Global change is a major threat to local groundwater resources. Climate change and population growth are factors that directly or indirectly augment the increasing uptake of groundwater resources. To outbalance the pressure on aquifers, managed aquifer recharge (MAR) schemes are increasingly being implemented. They enable the subsurface storage of surplus water for times of high demand. The complexity of MAR schemes makes their planning and implementation multifaceted and requires a comprehensive assessment of the local hydrogeological and hydrogeochemical conditions. Despite the fact that MAR is a widely used technique, its implementation is not well regulated and comprehensive planning and design guidelines are rare. The use of supporting tools, such as numerical and physical models or geographic information systems (GIS), is rising for MAR planning but their scope and requirements for application are rarely reflected in the available MAR guidelines. To depict the application potential and the advantages and disadvantages of the tools for surface infiltration MAR planning, this thesis comprises reviews on the past use of the tools as well as suggestions to improve their applicability for MAR planning. GIS is not mentioned by most MAR guidelines as a planning tool even though it is increasingly being used for MAR mapping. Through a review of GIS-based MAR suitability studies, this thesis shows that the MAR mapping process could be standardized by using the often-applied approach of constraint mapping, suitability mapping by using pairwise comparison for weight assignment and weighted linear combination as a decision rule, and a subsequent sensitivity analysis. Standardizing the methodology would increase the reliability and comparability of MAR maps due to the common methodological approach. Thus, the proposed standard methodology was incorporated into a web GIS that simplifies MAR mapping through a pre-defined workflow. Numerical models are widely used for the assessment of MAR schemes and are included into some MAR planning guidelines. However, only a few studies were found that utilized vadose zone models for the planning and design of MAR schemes. In this thesis, a review and a subsequent case study highlight that numerical modelling has many assets, such as monitoring network design or infiltration scenario planning, that make its utilization during the MAR planning phase worthwhile. Consequently, this study advocates the use of vadose zone models for MAR planning by showing their potential areas of application as well as their uncertainties that need to be regarded carefully during modelling. Physical models used for MAR planning are typically field or pilot sites, as some MAR legislation requests pilot sites as part of the preliminary assessment. Laboratory experiments are used less often and are mostly restricted to the analysis of very specific issues, such as clogging. This thesis takes on the issue of scaling laboratory results to the field scale by comparing results from three physical models of different scales and dimensionality. The results indicate that preferential flow paths, air entrapment and boundary influence limit the quantitative validity of laboratory experiments. The use of 3D tanks instead of 1D soil columns and the application of statistical indicators are means to increase the representativeness of laboratory measurements. Nevertheless, physical models have the potential to improve MAR planning in terms of detailed process assessment, scenario and sensitivity analyses. All tools discussed in this thesis have their merits for MAR scheme planning and should be advocated better in MAR guidelines by depicting their application potential, advantages and disadvantages. The information accumulated in this thesis is a step towards an advanced use of supporting tools for the planning and design of MAR schemes.:1 Introduction 1.1 Motivation 1.2 Objectives 1.3 Structure of the thesis 2 Status quo of the planning process of MAR schemes 2.1 Guidance documents on general MAR planning 2.2 Application of GIS, numerical and physical models for MAR planning 2.3 Planning of surface infiltration schemes 3 Using GIS for the planning of MAR schemes 