposed to explain wide mixing zones in coastal aquifers: (1) kinetic mass transfer coupled with transient conditions, which create the movement of the mixing zone, may widen mixing zones; and (2) aquifer stratification may widen the mixing zone. The hypotheses were tested by both multiscale numerical simulations and laboratory experiments. Numerical simulations were based on a variable-density groundwater model by varying mass transfer parameters, including immobile porosity, mobile porosity, and mass transfer coefficient, and the hydraulic conductivity contrast between aquifer layers. Laboratory experiments were conducted in a quasi-two-dimensional tank, where real beach sands were installed and foodstuff dyes were used to visualize the development of freshwater-seawater mixing zone. Major conclusions included (1) the mixing zone can be significantly widened when the mass transfer timescale and the period of transient boundary is comparable due to the nonequilibrium mass transfer effects; and (2) a thick mixing zone occurs in low-permeability layer when it overlays upon a fast flow layer. These results not only improve the understanding of the dynamics of mixing-zone development and its associated geochemical processes in coastal aquifers, but also identify hydrogeologic conditions for the model of sharp-interface approximation to be valid. In addition to better understanding the mechanisms and dynamics of mixing zone, this thesis also investigates cost-effective management of coastal groundwater resources. To protect and conserve limited water recourses in coastal regions, interest in aquifer storage and recovery (ASR) has been growing in recent years. ASR is a promising strategy for water resources management and has been widely used in many contaminated and saline aquifers. However, its performance may be significantly constrained by mass transfer effects due to the mobilization of solutes initially residing in immobile domains. Better understanding of kinetic mass transfer effects on ASR is needed in order to aid the decision-making process. A numerical model is developed to simulate ASR performance by combining the convergent and divergent dispersion models with a first-order mass transfer model. By analyzing the concentration history at the pumping well, we obtain simple and effective relationships for investigating ASR efficiency under various mass transfer parameters, including capacity ratio and mass transfer timescales, and operational parameters. Based on such relationships, one can conveniently determine whether a site with mass transfer limitations is appropriate or not for ASR and how many ASR cycles are required for achieving a positive recovery efficiency (RE).

The stable isotopes 2H and 18O, combined with noble gases and radioisotopes (e.g., 3H, 14C, 36Cl), are used to infer groundwater age and climate during recharge. Flow regimes within low-velocity flowpaths and long residence times could allow an aquitard-aquifer diffusive flux to alter isotope abundance. Consequently, the diffusion of isotopes (e.g., 14C, 2H and 18O) between aquifers and confining layers needs to be considered in such conditions. In this study, COMSOL Multiphysics was used to determine if diffusion of 18O (and 2H by proxy) from a bounding aquitard could explain observed downgradient enrichment of 2H and 18O within a regional aquifer. Using the geologic and hydraulic properties of the lower Wilcox aquifer of the Mississippi Embayment aquifer system in Missouri and Arkansas, the advection-dispersion equation was solved along a 1-D groundwater flow domain, coupled with a cross-contact aquitard-aquifer diffusive flux. Although the observed signal within the lower Wilcox was not matched, a sensitivity analysis indicated the importance of the isotope composition gradient between the aquifer and aquitard. Furthermore, groundwater velocity was suggested as a controlling influence on aquitard-aquifer exchange that could alter aquifer isotope composition.

Doctor of Philosophy / Department of Agronomy / P.V. Vara Prasad / The Ogallala Aquifer is a large underground water source located under the High Plains and is used as the primary irrigation source for producers in the region. Hyper-extraction of the Ogallala is causing a reduction in irrigation capacity for a large part of the region. Confined animal feeding operations in western Kansas rely upon irrigated crops, mainly corn [Zea mays (L.)] as a source of feed. Research has shown that forage sorghum [Sorghum bicolor (L.) Monech] could meet the demands of the confined animal feeding operations while using less water than corn. An experiment was designed to evaluate corn and forage sorghum in Western Kansas. The objective of this research was to evaluate the water use and growth characteristics of irrigated and dryland corn and forage sorghum. Field experiments were conducted at two locations (Tribune Experiment Station, Tribune and a cooperator’s field near Hoxie, Sheridan County Kansas) in 2011-2013. The experimental design at Tribune was a randomized complete block with four replications. A traditional replicated design was not possible at Hoxie. Multiple subsamples per plot were obtained and data are reported as means with standard errors. Corn and forage sorghum were grown under both dryland and fully irrigated conditions at both locations. Neutron access tubes were installed to monitor soil water. Aboveground biomass, intercepted solar radiation and volumetric soil water content were recorded at 5 sampling dates each growing season. Water use was similar between irrigated corn and forage sorghum. There were differences in biomass from year to year between the irrigated crops. Dryland water use was similar between the two crops and also had differences in biomass from year to year. Yields were significantly lower than average for all crops in 2012 due to drought conditions. Solar radiation interception correlated with aboveground biomass measurements. Aboveground biomass from the forage sorghum and corn was ensiled both years and analyzed for nutrient composition. This research suggests that forage sorghum silage may be an acceptable replacement for corn silage in areas with reduced irrigation capacities.

