As plantações florestais, historicamente, estão associada a intensos debates sobre o seu impacto na dinâmica da água do solo ou subterrânea. Nesse contexto, este trabalho buscou avaliar os possíveis impactos da mudança de cobertura do solo, de pastagem para eucalipto, sobre o aquífero freático em zona de afloramento do Sistema Aquífero Guarani. A área de pesquisa está localizada na bacia do Ribeirão da Onça, situada no município de Brotas, no centro-leste do Estado de São Paulo. Essa é monitorada desde 2004. Foram utilizados dois métodos para avaliar o impacto da mudança de uso do solo, o método iWTF e o método de Darcy. A partir desses métodos, estimou-se as taxas de recarga subterrânea, fluxo lateral, variação de armazenamento e percolação profunda. Além disso foram obtidas a variação do nível freático, espessura saturada e gradiente hidráulico horizontal para o aquífero na área de estudo. Durante os anos hidrológicos de 2005 a 2011, a recarga direta variou de 255 e 876 mm (iWTF), equivalente a 21% e 51% da precipitação anual correspondente. Após 2011, com a mudança de cobertura do solo de pastagem para eucalipto, não obstante os anos hidrológicos de 2012 e 2013 apresentarem precipitação próxima da média de longo período, a recarga direta foi estimada em cerca de 210 mm (2012) e 147 mm (2013), equivalentes a 13% e 10% da precipitação anual. A diminuição na recarga direta levou à redução da espessura saturada, variação do nível freático, gradiente hidráulico horizontal, fluxo lateral e armazenamento anual. Além disso, pode-se perceber que a plantação florestal está exercendo influência sobre a área de pastagem adjacente à plantação. Tem-se observado essa influência através da existência de fluxo transversal em direção à plantação florestal, o qual tem elevado o armazenamento no período de estiagem. Os resultados indicam que a plantação de eucalipto afetou significativamente o comportamento sazonal e anual do balanço hídrico na área de estudo. / Historically forest plantations are associated with intense debate about its impact on soil water dynamics or groundwater. Thus, the objective of this study was to evaluate the potential impacts of land cover change of pasture to eucalyptus on the groundwater in an outcrop zone of the Guarani Aquifer System. The study area is located in the Ribeirão da Onça watershed, located in the municipality of Brotas, in the center-east of the state of São Paulo. To assess the impact of land cover change, I used two methods: i. iWTF and ii. Darcy. From these methods, we estimated groundwater recharge rates, lateral flow, water storage variation and deep percolation. Furthermore, I obtained the water table variation, saturated thickness and horizontal hydraulic gradient into the aquifer in the study area. During the hydrological years 2005-2011, the direct recharge through the results of iWTF method varied between 256 and 876 mm, equivalent to 21% and 51% of the corresponding annual precipitation. After 2011, with the land cover change of pasture to eucalyptus, the direct recharge was computed at about 210 mm (2012) and 147 mm (2013), equivalent to 13% and 10% of the annual precipitation. I did not find significant difference in the annual precipitation in these years compared to the historical mean. Therefore, my findings have shown that the decrease of direct recharge are associated to the land cover change of pasture to eucalypts. The decrease in direct recharge leads to the reduction of saturated thickness, the water level variation, horizontal hydraulic gradient, lateral flow and annual storage. Moreover, it can be seen that the forest plantation has influenced the pasture area, adjacent to the plantation. It has been observed that influence through the existence of cross flow toward the forest plantation, which has high storage, especially in the dry season. The results indicate that the eucalyptus plantation significantly affected the seasonal and annual behavior of the water balance in the study area.

