Dans la région de Tahoua (Niger), qui fait partie du bassin des Iullemeden, le système aquifère multicouche profond du Continental Intercalaire/Hamadien (CI/H) représente une réserve essentielle. Il est utilisé pour l'alimentation en eau potable des populations, pour les besoins en eau des industries extractives, et pour l'abreuvage du bétail, en raison de la dégradation de la qualité et le très faible débit des nappes phréatiques, et de celles du Crétacé supérieur. Malgré quelques études hydrogéologiques classiques conduites sur ce système aquifère, il reste mal connu, notamment en ce qui concerne la répartition des différentes masses d'eau et leurs temps de résidence/renouvellement. Cette étude, principalement fondée sur une approche hydrogéochimique et isotopique, vise à améliorer les connaissances sur le système aquifère du CI/H afin d'optimiser sa gestion durable. Les données ont été obtenues à partir de cartes géologiques et des fiches techniques de forage, de diagraphie, et d'essais de pompage. En outre, des échantillons d'eau ont été prélevés dans 30 forages répartis régulièrement dans la zone d'étude (114 425 km2). Des paramètres (pH, t et CE) ont été mesurés in situ et les échantillons ont été acheminés au laboratoire GEOPS où des analyses chimiques (ions majeurs) et isotopiques (18O, 2H, 13C, 14C) ont été effectuées. À partir des coupes géologiques, la couche du CH est présente au-dessus des couches CI dans la partie sud de la région mais pas dans la partie nord. Cependant, la piézométrie est continue sur toute la région. Dans la partie située au nord (au-dessus de 16°N), les lignes d'écoulement sont dirigées des affleurements du CI (est) vers l'ouest, et dans la partie située au sud (au-dessous de 16°N), des affleurements du CH (nord-est) vers le sud-ouest. La teneur en isotopes stables de l'eau (vs V-SMOW) varie de -8 à -7 ‰ pour 18O et de -59 à -48 ‰ pour 2H dans la partie nord (CI) et de -6 à -5 ‰ pour 18O et - 51 à -41 ‰ pour 2H dans la partie sud (CH), montrant deux masses d'eau différentes. Toutes ces teneurs sont très inférieures à celles correspondant aux précipitations actuelles, qui ne contribuent donc pas significativement à la recharge. Ceci est en accord avec les "âges" des eaux souterraines (5 à 36 ka) calculés à partir des teneurs en 14C (1 à 57 pmC), qui sont également en bon accord avec la piézométrie. Ainsi, même si la piézométrie continue du système aquifère du CI/H indique que les pressions sont en équilibre entre les différentes couches, les caractéristiques géochimiques montrent des différences notables entre la partie sud, où la couche de CH est présente, et la partie nord, où elle est absente. Les échanges d'eau entre les différentes couches sont donc très limités. Dans toutes ces couches, les eaux souterraine sont vieilles (> 5ka) et ont été rechargées sous un climat plus frais qu'aujourd'hui. Il est probable qu'elles soient largement héritées de périodes humide du Pléistocène supérieur et de la "Période Humide Africaine" (~ 15-5 ka) et devraient être gérées comme une ressource fossile. / In the region of Tahoua (Niger), which is part of the Iullemeden basin, the deep multilayer aquifer system of the Continental Intercalaire/Hamadien (CI/H) represents an essential reserve. It is exploited for the drinking-water supply for the local population, for the extractive-industry's water use and for the watering of cattle, because of the degradation of water quality and the very low flow in shallow aquifers and Upper Cretaceous aquifers. Despite some classical hydrogeological studies, this system remains poorly known, particularly with regard to the distribution of the different water bodies and their residence/renewal times. This study, mainly based on a geochemical and isotopic approach, aims to improve knowledge on the CI/H system in order to optimize its sustainable management. Data were obtained from geological maps, and data-sheets of drilling, pumping and logging test. In addition, water samples were collected from 30 boreholes regularly distributed over the study area (114 425 km2). Some parameters (pH, t and EC) were measured in situ and the samples were sent to the GEOPS laboratory where chemical (major ions) and isotopic (stable isotopes in water, 14C, 13C) analyses were performed. From geological cross-sections, the CH layer is present above the CI layers in the southern part of the region but not in the northern part. However, piezometry is continuous over the whole region. In the northern part (above 16°N), the flow lines are directed from the CI outcrops (east) to west and in the southern part (below 16°N), from the CH outcrops (east) to south-west. Stable isotope contents of water (vs V-SMOW) range from -8 to -7 ‰ for 18O and from -59 to -48 ‰ for 2H in the northern part (CI) and from -6 to -5 ‰ for 18O and -51 to -41 ‰ for 2H in the southern part (CH), showing two different water masses. All these values are much