Dissertations / Theses on the topic 'Recharge'

Public water policy decision making tends to be too complex and dynamic to be described fully by traditional, rational models. Information intended to improve decisions often is rendered ineffective by a failure to understand the process. An alternative, holistic description of how such decisions actually are made is presented here and illustrated with a case study. The role of information in the process is highlighted. Development of a Regional Recharge Plan for Tucson, Arizona is analyzed as the case study. The description of how decisions are made is based on an image of public water policy decision making as 1) a structured, nested network of individuals and groups with connections to their environment through their senses, mediated by their knowledge; and 2) a nonlinear process in which decisions feed back to affect the preferences and intentions of the people involved, the structure of their interactions, and the environment in which they operate. The analytical components of this image are 1) the decision makers, 2) the relevant features of their environment, 3) the structure of their interactions, and 4) the products or outputs of their deliberations. Policy decisions analyzed by these components, in contrast to the traditional analysis, disclose a new set of relationships and suggest a new view of the uses of information. In context of information use, perhaps the most important output of the decision process is a shared interpretation of the policy issue. This interpretation sets the boundaries of the issue and the nature of issue-relevant information. Participants are unlikely to attend to information incompatible with the shared interpretation. Information is effective when used to shape the issue interpretation, fill specific gaps identified as issue-relevant during the process, rationalize choices, and reshape the issue interpretation as the issue environment evolves.

Public water policy decision making tends to be too complex and dynamic to be described fully by traditional, rational models. Information intended to improve decisions often is rendered ineffective by a failure to understand the process. An alternative, holistic description of how such decisions actually are made is presented here and illustrated with a case study. The role of information in the process is highlighted. Development of a Regional Recharge Plan for Tucson, Arizona is analyzed as the case study. The description of how decisions are made is based on an image of public water policy decision making as 1) a structured, nested network of individuals and groups with connections to their environment through their senses, mediated by their knowledge; and 2) a nonlinear process in which decisions feed back to affect the preferences and intentions of the people involved, the structure of their interactions, and the environment in which they operate. The analytical components of this image are 1) the decision makers, 2) the relevant features of their environment, 3) the structure of their interactions, and 4) the products or outputs of their deliberations. Policy decisions analyzed by these components, in contrast to the traditional analysis, disclose a new set of relationships and suggest a new view of the uses of information. In context of information use, perhaps the most important output of the decision process is a shared interpretation of the policy issue. This interpretation sets the boundaries of the issue and the nature of issue-relevant information. Participants are unlikely to attend to information incompatible with the shared interpretation. Information is effective when used to shape the issue interpretation, fill specific gaps identified as issue-relevant during the process, rationalize choices, and reshape the issue interpretation as the issue environment evolves.

This dissertation presents the results of a detailed physical and hydrogeophysical study of two soil-filled sinkholes mantled by ancient New River fluvial terrace deposits. Research was performed at the Virginia Tech Kentland Experimental Farms in Whitethorne, Virginia, USA between fall 2003 and spring 2007, and focused on characterizing infiltration, deep drainage, and recharge through soil-filled sinkholes. Using hydrogeophysical methods, the spatial and temporal distribution of soil moisture was modeled and potential recharge was quantified in two soil-filled sinkholes. Access-tube time domain reflectometry (TDR) was used to derive one-dimensional (1-D) soil moisture profiles. During access-tube installation, 470 soil samples were obtained from depths between 0.3 and to 9.0 m and characterized both physically and chemically. Using these data, a TDR calibration method was developed. Physio-chemical, TDR moisture, and 1-D electrical resistivity tomography (ERT) data were used to derive a numerically optimized form of Archieâ s Law which was used to convert ERT measurements into volumetric soil moisture. These results led to development of 2-D ERT-derived distributions of soil moisture in three transects across the two sinkholes in two terraces. Potential recharge was quantified using time-series ERT data with comparison to modeled cumulative potential evapotranspiration (PET) and cumulative precipitation between May 17 and October 9, 2006. The patterns of ERT-derived potential recharge values compared well with those expected from PET and precipitation data. Over the monitoring period from late spring to early fall during this study, results showed that a period of intense rain followed by a 31-day period of consistent rain, in which the rate of precipitation was equal to or exceeded PET, were the only periods in which significant amounts of potential recharge occurred (from 19 to 31% of cumulative precipitation during the study). Spatial distributions of ERT-derived moisture clearly revealed that significant amounts of infiltration occurred on sinkhole flanks and bottoms. Runoff during periods of intense rain flowed to the topographically lowest point in the sinkholes where it infiltrated and resulted in localized zones of enhanced infiltration and potential recharge to the water table.
Ph. D.