3.1 Implications from GIS-MCDA studies for MAR mapping 3.2 Development of web tools for MAR suitability mapping 4 Using numerical models for the planning of MAR schemes 4.1 Review on the use of numerical models for the design and optimization of MAR schemes 4.2 Planning a small-scale MAR scheme through vadose zone modelling 5 Using physical models for the planning of MAR schemes 5.1 Design of the experimental study 5.2 Comparison of three different physical models for MAR planning 6 Discussion and research perspectives 7 Bibliography 8 Appendix / Der globale Wandel stellt eine große Bedrohung für die lokalen Grundwasserressourcen dar. Klimawandel und Bevölkerungswachstum sind Faktoren, die, direkt oder indirekt, die zunehmende Nutzung von Grundwasserressourcen verstärken. Um diesen Druck auf die Grundwasserleiter auszugleichen, werden verstärkt Maßnahmen zur gezielten Grundwasserneubildung (managed aquifer recharge = MAR) durchgeführt. Dies ermöglicht die unterirdische Speicherung von überschüssigem Wasser für Zeiten hohen Bedarfs. Die Komplexität von MAR-Anlagen macht ihre Planung und Umsetzung kompliziert und erfordert eine umfassende Bewertung der lokalen hydrogeologischen und hydrogeochemischen Bedingungen. Trotz der weltweiten Implementierung von MAR ist dessen Planung wenig reguliert. Umfassende Planungs- und Gestaltungsrichtlinien sind rar. Der Einsatz unterstützender Werkzeuge, wie numerischer und physikalischer Modelle oder Geoinformationssysteme (GIS), nimmt bei der MAR-Planung zu, aber ihre Einsatzmöglichkeiten und ihre Anforderungen an die Anwendung spiegeln sich selten in den verfügbaren MAR-Richtlinien wider. Um das Anwendungspotential und die Vor- und Nachteile der Werkzeuge für die MAR-Planung darzustellen, wurden für diese Arbeit Recherchen über den bisherigen Einsatz der Werkzeuge durchgeführt. Zusätzlich wurden Vorschläge zur Erhöhung ihrer Anwendbarkeit für die MAR Planung gemacht. Der Schwerpunkt lag dabei auf Oberflächeninfiltrationsverfahren. GIS wird in keiner MAR-Richtlinie als Planungsinstrument erwähnt, obwohl es zunehmend für die MAR-Kartierung eingesetzt wird. Eine Recherche über GIS-basierte MAR-Eignungsstudien zeigte, dass der MAR-Kartierungsprozess standardisiert werden kann mittels des oft genutzten Ansatzes: initiales Ausschneiden von Gebieten, welche Restriktionen unterliegen, dem folgend die Eignungskartierung mittels Paarvergleich für die Wichtung der GIS-Karten und der gewichteten Linearkombination als Entscheidungsregel, sowie eine abschließende Sensitivitätsanalyse. Die Standardisierung der Methodik könnte die Zuverlässigkeit und Vergleichbarkeit von MAR-Karten aufgrund des gemeinsamen methodischen Ansatzes erhöhen. Daher wurde die standardisierte Methodik in ein Web-GIS integriert, das über einen definierten Workflow die MAR-Kartierung vereinfacht. Numerische Modelle werden häufig für die Beurteilung von MAR-Systemen verwendet und sind in einigen MAR-Planungsrichtlinien ausgewiesen. Es wurden jedoch nur wenige Studien gefunden, die die Modelle der ungesättigten Zone für die Planung und Gestaltung von MAR Standorten verwendeten. Die in dieser Arbeit durchgeführte Literaturrecherche und eine darauf aufbauende Fallstudie zeigen, dass die numerische Modellierung viele Vorteile bietet, wie z. B. beim Design eines Monitoring-Netzwerkes oder bei der Planung von Infiltrationsszenarien. Physikalische Modelle, die für die MAR-Planung verwendet werden, sind meist Feld- oder Pilotversuche, da einige MAR-Gesetzgebungen Pilotstandorte im Rahmen der Vorabbewertung verlangen. Laborexperimente werden seltener eingesetzt und beschränken sich meist auf die Analyse sehr spezifischer Fragestellungen, wie z.B. der Kolmatierung. Diese Arbeit beschäftigt sich mit der Skalierbarkeit von Laborergebnissen auf die Feldskale, indem sie Ergebnisse aus drei physikalischen Modellen verschiedener Maßstäbe und Dimensionen vergleicht. Die Ergebnisse deuten darauf hin, dass Makroporen, Lufteinschlüsse und der Einfluss der Randbedingungen die quantitative Aussagekraft von Laborversuchen einschränken. Der Einsatz von 3D-Tanks anstelle von 1D-Bodensäulen oder von statistischen Indikatoren ist ein Mittel zur Erhöhung der Repräsentativität von