Thesis (M.S.)--University of Southern California, 2007. / Includes bibliographical references (leaves 92-96).

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisors: Daene C. McKinney and Gary A. Pope. Vita. Includes bibliographical references.

La gestion durable des aquifères est une problématique grandissante depuis la fin du 20ème siècle. L'exploitation d’une ressource en eau souterraine est qualifiée de durable lorsque la capture des flux environnementaux est considérée comme acceptable sur le long terme. La modélisation hydrodynamique s'impose comme un outil indispensable pour remplacer une gestion réactive par une approche anticipative. Les paramètres hydrodynamiques qui caractérisent un aquifère et contrôlent les variables de sorties des modèles hydrodynamiques sont souvent mal connus. L’estimation de ces paramètres par la modélisation inverse souffre de la non-unicité de la solution optimale. Une approche simplifiée pour la quantification des incertitudes (analyse linéaire) est présentée comme une alternative pragmatique à des méthodes stochastiques inapplicables pour des modèles opérationnels. A partir de la réalisation d’une station expérimentale pilote, différentes méthodes (parfois complémentaires) ont été évaluées pour contraindre la recharge météorique et les propriétés hydrauliques d’un aquifère afin de réduire l’incertitude prédictive. La réalisation d’un modèle vertical couplé sol-surface a permis de démontrer que, dans le contexte étudié, la tension matricielle apporte suffisamment d’informations afin de contraindre la recharge prédite. Une interprétation conjointe d’un essai de nappe libre et des fluctuations piézométriques a permis une estimation intégrée de la recharge et des paramètres hydrodynamiques de la nappe libre. Ce travail de thèse a ainsi permis (i) de démontrer l’intérêt de disposer de méthodes algorithmiques pour la calibration et la quantification des incertitudes paramétriques pour un modèle hydrodynamique de gestion ; (ii) de mener une réflexion méthodologique sur l’utilisation de méthodes existantes afin d’apporter de l’information complémentaire fiable sur les paramètres hydrodynamiques ainsi que sur la recharge météorique. Ce travail offre des perspectives quant à la mise en place d’un réseau de suivi complet à l’échelle d’un bassin hydrogéologique. / The sustainable management of aquifers is a growing problem since the end of the 20th century. For groundwater withdrawals to be considered as sustainable, the capture of environmental flow should remain acceptable over a long-term period. Groundwater modeling is an essential tool to move from a reactive management to an anticipatory approach. Hydrodynamic parameters characterizing the aquifers are often poorly constrained by prior information or history matching. The estimation of these parameters by inverse modeling suffers from the non-uniqueness of the solution. This is an issue when predicted values by groundwater model are used to define legal frameworks. A simplified approach for the quantification of uncertainties (linear analysis) is presented as a pragmatic alternative to stochastic methods that cannot be applied to operational groundwater management models. The implementation of a pilot experimental station brings possibility to evaluate different approaches for the estimate of groundwater recharge and hydrodynamic parameters estimation in order to reduce the uncertainty of groundwater management models. A 1D coupled soil-surface model was used to demonstrate that, in the studied context, matrix potential measurements alone appear as sufficient to constrain coupled model-based estimates of recharge. In addition, a joint interpretation of an unconfined aquifer-test and water table fluctuations has been conducted. Reliable estimates of groundwater recharge can be obtained from water level records when considering long recharge events and a consistent value of drainable porosity. This thesis highlights (i) the necessity to use algorithmic methods for parameters estimation and uncertainty quantification for a groundwater management model; (ii) the interest of different methods to collect reliable hydrodynamic parameters and groundwater recharge estimation. This work can be used to support a monitoring network for parameters estimation at a basin scale.

No description available.

Indiana University-Purdue University Indianapolis (IUPUI) / Groundwater monitoring networks are subject to change by budgetary actions and stakeholder initiatives that result in wells being abandoned or added. A strategy for network design is presented that addresses the latter situation. It was developed in response to consensus in the state of Indiana that additional monitoring wells are needed to effectively characterize water availability in aquifer systems throughout the state. The strategic methodology has two primary objectives that guide decision making for new installations: (1) purposive sampling of a diversity of environmental variables having relevance to groundwater recharge, and (2) spatial optimization by means of maximizing geographic distances that separate monitoring wells. Design objectives are integrated in a discrete facility location model known as the p-median problem, and solved to optimality using a mathematical programming package.