In the city of Barcelona and the townships situated in the deltaic area of the Besòs River, groundwater is recognized as an aspect of urban water cycle management. There is groundwater seepage into infrastructure and buildings that in turn require drainage, a part of which is introduced into sewage systems. Sensitized by this issue, city councils have had hydrologic studies carried out to analyze its causes and to plan alternative ways of using these resources while reducing treatment costs, and minimizing the impacts that groundwater and drainage have on infrastructure and vice versa. Based on these studies, and starting in 2000 some of this has been used for municipal practices (garden irrigation and street cleaning). Subsequently, due to a drought that affected the region between April 2007 and January 2009, the government entity in charge of Catalonian water sources (ACA) aims to get greater use out of urban groundwater in this area. This requires a comprehensive understanding of the hydrogeological characteristics of the environment, the availability and quality of these resources, and the appropriate tools for proper assessment and management. This has been the framework of this thesis. Recharge is one of the most relevant aspects of water balance in aquifer systems in urban areas. Urbanization of the area alters the natural hydrological cycle and direct water recharge into aquifers by infiltration is reduced. In turn, evapotranspiration decreases and new recharge sources appear. This thesis presents, first, a methodology that allows for the quantifying of variability in space and time of the recharge in urban areas. Potential sources of recharge that have been considered are: (1) direct infiltration from rain and urban runoff, (2) losses from the sewer system, (3) losses from the water supply system, and (4) other specific sources of recharge (i.e. river infiltration, seawater intrusion, etc.). Recharge calculations are initially performed by applying analytical equations under various hypotheses. These results have been evaluated in the hydrogeological context through a numerical model of flow and transport in the whole area of study. Secondly, detection of some substances in groundwater has been analyzed. These substances and their degradation products, potentially present in recharging sources associated with urban environments, belong to so-called 'emerging organic pollutants'. These are organic chemical compounds used in the formulation of daily products for widespread use, such as pharmaceuticals, emulsions, care products and personal hygiene, household and industrial detergents, plastics, pesticides and herbicides, among others. There is relatively little known about these substances¿ introduction to and evolution in the aquifers. Organic pollutants whose evolution and behavior in the groundwater is better understood can be degraded by natural processes controlled mainly by oxidation-reduction reactions. Even in situ stimulation techniques have been developed which are able to accelerate these processes of natural attenuation of contaminated environments. A methodology is presented using an end-member mixing analysis (EMMA) and MIX to compute mixing ratios and identify hydrochemical reactions. The methodology consists of (1) identifying the potential sources of recharge, (2) characterising recharge sources and mixed water samples using hydrogeochemistry, (3) selecting chemical species to be used in the analysis and (4) calculating mixing ratios and when departures from the mixing line exist, identifying hidrochemical processes. This approach has been applied in a pilot area in the Besòs River Delta.
En la ciudad de Barcelona y municipios ubicados sobre los terrenos deltaicos del río Besòs, el agua subterránea es un factor que se tiene en cuenta en la gestión urbana del ciclo del agua. La filtración de aguas subterráneas en edificios e infraestructuras obliga el drenaje de estas aguas, parte de las cuáles son vertidas a la red de alcantarillado. Sensibilizados por esta problemática las administraciones implicadas encargaron estudios hidrogeológicos para analizar las causas y plantear alternativas para el aprovechamiento de estos recursos, reducir los costes del tratamiento, así como minimizar los impactos que las aguas subterráneas y drenajes puedan causar a las infraestructuras y viceversa. A raíz de estos estudios y desde el año 2000, parte de éstas se destinan a usos municipales (riego de jardines y limpieza de calles). Posteriormente y debido a un período de sequía que afectó desde abril de 2007 a enero de 2009, la entidad gestora de los recursos hídricos de Cataluña (Agència Catalana de l'Aigua, ACA) planteó un mayor aprovechamiento de los recursos de agua subterránea en este entorno urbano. Esto requiere un buen conocimiento de las características hidrogeológicas del medio, de la disponibilidad y calidad de estos recursos, así como de disponer de las herramientas adecuadas para su evaluación y correcta gestión. Esta tesis se enmarca en este contexto. La recarga es uno de los aspectos más relevantes del balance hídrico en los sistemas acuíferos de zonas urbanas. La urbanización del territorio altera el ciclo hidrogeológico natural, la recarga directa de agua a los acuíferos por infiltración se reduce, disminuye la evapotranspiración y aparecen nuevas fuentes de recarga. En esta tesis se presenta, en primer lugar, una metodología para cuantificar la variabilidad espacial y temporal de la recarga en zona urbana. Las fuentes potenciales de recarga que se han considerado son: (1) infiltración directa de lluvia y de agua de escorrentía, (2) pérdidas del sistema de alcantarillado, (3) pérdidas de la red de abastecimiento y (4) otras fuentes específicas de recarga como la infiltración de agua de río o la intrusión marina, entre otras. El cálculo de la recarga se ha realizado inicialmente definiendo y aplicando ecuaciones analíticas bajo diversas hipótesis. Estos resultados se han evaluado en el contexto hidrogeológico mediante un modelo numérico de flujo y transporte en toda la zona de estudio. En segundo lugar se analiza la presencia en las aguas subterráneas de algunas sustancias potencialmente presentes en fuentes de recargas asociadas a entornos urbanos, y de las que se tiene relativo poco conocimiento de su introducción y evolución en los acuíferos. Estas substancias o sus productos de degradación pertenecen a los denominados "contaminantes orgánicos emergentes"; se tratan de compuestos químicos orgánicos empleados en la formulación de productos de uso cotidiano y muy extendido, como son productos farmacéuticos, emulsiones, productos para el cuidado e higiene personal, detergentes domésticos e industriales, plásticos, pesticidas y herbicidas, entre otros. Contaminantes orgánicos cuya evolución y comportamiento en las aguas subterráneas es más conocido, pueden degradarse mediante procesos naturales controlados principalmente por procesos de oxidación-reducción. Incluso se han desarrollado técnicas de estimulación in-situ capaces de acelerar estos procesos de atenuación natural sobre medios contaminados. Se presenta una metodología para la evaluación de porcentajes de mezcla e identificación de procesos hidroquímicos. Para ello se emplean procedimientos y herramientas estadísticas. Esta metodología se ha aplicado a las aguas del río Besòs y las aguas subterráneas de una zona piloto en el Delta del Besòs.
En la ciutat de Barcelona i municipis ubicats sobre els terrenys deltaics del riu Besòs, l’aigua subterrània és un factor que es té en compte en la gestió urbana del cicle de l’aigua. La filtració d’aigües subterrànies en edificis i infraestructures obliguen el seu drenatge, una part de les quals s’aboquen a la xarxa de clavegueram. Sensibilitzats per aquesta problemàtica els ajuntaments implicats van encarregar estudis hidrogeològics per analitzar les causes i plantejar alternatives per l’aprofitament d’aquests recursos, reduir els costos del tractament, així com minimitzar els impactes que les aigües subterrànies i drenatges poden causar a les infraestructures i viceversa. A arrel d’aquest estudis i des de l’any 2000, part d’aquestes aigües es destinen a usos municipals (reg de jardins i neteja de carrers). Posteriorment i degut a un període de sequera que va afectar des de l’abril de 2007 fins gener de 2009, l’entitat gestora dels recursos hídrics de Catalunya (Agència Catalana de l’Aigua, ACA) va plantejar un major aprofitament d’aquests recursos d’aigua subterrània en aquest entorn urbà. Això requereix un bon coneixement del medi hidrogeològic, de la disponibilitat i qualitat, així com de les eines adequades per a la seva correcta avaluació i gestió. Aquest és el context en que emmarca aquesta tesis. La recarrega és un dels aspectes més rellevants del balanç hídric en els sistemes aqüífers de zones urbanes. La urbanització del territori altera el cicle hidrogeològic natural, la recàrrega directa d’aigua als aqüífers per infiltració es redueix, disminueix l’evapotranspiració i apareixen noves fonts de recàrrega. En aquesta tesis es presenta, en primer lloc, una metodologia per a quantificar la variabilitat espaial i temporal de la recàrrega en zona urbana. Les fonts potencials de recàrrega que s’han considerat són: (1) infiltració directa de pluja i aigua d’escorrentia, (2) pèrdues del sistema de clavegueram, (3) pèrdues de la xarxa d’abastament i (4) altres fonts específiques de recàrrega com infiltració d’aigua del riu o intrusió marina, entre altres. El càlcul de la recàrrega s’ha realitzat inicialment definint i aplicant equacions analítiques sota diverses hipòtesis. Aquests resultats s’han avaluat en el context hidrogeològic mitjançant un model numèric de flux i transport en tota la zona d’estudi. En segon lloc, també en tota la zona d’estudi, s’analitza la presència en les aigües subterrànies d’algunes substàncies potencialment presents en fonts de recàrrega associades a entorns urbans, i de les que es té relativament poc coneixement de la seva introducció i evolució en els aqüífers. Aquestes substàncies o els seus productes de degradació pertanyen als denominats ‘contaminants orgànics emergents’; es tracten de compostos químics orgànics emprats en la formulació de productes d’ús quotidià i molt estès, com són productes farmacèutics, emulsions, productes per la cura e higiene personal, detergents domèstics i industrials, plàstics, pesticides y herbicides, entre altres. Contaminants orgànics, l’evolució i comportament dels quals en les aigües subterrànies és més conegut, poden degradar-se mitjançant processos naturals controlats principalment per processos d’oxidació-reducció. Inclús s’han desenvolupat tècniques d’estimulació in-situ capaces d’accelerar aquests processos d’atenuació natural sobre medis contaminats. En una línea preliminar de detecció de processos d’atenuació es presenta, en tercer lloc, una metodologia que permet l’avaluació de percentatges de mescla e identificació de processos hidroquímics. Aquesta empra procediments i eines estadístiques. Consisteix en (1) identificació de las potencials fonts de recàrrega, (2) caracterització de les fonts de recàrrega i les mescles d’aigua emprant espècies químiques, (3) selecció de les especies químiques que van a ser emprades en l’anàlisi i (4) càlcul dels percentatges de mescla i identificació de processos hidroquímics d’aquells que es separen de la línea de mescla. Aquesta metodologia s’ha aplicat a les aigües del riu Besòs i les aigües subterrànies d’una zona pilot en el Delta del Besòs.