Labormessungen. Nichtsdestotrotz hat die Anwendung physikalischerModelle das Potenzial, die MAR-Planung in Bezug auf detaillierte Prozessbewertung, Szenarien und Sensitivitätsanalysen zu unterstützen. Alle beschriebenen Instrumente haben ihre Vorzüge bei der Bewertung von MAR-Anlagen und sollten in MAR-Richtlinien detaillierter berücksichtigt werden, indem ihr Anwendungspotenzial, ihre Vor- und ihre Nachteile dargestellt werden. Die für diese Arbeit zusammengestellten Informationen sind ein Schritt zur Förderung der beschriebenen Planungsinstrumente für die Planung und Gestaltung von MAR-Anlagen.:1 Introduction 1.1 Motivation 1.2 Objectives 1.3 Structure of the thesis 2 Status quo of the planning process of MAR schemes 2.1 Guidance documents on general MAR planning 2.2 Application of GIS, numerical and physical models for MAR planning 2.3 Planning of surface infiltration schemes 3 Using GIS for the planning of MAR schemes 3.1 Implications from GIS-MCDA studies for MAR mapping 3.2 Development of web tools for MAR suitability mapping 4 Using numerical models for the planning of MAR schemes 4.1 Review on the use of numerical models for the design and optimization of MAR schemes 4.2 Planning a small-scale MAR scheme through vadose zone modelling 5 Using physical models for the planning of MAR schemes 5.1 Design of the experimental study 5.2 Comparison of three different physical models for MAR planning 6 Discussion and research perspectives 7 Bibliography 8 Appendix

Costa Rica’s annual mean precipitation is above 3300 mm, but this precipitation is not evenly distributed in time or space, producing clear differentiated wet and dry seasons in most of the country. Droughts are also common phenomena which greatly affect the availability of water resources. Managed aquifer recharge (MAR) schemes are being taken into consideration to enhance the underground water storage capacity of the country. The present study constitutes the first assessment for the identification of suitable sites for the implementation of MAR technology spreading methods (SM) in Costa Rica. The suitable sites are identified by means of a geographic information system multi-criteria decision analysis (GIS-MCDA) based on four criteria: hydrogeological aptitude, terrain slope, top soil texture and drainage network density. Four steps are performed in order to identify these sites: problem definition, screening for suitable areas, suitability mapping, and sensitivity analysis. The suitability map was divided in two zones after the screening: suitable and unsuitable, the first zone was further divided in five classes according to the weighted linear combination (WLC) ranking. The results indicate that 61% of the country is suitable for conducting SM. This map is a tool for future implementation of MAR techniques in the country.

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

Costa Rica’s annual mean precipitation is above 3300 mm, but this precipitation is not evenly distributed in time or space, producing clear differentiated wet and dry seasons in most of the country. Droughts are also common phenomena which greatly affect the availability of water resources. Managed aquifer recharge (MAR) schemes are being taken into consideration to enhance the underground water storage capacity of the country. The present study constitutes the first assessment for the identification of suitable sites for the implementation of MAR technology spreading methods (SM) in Costa Rica. The suitable sites are identified by means of a geographic information system multi-criteria decision analysis (GIS-MCDA) based on four criteria: hydrogeological aptitude, terrain slope, top soil texture and drainage network density. Four steps are performed in order to identify these sites: problem definition, screening for suitable areas, suitability mapping, and sensitivity analysis. The suitability map was divided in two zones after the screening: suitable and unsuitable, the first zone was further divided in five classes according to the weighted linear combination (WLC) ranking. The results indicate that 61% of the country is suitable for conducting SM. This map is a tool for future implementation of MAR techniques in the country.

