A importância do estudo de aqüíferos livres e rasos se evidencia quando se leva em conta que tais aqüíferos são altamente vulneráveis a contaminação e que em geral se encontram em regiões densamente povoadas. Com o objetivo de melhor compreender a dinâmica do fluxo de água subterrânea na zona saturada destas formações aqüíferas, foi construído e calibrado um detalhado modelo tridimensional e transiente para representar o fluxo subterrâneo em uma porção de um aqüífero livre e raso que ocorre no Parque Ecológico do Tietê, no Município de São Paulo. Este modelo, baseado em dados de cargas hidráulicas de 81 poços de monitoramento instalados em uma área de 320m2 medidas diariamente, em valores diários de precipitação na área e em 75 determinações de condutividades hidráulicas, foi construído e executado através do software Visual MODFLOW e calibrado por meio do software PEST, através de um método de regressão não linear. Os resultados gerados por este modelo para um evento de recarga rápida indicam que a distribuição de cargas hidráulicas na área de estudo é governada pela recarga regional, pela distribuição das condutividades hidráulicas horizontais e pelas vazões específicas das camadas superiores da formação, mas é praticamente independente da intensidade e distribuição temporal da recarga local, que influencia apenas os níveis mais rasos da formação. Além disso, verifica-se o caráter extremamente dinâmico do fluxo, que responde rapidamente ao evento de recarga regional, apresentando alterações significativas de intensidade e direção no intervalo de apenas alguns dias. Tais resultados, verificados apenas por meio de um modelo tão detalhado como o produzido neste trabalho, sugerem que estratégias comuns de avaliação podem não ser capazes de avaliar suficientemente bem o comportamento deste tipo de aqüífero. / The importance of studying unconfined and shallow aquifers is verified when taking into account that these aquifers are highly vulnerable to contamination and that they are often located under heavily populated regions. A detailed three-dimensional and transient model, which represents the groundwater flow in an area of an unconfined and shallow aquifer at the Parque Ecológico do Tietê, in the Municipality of São Paulo, Brazil, was created and calibrated with the objective of enhancing the comprehension of the dynamics of the groundwater flow in the saturated zone of these formations. This model was based on hydraulic head data of 81 monitoring wells, which were installed in an area of 320 m2 and measured on a daily basis, on daily values of precipitation occurring in the area and 75 determinations of hydraulic conductivities. The model was created and run using the software Visual MODFLOW and calibrated using the software PEST, based on a non-linear regression method. The results generated by this method for an event of rapid recharge indicate that the distribution of the horizontal hydraulic conductivities and by the specific yield of the upper layers of the formation, but it is mostly disconnected from the intensity and temporal distribution of the local recharge, that only influences the shallowest levels of the formation. Furthermore, the extremely dynamic character of the flow can be verified, which responds rapidly to the regional recharge event, presenting significant changes of intensity and direction within only a few days. These results, which were only observable through a very detailed model such as the one produced and presented in this study, suggest that commonly employed evaluation strategies may not be capable of evaluating this kind of aquifer in a satisfactory way.