The estimation of mountain-front recharge to regional aquifers is approached from a hydroclimatic standpoint. Analytical models of the seasonal water yield and streamflow are developed in this dissertation. These models are specialized for hard-rock mountainous watersheds where deep percolation occurs through fractures exclusively. Input variables are considered to be stochastic, and a relationship between precipitation and surface runoff is derived by using a deterministic physical process. Streamflow models for the summer and winter rainy seasons are developed separately in terms of known parameters of the storm process and unknown parameters of the physical process. The winter model considers the generation of surface runoff from both rainfall and snowmelt. These models include the long-term effective subsurface outflow from the mountainous watershed, or mountain-front recharge, as one of the parameters to be identified. The parameter estimation problem is posed in the framework of maximum likelihood theory, where prior information about the model parameters and a suitable weighting scheme for the error terms in the estimation criterion are included. The issues of model and parameter identifiability, uniqueness and stability are addressed, and strategies to mitigate identifiability problems in our modeling are discussed. Finally, the seasonal streamflow models are applied to three mountainous watersheds in the Tucson basin, and maximum likelihood estimates of mountain-front recharge and other model and statistical parameters are obtained. The analysis of estimation errors is performed in both the eigenspace and the original space of the parameters.

En las últimas décadas la literatura se ha centrado en la estimación de la recarga natural y los parámetros que la controlan, incluyendo clima, vegetación, suelo, y topografía. Por el contrario, pocos son los trabajos centrados en la recarga de acuíferos a partir de zonas cultivadas intensamente regadas. Aunque estos han mejorado la compresión sobre el proceso de recarga, todavía resultan incompletos a la hora de estimarla a partir del mencionado uso de suelo. En este contexto, los objetivos de esta tesis son: (i) mejorar la compresión de la recarga a partir de zonas intensamente regadas, y (ii) proporcionar nuevas herramientas para su caracterización. Algunas de las metodologías proporcionadas pueden ser fácilmente reproducidas por profesionales para inferir información cuantitativa.
Ensayos en campo, incluyendo diferentes tipos de cultivo y prácticas agrícolas, son llevados a cabo en al área del Campo de Cartagena, sureste de España, una región semi-árida donde la agricultura intensiva es el principal uso de suelo. El desarrollo de metodologías con observaciones en el medio saturado y no saturado, junto con la modelación numérica, fueron usados para mejorar la compresión de los procesos que controlan la recarga a partir de zonas intensamente regadas. Las aproximaciones desarrolladas pueden ser resumidas como sigue:

Ensayo de campo a lo largo de seiscientos días bajo cultivos hortícolas anuales y riego por goteo. La distribución del contenido de agua en la zona de raíces y bajo esta fue simulada considerando un modelo de flujo no saturado. El contenido de agua y la succión fueron medidos a diferentes profundidades y empleados para la calibración y validación del modelo.

Ensayo de trazador (tritio) en campo en una parcela experimental con riego por goteo y cultivos hortícolas anuales durante cuatrocientos treinta días. El movimiento de trazador a lo largo del perfil de suelo fue simulado considerando transporte multifásico. Los perfiles de concentración de trazador, a partir de un espaciado y limitado número de muestras destructivas, fueron usados para calibrar y validar el modelo.


Experimento de larga duración (nueve años hidrológicos) para diferentes tipos de cultivo: cultivos hortícolas anuales, cultivos hortícolas perennes y árboles frutales. La recarga producida por cada tipo de cultivo fue estimada a partir del balance de agua en suelo, zona no saturada y acuífero. Las fluctuaciones del nivel freático registradas a lo largo del mencionado periodo fueron usadas para calibrar y validar el modelo. Esta experiencia permitió evaluar la fiabilidad de las estimaciones de recarga a partir de las otras dos metodologías previas (a corto plazo) para el tipo de cultivo coincidente (cultivos hortícolas anuales).