O Aeroporto Internacional Governador André Franco Montoro (GRU), São Paulo, depende inteiramente da água subterrânea para suprir sua demanda. Entretanto, a prática de extração excessiva, que aumenta continuamente para atender à demanda de um número cada vez maior de passageiros e às dificuldades envolvidas com a recarga natural do aqüífero, levou a Empresa Brasileira de Infraestrutura Aeroportuária (Infraero) a procurar outras fontes de abastecimento. Embora a busca de solução para o problema da escassez da água, passe pela opção de recarga gerenciada do aqüífero, a falta da experiência nacional nessa área restringe a tomada da decisão na adoção dessa prática no país. Objetivando contribuir com estudos de viabilidade técnica da recarga gerenciada de aqüíferos em geral e, em particular, do Aeroporto Internacional Governador André Franco Montoro, este trabalho tem o objetivo de verificar, em escala piloto, a capacidade do solo-aqüífero do aeroporto em tratar adequadamente o esgoto gerado localmente. Para atingir esse objetivo, uma área adequada foi selecionada entre as diversas avaliadas, para a construção de uma unidade piloto de recarga de aqüífero. No local selecionado, amostras indeformadas da camada não saturada foram coletadas, caracterizadas e, posteriormente, montadas em colunas experimentais especiais, pelas quais o esgoto foi infiltrado de maneira controlada. Como os resultados desta primeira fase experimental não foram adequadamente atendidos, foi decidido efetuar coletas de amostras indeformadas em uma segunda área do aeroporto, que indicou a existência de uma camada vadosa mais profunda, mas perfil de solo semelhante ao perfil anterior. Os ensaios de colunas foram efetuados com amostras de ambas as áreas, indicando que o solo superficial do aeroporto deverá ser eliminado, ou substituído por uma camada de areia grossa para permitir uma recarga gerenciada que permita a produção de águas com qualidade adequada para os usos preconizados. Os diferentes cenários utilizados nesta pesquisa envolveram a infiltração nas colunas de recarga com esgotos secundários produzidos no aeroporto, após passagem por duas lagoas de retenção, a infiltração do mesmo efluente tratado por um processo físico-químico de coagulação/floculação/sedimentação e pelo mesmo efluente das lagoas de retenção após tratamento por um sistema de membranas de ultrafiltração. Os resultados obtidos são considerados como resultados parciais, uma vez que toda a profundidade do aqüífero não foi utilizada e pelo fato de que, face às restrições acadêmicas vigentes o tempo disponível para a realização da pesquisa foi extremamente restringido. Entretanto, considera-se este trabalho como pioneiro, pelo fato dele se constituir na primeira pesquisa sobre recarga gerenciada no Brasil e, ainda, por fornecer subsídios teóricos e práticos para suportar outros estudos semelhantes que se farão necessários para compreender e promover a prática de recarga gerenciada de aqüíferos no Brasil. / The Governor André Franco Montoro International Airport, São Paulo, entirely depends on groundwater to meet its demand. However, excessive extraction practice which increase continuously in order to attend the demand of increasing number of passengers and the difficulty involved with natural recharge of its aquifer led the Federal Airport Administration Agency (Infraero) to search for other sources of water supply. Although the search for solution for water scarcity problem goes through managed aquifer recharge, lack of national experience in this area restricts decision making in adopting this practice in the country. Contributing to the technical feasibility studies of managed aquifer recharge in general and the Governor André Franco Montoro International Airport in particular, this research has the objective of verifying at the pilot scale level, the capacity of airport soil-aquifer in adequately treating wastewater generated locally. In order to reach this objective, an adequate location was selected within the alternatives evaluated for the construction of a pilot unit for aquifer recharge. Undeformed samples were collected from the unsaturated layer of the selected place, characterized and afterwards, recharged through special experimental columns with wastewater which was filtered in a controlled form. As the results of the first experimental phase were not adequately met, a decision was made to collect undeformed samples from a second location in the airport. The collection indicated the existence of deep unsaturated layer with the soil profile being similar to the profile of the soil layer from which the first samples were collected. The soil column tests were carried out with samples from both areas, indicating that superficial part of airport soil will be eliminated or substituted with a coarse sandy layer in order to permit a managed aquifer recharge which allows production of water that meets the quality of its required uses. Of the different scenarios verified in this research was infiltration of secondary wastewater produced at the airport through soil columns. Another was infiltration of wastewater after its pre-treatment by physicalchemical processes of coagulation/flocculation/sedimentation and still a third scenario, through pre-treatment of secondary effluent by ultrafiltration membrane. The results obtained are considered partial since the total aquifer depth was not used and the fact that academic restrictions limited excessively the time period of the research. However, considering this as a pioneer work, and the fact that it constitutes the first research about managed aquifer recharge in Brazil, and with it, bringing theoretical and practical contributions to support other similar studies which would be necessary in understanding and promoting managed aquifer recharge practice in Brazil.