lower than those corresponding to present-day precipitation, which does not significantly contribute to recharge. This is in agreement with the groundwater "ages" (5 to 36 ka) calculated from 14C contents (1 to 57 pmC), which are also in good agreement with piezometry. Therefore, even if the continuous piezometry of the deep aquifer system of CI/H indicates that pressures are in equilibrium between the different layers, the geochemical features show noticeable differences between the southern part, where the CH layer is present, and the northern part, where it is absent. Thus, water exchanges between the different layers are very limited. In all these layers, groundwater is old (> 5ka) and was recharged under a cooler climate than at present. Probably, it is largely inherited from Upper-Pleistocene wet periods and from the "African Humid Period" (~15-5 ka) and should be managed as a fossil resource

Der weltweit steigende Energiebedarf stellt die Menschheit vor immer größere Herausforderungen. Im Angesicht des Klimawandels und der begrenzten Verfügbarkeit von fossilen Energieträgern liegt eine besondere Verantwortung bei der Entwicklung von erneuerbaren Energieressourcen. Dabei spielt die Geothermie eine besondere Rolle, da sie zur Deckung der Grundlast geeignet ist. Zu der Bewertung von geothermischen Potentialen leisten die Geowissenschaften einen großen Beitrag. Das geothermische Potential eines Standorts hängt vor allem von der Art und Ausbreitung von Störungszonen ab, da sie wesentlich den Grundwasserfluss kontrollieren. In dieser Arbeit werden verschiedene geowissenschaftliche Methoden miteinander kombiniert, um die Wirksamkeit von Störungszonen zu bewerten. Strukturgeologische Kartierungen und hydrogeologische Felduntersuchungen erklären die Ausbreitung und hydraulische Funktion von Störungszonen im Untersuchungsgebiet. Geohydrochemische Untersuchungen geben Auskunft über Fluid- und Gesteinszusammensetzung und deren Wechselwirkungen. Numerische Simulationen des Gebietes zeigen, dass sowohl Störungszonen als auch Fluideigenschaften wichtig für die Verteilung von Druck und Temperatur im Reservoir sind. Das Untersuchungsgebiet ist das Hochenthalpy-Geothermiefeld Lahendong in Sulawesi (Indonesien). Ein Kraftwerk produziert hier 80 MW Elektrizität. Die ersten Untersuchungen im Gebiet starteten in den 1970er Jahren. Jedoch sind Genese und Verteilung der thermalen Wässer noch nicht komplett verstanden. Das aktuelle konzeptionelle Modell zeigt eine Aufteilung in mehrere Reservoirbereiche. Die verschiedenen Bereiche sind durch horizontal impermeable Störungszonen voneinander getrennt. Den nördlichen Bereich kennzeichnen saure Wässer und den südlichen Teil pH-neutrale Wässer. Auch die Produktivität variiert stark zwischen den beiden Reservoirbereichen. In vertikaler Richtung sind Störungszonen jedoch durchlässig, was dazu führt, dass heiße Quellen entlang von Störungen oder deren Kreuzungspunkten auftreten. Die Reservoirgesteine in Lahendong sind basaltische Andesite, Tuffe und vulkanische Brekkzien. Die Permeabilitätsverteilung der Störungszonen wird durch die Ausbreitung von Rissen kontrolliert. Risse sind vor allem in der Bruchzone der Störung verbreitet, was zu einer hydraulischen Durchlässigkeit parallel zur Störung führt. Die Unterteilung des Reservoirs in Lahendong wird durch diese Rissverteilung bestimmt. Der nördliche saure Teil des Reservoirs ist durch höhere Produktivitätsraten, Gasaustritte an der Oberfläche und stark alterierte und geklüftete Gesteine im Untergrund charakterisiert. Der südliche Abschnitt ist heißer und hat weniger stark alterierte Gesteine. Die beobachteten Reservoireigenschaften wurden von hydrochemischen und hydraulischen Modellierungen bestätigt. Der Grundwasserfluss mit Neubildung und Austritten aus dem Reservoir ist im Gelände und im Modell vor allem durch Störungszonen kontrolliert. Jedoch ist der Grundwasserfluss auch durch den Aggregatzustand des Wassers beeinflusst. Für die Modellierung von 2-Phasen-Ausbreitung müssen die Permeabilitäten angepasst werden, um gleiche Temperatur- und Druckbedingungen zu modellieren. Der Hauptbeitrag dieser Arbeit liegt in der Demonstration, dass eine systematische strukturgeologische Analyse für das Verständnis von Grundwasserfluss in geothermischen Reservoiren unentbehrlich ist. Es wurde bestätigt, dass die Kombination von tektonischen, hydrogeologischen und geohydrochemischen Informationen den wichtigsten Beitrag für das Verständnis von Grundwasserströmungen leistet. Die Grundwasserströmung ist der wichtigste Faktor für die Wahl des richtigen Standortes für Produktion und Injektion in geothermischen Feldern. Eine detaillierte Analyse gewährleistet eine nachhaltige Nutzung des Feldes und verringert Risiken, wie schwach produzierende Bohrungen oder die Produktion von stark korrosiven Wässern. Auf dieser Grundlage kann eine Felderweiterung geplant werden, wie es in Lahendong angedacht ist.