Para las tres aproximaciones, el cubrimiento de suelo por las plantas y el crecimiento de raíces han sido incluidos en la condición de contorno superior. La evapotranspiración se ha dividido en evaporación y transpiración como una función del índice de área de hoja, y es limitada por el contenido de agua en el suelo. La transpiración a su vez ha sido distribuida a través del perfil de suelo como una función del contenido de agua y profundidad de raíces.
Valores similares de recarga han sido obtenidos a partir de las tres técnicas, aunque el modelo de flujo no saturado la sobreestima ligeramente. La evapotranspiración real fue siempre más baja que la potencial, ya que el contenido de agua en suelo fue insuficiente para mantener la extracción de agua por parte de las raíces, a pesar de la alta frecuencia de riego. Aunque las prácticas agrícolas por parte de los agricultores son las correctas, con una alta eficiencia de riego, se obtuvieron altos valores de recarga. La lluvia es distribuida de manera irregular en unos pocos eventos intensivos, algo por otro lado muy común en regiones semi-áridas, lo que contribuye de manera significativa a la percolación profunda, debido al constante alto contenido de humedad en el suelo.
In the past decades a large body of literature has focused on the assessment of the natural recharge and parameters of control (including climate, vegetation, soils, and topography). On the contrary, only few papers focused on aquifer recharge from intensively irrigated farmland. Although findings have improved the understanding of recharge phenomena, they still fail to characterize many features of aquifer recharge from the mentioned land use. In this context, the aims of this thesis are: (i) to improve the understanding of aquifer recharge from intensively irrigated farmland, and (ii) to provide new tools for its characterization. Also, this thesis provides a framework that can be easily used by practitioners to infer quantitative information.
Field tests, including different crop types and agricultural management, were carried out in the Campo de Cartagena area of southeast Spain, a semi-arid region where intensive irrigated agriculture is prevalent. The development of methodologies, with field observations in both saturated and unsaturated media, along with the application of numerical modelling were used to understand the processes governing the recharge from irrigated farmland. The developed approaches can be summarized as follows:

A field experiment with annual row crops and drip irrigation. Soil moisture dynamics through the root zone and below were simulated from unsaturated flow approach. Soil moisture and pressure head data at different depths were recorded along six hundred days for model calibration and prediction.

A tracer test (tritium) in field along four hundred thirty days. The test was carried out in an experimental plot with drip irrigation and annual row crops. The tracer transport in soil was simulated considering a multiphase approach. Tracer concentration profiles, from a limited and sparse number of destructive samples, were used to calibrate and validate the modelling approach.

A long-term field experiment (based on nine hydrologic years) for different crop types, annual row crops, perennial vegetables and fruit trees. The recharge produced from each crop type was estimated from a water balance approach, including soil, vadose zone and aquifer. Water table fluctuations, recorded along the mentioned period, were used for model calibration and predictions. This long-term approach permits to evaluate recharge estimates reliability of the two previous methodologies (short-term) for the type of crop overlapped (annual row crops).
For the three approaches, ground cover and root depth are assumed as upper boundary conditions. Evapotranspiration is allocated to evaporation and transpiration as a function of leaf-area-index and is limited by soil moisture content; transpiration is distributed through the soil profile as a function of soil moisture and root depth.

Similar recharge values have been obtained from the three techniques, although the unsaturated flow approach slightly overestimates values. Actual evapotranspiration was always lower than potential evapotranspiration, because soil moisture was insufficient to sustain the potential uptake, despite high irrigation frequency. Although the agricultural practices from farmers are sound, high irrigation efficiency, high recharge values are achieved. Rainfall is unevenly distributed into a few intensive events, likewise very common in semi-arid regions, and it meaningfully contributes to deep percolation, due to consistently high soil water content.

Storing freshwater in brackish aquifers using artificial recharge has been predicted (using a rigorous numerical modelling technique) to be a very beneficial water management alternative for Kuwait. Two possible practices of freshwater injection and recovery have been identified. First, through a seasonal cycle, desalination plants can operate at their optimum capacity all over the year irrespective of seasonal fluctuations in water demand, and also the aquifer yield can be increased at the same time. The optimum location for this storage is suggested to be the Shigaya-B well field, mainly because of the high specific injection rates of the injection wells, and its location in a highly depleted area. The other benefit of artificial recharge to Kuwait is using the aquifer as a long-term strategic reserve for freshwater to be used later during the emergency conditions. The Shigaya-A wellfield is suggested to be the optimum site for this storage, mainly because of the high freshwater recovery efficiency, and the sufficient depth of aquifer head allowing additional build-up inside the injection wells due to well face clogging. Using a sub-regional numerical model, the optimum management variables required to inject and recover freshwater at the two types of storages have been identified, including; number and geometry of injection/recovery wells, their injection/recovery rates, and the duration of injection necessary to recover the intended quantity and quality of freshwater. Also, the recovery efficiency of freshwater storage and recovery practice has been estimated. From an analysis of freshwater injection-withdrawals field experimental data (for a single well, SU-IO), using a single-well numerical model, it was possible to quantify the clogging factor, and differentiate between its different causes. It has been found that most of the clogging occurred due to air entrapment, and not due to the formation or recharge water properties. This means that clogging during this experiment is due to a fault in the injection system, and that well injection capacity is likely to be higher if this avoided. Further modelling was implemented to devise methods for minimising displacement and quality deterioration of the artificially-recharged freshwater mound, by the regional groundwater flow, if it is stored for a long time. The preferred methods involve operation of "hydraulic gradient-control" pumping wells outside the storage area to create a zone of zero hydraulic gradient ( stagnation zone) around the stored water mound. A management model using the response matrix approach was implemented to determine the optimum pumping rates of these wells necessary to produce the intended hydraulic gradient. By the time all the usable stored water is irrecoverable without these controls (after 4 years), it was possible using this technique to recover about 55 % of this water.

The potential of estimating steady recharge to deep unconfined aquifers by comparing observed water levels to the water levels produced by a series of simulated cases was examined. Finite-element simulations were performed on an idealized region to examine the sensitivity of the water table position to anisotropy, recharge, grid density, horizontal layering, and region geometry. The position of the water table was found to be particularly sensitive to region geometry, medium heterogeneity and anisotropy. A graphical method based on comparison of water levels at three observation points to simulated water levels produced a good estimate of dimensionless recharge and the anisotropy ratio. Determination of the absolute value of recharge requires accurate determination of region geometry and hydraulic conductivity so that computer simulations are representative. An analytical solution to the Boussinesq equation was found to give a poor estimate of water table position and hence recharge for this case.