A importância do estudo de aqüíferos livres e rasos se evidencia quando se leva em conta que tais aqüíferos são altamente vulneráveis a contaminação e que em geral se encontram em regiões densamente povoadas. Com o objetivo de melhor compreender a dinâmica do fluxo de água subterrânea na zona saturada destas formações aqüíferas, foi construído e calibrado um detalhado modelo tridimensional e transiente para representar o fluxo subterrâneo em uma porção de um aqüífero livre e raso que ocorre no Parque Ecológico do Tietê, no Município de São Paulo. Este modelo, baseado em dados de cargas hidráulicas de 81 poços de monitoramento instalados em uma área de 320m2 medidas diariamente, em valores diários de precipitação na área e em 75 determinações de condutividades hidráulicas, foi construído e executado através do software Visual MODFLOW e calibrado por meio do software PEST, através de um método de regressão não linear. Os resultados gerados por este modelo para um evento de recarga rápida indicam que a distribuição de cargas hidráulicas na área de estudo é governada pela recarga regional, pela distribuição das condutividades hidráulicas horizontais e pelas vazões específicas das camadas superiores da formação, mas é praticamente independente da intensidade e distribuição temporal da recarga local, que influencia apenas os níveis mais rasos da formação. Além disso, verifica-se o caráter extremamente dinâmico do fluxo, que responde rapidamente ao evento de recarga regional, apresentando alterações significativas de intensidade e direção no intervalo de apenas alguns dias. Tais resultados, verificados apenas por meio de um modelo tão detalhado como o produzido neste trabalho, sugerem que estratégias comuns de avaliação podem não ser capazes de avaliar suficientemente bem o comportamento deste tipo de aqüífero. / The importance of studying unconfined and shallow aquifers is verified when taking into account that these aquifers are highly vulnerable to contamination and that they are often located under heavily populated regions. A detailed three-dimensional and transient model, which represents the groundwater flow in an area of an unconfined and shallow aquifer at the Parque Ecológico do Tietê, in the Municipality of São Paulo, Brazil, was created and calibrated with the objective of enhancing the comprehension of the dynamics of the groundwater flow in the saturated zone of these formations. This model was based on hydraulic head data of 81 monitoring wells, which were installed in an area of 320 m2 and measured on a daily basis, on daily values of precipitation occurring in the area and 75 determinations of hydraulic conductivities. The model was created and run using the software Visual MODFLOW and calibrated using the software PEST, based on a non-linear regression method. The results generated by this method for an event of rapid recharge indicate that the distribution of the horizontal hydraulic conductivities and by the specific yield of the upper layers of the formation, but it is mostly disconnected from the intensity and temporal distribution of the local recharge, that only influences the shallowest levels of the formation. Furthermore, the extremely dynamic character of the flow can be verified, which responds rapidly to the regional recharge event, presenting significant changes of intensity and direction within only a few days. These results, which were only observable through a very detailed model such as the one produced and presented in this study, suggest that commonly employed evaluation strategies may not be capable of evaluating this kind of aquifer in a satisfactory way.

More than two million people in the Chaco-Pampean plain in central Argentina are affected by high As levels in groundwater. The concentrations of As are far exceeding the WHO standard limit for safe drinking water of 0.1 μg/L and the provisional Argentinean limit of 0.5 μg/L. The NE of La Pampa province is one of the areas affected with geogenic As in shallow aquifers within the Chaco-Pampean plain. These aquifers are in closed basins and they are only available water resource of the region for drinking and agriculture purposes. The Pampean aquifer is composed of a multi-layered system of Quaternary loess deposits covered by aeolian sands and also containing layers of rhyolitic volcanic ash, which is considered the primary source of As. Volcanic ash layers can be visible in the shallow sediments or intermixed in the loess. During the weathering of volcanic ash sediments As is dissolved to the aqueous phase and can be quickly adsorbed or co-precipitated on secondary Fe, Al and Mn oxy-hydroxides under favourable conditions. Also, previous more arid climatic conditions have led to the formation of carbonate "calcrete" layers in the top sequences of the loess and this has affected the geochemistry of the aquifer. Two sites were investigated in the NE of La Pampa province in order to assess (i) the quality of groundwater for drinking water use, (ii) the distribution of As and other trace elements in shallow aquifers and (iii) to understand better the factors controlling its mobility in groundwater. The results showed that groundwater was circum-neutral to alkaline and under moderate oxidizing conditions. The predominant groundwater composition was of Na-HCO3 for fresh water and Na-Cl-SO42- for brackish water types. High salinity levels are evidenced by the high Electrical Conductivity and might be explained by to the high evaporation rates. Groundwater sampled in both areas was enriched with As, F and other trace elements at different ranges of concentration. From the total As concentrations, arsenate As(V) predominated over arsenite As(III) species. Shallow groundwater is also enriched with fluoride exceeding the WHO standard limit of 1.5 mg/L and placed in the same As hotspots. One possible factor controlling the mobility of As is the high pH of groundwater, which is controlled by the carbonates equilibrium. Under this high pH conditions As is less strongly bind to Fe, Al and Mn oxy-hydroxides and can be easily mobilized to groundwater when other competing ions are getting adsorbed on the surface sites of binding minerals.