A comprehensive methodology of hydraulic testing in fractured rocks is presented. The methodology utilizes geological and geophysical information as background. It consists of conventional single-hole packer tests in conjection with a newly developed cross-hole packer test. The cross-hole method involves injecting fluid into a packed-off interval in one borehole and monitoring hydraulic head variations in packed-off intervals in neighboring boreholes. Borehole orientation is unrelated to the principal hydraulic conductivity directions which, therefore, need not be known a priori. The method yields complete information about the directional nature of hydraulic conductivity in three dimensions on a scale comparable to the distance between the test boreholes. In addition to providing all six components of the hydraulic conductivity tensor, the cross-hole method also yields the specific storage of the fractured rock mass. While the theory behind this method treats the rock as a homogeneous, anisotropic, porous medium, the test provides detailed information about the degree to which such assumptions may actually be vaild in the field. The method may also be useful as a tool for detecting, in the vicinity of the test area, major fractures or faults that have not been intercepted by boreholes. Preliminary results from a granitic site near Oracle in southern Arizona are presented together with details of the instrumentation designed and constructed specifically for that site.

Deep injection wells (DIW) in Florida are regulated by the U.S. Environmental Protection Agency (USEPA) and the state of Florida through the Underground Injection Control regulations contained within the Safe Drinking Water Act. Underground injection is defined as the injection of hazardous waste, nonhazardous waste, or municipal waste below the lowermost formation containing an underground source of drinking water within one-quarter mile of the wellbore. Municipalities in Florida have been using underground injection as an alternative to surface disposal of treated domestic wastewater for nearly 40 years. The research involved collecting data as of September, 2007 on all the Class I DIWs in the state of Florida and evaluating the differences between them. The analysis found regional differences in deep well practice and canonical correlation analyses concluded that depth below the USDW is the most significant factor to prevent upward migration of the injected fluid. / by Jie Gao. / Thesis (M.S.C.S.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.

A groundwater flow model was constructed for the Rincon Valley area and Mesilla Basin. The system is dominated by the complex interaction of the Rio Grande, canals, laterals, and drains with groundwater pumping. The primary purpose of the model was to aid the New Mexico -Texas Water Commission in assessing options for water resources development in the Lower Rio Grand Basin from Caballo Reservoir in New Mexico to El Paso, Texas. One such assessment was to evaluate the effect of secondary irrigation releases from Caballo Reservoir on the water budget. In addition, the model will eventually be linked to a surface water model (BESTSM) being utilized by the New Mexico -Texas Water Commission to evaluate water supply alternatives for El Paso, Texas. Stress periods were specified on a seasonal basis, a primary irrigation season from March through October and a secondary irrigation season from November through February. Analysis of model output indicates that groundwater pumping decreases Rio Grande flows, secondary irrigation season releases do not alter the water budget significantly, and that recharge and discharge from aquifer storage are strongly related to the season.

This aim of this study was to improve the understanding and functioning of the Table Mountain Group aquifer system and contribute to the sustainable development of this potential source for water supply in the Montagu area.