Análises hidroquímicas e isotópicas de oxigênio-18, deutério e carbono inorgânico dissolvido foram utilizados para a caracterização dos recursos hídricos superficiais e subterrâneos no entorno da Lagoa da Confusão - Tocantins. O objetivo principal do trabalho é caracterizar e compreender a dinâmica dos recursos hídricos superficiais e subterrâneos da região a partir de suas características geoquímicas e isotópicas. Para isso, foi realizada a caracterização hidroquímica e avaliação da qualidade das águas, englobando conhecimentos da geoquímica do aquífero para entender a dinâmica das águas, ter um diagnóstico da área e auxiliar a gestão dos recursos hídricos da região. A dissertação apresenta os resultados do artigo intitulado “Caracterização hidroquímica das águas superficiais e subterrâneas no entorno da Lagoa da Confusão, Tocantins, Brasil”. Nesse estudo, análises hidroquímicas foram aplicadas para determinar as características das águas superficiais e subterrâneas e suas relações com o meio, na região da Lagoa da Confusão. O estudo permitiu identificar os tipos hidrogeoquímicos predominantes, que contemplam águas bicabornatadas cálcicas ou magnesianas, sendo constado a dominância de espécies iônicas de HCO3 - , Ca2+ e Mg2+. Os resultados demonstram que as águas da área são influenciadas pelas formações geológicas e pelo uso e ocupação dos solos, sendo o estudo da hidroquímica uma importante ferramenta para conhecimento, gestão e monitoramento dos recursos hídricos da região. Apresenta-se também nesse estudo, os resultados do artigo intitulado “Isótopos Estáveis Aplicados ao Estudo dos Fluxos Hídricos no Entorno da Lagoa da Confusão, TO, Brasil”. Por meio desse trabalho, verificou-se que a dinâmica de fluxo e o pouco tempo de confinamento indicado pela composição isotópica das águas subterrâneas estão intimamente relacionados às características ambientais e geológicas da área. Os resultados das análises de δ18O e δD evidenciam a existência do sistema cárstico que favorece uma rápida circulação dos fluxos hídricos, e determina as características hidroquímicas da água. Para as águas superficiais obteve-se para as amostras analisadas no rio Urubu e na Lagoa da Confusão valores superiores às águas subterrâneas. Verificou-se uma interação entre as águas superficiais e subterrâneas da área, sendo os recursos hídricos superficiais abastecidos em períodos de estiagem por águas subterrâneas. Os valores da razão isotópica de carbono inorgânico dissolvido (δ13CCID) foram predominantemente negativos, indicando uma maior contribuição de processos de dissolução de carbonatos por H2CO3. Os resultados das análises isotópicas caracterizam a presença de um aquífero cárstico na área de estudo, na qual a composição química da água é alterada pela interação água-rocha e dissolução das rochas carbonáticas, esse sistema ainda evidenciado pela ocorrência de cavernas e dolinas na área estudada. De forma geral, o estudo mostrou que a dinâmica e composição das águas superficiais e subterrâneas do entorno da Lagoa da Confusão são determinadas pelas características geológicas e pelo uso e ocupação dos solos, sendo o estudo uma importante ferramenta para conhecimento e monitoramento dos recursos hídricos da região. / Hydrochemical and isotopic analyzes of oxygen-18, deuterium and dissolved inorganic carbon were used to characterize surface water and groundwater resources near Lagoa da Confusão - Tocantins. The study main objective is to characterize and understand the dynamics of the superficial and groundwater resources of the region based on their geochemical and isotopic characteristics. To perform the study, it was carried out a hydrochemical characterization and water quality assessment. Both analyzes took into consideration the geochemistry of the aquifer to understand water dynamics as well as to get a more detailed overview of the study area and to help with water management resources in the region. The dissertation presents the results of the article entitled "Hydrochemical characterization of surface and groundwater in the surroundings of Lagoa da Confusão, Tocantins, Brazil". In that study, hydrochemical analyzes were applied to determine surface and groundwater characteristics likewise their interactions with the nearby environment in the Lagoa da Confusão region. The study identified the predominant hydrogeochemical types that can be found in calcic or magnesian bicarbonate water; as such, it observed the dominance of ionic species of HCO3 - , Ca2+ and Mg2+. The results show that the water in the study area is influenced by the local geological formations as well as the land use and occupation of it; therefore, the study of hydrochemistry is an important tool for the study, management and monitoring of water resources in the region. The results of the article entitled "Stable Isotopes Applied to the Study of Water Flows in the Confusion Lagoon Environment, TO, Brazil" are also presented in this study. The research verified that the dynamic flow and the short time confinement, which it was indicated by the isotopic composition of the groundwater, are closely related to the environmental and geological characteristics of the study area. The results of the δ18O and δD analyzes show the existence of a karstic system that contribute to a fast water flow, and it determines the hydrochemical characteristics of the water. For surface water, it was obtained higher values than those from groundwater samples from the Urubu river and Lagoa da Confusão. There was an interaction between surface and groundwater of the study area, since it noticed that surface water resources have been supplied by groundwater sources during drought periods. The values of the isotopic ratio of dissolved inorganic carbon (δ13CCID) were predominantly negative, indicating a greater contribution of carbonate dissolution processes by H2CO3. The results of the isotopic analyzes characterize the presence of a karst aquifer in the study area, in which the chemical composition of the water is altered by the water-rock interaction and the dissolution of the carbonate rocks; besides that, the occurrence of caves and dolines in the study area evidences of those processes. Therefore, the study showed that the dynamics and composition of the surface and groundwater surrounding the Confusion Lagoon are determined by the geological characteristics and the land use and occupation; thus, the result of the study are an important tool for understanding and monitoring the water resources in that region.