Due to the low amount or unfavorable annual distribution of precipitation the exploration, allocation, sustainable exploitation, and protection of replenishable as well as fossile water resources are challanging tasks in semiarid and arid regions. Beside a few natural or artifcial surface water reservoirs the porous underground at the same time is the largest storage and transport medium for water and provides protection against evaporation and to a certain degree against surcficial introduction of contaminants. This situation is characteristic for the Near East and thus for the selected investigation areas, that are located in Israel and the West Bank, and that are subject of the conducted partail studies that are presented. The work focuses on three main subjects. On the one hand, it deals with the characterization of the young groundwater components of the discharge of four major springs of Wadi Qilt and Jericho, as well as of sampled deep wells of three important well fields. All of these objects discharge or abstract water from the Upper and Lower Judea Group Aquifer. With a thickness of about 750 m it is one of the most important groundwater reservoirs of the region and comprises mainly to varying degrees karstified and fractured limestones and dolomites. These formations underwent uplift during Senonian to Eocenian times forming a pair of double-plunging anticlinal structures (Hebron and Ramallah or Judea and Samaria Mountains, respectively) that are again subdivided into minor anticlines and synclines. The groundwater replenishment is restricted to the winter season between October and April, and to the crestal area of the mountains, where the otherwise covered aquifer rocks crop out. A strategy was developed to interpret the applied tracers for all locations in a similar way using a lumped parameter approach, which enables a direct comparison. On the other hand, the work investigates salinization processes in the Shallow Aquifer of Jericho and their discrimination. Potential sources for salinization are remnant brines that are activated to flow into the range of well extraction due to groundwater overexploitation, dissolution of salts, or formation waters from the Lisan formation. These layers represent the sediments of Lake Lisan, the Pleistocene precursor of the Dead Sea. A discrimination of the salinization mechanisms is important to develope reasonable measures to limit or lower the salt concentration in the affected wells. Consequently, the relevant measured but also potential main hydrochemical indicators and isotope tracers are identified. The large uncertainties with respect to the establishment of a well-founded water balance and to the insuffcient knowledge about the geology of the small-scale area of Jericho are discussed. Because the interpretation of the measured helium samples from the fractured and karstified aquifer of the Cretaceous Judea Group is limited, the dependencies of the He-4 accumulation in groundwater in an idealized dual-continuum aquifer are investigated with respect to the relation of the He-4 mass fluxes and the system response time to the varied parameters (groundwater head gradient, hydraulic conductivities, dispersivities, porosities) by means of a sensitivity analysis. Although the system response time is not a system variable as such it clearly turned out that knowledge about it may be an important information for the interpretation of He concentrations in groundwaters of non-stationary systems. To enhance the visual post-processing of the parameter sensitivity analysis an easily interpretable way of data presentation is introduced. / Semiaride und aride Gebiete stellen aufgrund des niedrigen oder ungünstig verteilten Niederschlagsdargebots eine besondere Herausforderung bezüglich Erkundung, Bereitstellung, nachhaltiger Nutzung und Schutz sich neu bildender, aber auch fossiler Wasserresourcen dar. Abgesehen von wenigen natürlichen oder künstlich angelegten Oberflächenreservoiren ist der poröse Untergrund dabei gleichzeitig Hauptspeicher und Transportmedium für Wasser und bietet einen Schutz gegen Verdunstung und bis zu einem gewissen Grade gegen oberflächig einwirkende Verunreinigungen. Diese Situation ist charakteristisch für den Nahen Osten und damit für die im Rahmen der vorliegenden Arbeit beschriebenen Teiluntersuchungsgebiete, die sich in Israel und der West Bank befinden. Die Arbeit behandelt drei