Dans un contexte global d'augmentation de la population, les réserves en eau des nappes phréatiques sont de plus en plus sollicitées. Pour pallier à cette exploitation, des systèmes d’infiltration artificiels ont été mis en place pour recharger les nappes avec de l’eau de surface. Néanmoins, ces systèmes subissent des pertes d’efficacité liées au colmatage du support d’infiltration par des processus physiques, chimiques ou biologiques. Face à ce phénomène, le travail de thèse a pour but de tester la faisabilité d’une technique d’ingénierie écologique par introduction d’un gastéropode, V. viviparus, pour limiter le colmatage de l’interface eau/sédiment de bassins d’infiltration utilisés pour recharger artificiellement l’aquifère sous-jacent au Rhône. Par des approches expérimentales, deux volets ont été abordés, (1) la dynamique des interactions biofilm/brouteur et les conséquences sur l’état physiologique du gastéropode et (2) la dynamique des interactions biofilm/gastéropode et les conséquences sur les propriétés hydrauliques et écologiques de l’interface eau/sédiment. Les résultats ont mis en évidence que (1) V. viviparus pouvait se maintenir dans les bassins d’infiltration aux différentes saisons, (2) V. viviparus pouvait limiter le colmatage biologique de l’interface eau/sédiment soit par ses actions trophiques (broutage), soit par des actions physiques (déplacement, pelletisation) et (3) V. viviparus n’a pas eu d’effet positif sur l’infiltration lorsque le colmatage était chimique. Pour conclure, V. viviparus apparait comme un bon candidat pour des solutions d’ingénierie écologique visant à restaurer des interfaces eau/sédiment, colmatées par un biofilm phototrophe. Ce travail ouvre des perspectives sur l’utilisation de solutions basées sur la nature à plus large échelle spatiale (e.g. pilote) et à des milieux naturels comme les zones humides / With the global increase of the population, groundwater reserves are increasingly exploited. To circumvent this problem, managed aquifer recharge systems using surface water are used worldwide. Nevertheless, the hydraulic performance of these systems is often altered by physical, chemical or biological clogging. This work aim to test the sustainability of ecological engineering solution based on the introduction of the gastropod, V. viviparus, to attenuate the clogging of the water/sediment interface of infiltration basins use for the recharge of the Rhône river aquifer. Two sections have been addressed with experimental approaches, (1) dynamic of biofilm/grazer interaction and its consequences on the physiological state of the gastropod and (2) dynamic of biofilm/grazer interaction and its consequences on the hydraulic and ecological properties of the water/sediment interface. Results show that (1) V. viviparus is able to survive in the infiltration basins at contrasted seasons, (2) V. viviparus can attenuate the biological clogging of the water/sediment interface, ether by trophic interaction (grazing) or physical actions (crawling activity, pelletization), and (3) V. viviparus has no positive effect on infiltration in case of chemical clogging. To conclude, V. viviparus appears to be a good candidate for ecological engineering solutions aiming to preserve and restore water/sediment interface impacted by biological clogging. This work provides useful information for the study of natured based solutions at larger scale (experimental pilot) and in natural ecosystems as wetlands

O Aeroporto Internacional Governador André Franco Montoro (GRU), São Paulo, depende inteiramente da água subterrânea para suprir sua demanda. Entretanto, a prática de extração excessiva, que aumenta continuamente para atender à demanda de um número cada vez maior de passageiros e às dificuldades envolvidas com a recarga natural do aqüífero, levou a Empresa Brasileira de Infraestrutura Aeroportuária (Infraero) a procurar outras fontes de abastecimento. Embora a busca de solução para o problema da escassez da água, passe pela opção de recarga gerenciada do aqüífero, a falta da experiência nacional nessa área restringe a tomada da decisão na adoção dessa prática no país. Objetivando contribuir com estudos de viabilidade técnica