O objetivo do presente trabalho foi avaliar os aspectos quantitativos da água subterrânea (recarga, parâmetros hidráulicos e variáveis envolvidas para essa quantificação) no aqüífero freático de uma área intensamente urbanizada. Duas sub-bacias contíguas do rio Monjolinho (bacia do córrego do Gregório e bacia do córrego do Tijuco Preto), localizadas na região central do município de São Carlos - SP, foram escolhidas como área de estudo. As bacias cobrem um área de 22,8 Km2 e apresentam índice de impermeabilização total estimado de 72,5%. Para este estudo foi instalada uma rede de monitoramento permanente, composta por 20 piezômetros. Os dados de nível freático foram coletados com freqüência semanal no período de 1 ano hidrológico (fevereiro de 2004 a janeiro de 2005). Os métodos utilizados para a estimativa da recarga foram: Water Table Fluctuation (WTF) e aproximação Darcyana com base na variação do nível freático, e o balanço hídrico, utilizando dados de três estações hidrometeorológicas localizadas no interior dos limites das bacias. Os valores de condutividade hidráulica de cada piezômetro, utilizados na aproximação Darcyana, foram determinados com a técnica slug test, variando de 2,6.10-7 a 6,0.10-5 m/s. Os valores de rendimento específico, utilizados no método WTF, foram estimados pela equação empírica de Biecinski, com variação de 0,07 a 0,15. A recarga efetiva estimada pelo método WTF representou 16,4% da precipitação (1596,5 mm) ocorrida durante o ano hidrológico, enquanto que a recarga efetiva estimada pela aproximação Darcyana representou 16,3% da precipitação. No método do balanço hídrico foi obtida uma recarga potencial de 277,0 mm, equivalente a 17,4% do total de chuvas do ano hidrológico considerado. Os resultados apresentados fornecem subsídios para uso racional dos recursos hídricos subterrâneos, assim como incentivam o desenvolvimento de novas pesquisas na área de aqüíferos em centros urbanos. / The objective of this work was to evaluate groundwater recharge (rate, hydraulic parameters and related variables necessary for estimation) in an unconfined aquifer of a highly urbanized area. The study area is composed by two contiguous sub-basins (Gregório creek and Tijuco Preto creek) in córrego do Monjolinho basin, located in São Carlos (Brazil). The total area of these basins is 22.8 Km2 with an estimated impermeabilization coefficient of 72.5%. For this study a permanent monitoring network composed by 20 piezometers was constructed. Data collection was performed during one hydrologic year (February 2004 to January 2005). The recharge rate was estimated by water table fluctuation (WTF), Darcyan approach and water balance. The hydraulic conductivity, used as input in the Darcyan approach, was determined by slug tests performed in each piezometer, ranging from 2.6.10-7 m/s to 6.0.10-5 m/s. The specific yield, which is necessary for the WTF method, was evaluated using Biecinski\'s varying between 0.07 and 0.15. The recharge rate estimated by WTF amounts to 16.4% of the annual precipitation (1596.5 mm) observed in the considered hydrologic year, while the Darcyan approach indicates a rate of 16.3%. The water balance method, based on data obtained from three hydrometeorological stations located inside the watersheds, results in a potential recharge rate of 277.0 mm. This value represents 17.4% of the observed precipitation in the period. The results obtained in this work may be used as support to groundwater resources management in urban area or as reference for future research works in the field.