As florestas de mangue estabilizam a zona costeira da erosÃo e atuam como zona tamponante entre o continente e o mar. Apresentam elevado grau de resiliÃncia e desempenham um importante papel no fluxo de energia e ciclo de nutrientes. SÃo influenciadas pelo crescimento da carcinicultura que pode causar sÃrios impactos ambientais, particularmente na regiÃo nordeste do Brasil devido à emissÃo de sÃlidos em suspensÃo e nutrientes para os estuÃrios. Avaliar a capacidade de retenÃÃo capaz de minimizar o impacto dos efluentes contendo elevados teores de fÃsforo e material particulado em suspensÃo e distinguir esta capacidade entre Ãreas de reconhecida contaminaÃÃo e Ãreas com caracterÃsticas naturais constituÃram o objetivo desta dissertaÃÃo. As coletas de Ãgua e sedimento ocorreram em 2 campanhas no rio Jaguaribe (impactado) e em 1 no rio Pacoti (natural) em marà sizÃgia durante 13 horas. Os parÃmetros pH, OD, %OD, temperatura, salinidade e condutividade foram medidos in situ com multisonda portÃtil. O MPS foi obtido por gravimetria (APHA, 2001). As fraÃÃes de fÃsforo na Ãgua e no sedimento foram determinadas segundo Grasshoff et al. (1999). A extraÃÃo de TP no sedimento seguiu Berner & Rao (1994). As medidas de fluxo foram calculadas segundo OVALLE et al (1990) e a estimativa do balanÃo de massa foi obtida de forma simplificada a partir do balanÃo entre os processos de entrada e saÃda de acordo com a mudanÃa de marÃ. Os parÃmetros hidroquÃmicos se mostraram semelhantes para as duas Ãreas de estudo, com exceÃÃo do OD, que alcanÃou valores sub-Ãxicos para a gamboa do Jaguaribe. O MPS variou entre 23,1 e 172,9 mg.L-1 para as duas campanhas na gamboa do Jaguaribe e entre 23,5 e 97,7 mg.L-1 para a gamboa do Pacoti, tendo sido considerados aceitÃvel quando comparado a outros trabalhos. As concentraÃÃes de fÃsforo para a gamboa do rio Jaguaribe variaram para o DPO4 entre 2,1 e 6,5 μM na gamboa do Jaguaribe, e 0,1 e 0,9 μM na gamboa do Pacoti; para o T-PO4 entre 3,2 e 15,9 μM para a gamboa do Jaguaribe e 2,9 a 7,3 μM para a gamboa do Pacoti; e para o Part-PO4, entre 1,3 e 11,9 μM para a gamboa do Jaguaribe e 2,8 a 7,7 μM para a gamboa do Pacoti; tendo o Jaguaribe apresentado maiores concentraÃÃes que o Pacoti em todas as campanhas e fraÃÃes, provavelmente relacionando o fÃsforo presente aos efluentes de carcinicultura. O fÃsforo no sedimento variou de 180,6 e 224,9 μg de P/g para o TP na gamboa do Jaguaribe e na gamboa do Pacoti foi de 117,5 μg de P/g, mostrando que as maiores concentraÃÃes de P no sedimento ocorreram na gamboa do Jaguaribe. Os fluxos de MPS (Flx MPS) variaram de 0 a 184,5 g.s-1, na primeira campanha na gamboa do Jaguaribe, 0 a 36,4 g.s-1, na gamboa do rio Pacoti e entre 0 e 836,5 g.s-1 na segunda campanha do Jaguaribe, onde, nesta, os valores foram quase uma ordem de grandeza maiores que na anterior e seu comportamento foi mais acentuado durante a marà vazante. O Flx D-PO4 na gamboa do rio Jaguaribe variou de 0 a 709 mg.s-1 e 0 a 9.113 mg.s- 1, enquanto que na gamboa do Pacoti variou de 0 a 13,4 mg.s-1. Para o Flx T-PO4, foi observada variaÃÃo de 0 a 1.248 mg.s-1 e de 0 a 11.065 mg.s-1 na gamboa do Jaguaribe, e de 0 a 295 mg.s-1 na gamboa do Pacoti, e o Flx Part-PO4 variou de 0 a 539 mg.s-1 e de 0 a 3.471 mg.s-1 para as campanhas do Jaguaribe, e de 0 a 281 mg.s-1 para a gamboa do Pacoti. O fluxo das fraÃÃes de P e do MPS estÃo estreitamente relacionados a velocidade da corrente. As estimativas de balanÃo de massa mostraram que o rio Jaguaribe retÃm tanto as fraÃÃes de fÃsforo quanto os teores de MPS, corroborando com a hipÃtese gerada por este trabalho. Entretanto, sua capacidade de suporte està diminuÃda em comparaÃÃo com os resultados de balanÃo encontrados para o rio Pacoti, que apresentou uma retenÃÃo de materiais bem mais significativa do que o rio Jaguaribe, caracterizando-o com uma grande capacidade de suporte. O rio Jaguaribe, por sua vez, provavelmente pode estar entrando em um processo de envelhecimento acelerado pela aÃÃo antrÃpica que causa impacto em suas Ãguas que esta diminuindo sua capacidade depuradora. / The mangrove forests stabilize the coastal erosion zone and act as a buffering between the continent and the sea. This forest presents high resilient degree, suggested to be used as marker of environmental changes. They play an important role in the energy flow and nutrients cycles. They are suffering with the growth of shrimp ponds. This tends to be responsible of causing serious environmental impacts, particularly in the northeast of Brazil and being associated with the emission of solids in suspension and nutrient in estuaries. The mangroves growth has a retention capacity capable to minimize the impact of the effluents that can be distinguished between areas being recognized contaminated and areas with natural characteristics, for that we were intended to test this capacity through the study of phosphorus and TSS mass balance in these estuaries. Sampling of water and sediment was in 2 campaigns: in the Jaguaribe creek (impacted) and in the Pacoti creek (natural) at tidal cycle. The parameters pH, OD, %OD, T, salinity and cond were measured in situ with portable multimode. TSS was obtained by gravimetric method (APHA, 2001). The fractions of phosphorus in water and in sediments were according to the Grasshoff et al. (1999). The TP extraction in sediment followed Berner & Rao (1994). The flow measures were calculated according to OVALLE et al (1990) and the estimate of the mass balance was obtained in simplified ways starting from the mass between the entrance processes to the agreement with the tide change. The hydrochemistry parameters showed the same for the two study areas, except for OD, that reached suboxic values for Jaguaribe creek. TSS varied between 23,1 and 