The transformation of nitrogen in treated effluent during recharge at the Sweetwater Underground Storage and Recovery Facility was examined. The procedure consisted of obtaining samples of percolating water and groundwater below a 3.3 acre infiltration basin, carried out over the recharge season October 29, 1991 - May 23, 1992 and during an entire 4 day wetting/6 day drying cycle. Nitrate concentrations decreased in the profile and in groundwater throughout the season. During the wetting/drying cycle the nitrate level decreased from a maximum of over 20 mg/L NO₃⁻-N at a depth of 5 feet to about 10 mg/L NO₃⁻-N at 17 feet. Below 17 feet, the nitrate level remained approximately constant. A 36% reduction in total nitrogen concentration was observed between source water and groundwater. Results suggest that soil aquifer treatment (SAT) may be useful in reducing the total nitrogen concentration of effluent.

Le travail présenté dans cette thèse porte sur la conception des solutions de recharge à base d'énergie solaire pour des véhicules électriques. Les présents travaux ont pour but de concevoir et de réaliser des prototypes de station de recharge de véhicule électrique ainsi que de proposer des outils d'optimisation de fonctionnement de ces stations de recharge. Tout d'abord, nous avons présenté la méthode suivie pour la conception et la réalisation d'une station de recharge solaire mobile autonome. Ensuite, nous avons présenté une étude expérimentale de la station de recharge PV 16kWc. Cette étude expérimentale est étalée sur la période du Janvier - Août 2019. L'analyse des résultats de cette étude expérimentale permet de déduire que la station réalisée permet de produire une énergie de l'ordre de 10.8MWh par ans et permet d'éviter des émissions CO2 de l'ordre de 4.8 tonnes par ans. Nous avons aussi étudié la topologie de station de recharge avec bus bipolaire. Puisque les convertisseurs DC/DC trois-niveaux sont la partie la plus intéressante de cette topologie, nous avons détaillé la méthode suivie pour élaborer un modèle moyen petits-signaux. Ensuite, une analyse du contrôle d'équilibrage du bus bipolaire permet d'identifier la meilleure option à choisir pour garantir l'équilibrage du bus, ainsi qu'une nouvelle méthode d'équilibrage ont été présentées, cette dernière offre la possibilité d'équilibrage sans ajout de capteurs comme dans la méthode classique. Enfin, le principe de fonctionnement de l'unité de gestion d'énergie proposée pour cette topologie est présenté. Cette dernière à été évaluée en simulations
This thesis focuses on the design of solar-based charging solutions for electric vehicles. The purpose of this work is to design and produce prototypes of electric vehicle charging stations and to propose tools to optimize the operation of these charging stations. First of all, we presented the followed method for the design and construction of a stand-alone mobile solar charging station. Then we presented the conception of solar charging station of 16kWc. An experimental study is performed over the period of January - August 2019. The results analysis of this experimental study showed that the produced energy is of the order of 10.8MWh per year and avoids CO2 emissions of 4.8 tonnes per year. About 50 electric cars per months could be charged by solar energy. We also studied a topology of charging station with bipolar DC bus. Since the three-level DC/DC converters are the most important elements of this topology, we have detailed the followed method for small-signal modelling of these converters. Then, an analysis of the voltage balance control of the bipolar bus was carried out to identify the best option to choose to guarantee the balance of the bus and a new balancing method were presented. This last method offers the possibility of balancing the DC bus without adding extra sensors sensors as in the classical method. Finally, the operating principle of the energy management unit proposed for this topology is presented and evaluated in simulations

La Recàrrega Artificial d'aqüífers és una tècnica extremadamente poderosa per optimitzar la gestió dels recursos hídrics. De cara a eliminar actituds escèptiques respecte a la seva aplicabilitat en nombroses situacions, és essencial adquirir més coneixements sobre els conceptes quantitatius més importants. Un tema crític és el de la minimització de la colmatació en dispositius de recàrrega. Atesa la extraòrdinaria importància d'aquest problema, es va efectuar una intensa recerca bibliogràfica que permetés determinar els processos bàsics que tenen lloc en la colmatació de plantes de recàrrega. Això, juntament amb la informació de tipus tecnológic subministrada per gestors de plantes de recàrrega, ha permès proposar un model matemàtic conceptual que integra els processos principals: retenció de partícules en suspensió portades per l'aigua de recàrrega, precipitació de minerals, creixement bacterià, generació de gas y compactació. Amb l'ajuda dels codis ja existents, l'esmentat model fou posteriorment incorporat a un programa d'elements finits tridimensionals que és capaç de tractar els cinc processos citats. El programa ha estat aplicat a tres casos de laboratori i a un experiment de camp amb el fi d'establir la validesa del marc conceptual adoptat.

Aquesta tesi descriu els aspectes principals del model, els seus fonaments teòrics, la implementació numèrica i l'aplicació als exemples citats. La varietat de condicions simulades i els resultats aconseguits confirmen que el programa pot reproduir de forma satisfactòria una ampli ventall de problemes de colmatació, entre les quals s'inclouen sistemes superficials (bassas) i profunds (pous), flux radial i vertical, transport reactiu multicomponent, i d'altres. Això demostra la utilitat del programa per integrar dades de naturalesa completament diferente. A pesar de les limitacions inherents a tota formulació matemàtica, la modelació integrada proporciona estimacions quantitatives del potencial colmatant. Consegüentment, pot ser considerada com a una eina bàsica per al disseny i gestió de plantes de recàrrega i, eventualment, amb un fi predictiu.
La Recarga Artificial de acuíferos es una técnica extremadamente poderosa para optimizar la gestión de los recursos hídricos. De cara a eliminar actitudes escépticas respecto a su aplicabilidad en numerosas situaciones, es esencial adquirir más conocimientos sobre los conceptos cuantitativos más importantes. Un tema crítico es el de la minimización de la colmatación en dispositivos de recarga. Dada la extraordinaria importancia de este problema, se efectuó una intensa búsqueda bibliográfica que permitiera determinar los procesos básicos que tienen lugar en la colmatación de plantas de recarga. Esto, junto con la información de tipo tecnológico suministrada por gestores de plantas de recarga, ha permitido proponer un modelo matemático conceptual que integra los procesos principales: retención de partículas en suspensión en el agua de recarga, precipitación de minerales, crecimiento bacteriano, generación de gas y compactación. Con la ayuda de códigos ya existentes, dicho modelo fue posteriormente incorporado en un programa de elementos finitos tridimensional que es capaz de tratar los cinco procesos citados. El programa ha sido aplicado a tres casos de laboratorio y a un experimento de campo con el fin de establecer la validez del marco conceptual adoptado.