Este trabalho visa avaliar a recarga e o sistema de fluxo do aqüífero Guarani com o auxílio de um modelo numérico, aplicado à área delimitada pelas bacias hidrográficas dos rios Jacaré-Guaçú e Jacaré-Pepira (sub-bacias do rio Tietê, na região central do Estado de São Paulo, Brasil). Com este fim, foi estabelecido um modelo conceitual para o sistema de escoamento subterrâneo. Técnicas em SIG foram utilizadas no armazenamento, processamento e análise de dados levantados em intensa revisão bibliográfica, bem como, gerados mapas com as características dimensionais e hidrogeológicas. Os fenômenos hidrológicos mais significativos foram selecionados, resultando na construção do modelo conceitual para estimativa de fluxo e recarga do aqüífero, que possui na área de estudo significativa extensão de afloramento. Foram atribuídas seis zonas de recarga correspondentes a formações e estruturas geológicas que compõem o aqüífero semiconfinado e livre. O modelo foi calibrado pelas vazões de base, obtidas de hidrogramas diários, e pelos níveis estáticos de poços. Uma análise de sensibilidade foi realizada envolvendo os parâmetros de ajuste da calibração. Os resultados mostram existir interação entre as recargas do aqüífero, provenientes das duas bacias, e indicam que o aqüífero essencialmente drena a sua recarga através dos rios. Os fluxos laterais (fluxo subterrâneo entre bacias), a descarga profunda e a explotação por poços representam pequenas saídas em comparação à recarga total, contudo, a ação dos poços apresenta efeitos com alguma tendência regional no entorno dos maiores centros urbanos da área de estudo. A determinação das vazões de base identificou os trechos ao longo dos rios nos quais o aqüífero os carrega e é carregado. Apesar do aqüífero essencialmente abastecer os rios, os trechos nos quais os rios o carregam são significativos e importantes por serem trechos nas quais o aqüífero é potencialmente mais vulnerável. / This work aims to assess the recharge and flow system of the Guarani aquifer with the aid of a numeric model, applied to the area delimited for the hydrographic basins of the rivers Jacaré-Guaçú and Jacaré-Pepira (sub-basin of the Tietê river, in the central region of São Paulo State, Brazil). Thus, a conceptual model for groundwater flow system was established. GIS based tools was used in the storage, processing and analysis of data raised in intense bibliographical revision as well as generated maps with the dimensional and hydrogeologic characteristics. Main hydrologic phenomena were selected, leading to a groundwater conceptual model for evaluation of recharge and groundwater flow, taking into account the significant outcrop region in the study area. The geologic formations and structures were attributed to six corresponding zones of recharge that compose the semi-confined and free aquifer. The model was calibrated by the baseflow from daily hydrograms and by the static level from wells. It was carried out a sensitivity analysis including the calibration parameter set. The results show that there is interaction between aquifer recharge from the two basins and that the aquifer mainly drain its recharge into the rivers. The lateral flows (groundwater flows between basins), the deep discharge and the groundwater exploitation from wells represent small exits in comparison to the total recharge; however, the action of the wells presents effect with some regional trend in the vicinity of the biggest urban centers of the study area. The determination of the baseflows identified the stretches to long of the rivers in which the aquifer loads and is loaded. Despite the aquifer essentially supplying the rivers, the stretches in which the rivers load it are significant and important for being stretches in which the aquifer is potentially more vulnerable.

Ce travail de thèse a pour oblectif de simuler numériquemetn les impacts de recharges sédimentaires sur la morphodynamique du tronçon du Vieux-Rhin situé entre les barrages de Kembs et Breisach. Dans le cadre du projet InterReg de redynamisation du Vieux-Rhin, ces simulations sont primordiales pour évaluer l'efficacité des scénarios de recharge sédimentaire ainsi que lesrisques associés , tels que la fixation des dépôts ou encore la déstabilisation du lit pavé. a l'échelle du vieux-Rhin entioer (50 km) les simulations numériques 1D des années 1950, 1990 et 2009 ont permis d'appréhender la dynamique fluviale du lit en tenant compte de l'impact de la végétation. Les modélisations des processus granulométriques en jeu dans les recharges sédimentaires ont été préalablement testés et améliorés sur des expériences de laboratoires avec le modèles numériques 1D RubarBE. Dans ces modélisations, le tri granulométrique longitudinal, les