Hauptthemen. Einerseits geht sie auf die Charakterisierung der Jungwasseranteile im Abfluß vier bedeutender Quellen des Wadi Qilts und Jerichos sowie in beprobten tiefen Brunnen dreier wichtiger Brunnenfelder ein. Alle diese Objekte entwässern bzw. entnehmen Wasser aus dem Oberen oder Unteren Judea Group Aquifer. Mit ca. 750 m Mächtigkeit stellt dieser eines der bedeutensten Grundwasserreservoire der Region dar und besteht hauptsächlich aus unterschiedlich stark verkarsteten und gestörten Kalkstein- und Dolomitformationen, welche zwischen dem Senon und Eozän in Form einer in sich weiter gegliederten, beid-seitig abtauchenden Doppelantiklinalstruktur herausgehoben wurde (Hebron und Ramallah bzw. Judea und Samaria Mountains). Die Grundwasserneubildung ist beschränkt auf die Zeit zwischen Oktober und April sowie auf die Kammlagen des Gebirges, wo die sonst bedeckten Schichten des Aquifers ausstreichen. Es wurde eine Strategie entwickelt, die eingesetzten Tracer auf ähnliche Weise mit Hilfe von Lumped Parameter-Modellen für alle Lokationen zu interpretieren und somit eine Vergleichbarkeit zu gewährleisten. Andererseits untersucht die Arbeit Versalzungsprozesse im Shallow Aquifer von Jericho und deren Abgrenzung untereinander. Mögliche Hauptquellen der Versalzung sind durch überhöhte Grundwasserentnahme verstärke Zuflüsse von Solen, die Lösung von Salzen aus der Lisan-Formation oder Formationswässer der Lisan-Formation, welche die Ablagerungen des Lisan-Sees, des Pleistozänen Vorgängers des heutigen Toten Meeres, repräsentieren. Eine Unterscheidung der Mechanismen hat dabei durchaus Bedeutung für die Festlegung geeigneter Gegenmaßnahmen. Demzufolge werden die ermittelten, aber auch weitere, potentielle hydrochemische Hauptindikatoren und Tracer benannt. Unsicherheiten sowohl hinsichtlich der Aufstellung einer Wasserbilanz, als auch einer unzureichend bekannten Geologie für das sehr kleinräumige Gebiet von Jericho werden diskutiert.

Due to the low amount or unfavorable annual distribution of precipitation the exploration, allocation, sustainable exploitation, and protection of replenishable as well as fossile water resources are challanging tasks in semiarid and arid regions. Beside a few natural or artifcial surface water reservoirs the porous underground at the same time is the largest storage and transport medium for water and provides protection against evaporation and to a certain degree against surcficial introduction of contaminants. This situation is characteristic for the Near East and thus for the selected investigation areas, that are located in Israel and the West Bank, and that are subject of the conducted partail studies that are presented. The work focuses on three main subjects. On the one hand, it deals with the characterization of the young groundwater components of the discharge of four major springs of Wadi Qilt and Jericho, as well as of sampled deep wells of three important well fields. All of these objects discharge or abstract water from the Upper and Lower Judea Group Aquifer. With a thickness of about 750 m it is one of the most important groundwater reservoirs of the region and comprises mainly to varying degrees karstified and fractured limestones and dolomites. These formations underwent uplift during Senonian to Eocenian times forming a pair of double-plunging anticlinal structures (Hebron and Ramallah or Judea and Samaria Mountains, respectively) that are again subdivided into minor anticlines and synclines. The groundwater replenishment is restricted to the winter season between October and April, and to the crestal area of the mountains, where the otherwise covered aquifer rocks crop out. A strategy was developed to interpret the applied tracers for all locations in a similar way using a lumped parameter approach, which enables a direct comparison. On the other hand, the work investigates salinization processes in the Shallow Aquifer of Jericho and their discrimination. Potential sources for salinization are remnant brines that are activated to flow into the range of well extraction due to groundwater overexploitation, dissolution of salts, or formation waters from the Lisan formation. These layers represent the sediments of Lake Lisan, the Pleistocene precursor of the Dead Sea. A discrimination of the salinization mechanisms is important to develope reasonable measures to limit or lower the salt concentration in the affected