A contaminação da água subterrânea por nitrato em áreas urbanas é um problema muito comum no Brasil. Geralmente muito dos estudos restringem-se em descrever somente os problemas associados às porções mais superficiais dos aquíferos. Mais recentemente, alguns trabalhos têm detectado a presença de nitrato nas partes mais profundas de aquíferos livres no Estado de São Paulo. Então, o principal objetivo desse trabalho foi o de avaliar os impactos potenciais do saneamento urbano no Aquífero Adamantina (livre, de porosidade primária, com 120 m de espessura saturada) na cidade de Urânia, simulando diferentes cenários de usos da terra, usando modelos numéricos de fluxo e transporte, com os softwares MODFLOW e MT3DMS. A cidade de Urania é abastecida por água subterrânea e a rede de esgoto cobre quase a totalidade da área urbana, em um sistema operado pela SABESP (Companhia de Saneamento Básico do Estado de São Paulo). Poços privados e sistemas de saneamento in situ são práticas bastante comuns na cidade. Os resultados da modelagem de fluxo permitiram identificar que o tempo de trânsito das águas subterrâneas entre sua área de recarga e a porção inferior do Aquífero Adamantina (120 m da superfície), sem a operação de poços de produção, é de aproximadamente 60 anos. Este tempo diminui para menos de 40 anos quando estes poços estão bombeando. Caso a contaminação por nitrato seja de uma fonte constante em toda a área urbana, os resultados da modelação mostram que o aquífero tem capacidade de diluir apenas 30% da contaminação inicial. Considerando a construção de uma rede de esgoto totalmente eficiente, o modelo indicou que o tempo de recuperação das porções rasa e intermediária do aquífero é de 10 anos. Já na porção mais profunda, a contaminação perduraria por um período de 90 anos após o encerramento da fonte, com uma fração de 11% de sua concentração inicial, após 10 anos. Assim, conclui-se que a efetividade de estender a rede de esgoto no município em um período de 10 anos é uma medida interessante para mitigação do aquífero frente à contaminação por nitrato. A capacidade máxima de diluição do contaminante pelo aquífero na área urbana de Urânia corresponde a fontes de contaminação de até 100 mg/L de nitrato oriundas de áreas de 65 m x 65 m na zona urbana do município, com um espaçamento de 130 m x 130 m entre elas. A alternativa de contenção da contaminação para porções inferiores do aquífero por meio da existência de poços de produção com seção filtrante inserida na porção rasa do aquífero, visando à utilização desta água bombeada para usos menos nobres, enquanto os poços de produção destinados ao consumo humano, cujos filtros estariam posicionados na porção profunda, permaneceriam protegidos, somente se mostrou interessante quando as concentrações originais de nitrato forem inferior a 56 mg/L, pois, desse modo, a capacidade de diluição do aquífero faria com que a concentração em água da porção profunda fosse inferior ao limite de potabilidade. / Groundwater contamination by nitrate in urban areas is a very common problem in Brazil. Until now, many studies just describe the problem associated to shallowest part of aquifers. More recently, some works have detected the presence of nitrate in the deeper portion of some important unconfined aquifers in Sao Paulo state. Considering this potential problem, the main objective of this work was to evaluate the potential impacts of urban sanitation into the Adamantina Aquifer (primary porosity, unconfined aquifer with 120 m of saturated zone thickness) in the city of Urânia, simulating different land occupation scenarios using flow and transport mathematical models, respectively MODFLOW and MT3DMS codes. The city of Urânia is totally supplied by groundwater and the sewage mains cover almost all the urban area. Both water and sewage mains are operated by the SABESP (State of Sao Paulo water company), but it is necessary to recognize an important number of private wells and also septic tanks and pit latrines operating in the city. The numerical model results could estimate the groundwater transit time from the recharge to the Adamantina Aquifer bottom (120 mbs) in 60 years. When the water wells are pumping, this time is reduced to 40 years. A big impact is expected when the city is not served by any sewage mains and all effluent is infiltrated direct into the soil. In this case, considering a concentration of 100 mg/L, the nitrate will reach the whole aquifer (including its bottom part) with 70% of the original concentration, in 60 years. Taking into the consideration that all domestic effluent is drained by the public sewage mains, the time for recovery is about 10 years for the shallower and intermediate parts of the aquifer. For the deeper part, it takes more than 90 years, but the expected concentration is < 11% of the original one, after 10 years. This permits to conclude that the construction of an efficient public sewage mains network could be a good solution in a time frame of 10 years. It is also possible to define that to dilute a constant load of nitrate of 100 mg/L in an area of 65x65 m, it is necessary to have an area of 130 m x 130 m to keep the water below the Brazilian potable standards.