da recarga gerenciada de aqüíferos em geral e, em particular, do Aeroporto Internacional Governador André Franco Montoro, este trabalho tem o objetivo de verificar, em escala piloto, a capacidade do solo-aqüífero do aeroporto em tratar adequadamente o esgoto gerado localmente. Para atingir esse objetivo, uma área adequada foi selecionada entre as diversas avaliadas, para a construção de uma unidade piloto de recarga de aqüífero. No local selecionado, amostras indeformadas da camada não saturada foram coletadas, caracterizadas e, posteriormente, montadas em colunas experimentais especiais, pelas quais o esgoto foi infiltrado de maneira controlada. Como os resultados desta primeira fase experimental não foram adequadamente atendidos, foi decidido efetuar coletas de amostras indeformadas em uma segunda área do aeroporto, que indicou a existência de uma camada vadosa mais profunda, mas perfil de solo semelhante ao perfil anterior. Os ensaios de colunas foram efetuados com amostras de ambas as áreas, indicando que o solo superficial do aeroporto deverá ser eliminado, ou substituído por uma camada de areia grossa para permitir uma recarga gerenciada que permita a produção de águas com qualidade adequada para os usos preconizados. Os diferentes cenários utilizados nesta pesquisa envolveram a infiltração nas colunas de recarga com esgotos secundários produzidos no aeroporto, após passagem por duas lagoas de retenção, a infiltração do mesmo efluente tratado por um processo físico-químico de coagulação/floculação/sedimentação e pelo mesmo efluente das lagoas de retenção após tratamento por um sistema de membranas de ultrafiltração. Os resultados obtidos são considerados como resultados parciais, uma vez que toda a profundidade do aqüífero não foi utilizada e pelo fato de que, face às restrições acadêmicas vigentes o tempo disponível para a realização da pesquisa foi extremamente restringido. Entretanto, considera-se este trabalho como pioneiro, pelo fato dele se constituir na primeira pesquisa sobre recarga gerenciada no Brasil e, ainda, por fornecer subsídios teóricos e práticos para suportar outros estudos semelhantes que se farão necessários para compreender e promover a prática de recarga gerenciada de aqüíferos no Brasil. / The Governor André Franco Montoro International Airport, São Paulo, entirely depends on groundwater to meet its demand. However, excessive extraction practice which increase continuously in order to attend the demand of increasing number of passengers and the difficulty involved with natural recharge of its aquifer led the Federal Airport Administration Agency (Infraero) to search for other sources of water supply. Although the search for solution for water scarcity problem goes through managed aquifer recharge, lack of national experience in this area restricts decision making in adopting this practice in the country. Contributing to the technical feasibility studies of managed aquifer recharge in general and the Governor André Franco Montoro International Airport in particular, this research has the objective of verifying at the pilot scale level, the capacity of airport soil-aquifer in adequately treating wastewater generated locally. In order to reach this objective, an adequate location was selected within the alternatives evaluated for the construction of a pilot unit for aquifer recharge. Undeformed samples were collected from the unsaturated layer of the selected place, characterized and afterwards, recharged through special experimental columns with wastewater which was filtered in a controlled form. As the results of the first experimental phase were not adequately met, a decision was made to collect undeformed samples from a second location in the airport. The collection indicated the existence of deep unsaturated layer with the soil profile being similar to the profile of the soil layer from which the first samples were collected. The soil column tests were carried out with samples from both areas, indicating that superficial part of airport soil will be eliminated or substituted with a coarse sandy layer in order to permit a managed aquifer recharge which allows production of water that meets the quality of its