évolutions morphologiques et le phénomène de capture des sédiments les plus fins ont été reproduits. Les modélisations bi-dimensionnelle à l'échelle des sites d'injections ont été réalisées avec le modèle numérique Rubar20TS. Les évolutions morphologiques des recharges ont été simulées et les zones favorisant les dépôts sédimentaires ont été identifiées. Les conclusions suivantes ont été tirées des simulations d'un banc sédimantaire et des scénarios de redynamisation : des flancs de banc pentus facilitent la mobilisation sédimentaire ; le choix du site et de la largeur du banc semblent très imporants afi de créer des conditions suffisament dynamiques en bordure de banc ; l'injection d'un banc de galets apparaît plus efficace qu'une érosion latérale de berge. Un scénario de recharge sédimentaire optimal pourrait consister en des injections de bancs latéraux étroits d'un volume d''environ 20 000 m3 répétées dans le temps et/ou dans l'espace. / Pas de résumé en anglais

The worldwide natural occurrence of high levels of arsenic (As) in groundwater and its deleterious effects on human health have inspired a great amount of related research in public health and geosciences internationally. With >100 million people in South and Southeast Asia exposed to >10 µg/L As in shallow groundwater that they use for drinking, the installation of deeper, low-As wells has emerged as a major strategy for lowering the exposure. As the magnitude of deep pumping continues to increase, this work focuses on the geochemical and hydrologic questions surrounding the vulnerability and sustainability of low-As aquifers in Bangladesh, the country most affected by As crisis. In an effort to better understand the residence time of groundwater in low-As aquifers at depth, radiocarbon (14C) and 13C in dissolved inorganic carbon, tritium (3H), stable isotopes of hydrogen (2H) and oxygen (18O), and noble gas concentrations were measured across a ~25 km2 area of Araihazar, ~30 km east of Dhaka. Groundwater from >120 m depth is shown to be ~10,000 years old and its isotopic signatures indicate that recharge occurred at the time of changing climate from the late Pleistocene to early Holocene, with little recharge occurring since. In contrast, the intermediate depth low-As aquifers (<120 m) have a heterogeneous distribution of groundwater chemistry and ages, and contain groundwater recharged <60 years ago in certain locations. In one such area surrounding a small village, the effects that subsurface clay layer distribution has on recharge patterns and redox status of the intermediate aquifer was investigated. The relevant hydrogeologic and geochemical processes that led to documented failures of a community well at the site were assessed using a combination of solid and water phase geochemistry with tritium-helium (3H/3He) dating, hydraulic head monitoring, and pumping tests. Organic matter seeping from a compressible clay layer, which is subject to a pumping-induced, downward hydraulic gradient, reduces iron oxides and helps release As in the grey, upper part of the intermediate aquifer. No recent recharge was detected by 3H measurements in the upper, grey sand layer, however a layer of orange sand beneath it contains groundwater that was recharged 10-60 years ago. This groundwater laterally bypasses the confining clay layer to recharge the middle of the aquifer and contains dissolved As levels of <10 µg/L. In this particular case, the pore water that leaches from clay layers contributes to As contamination, whereas the lateral recharge with shallow groundwater coincides with the low-As depth. Thus, clay layers may not always protect the low-As aquifers from As contamination, even if they can block direct vertical recharge with shallow groundwater enriched in As and organics. Finally, the adsorption of As to aquifer sediments, as a natural mechanism of the low-As aquifer defense against contamination, was assessed in the field via a column study. The column experiments were conducted by pumping shallow, high-As groundwater through freshly collected sediment cores to quantify the retardation of As transport through the aquifer. This study demonstrated an elegant method of assessing contaminant transport under nearly in situ conditions that resulted in sorption estimates similar to those made by field studies using more challenging methods or located at hard-to-find sites with convenient flow patterns. My work, therefore, contributed to a better understanding of low-As aquifers in Bangladesh from the perspectives of both the groundwater flow and water-sediment interactions on various scales, and it integrated methods that can be employed elsewhere to characterize aquifers and study contaminant transport.