Esta pesquisa, para fins de determinação do comportamento de microrganismos termotolerantes em águas de aqüífero freático, foi realizada em terrenos aluviais na ETE de Vila dos Remédios, Salesópolis - SP. No local foram instalados uma vala de infiltração para esgoto doméstico bruto e 55 poços de monitoração da água subterrânea, de modo a caracterizar a pluma de contaminação em seu deslocamento ao longo da área ensaiada. Seguindo as normas técnicas de coleta e análise físico-químicabacteriológica das águas subterrâneas foram executadas, com o intuito de conhecimento específico do local de pesquisa, 55 poços com amostragem e caracterização litológica do solo local até profundidade de 2,5m, prospecção geofísica eletrorresistiva de caracterização inicial e eletromagnética (EM-31) de acompanhamento do deslocamento da pluma de contaminação, amostragem e caracterização físico-química-bacteriológica do esgoto bruto e das águas subterrâneas. Dois mil litros de esgoto bruto, coletado diretamente da rede, foi introduzido no solo através de vala de infiltração, de modo a caracterizar uma injeção pontual, sem transbordamento e de maneira contínua, com uma taxa de infiltração de aproximadamente 80L/h. O deslocamento da pluma de contaminação formada no aqüífero freático saturado foi monitorado através de amostras de água coletadas sistematicamente, ao longo do tempo, cujos resultados permitiram calcular a velocidade de deslocamento da pluma, como sendo de 8,6 x 10-4 cm/s e, um decaimento de organismos termotolerantes em ambiente de aqüífero saturado de 21dias. Estes resultados permitem o cálculo direto de perímetros de proteção aplicáveis a poços e fontes naturais de captação de água subterrânea, no caso de possibilidades de contaminação por esgoto domiciliar, neste contexto litológico. / The objective of this research was to study the behavior of thermo-tolerant microorganisms in the phreatic aquifer, in alluvial terrains where the sewage was disposed. The study area was close to the sewage treatment plant of Vila dos Remédios, Salesópolis, SP. An injection trench and 55 monitoring wells were installed in the area. The sewage was discharged in the trench and samples of the groundwater were taken to study the contamination plume migration and its physic-chemical and bacteriological characteristics through the time. The wells were constructed with 2.0 meters of depth and the samples were used to characterize the lithological setting. An initial eletroresistivity survey was performed and, together with the groundwater sampling, electromagnetic survey (EM-31) was periodically conducted to evaluate the plume migration. Two thousand liters of domestic sewage \"in natura\" was introduced in the trench to characterize a punctual injection, with a continuous infiltration rate of 80L/h. The migration of the contamination plume was continuously monitored during nine months and the results allowed calculating the migration speed as being 7,67x10-4 cm/s. The thermo-tolerant microorganisms were extinguished 21 days after the sewage injection. These results allow calculating the protection perimeter applied to groundwater wells and natural springs to avoid sewage contamination in the same lithological context.

Este trabalho estabeleceu cenários típicos para o Estado de São Paulo, a partir de dados de investigações ambientais de empreendimentos que armazenam, manipulam ou comercializam combustíveis derivados de petróleo (posto de combustíveis, TRR - transportador retalhista e revendedor, garagem e bases). As plumas de contaminação em fase dissolvida foram caracterizadas a partir de dados levantados em campo e dos resultados obtidos com o modelamento das plumas, usando o modelo Domenico. Desse modo, foi possível comparar as características das plumas reais com as calculadas e posteriormente discutir sobre os perímetros de proteção de poços de abastecimento (PPP). Uma das conclusões é de que não existe correlação entre a extensão das plumas de fase dissolvida (benzeno) real e a calculada. E ao comparar as extensões das plumas calculadas (Domenico) com os PPP calculados por modelo numérico, pode-se notar que somente em 3 cenários houve alguma correlação. Uma das principais recomendações é a reavaliação dos PPP, considerando os dados deste trabalho. / The current work has aimed to establish typical hydrogeological scenarios within the boundaries of São Paulo state, Brazil, based on environmental assessment data obtained at sites that store, manipulate or commercialize petroleum originated fuel (gas stations, TRR and fuel distribution plants). The dissolved phase contamination plumes were characterized based on field obtained data and numeric modeling, adopting Domenico model. In this way, it was possible to analyze the features of the real contamination plumes, compared with the modeled ones, and establish a discussion about production wells protection perimeter (PPP). One of the main conclusions is that there is no correlation between the extension of the real dissolved plumes (benzene) and the modeled ones. While comparing the extension of the modeled plumes (Domenico) with the PPP calculated by numeric modeling, it is possible to observe that only 3 of the analyzed scenarios have presented some identifiable correlation. One of the main recommendations is to perform a reevaluation of the PPP methodology, taking into account the data obtained in the current work.