wells. Consequently, the relevant measured but also potential main hydrochemical indicators and isotope tracers are identified. The large uncertainties with respect to the establishment of a well-founded water balance and to the insuffcient knowledge about the geology of the small-scale area of Jericho are discussed. Because the interpretation of the measured helium samples from the fractured and karstified aquifer of the Cretaceous Judea Group is limited, the dependencies of the He-4 accumulation in groundwater in an idealized dual-continuum aquifer are investigated with respect to the relation of the He-4 mass fluxes and the system response time to the varied parameters (groundwater head gradient, hydraulic conductivities, dispersivities, porosities) by means of a sensitivity analysis. Although the system response time is not a system variable as such it clearly turned out that knowledge about it may be an important information for the interpretation of He concentrations in groundwaters of non-stationary systems. To enhance the visual post-processing of the parameter sensitivity analysis an easily interpretable way of data presentation is introduced.:Impressum Kurzfassung Abstract List of Figures List of Tables Introduction Geology and hydrogeological background Theory and application of environmental tracers to characterize groundwater flow Methodology Results Summary Conclusions / Semiaride und aride Gebiete stellen aufgrund des niedrigen oder ungünstig verteilten Niederschlagsdargebots eine besondere Herausforderung bezüglich Erkundung, Bereitstellung, nachhaltiger Nutzung und Schutz sich neu bildender, aber auch fossiler Wasserresourcen dar. Abgesehen von wenigen natürlichen oder künstlich angelegten Oberflächenreservoiren ist der poröse Untergrund dabei gleichzeitig Hauptspeicher und Transportmedium für Wasser und bietet einen Schutz gegen Verdunstung und bis zu einem gewissen Grade gegen oberflächig einwirkende Verunreinigungen. Diese Situation ist charakteristisch für den Nahen Osten und damit für die im Rahmen der vorliegenden Arbeit beschriebenen Teiluntersuchungsgebiete, die sich in Israel und der West Bank befinden. Die Arbeit behandelt drei Hauptthemen. Einerseits geht sie auf die Charakterisierung der Jungwasseranteile im Abfluß vier bedeutender Quellen des Wadi Qilts und Jerichos sowie in beprobten tiefen Brunnen dreier wichtiger Brunnenfelder ein. Alle diese Objekte entwässern bzw. entnehmen Wasser aus dem Oberen oder Unteren Judea Group Aquifer. Mit ca. 750 m Mächtigkeit stellt dieser eines der bedeutensten Grundwasserreservoire der Region dar und besteht hauptsächlich aus unterschiedlich stark verkarsteten und gestörten Kalkstein- und Dolomitformationen, welche zwischen dem Senon und Eozän in Form einer in sich weiter gegliederten, beid-seitig abtauchenden Doppelantiklinalstruktur herausgehoben wurde (Hebron und Ramallah bzw. Judea und Samaria Mountains). Die Grundwasserneubildung ist beschränkt auf die Zeit zwischen Oktober und April sowie auf die Kammlagen des Gebirges, wo die sonst bedeckten Schichten des Aquifers ausstreichen. Es wurde eine Strategie entwickelt, die eingesetzten Tracer auf ähnliche Weise mit Hilfe von Lumped Parameter-Modellen für alle Lokationen zu interpretieren und somit eine Vergleichbarkeit zu gewährleisten. Andererseits untersucht die Arbeit Versalzungsprozesse im Shallow Aquifer von Jericho und deren Abgrenzung untereinander. Mögliche Hauptquellen der Versalzung sind durch überhöhte Grundwasserentnahme verstärke Zuflüsse von Solen, die Lösung von Salzen aus der Lisan-Formation oder Formationswässer der Lisan-Formation, welche die Ablagerungen des Lisan-Sees, des Pleistozänen Vorgängers des heutigen Toten Meeres, repräsentieren. Eine Unterscheidung der Mechanismen hat dabei durchaus Bedeutung für die Festlegung geeigneter Gegenmaßnahmen. Demzufolge werden die ermittelten, aber auch weitere, potentielle hydrochemische Hauptindikatoren und Tracer benannt. Unsicherheiten sowohl hinsichtlich der Aufstellung einer Wasserbilanz, als auch einer unzureichend bekannten Geologie für das sehr kleinräumige Gebiet von Jericho werden diskutiert.:Impressum Kurzfassung Abstract List of Figures List of Tables Introduction Geology and hydrogeological background Theory and application of environmental tracers to characterize groundwater flow Methodology Results Summary Conclusions

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