Esta tesis describe los aspectos principales del modelo, sus fundamentos teóricos, la implementación numérica y la aplicación a los ejemplos citados. La variedad de condiciones simuladas y los resultados logrados confirman que el programa puede reproducir de forma satisfactoria una amplia gama de problemas de colmatación, entre las que se incluyen sistemas superficiales (balsas) y profundos (pozos), flujo radial y vertical, transporte reactivo multicomponente, y otros. Esto demuestra la utilidad del programa para integrar datos de naturaleza completamente diferente. A pesar de las limitaciones inherentes a toda formulación matemática, la modelación integrada proporciona estimaciones cuantitativas del potencial colmatante. Por consiguiente, puede ser considerada como una herramienta básica de cara al diseño y gestión de plantas de recarga y, eventualmente, de cara a la predicción.
Artificial Recharge of groundwater is an extremely powerful technique to optimise the management of water resources. In order to eliminate sceptical misconceptions concerning its applicability to numerous situations, it is essential to gain insight into the fundamental quantitative concepts. A critical point is the minimisation of clogging of the recharge device. Given the extraordinary importance of this problem, an intensive bibliographic research was conducted to determine the basic processes underlying the clogging of recharge plants. This, in combination with technological information supplied by Artificial Recharge operators, allowed to propose a conceptual mathematical model that could integrate the main processes. Attachment of suspended solids carried by recharge water, mineral precipitation, bacterial growth, gas binding and compaction of the upper soil layer were found to be determinant in clogging development. Based on existing investigation codes, such model was implemented into a three-dimensional finite element code that is able to cope with the referred mechanisms. The code was applied to three laboratory cases and to one field experiment in order to assess the validity of the adopted framework.

This thesis includes the main concepts of the model, its theoretical background, numerical implementation and the application to the referred cases. The variety of simulated conditions and the results achieved with the model confirm that the code can reproduce successfully a wide range of clogging problems, including surface (basins) and deep (wells) systems, vertical and radial flow, multiphase transport and other options. This demonstrates the usefulness of the code to integrate data which are completely different in nature. In spite of the limitations inherent to all mathematical formulations, integrated modelling provides quantitative estimates of the clogging potential. Consequently, can be considered as a basic tool for design and management of recharge plants, and, eventually, for predictive purposes.

Kunskap om grundvattenbildningen är nödvändig för att man ska kunna förutsäga konsekvenserna av grundvattenuttag och underjordsbyggande. Grundvattenbildningen i berggrunden är dock svår att uppskatta. Syftet med avhandlingen var att öka förståelsen av grundvattenbildningen i kristallin berggrund, att undersöka hur grundvattenbildningen ska uppskattas samt att utveckla nya modeller för att beskriva grundvattenbildningen. Studien grundades på tre angreppssätt: grundvattendatering med freoner (CFC), geohydrauliska observationer och matematisk modellering.

Koncentrationerna av CFC-11 och CFC-113 befanns vara låga i det undersökta berggrundvattnet, vilket i kombination med låga syrgashalter tyder på anaerob nedbrytning. Koncentrationerna av CFC-12 och tritium överensstämde ganska väl, vilket betyder att den skenbara åldern kan vara den sanna åldern. Resultaten tyder på att CFC-datering inte är pålitlig i skogsmiljöer med finkornigt jordtäcke.

Vid nederbörd observerades ett snabbt gensvar i den hydrauliska potentialen i den studerade bergakviferen, trots det 10 m mäktiga moräntäcket. En avsevärd del av de observerade potentialvariationerna befanns vara belastningseffekter, som inte innebar någon magasinsförändring eller något vattenflöde. Berggrundens belastningseffektivitet uppskattades, ur potentialens svar på lufttrycksförändringar, till 0,95. Ytbelastningen beräknades från mätningar av lufttryck, vatten i jordtäcket och snö. Omkring 20 % av årstidsvariationen hos den hydrauliska potentialen uppskattades bero på enbart belastningsförändringar. En enkel begreppsmässig modell kunde användas för att simulera den observerade hydrauliska potentialen. För att beskriva enskilda grundvattenbildningstillfällen på bästa sätt var det nödvändigt att ta hänsyn till effekten av ytbelastningen.

Numeriska experiment gjordes med en modell av en jord–bergprofil. När berget modellerades som ett heterogent kontinuum bildades omättade zoner i berget vid stora hydrauliska gradienter. Fenomenet uppträdde i områden där låggenomsläppliga zoner låg uppströms höggenomsläppliga zoner, och ledde till minskad hydraulisk konduktivitet i berget.

Knowledge about the groundwater recharge is essential for the prediction of impacts of groundwater withdrawal and underground construction. Recharge in the bedrock is, however, difficult to estimate. The objectives of this thesis were to increase the understanding of groundwater recharge in crystalline bedrock, to investigate how the recharge could be estimated, and to develop new models to describe the recharge. The study was based on three approaches: groundwater dating using chlorofluorocarbons (CFCs), geohydraulic field measurements, and mathematical modelling.

Low concentrations of CFC-11 and CFC-113 were found in the bedrock groundwater, which in combination with low dissolved-oxygen levels indicated anaerobe degradation. The CFC-12 and tritium concentrations agreed fairly well, which means that apparent ages could be true ages. The results suggest that CFC dating may not be reliable at forested, humid sites covered by fine-grained soil.

A quick response in hydraulic head to precipitation was observed in the studied bedrock, despite the 10-m thick till cover. A substantial portion of observed head variations was found to be loading effects, involving no storage changes or water flow. The loading efficiency of the bedrock was estimated, from the air-pressure response, to be 0.95. The surface loading was calculated from measurements of air pressure, water in the soil, and snow. About 20% of the seasonal variation of the hydraulic head was estimated to be related to loading changes only. A simple conceptual model could be used to simulate the observed hydraulic heads. The loading effect had to be included to properly describe individual recharge events.

Numerical experiments were performed with a soil–bedrock profile. When the rock was modelled as a heterogeneous continuum, unsaturated zones developed at high hydraulic gradients. The phenomenon appeared in areas where low-conductive zones were located upstream of high-conductive zones, decreasing the effective hydraulic conductivity of the material.