A estimativa da vulnerabilidade natural de aqüíferos é uma das primeiras tarefas a ser realizada para o planejamento, controle e prevenção da qualidade das águas subterrâneas e criação de perímetros de proteção para as mesmas. Nesse estudo o modelo GOD (G - groundwater confinement, O - overlay strata e D - depth to groundwater) (FOSTER et al. 1998) foi adotado para a estimativa da vulnerabilidade natural dos aqüíferos pertencentes à Unidade de Gerenciamento dos Recursos Hídricos do Estado de São Paulo das Bacias Hidrográficas dos Rios Piracicaba, Capivari e Jundiaí, sendo realizada uma extensa pesquisa sobre as características fisiográficas e ambientais da área de estudo, e critérios hidrogeológicos adotados para a estimativa de vulnerabilidade de aqüíferos. O modelo GOD utiliza como parâmetros o tipo de confinamento da água subterrânea, a litologia da zona vadosa e a profundidade do nível da água. Para a elaboração do respectivo mapa, foram adotados como base de dados o Mapa Geológico do Brasil ao Milionésimo (CPRM, 2004) e o Mapa de Águas Subterrâneas do Estado de São Paulo (DAEE, IG, IPT e CPRM, 2005). Apesar da notoriedade do modelo GOD e de sua extensa aplicação no Brasil e América Latina, foi sugerido ao final dessa pesquisa a inclusão da pluviometria como quarto parâmetro a ser considerado ao modelo GOD para a elaboração de mapas de vulnerabilidade em escalas inferiores a 1:250.000. Como incremento à pesquisa acadêmica, foram aplicados métodos geoestatíscos como a krigagem residual para a interpolação dos dados de elevação de cinco imagens SRTM, a análise de regressão múltipla dos índices pluviométricos anuais obtidos pelas estações pluviométricas do DAEE presentes na região e, a krigagem com deriva externa dos dados de saída da análise de regressão múltipla. Os mapas de vulnerabilidade, assim como as figuras dos resultados da krigagem residual das imagens SRTM e krigagem por deriva externa dos índices pluviométricos médios anuais, foram desenvolvidos utilizando o software específico para integração de Sistemas de Informação Geográfica SIG. / The natural aquifer vulnerability estimative is one of the primary tasks to be accomplished for a groundwater planning, control and prevention program, that would for example aim a protection perimeter design for human use or environmental protection. In this study the GOD model (G from groundwater confinement; O from overlay strata; D from depth to groundwater) (FOSTER et al. 1998) was applied for the natural groundwater vulnerability estimative of Sao Paulo State Water Resource Management Unit of the Hydraulic Basins of Piracicaba, Capivari and Jundiaí. An intensive bibliographic research related to physiographic and environmental characteristics from the researched area, and hydrogeologic criteria used for aquifer vulnerability estimative were also included. The GOD model uses as parameters the type of groundwater confinement, the vadoze zone representative litology and depth to groundwater in meters. To perform the estimative analysis and map elaboration the Brazilian Geologic Map 1:1.000.000 (CPRM, 2004) and the Sao Paulo State Groundwater Map (DAEE, IG, IPT and CPRM, 2005) were used as input database. In spite of the fact that the GOD model is well known and have been extensively applied both in Brazil and South America, it was suggested in this study the insertion of a pluviometric index as a fourth parameter to be considerate in the GOD model, for a groundwater vulnerability estimative in scales lower than 1:250.000. As an increment for academic research, it was also applied geostatistic methods as residual krigage of five SRTM images, multiple regression analysis of annual mean pluviometric data obtained from DAEEs pluviometric stations and, krigage with external derivation from the multiple regression analysis output data. All maps, figures and GOD model input data were developed, designed and analyzed using specific software for Geographic Information System integration, better known as GIS.