This thesis reports on research from a full-scale demonstration project to recharge a depleted aquifer with treated sewage effluent from the Paphos (Cyprus) wastewater treatment plant. The project artificially recharged the Ezousas river basin, located in the south-western coastal plain of Cyprus, with tertiary treated, disinfected effluent through a network of artificial infiltration ponds. The aims of the research were to determine the capacity of the aquifer to provide a suitable buffer for the flow from the wastewater without flooding and to measure the changes in reclaimed water quality. The aquifer hydraulics and treatment capacity, including recharge basins, were analysed using field and laboratory measurements. A geological field survey and modelling was used to assess, both by practice and theory the effectiveness of the Ezousas river aquifer for storage and recovery of the reclaimed water. The aquifer was found to be mainly composed of alluvium with typical hydraulic characteristics. The average porosity was 20% and hydraulic conductivity around 90 m/day, it was concluded the aquifer would be able to accept all the annual output of the treatment plant which was 5 Mm3 /a. The recharge network consisted of five groups of infiltration basins arranged on both banks of the River Ezousas about 2km upstream of the wastewater treatment plant. Each infiltration basin contained two, four or six recharge ponds, each basin was 2,000m2 in area with a depth of 1.5 m. A recharge pattern consisting of alternating weeks of wet-fill and drying cycles was found necessary to maintain the unsaturated zone below the ponds in order to maximise the amount of water that could be recharged whilst optimising water quality. The hydraulic impact of the artificial recharge and extraction from the field measurements of borehole water levels indicated recharged water down to 15m below the surface. Tracer tests on the groundwater flow, capture zone, residence times and mass balances of recharged and native waters gave widely varying residence times between 30 days and 5 years, these were attributed to the complex flow patterns found. Recharged water was sampled using a series of extraction wells located along the downstream river basin, starting at the infiltration ponds and then at stages downstream. Eight production and monitoring wells were tested including control samples up-gradient (upstream) from the ponds, to about 7km down-gradient (downstream). Water quality was analyzed for the standard wastewater constituents including indicator organisms, organic matter, nutrients N and P and the metals. It was one of the recommendations of the thesis however that attention also be paid to the persistent organics, including the pesticides, biocides, plasticizers and pharma residues. The chemical data was used to build and validate a solute transport model of the ponds and surrounding area to predict the transport and fate of priority contaminants. In this way, the geo-chemical potential for the retardation, attenuation and chemical or biochemical degradation processes taking place in the unsaturated and saturated zone were assessed. From the results it was concluded that for most analytes, which included metals, nitrate and common salts, the main processes were mixing and dilution by the native ground water. The extracted water was then a mix of waters according to the different residence times and flow of natural groundwater, giving a stable water quality for irrigation. A third reaction involving cation exchange with the local geology was however identified which reduced the concentrations of copper and phosphate beyond what was expected from just mixing. It was also concluded that denitrification did not occur because of a combination of the high quality of the effluent, the operational cycling of the ponds and the high porosity of the vadose zone. Previous work has found denitrification if the recycled water still contains organic matter, further work was recommended to determine the critical organic concentrations. The renovated water from the Ezousas wastewater reuse Project was able to meet the health and agronomic requirements for unrestricted irrigation. The risk of flooding with sewage effluent resulting from hydraulic mounding was also investigated to define the growth and decay of the mound. It was possible to report that after more than fifteen years of operation and a total infiltration of 40Mm3, there have been no signs of reduced hydraulic capacity or water quality.