Deteriorating water quality in the face of a rising demand for agricultural products triggered interest in the groundwater resources of the Najd dessert, an arid region of southern Oman. Groundwater in this area usually is abstracted from one of the largest aquifers on the Arabian Peninsula, the Umm Er Radhuma aquifer. Increased discharge stands in contrast to limited precipitation: the monsoon is an annual event but it is regionally limited; cyclones infrequently occur within the range of three to seven years. Both are possible sources for groundwater recharge in the Najd. With these preconditions in mind, the present study investigates recharge to the Najd groundwaters as part of an active flow system and evaluates the mean residence time in the deep groundwaters. The tools of choice are a groundwater flow model combined with environmental isotope tracer data. The two-dimensional flow model replicates the characteristics of the aquifer system from the potential recharge area in the south (Dhofar Mountains) to the discharge area in the north (Sabkha Umm as Sammim). The south-to-north gradients and the observed artesian heads in the confined aquifer are reproduced. Simulation results indicate that changes between wet and dry periods caused transient responses in heads and head gradients lasting for several thousand years. Based on the used parameters the model calibration indicated, that a recharge rate of around 4 mm a−1 is sufficient to reproduce current groundwater levels. Since rising groundwater levels were documented after cyclone Keila in November 2011, modern recharge evidently occurs. 36-Cl concentrations and dissolved-helium concentrations indicate that the deep groundwaters in the central Najd are up to 550,000 years old. Thus, radiocarbon values indicating groundwater residence times for the central Najd up to 20,000 years and the northern Najd up to 35,000 years underestimate the groundwater residence times and seem to have been strongly affected by mixing during sampling. Decreasing 36-Cl and increasing 4-He concentrations confirm the expected trend in the direction of groundwater flow and prove to be more robust tracers for age dating of Najd groundwaters. Backward pathline tracking was used to simulate the groundwater ages. The tracking results show that a total porosity value between 15 and 20 % is consistent with the range of the observed chlorine-36 and heliumbased ages. The results and parameters obtained in the present study provide the basis for future 3D-groundwater models designed to evaluate the water resources available to the Najd’s agricultural complex. In addition, the developed 2D-model allows for studies of paleoclimate scenarios and their influence on the groundwater regime
Ein steigender Bedarf nach landwirtschaftlichen Produkten - und damit Wasser - bei gleichzeitiger Abnahme des verfügbaren Wassers in Qualität und Menge in den bisherigen Anbaugebieten, führt zu einer intensiven Nutzung der Grundwasserressourcen der ariden Najd-Region in der Provinz Dhofar, im Süden des Sultanats Oman. Als Quelle dienen die Grundwasservorräte des Umm Er Radhuma-Aquifers, einer der Hauptaquifere auf der arabischen Halbinsel. Der steigenden Nutzung stehen mit dem jährlichen Monsoon, der regional limitiert ist, und unrgelmässigen, zwischen 3 und 7 Jahren auftretenden Unwettern (Zyklonniederschlag) nur begrenzte Niederschlagsmengen als Quellen für eine mögliche Zufuhr von Wasser (Grundwasserneubildung) zum Aquifersystem gegenüber. Der Ansatz der vorliegenden Arbeit besteht darin, mit Hilfe eines Grundwassermodells und der Einbeziehung von Umweltisotopen das tiefe und zur Nutzung geförderte Grundwasser in der Najd-Region als Teil eines aktiven Fließsystemes zu untersuchen und mittlere Verweilzeiten des Grundwassers abzuleiten. Ein 2D-Grundwassermodell entlang einer Fließlinie vom Dhofar Gebirge im Süden zur Sabkha Umm as Sammim im Nordosten wurde entwickelt. Das Modell reproduziert den Süd-Nord-Gradienten als auch den aufwärts gerichteten Gradienten mit höheren Grundwasserständen in den tiefen Grundwasserleitern. Die Simulationen zeigen, dass der Wechsel von ariden und humiden Phasen (wenig bzw. viel Grundwasserneubildung) zu Veränderungen der Grundwasseroberfläche führt die mehrere tausend Jahre anhalten können. Das kalibrierte Grundwassermodel zeigt, dass mit einer Neubildungsrate von 4 mm a−1 die natürlichen Grundwasserverhältnisse im Najd abgebildet werden können. Dass eine moderne Grundwasserneubildung stattfindet, konnte mittels Loggermessungen anhand steigender Grundwasserstände im tiefen Aquifersystem nach dem Extremunwetter im November 2011 (Zyklon Keila) eindeutig nachgewiesen werden. Die Analyse der 36Cl- und 4He-Konzentrationen zeigt, dass die tiefen Grundwasser im zentralen Najdgebiet bis 550 000 Jahren alt sein können. Das bedeutet allerdings, dass die über 14C Daten berechneten Grundwasseralter mit ca. 20 000 Jahren für das zentrale Najdgebiet und bis zu 35 000 Jahren für den nördlichen Najd, die Grundwasseralter deutlich unterschätzen. Die abnehmenden 36Cl und ansteigenden 4He Konzentrationen zeigen den erwarteten Trend in Grundwasserfließrichtung und können als aussagefähige Tracer für die Bewertung der Verweilzeiten und Alter des fossilen Grundwassers der Najd-Region angesehen werden. Mit Hilfe des Partickeltrackings wurden die Grundwasseralter, basierend auf den Isotopentracern, im Grundwassermodel simuliert. Die Porosität wurde dabei für das Aquifesystem mit Werten zwischen 15 und 20 % bestimmt. Die generierten Parameter und das gewonnene Systemverständnis sind eine wichtige Basis für zukünftige 3D-Modellstudien welche die Verfügbarkeit der Wasserresourcen im Najd untersuchen werden. Weitere Anwendungen für das in dieser Studie aufgebaute 2D-Modell sind Untersuchungen zum Paläoklima und dessen Einfluss auf das Grundwassersystem