A hydrogeologic investigation was completed of the alluvial aquifer near the Osceola County Rural Water System (OCRWS) H-Series well-field, located in Osceola County, Iowa. The primary purpose of the investigation was to quantify drought resiliency benefits of engineered systems on a well-field scale through the use of a groundwater model. Specifically, a groundwater flow model was developed for the OCRWS H-Series well-field to quantify groundwater withdrawal and storage benefits of: • One rock riffle structure placed within the well-field • Two rock riffle structures placed within the well-field • An excavated, historic river channel system combined with one rock riffle structure The objective of these engineered systems is to increase the groundwater storage within the aquifer. Riffles and channel systems provide additional groundwater storage during periods of normal or above normal precipitation by raising the stage of the river. This additional storage, reflected in groundwater heads, is then available to maintain water production during a drought. Groundwater model results showed that all three of the engineered systems quantified substantially improved groundwater storage and induced recharge during the drought simulations. While each system was shown to influence the aquifer, benefits to groundwater storage and induced recharge from the two riffle system was shown to provide the greatest amount of drought resiliency benefit. Through the use of a cost-benefit analysis, the two riffle system was also shown to be the most cost-effective method in this study in terms of achieving additional groundwater storage and induced recharge to the aquifer.

Sinusoidal variations in recharge can induce cyclical flows in surface water and groundwater. In this thesis, such time-dependent flows are explored in a coupled lakeaquifer system. The modelling extends previous steady state results and introduces new flow-visualisation techniques. Local responses in a 2D vertical section are illustrated for lakes within a 1D regional groundwater mound. The theory employs complex variables to decouple the periodic groundwater flows into separate steady state and fluctuating components. The time dependent behaviour causes the lake-aquifer flow to change between flowthrough, recharge and discharge regimes. Corresponding fluctuations between inflow and outflow across the lakebed allow interchange of lake water with the aquifer (recycling and recapture). This also gives rise to sinuous flowpaths that can result in apparent dispersion; the number and size of waves, cusps and loops is characterised by a nondimensional waviness ratio. Streakline plots are introduced and provide an intuitive impression of the time-dependent groundwater motion. Such plots are enhanced by animation and illustrate the complex and potentially dispersive nature of the flows. Interplay between the steady state and fluctuating responses determines the type and strength of flow regime transition. Importantly, there is an inverse relationship between head and flow in the fluctuating response. This is characterised by a dimensionless response time; a function of the aquifer geometry, hydraulic properties and period of fluctuation. During fast response, the recharge propagates mainly as fluctuation in flow, with small phase lags; particle trajectories form elliptical paths in the visualised flows. With a slower aquifer response, variation in recharge is manifest mostly as fluctuation in water level; cyclical perturbations in the flows are small and flows are nearly in steady state. The position of a lake within the regional setting, size of the lake, and ratio of lake to aquifer recharge are important to the steady state response. Flow-through regimes occur throughout the regional setting, but dominate when the lake is lower in the system and groundwater flow is greater. Discharge and recharge regimes occur higher in the flow system, when the ratio of lake to aquifer recharge is large in magnitude.

Groundwater is critical in Texas, representing 60 percent of total water used in 2008. Water demands in Texas are projected to increase 22 percent, largely from an almost doubling of population, within the next 50 years; this ever-increasing pressure on Texas water supplies underscores the need to optimize management of water resources. The objective of this study was to assess regulations, scientific information, and rulemaking by groundwater conservation districts (GCDs) that support policies that achieve the legislative intent of GCDs to protect and conserve groundwater resources of the states aquifers. This study's scope was the Carrizo-Wilcox Aquifer and managing GCDs and the following key topics were evaluated 1) management and protection issues; 2) if and how GCDs are utilizing science in development of management plans and rules; 3) whether GCDs are implementing management plans and using enforcement actions; 4) determining if GCDs would have production budgets in conflict with the Regional and State Water Plan and use of the aquifer; 5) and comparing the management plans of GCDs for compatibility. Two online surveys were developed to solicit responses from GCDs and interested parties. Results show that the predominant management issues stemmed from the uncertainty in how groundwater production was regulated and how future permitting would proceed. Environmental interest groups were concerned that GCDs would not adequately incorporate science that supports groundwater production budgets. Stakeholder groups perceived groundwater conservation management as adversely impacting their individual property rights and their region’s ability to develop water management strategies that address projected water budgets. Few formal enforcement actions have been taken by GCDs since 2007. Current water budgets and desired future conditions by the GCDs for the Carrizo-Wilcox Aquifer do not conflict or result in long-term deficits with respect to water budget projections established by the 2011 Regional Water Plans. GCDs adopted groundwater management plans that addressed goals including conservation and recharge, as outlined in the Texas Water Code, by creating varied objectives and standards. Unanimous public acceptance of the management plans and rules established by the GCDs may never be accomplished, but acceptance will improve through the continuation of public communication, stakeholder coordination, and education. / text