172,9 mg.L-1 for two campaigns in the Jaguaribe creek and 23,5 and 97,7 mg.L-1 for the Pacoti creek, having been considered acceptable when compared the other works. The phosphate concentrations for Jaguaribe creek varied for D-PO4 between 2,1 and 6,5 μM in Jaguaribe creek, and 0,1 and 0,9 μM in Pacoti creek; for T-PO4 between 3,2 and 15,9 μM for Jaguaribe creek and 2,9 to 7,3 μM for Pacoti creek; and for Part-PO4, between 1,3 and 11,9 μM for Jaguaribe creek and 2,8 to 7,7 μM for Pacoti creek; tends Jaguaribe presented larger concentrations that Pacoti in all the campaigns and fractions, probably due to the effluents of shrimp pond. The phosphorus in the sediment varied from 180,6 to 224,9 μg of P/g for TP in Jaguaribe creek and in Pacoti creek it was of 117,5 μg of P/g, showing that the largest concentrations of P in the sediment happened in Jaguaribe. The flows of TSS (Flx TSS) varied from 0 to 184,5 g.s-1, in the first campaign in Jaguaribe creek, 0 to 36,4 g.s-1, in Pacoti creek and between 0 and 836,5 g.s-1 in the second campaign of Jaguaribe, where the values were almost an order of greatness larger than in the previous and your behavior was more accentuated during the ebb tide. Flx D-PO4 in Jaguaribe creek varied from 0 to 709 mg.s-1 and 0 to 9.113 mg.s-1, while in Pacoti creek it varied from 0 to 13,4 mg.s-1. To Flx T-PO4, variation was observed from 0 to 1.248 mg.s-1 and from 0 to 11.065 mg.s-1 in Jaguaribe creek, and from 0 to 295 mg.s-1 in Pacoti creek, and Flx Part-PO4 varied from 0 to 539 mg.s-1 and from 0 to 3.471 mg.s-1 for the campaigns of Jaguaribe, and from 0 to 281 mg.s-1 for Pacoti creek. The fluxes of the fractions of P and of TSS are much related with current speed. The estimates of mass balance showed that the river Jaguaribe retains the phosphorus fractions as much as the TSS, corroborating with the hypothesis generated by this work. However, their support capacity it is reduced in comparison with the balance results found for the river Pacoti that presented retention of materials much more significant than the creek in Jaguaribe River, characterizing him with a great support capacity. However, Jaguaribe River can probably be entering in an accelerated process of aging caused by the antrophic actions that impacts in its waters.

Ce travail de thèse s’inscrit dans une démarche d’approfondissement des connaissances du fonctionnement des aquifères karstiques. Pour cela, le site pilote des Sources du Toulon, siège d’une alimentation multiréservoirs, a été choisi et offre une fenêtre d’observation privilégiée sur les relations hydrogéologiques entre les aquifères de la marge Nord du Bassin aquitain. Elles sont utilisées depuis 1832 pour l’alimentation en eau potable de la ville de Périgueux, et constituent actuellement son unique ressource.L’objectif de ce travail a été de tester une approche multi-traceurs et un suivi haute-résolution pour caractériser le fonctionnement et la vulnérabilité d’un aquifère karstique multicouche.L’utilisation d’une approche couplée hydrodynamique et hydrochimie a mis en évidence l’alimentation des Sources du Toulon par une ressource profonde et captive en complément d’un aquifère libre plus superficiel. Ces informations ont été intégrées dans le contexte hydrogéologique global de la zone d’étude pour proposer une nouvelle délimitation du bassin d’alimentation des Sources du Toulon.L’utilisation d’un suivi haute-résolution a permis de préciser le fonctionnement hydrogéologique du système karstique étudié. Il en ressort des fonctionnements différents suivants les crues, avec des transferts de masse pouvant s’étendre de quelques jours à quelques semaines.L’apport des isotopes des nitrates (δ15N-NO3- ; δ18O-NO3-) a permis d’identifier deux origines des nitrates mesurés dans les eaux de surface et souterraines : les fertilisants minéraux de synthèse utilisés pour l’agriculture, et les rejets d’assainissement individuels.L’évaluation temporelle de la vulnérabilité spécifique des Sources du Toulon à certains marqueurs de contamination tels que les particules, les éléments bactériologiques et les nitrates a permis de distinguer plusieurs masses d’eau superficielles et subsuperficielles participant à l’alimentation pendant les crues, et jouant un rôle différent dans le transfert des contaminants. / This work is included in an approach for a better knowledge of karst aquifers. For this, the Toulon Springs pilot site was chosen, and provides the opportunity to study relationships between multilayered karst aquifers of the northern edge of the Aquitaine sedimentary basin. Toulon Springs are major regional springs and are located in Périgueux (Dordogne County, France). They have been supplying water to the metropolitan area of Périgueux since 1832.This work aim to test an innovative multitracer approach coupled with a physicochemical high-resolution auto-monitoring to characterize functioning and vulnerability of a multilayered karst aquifer.The use of a coupled hydrodynamic and hydrochemical approach has highlighted Toulon Springs supply by a deep and captive aquifer, in addition to a more subsuperficial aquifer. This information has been incorporated into the global hydrogeological situation of the study area to propose a new delineation of Toulon Springs hydrogeological cathment.The use of a high-resolution monitoring enables to specify the hydrogeological functioning of the studied karst system. The analysis performed on several flood events, identify that mass transfer can range from a few days to a few weeks.The use of nitrate isotope (δ15N-NO3- ; δ18O-NO3-) enables to identify two main nitrate sources in both surface water and groundwater: (i) inorganic fertilizer; (ii) sewage from individual house.The last part of this work was to analyse Toulon Springs temporal vulnerability during floods to marker of contamination such as particles, dissolved organic carbon, nitrate, and bacteria. Hence, several water type from surface runoff, unsaturated zone and saturated zone were identify as responsible of contaminant transfer: (i) water from saturated zone is responsible of vulnerability to mineral particles ; (ii) water from unsaturated zone is responsible of vulnerability to nitrare ; (iii) water from surface runoff is responsible of vulnerability to bacteria contamination.