required uses. Of the different scenarios verified in this research was infiltration of secondary wastewater produced at the airport through soil columns. Another was infiltration of wastewater after its pre-treatment by physicalchemical processes of coagulation/flocculation/sedimentation and still a third scenario, through pre-treatment of secondary effluent by ultrafiltration membrane. The results obtained are considered partial since the total aquifer depth was not used and the fact that academic restrictions limited excessively the time period of the research. However, considering this as a pioneer work, and the fact that it constitutes the first research about managed aquifer recharge in Brazil, and with it, bringing theoretical and practical contributions to support other similar studies which would be necessary in understanding and promoting managed aquifer recharge practice in Brazil.

No description available.

[Truncated abstract] Managed Aquifer Recharge (MAR) is a technique that can be used to capture and store water in aquifers for later reuse. This method recycles water that would normally be lost or discarded to the environment. MAR has been observed to have the potential for improving the quality of recharged water through a combination of physical, chemical and biological processes. The aim of this study was to investigate the changes in groundwater microbial population structure during MAR and the major influences that drive these population changes. Biogeochemical MAR studies have the potential to assist in the improved prediction of the removal of contaminants such as nutrients, pathogens and trace organics from the recharged water. Biological clogging during recharge also has the potential to overwhelm an aquifers ability to process wastewater thus reducing the hydraulic conductivity of the aquifer. Therefore further research into the spatial and temporal biogeochemical processes that occur during MAR is required. The geochemical and microbial population dynamics of two contrasting MAR techniques were investigated at two different geographical locations (Perth, Western Australia and Adelaide, South Australia). These MAR sites contained aquifers of dissimilar properties that were recharged with wastewater that contrasted in water quality. The Perth MAR site received secondary treated effluent which continuously infiltrated the unsaturated zone into an unconfined aquifer aided by infiltration galleries. Reclaimed water was extracted from a well at distance from the infiltration gallery. ... Notably the background and recovered water was most dissimilar in microbial and chemical population structure to that described for the infiltration gallery and injection well. Microbial and chemical evidence suggested that the background and extraction well groundwater were unaffected by plume migration. These results suggested that extraction well groundwater was similar in quality to that of ambient groundwater. Significant geochemical and microbial changes of secondary treated effluent during infiltration and lateral movement through aquifer were implicated in addition to the forced hydraulic gradient created from extracting fives time the volume of infiltrating wastewater. This study demonstrated that microbial populations and the geochemical processes associated with MAR can be studied and compared. Multivariate statistical methodology greatly simplified a vast array of dynamic biogeochemical information that could be dissected for meaningful interpretation over distance and time. The study evaluated the major biogeochemical influences which resulted in microbial and geochemical changes where it was noted that microbial populations were more dynamic than geochemical variation over time. Additionally biogeochemical comparative analysis indicated that microbial populations could change in population structure before a shift in aquifer geochemistry was detected. It is anticipated that the results from this study will benefit further research into the biogeochemical processes involved in water quality changes (e.g. nutrient removal, pathogen decay and biodegradation of trace organics) as well as controlling biological clogging of MAR schemes.