Seepage is an important component of the water budget in closed basins that do not have surface water drainage features. In the shallow water table environment of Florida, internal drainage of soil controls flooding. With the recent rapid population growth and urban development in the state, a simple, field-based method is needed to estimate seepage rates. In this study five locations in Hillsborough County, Florida, were instrumented with wells with pressure transducers measuring water level fluctuations at 1 minute resolution. For closed basins with lakes, evaporation (E) rates were determined using data from a weather station and Penman-Monteith FAO56 method, and then seepage rates were calculated from a water budget. Seepage rates varied greatly depending on conditions specific to the site. The seepage rates found for the three surface water sites in this study were 1.1 cm/d for a retention pond surrounded with dense vegetation, 0.5-0.8 cm/d for a natural lake located close to a groundwater pumping site, and 0.4 cm/d for another natural lake with no groundwater pumping in the proximity. Two methods to estimate seepage rates into semi-confined aquifers were compared: (a) mass balance approach and (b) Darcy's equation. At one of the sites the rate was 0.1 cm/d, and at the other site (sinkhole) it ranged between 0.8 cm/d during the wet season and 0.2 cm/d during the dry season when the head difference between the surficial and Floridan aquifers became smaller. The results of the study indicate that simple and relatively inexpensive field methods can estimate seepage within a narrow range and give reasonable seepage predictions that can be used in flood modeling. The obtained values indicate that seepage does not provide adequate drainage relief in closed basins. Another important finding is the magnitude of the local recharge to the Floridan aquifer. Further sensitivity studies on hydrological models that use seepage as one of the inputs may indicate that lower data collection resolution or simpler ET estimation methods are acceptable.

This research project focuses on the Walla Walla River Basin located on the east side of the states of Oregon and Washington, USA. With the support and collaboration of the Walla Walla Basin Watershed Council, this work embraces four research topics. The first topic includes the feasibility study of artificial aquifer recharge in the Walla Walla Basin. Through development and application of a regional hydrological model, a methodology for evaluating locations of artificial aquifer recharge is presented with a test case. The second research topic evaluates the recharge rates observed from pilot test studies of artificial aquifer recharge. Scale dependence of recharge rates should be considered when excessive induced groundwater mounding forms beneath the infiltrating basins. The third topic utilizes groundwater tracers and simulation models to evaluate the hydraulic connection of springs to infiltrating basins of artificial aquifer recharge. Finally, the fourth topic as a proof of a technique, utilizes distributed temperature sensing technology with a pair of black and white coated fiber optic cables to estimate the effective exposure to solar radiation over the Walla Walla River. / Graduation date: 2013

L'étude de la région de Djahrom est tout spécialement intéressante car elle comprend un bassin versant bien délimité ou la nappe est située à une profondeur assez importante qui limite les phénomènes d'évaporation et où il parait possible d'envisager une recharge artificielle.

L'aquifère du Trarza s'étend sur environ 40 000 km2 dans le sud-ouest mauritanien, entre le fleuve Sénégal au sud, l'Océan Atlantique à l'ouest et les formations métamorphiques de la chaîne des Mauritanides au nord et à l'est ; il est contenu dans les sédiments du Continental Terminal et du Quaternaire. L'objectif de cette thèse est d'étudier avec une double approche géochimique (ions majeurs, 18O, 2H, 14C, 13 C) et hydrodynamique les processus de recharge de la nappe en réponse aux changements environnementaux. Les campagnes de terrain menées entre 2010 et 2012 ont significativement complété les rares mesures anciennes. Le niveau de la nappe ne semble pas avoir connu d'évolution significative durant les cinquante dernières années malgré un pompage localement important. L'écoulement général des eaux souterraines de la nappe se produit du sud vers le nord, c'est-à-dire du fleuve Sénégal vers la dépression au nord de Boutilimit où la nappe est à plus de 30 m sous le niveau de la mer. Le croisement des approches hydrodynamique et géochimique a montré que, dans cette zone semi-aride, la dynamique de la nappe est influencée par les multiples changements actuels et anciens de l'environnement (depuis les transgressions quaternaires et les paléotracés du fleuve jusqu'aux différents barrages régulant le cours du fleuve Sénégal). La nappe est principalement alimentée par l'infiltration latérale des eaux de surface du fleuve Sénégal et dans une moindre proportion par les précipitations. La minéralisation des eaux souterraines reste largement influencée par les résidus des transgressions quaternaires. L'évaporation marque fortement les eaux de surface avant et durant leur infiltration. Des calculs encore très préliminaires faits par différentes méthodes indépendantes suggèrent une recharge annuelle inférieure ou égale à 5 % des précipitations, soit de 5 à 10 mm.