<p>The analysis of geologic, hydrologic and hydrogeologic data interpreted to give the characteristics of the Cape Flats aquifer showed the quality of groundwater from the aquifer is suitable for development as a water resource. The conceptual model of the Cape Flats sand shows an unconfined sandy aquifer, grading into semi-confined conditions in some places where thick lenses of clay and peat exists. Recharge rates through the saturated zone of the Cape Flats aquifer have been determined by water table fluctuation (WTF), rainfall-recharge relationship, soil water balance and chloride mass balance methods (CMB). Recharge rates using the WTF vary considerably between wet and dry years and between locations, with a range of 17.3% to 47.5%. Values obtained from empirical rainfall-recharge equation (method 2) agree with those of the WTF. Recharge estimates from the water balance model are comparatively lower but are within the range calculated using empirical method 2 (i.e. 87 &ndash / 194 mm or 4 &ndash / 21% of MAP). These recharge rates also agree with estimates from the series of other methods applied to sites located in the north-western coast of Western Cape and are comparable to recharge rates obtained elsewhere in the world.</p>

<p>The analysis of geologic, hydrologic and hydrogeologic data interpreted to give the characteristics of the Cape Flats aquifer showed the quality of groundwater from the aquifer is suitable for development as a water resource. The conceptual model of the Cape Flats sand shows an unconfined sandy aquifer, grading into semi-confined conditions in some places where thick lenses of clay and peat exists. Recharge rates through the saturated zone of the Cape Flats aquifer have been determined by water table fluctuation (WTF), rainfall-recharge relationship, soil water balance and chloride mass balance methods (CMB). Recharge rates using the WTF vary considerably between wet and dry years and between locations, with a range of 17.3% to 47.5%. Values obtained from empirical rainfall-recharge equation (method 2) agree with those of the WTF. Recharge estimates from the water balance model are comparatively lower but are within the range calculated using empirical method 2 (i.e. 87 &ndash / 194 mm or 4 &ndash / 21% of MAP). These recharge rates also agree with estimates from the series of other methods applied to sites located in the north-western coast of Western Cape and are comparable to recharge rates obtained elsewhere in the world.</p>

Low-lying coastal plains comprised of unconsolidated infill are internally complex hydrogeological settings, due to the high level of heterogeneity in the infill material. In order to resolve the hydrogeological processes active in these complex settings, an integrated multi-disciplinary, geoscientific approach is required. This research determines quantitatively, the effects of sedimentary aquifer heterogeneity on groundwater flowpaths and groundwater processes within a heavily laterised, coastal plain setting. The study site is the Bells Creek catchment in southeast Queensland, Australia. The methodology developed in this study provides a new approach to enable the determination of groundwater flowpaths and groundwater processes at macroscale resolution within other shallow alluvial and coastal plain aquifers. The multi-disciplinary approach utilises sedimentological, geophysical, chronological and hydrogeological techniques (including hydrochemistry and groundwater flow modelling) to develop a high-resolution aquifer framework, and to determine accurately, both groundwater flowpaths and relative flow rates. Sedimentary framework is confirmed to be the principal factor controlling the distribution of aquifer permeability pathways in any given setting, and is therefore, the dominant control over groundwater flow and processes. For the Bells Creek catchment, interpretation of stratigraphic and sedimentary data allowed the compilation of a detailed sedimentary framework. This interpretation demonstrated that weathering of the low-lying arkose sandstone bedrock has developed thick lateritic profiles. Within the weathering profiles, cemented, iron-rich horizons have resisted erosion and developed raised and elongated ridges in the modern landscape, while other clay-rich weathered layers have submitted to erosion and downgraded around those iron-rich ridges. Consequently, alluvial deposition throughout the Late Quaternary has been restricted to narrow, and relatively deep valleys containing sandrich channels, and thin floodplains at shallow depth. From a hydrogeological perspective, there is significant macroscopic aquifer heterogeneity between fine-grained lateritic mixed clay layers, floodplain clays, ironcemented ferricrete horizons, and permeable sand-rich alluvial aquifers. This variability of aquifer material has created a complex subsurface arrangement of permeability pathways. Application of Ground Penetrating Radar (GPR) in this setting enabled accurate definition of alluvial channel boundaries and the high degree of connectedness within the channels themselves. Interpretation of a comprehensive GPR dataset (that covered the entire catchment) allowed refinement of the sedimentary framework previously established to develop a detailed threedimensional aquifer framework. Finite-difference groundwater modelling and particle tracking analysis (using MODFLOW and MODPATH) has clearly demonstrated that the macroscopic heterogeneity within the various aquifer materials of the plain has marked impacts on groundwater pathways, and especially groundwater travel times. The variability between a maximum residence time of 18 months for groundwater within the alluvium, compared to hundreds of years for groundwater within the mixed clay layers of the laterite, clearly demonstrates the importance of accurately defining the spatial distribution of the various aquifer materials in a groundwater flow investigation. In this setting, the interconnection of the narrow alluvial channels feeding into a deeper alluvial delta has provided an effective conduit for shallow groundwater flow. The role of the alluvial delta in discharging the bulk of fresh groundwater from the central plain into the coastal and estuarine aquifers to the east, is certainly critical in preventing saline intrusion from encroaching further west. Hydrochemical and isotopic indicators have identified the dominant recharge processes and groundwater flowpaths within the plain, and indicated that the processes are strongly related to sub-surface permeability distributions determined in the aquifer framework (and groundwater modelling), as well as seasonal fluctuations in rainfall. In the northwest of the plain, sandstone hills provide a delayed and slightly mineralized component of groundwater recharge into adjacent highly permeable, unconfined alluvial aquifers; these aquifers also recharge directly via precipitation. Aluminosilicate weathering in the bedrock hills and eastern peripheries of the laterised bedrock are a source of excess Na, SiO2, and HCO3 to the alluvial groundwater. As this groundwater flows down-gradient to the east, however, its chemical composition evolves by sulfate reduction, silica equilibrium and ion exchange processes into a more mature Na-Cl type. Within the shallow coastal aquifers proximal to the eastern shoreline, sulfate enrichment is occurring (associated with increases in Ca, HCO3, Fe and Al) resulting in major deterioration in groundwater quality. The deterioration is produced by saline intrusion from the adjacent estuary coupled with oxidation of sulfide materials in shallow marine and estuarine clays. Reverses in salinity in those coastal aquifers have been correlated with surges in fresh recharge waters from unconfined coastal dunes and semi-confined landward alluvium, following significant rainfall events. The multi-disciplinary methodology developed, provides an effective approach for accurately defining the three-dimensional distribution of shallow aquifer material of varying permeability via detailed stratigraphic interpretation and GPR analysis. Utilising this aquifer framework, finite-difference groundwater modelling aided by hydrogeological data and hydrochemical analysis, allows accurate determination of groundwater flowpaths and groundwater processes. This research provides a new hydrogeological analogue for alluvial channel aquifers within a laterised coastal plain setting. Key Words: groundwater flow, aquifer heterogeneity, numerical modelling, hydrochemistry, recharge, ground penetrating radar, coastal plain aquifers, weathering, alluvial channels.

This work was developed with the objective of evaluating the variation of the index of quality of the water in the river Saúde North coast of Alagoas, relating parameters of quality of the water as well as the own index, with the rainy and dry periods defined through climatological studies. The period of collections was understood among the months from May to December of 2004, being the months from May to August, defined as being the rainy period, and from September to December the dry season. The chemical parameters of the water were collected: Dissolved oxygen, pH, Turbidez, Salinity, Material in Suspension, Chlorophyll, Electric Conductivity, Nitrate, Nitrite, Temperature and Transparency of the water. Also the precipitation was collected in the station Peixe Boi located in project Peixe Boi headquarters, in the North coast of Alagoas. The found results had shown low values of water quality, which is due the lack of biological parameters in the calculation of the index. The index used for the calculation was Bascaràn, the variation of that index was detected in relation to the dry and rainy periods tends a light increase in the rainy period and stability in the dry period. Key Words: Meteorology, Quality of the water, Hydrochemistry / Este trabalho foi desenvolvido com o objetivo de avaliar a variação do índice de qualidade da água no rio Saúde Litoral norte de Alagoas, relacionando parâmetros de qualidade da água bem como o próprio índice, com os períodos chuvoso e seco definidos através de estudos climatológicos. O período de coletas ficou compreendido entre os meses de maio a dezembro de 2004, sendo os meses de maio a agosto, definidos como sendo o período chuvoso, e de setembro a dezembro uma estação seca. Foram coletados os parâmetros químicos da água: Oxigênio Dissolvido, pH, Turbidez, Salinidade, Material em suspensão, Clorofila, Condutividade Elétrica, Nitrato, Nitrito, Temperatura e Transparência da água. Também foi coletada a precipitação na estação Peixe Boi localizada na cede do projeto Peixe Boi, no litoral norte de Alagoas. Os resultados encontrados mostrara baixos valores de qualidade da água, isso de deve a falta de parâmetros biológicos no calculo do índice. O índice usado para o calculo foi o Bascaràn, foi detectada a variação desse índice em relação ao período seco e chuvoso tendo um leve aumento no período chuvoso e estabilidade no período seco.

Este trabalho buscou avaliar a qualidade da água subterrânea de poços ponteira, que captam água do Sistema Aquífero Quaternário Costeiro (SAQC) na região de Osório (RS), através da aplicação de diferentes métodos. Para a realização do estudo foi feito um inventário e cadastramento de poços, o levantamento e interpretação de dados geológicos e hidrogeológicos, além da coleta e análise de amostras de água. Para este trabalho foram utilizados dados físico-químicos e bacteriológicos, obtidos através das análises de água (campo e laboratório), que foram coletadas em 26 poços. A avaliação dos resultados foi realizada através dos diagramas de Piper e Stiff, da comparação com os Valores Máximos Permitidos (VMP) em portarias de potabilidade e da aplicação de métodos de avaliação da qualidade da água e risco a saúde. Os resultados obtidos permitiram evidenciar que no município, a principal forma de captação da água subterrânea, ocorre por meio de poços ponteira que possuem profundidades na sua maioria, inferiores a 20 metros e que captam água de aquíferos granulares livres associados a camadas de sedimentos arenosos. Além disso, a maior parte das águas subterrâneas apresentaram valores de pH entre 5,6 e 6,5 e valores de condutividade elétrica (CE) entre 0 a 200 uS/cm. As concentrações de nitrato variaram entre 0 e 2 mg/L N-NO3, de cloretos e sódio não ultrapassam 30 mg/L, os sólidos totais dissolvidos entre 0 e 200 mg/L, indicando a ocorrência de águas doces com baixa mineralização. Os resultados das análises bacteriológicas indicaram a presença de Escherichia coli e coliformes totais. A comparação dos resultados das análises com os VMP da portaria do Ministério da Saúde Nº 2914/11 (Brasil, 2011), indicaram a ocorrência de poços que apresentam alterações nos parâmetros pH, amônia, ferro, cor, manganês, turbidez, bem como presença de Coliformes Totais e E.coli. Com o uso do Índice de Qualidade da Água Subterrânea (IQUAS), foram classificadas amostras de água como ótimas, boas e péssimas. Já o cálculo do Índice Relativo de Risco (IRR) evidenciou a ocorrência de amostras que apresentaram valores altos, a Avaliação de Risco à Saúde, indicou a ocorrência de amostras que apresentaram Risco não Carcinogênico. Por fim a partir deste estudo pode-se verificar que o uso de diferentes métodos para avaliação da qualidade da água, tem grande importância, pois torna mais consistente essa avaliação, já que cada método envolve a análise de diferentes parâmetros. / The aim objective of this work was to evaluate the groundwater quality of wells, which capture water from the Coastal Quaternary Aquifer System (SAQC) in the region of Osorio (RS), by applying different methods. In order to carry out the study, an inventory and registration of wells, the survey and interpretation of geological and hydrogeological data, as well as the collection and analysis of water samples. For this work, physicochemical and bacteriological data were obtained through water analysis (field and laboratory), which were collected in 26 wells. The evaluation of the results was carried out through the Piper and Stiff diagrams, the comparison with the Maximum Permitted Values (VMP) in potable water consumption and the application of water quality and health risk assessment methods. The results obtained showed that in the municipality, the main way of captation of groundwater occurs through pointer wells that have a depth of less than 20 meters and capture water from unconfined granular aquifers associated with layers of sandy sediments. In addition, most groundwater had pH values between 5.6 and 6.5 and values of electrical conductivity (EC) between 0 and 200 uS/cm. Nitrate concentrations ranged from 0 to 2 mg / L NNO3, with sodium chloride not exceeding 30 mg/L, total solids dissolved between 0 and 200 mg/L, indicating the occurrence of fresh water with low mineralization. The results of the bacteriological analyzes indicated the presence of Escherichia coli and total coliforms in 4 wells. The comparison of the results of the analyzes with the MPV of Ministry of Health No. 2914/11 (Brazil, 2011) indicated the occurrence of wells that present alterations in pH, ammonia, iron, color, manganese, turbidity and presence of Total Coliforms and E. coli. With the use of the Underwater Water Quality Index (IQUAS), 9 water samples were classified as optimal, 2 as good and 4 bad. The calculation of the Risk Index (IRR) evidenced the occurrence of 7 samples that presented high values, the Health Risk Assessment, indicating the occurrence of 2 samples that presented non-Carcinogenic Risk. Finally, from this study we can verify that the use of different methods to evaluate water quality, is of great importance, since it makes this evaluation more consistent, since each method involves the analysis of different parameters.