The purpose of the study is to understand quantitatively the spatial distribution of groundwater recharge in the Sana'a Basin, Yemen i.e. irrigation recharge, wadi recharge and urban recharge and to assess the impact of these components on the groundwater quality. A combination of field measurements and modelling was used to determine the irrigation return for several crops and soil types. Over the basin, the total return flows, between 20 to 40 % of the water applied, are about 30 MCM/year. A method was developed to calculate recharge through ephemeral wadi beds using an indirect approach, requiring only daily rainfall data and geomorphological observations. The technique combines a rainfall-runoff model with calculation of daily water balance for the wadi channel. The method was applied to two wadis with sufficient subsurface data to estimate groundwater recharge independently from calibration of groundwater models for the shallow aquifer. The values of infiltration calculated by groundwater flow model were in good agreement with the results of the channel water balance model. Regression analysis was used to derive a generalised relationship between recharge and wadi flows. Application of this technique allows extension of wadi recharge estimates to numerous ungauged wadis over 20 years. Wadi recharge over the Sana'a basin is erratic and varies between 129 MCM and 3 MCM with an average of 38 MCM/year. An inventory of abstraction by private wells in Sana'a city, has allowed an improved estimation of urban recharge over the last 20 years, an average of 60% of the water abstracted (76% supplied). Water chemistry indicates that the shallow aquifer within the plain and lower reaches of major wadis has been polluted. However, dilution is taking place through mixing with the deep fresh water through the boreholes. Total annual recharge varies between 143 MCM and 21 MCM with an average of 66 MCM. This represents a significant amount of the annual average abstraction of 82 MCM. Previous estimate of recharge to aquifers of the basin has been less soundly based.

Estimating the quantity of water that reaches the water table following an infiltration event is vital for modeling and management of water resources. Estimating the time scale of groundwater recharge after a rainfall event is difficult because of the dependence on nonlinear soil characteristics and variability in antecedent conditions. Modeling the flow of water through the variably saturated zone is computationally intensive since it requires simulation of Richards' equation, a nonlinear partial differential equation without a closed-form analytical solution, with parametric relationships that are difficult to approximate. Hence, regional scale coupled (surface water - groundwater) hydrological models make simplistic assumptions about the quantity and timing of recharge following infiltration. For simplicity, such models assume the quantity of recharge to be a fraction of the total rainfall and the time to recharge the saturated groundwater is scaled proportionally to the depth to water table, in lieu of simulating computationally intensive flow in the variably saturated zone. In integrated or coupled (surface water - groundwater) regional scale hydrological models, better representation of the timing and quantity of groundwater recharge is required and important for water resources management. This dissertation presents a practical groundwater recharge estimation method and relationships that predict the timing and volume accumulation of groundwater recharge to moderate to deep water table settings. This study combines theoretical, empirical, and simulation techniques to develop a relatively simple model to estimate the propagation of the soil moisture wetting front through variably saturated soil. This model estimates the time scale and progression of recharge following infiltration for a specified depth to water table, saturated hydraulic conductivity and equilibrium moisture condition. High-resolution soil moisture data from a set of experiments conducted in a laboratory soil column were used to calibrate the HYDRUS-1D model. The calibrated model was used to analyze the time scale of recharge by varying soil hydraulic properties and simulating the application of rainfall pulses of varying volume and intensities. Modeling results were used to develop an equation that relates the non-dimensional travel time of the wetting front to excess moisture moisture content above equilibrium. This research indicates that for a soil with a known retention curve, the wetting front arrival time at a given depth can be described by a power law, where the power is a function of the saturated hydraulic conductivity. This equation relates the non-dimensional travel time of the wetting front to excess moisture content above the equilibrium moisture content. Since the equilibrium moisture content is dependent on the water retention curve, the powers in the equation governing the timing of recharge depend on the saturated hydraulic conductivity for a large variation in water retention curve. Also, the power law relates recharge (normalized by applied pulse volume) to time (normalized by the time of arrival of wetting front at that depth). The resulting equations predicted the model simulated normalized (relative) recharge with root mean square errors of less than 14 percent for the tested cases.

There is currently worldwide interest in the effect of human activity on tile global environment, especially the effect of greenhouse gases and land-use change on the global climate, and models are being developed to study both global change and the local effects of global change. The research reported here (funded by CNPq-Brazil) involves the development of GRASP:Groundwater Recharge modelling Approach with a Scaling up Procedure. GRASP has been integrated into the UP (Upscaled Physically-based) macromodel, developed under the UK NERC TIGER programme, which is designed for studying the effects of climate and land-use change on the availability and quality of water resources. The UP macromodel will be coupled to the UK Meteorological. Office's Unified (weather and climate) model to create a state-of-the-art coupled atmospheric/hydrological model. Several important requirements for the design of new large-scale hydrological models are identified in a wide ranging review on GCMs; (General Circulation Models) and physically -based hydrological modelling, and these requirements have been applied in the development of GRASP(and UP). The main requirements are a physical basis, proper treatment of spatial variability, and simplicity. Using the concept of partial analysis, two point-scale models, SM (Soil Moisture content approach) and TF (Transfer Function approach), are developed for recharge, both based on the one-dimensional Richards' equation. SM is a simple two-parameter model relating recharge to water storage in the unsaturated zone, and several unsuccessful attempts are made to link its parameters to physical propcrties. TF is a transfer function model, and is parameterised using the matric potential and unsaturated hydraulic conductivity functions using a new approach developed especially for GRASP. Both SM and TF are verified against numerical solutions of Richards' equation.

Managed aquifer recharge (MAR) is the purposeful recharge of an aquifer for later recovery or environmental benefits and represents a valuable method for sustainable water resources management. Models can be helpful tools for the assessment of MAR systems. This review encompasses a survey and an analysis of case studies which apply flow and transport models to evaluate MAR. The observed modeling objectives include the planning or optimization of MAR schemes as well as the identification and quantification of geochemical processes during injection, storage and recovery. The water recovery efficiency and the impact of the injected water on the ambient groundwater are further objectives investigated in the reviewed studies. These objectives are mainly solved by using groundwater flow models. Unsaturated flow models, solute transport models, reactive geochemical models as well as water balance models are also frequently applied and often coupled. As each planning step to setup a new MAR facility requires cost and time investment, modeling is used to minimize hazard risks and assess possible constraints of the system such as low recovery efficiency, clogging and geochemical processes.

Managed aquifer recharge (MAR) is the purposeful recharge of an aquifer for later recovery or environmental benefits and represents a valuable method for sustainable water resources management. Models can be helpful tools for the assessment of MAR systems. This review encompasses a survey and an analysis of case studies which apply flow and transport models to evaluate MAR. The observed modeling objectives include the planning or optimization of MAR schemes as well as the identification and quantification of geochemical processes during injection, storage and recovery. The water recovery efficiency and the impact of the injected water on the ambient groundwater are further objectives investigated in the reviewed studies. These objectives are mainly solved by using groundwater flow models. Unsaturated flow models, solute transport models, reactive geochemical models as well as water balance models are also frequently applied and often coupled. As each planning step to setup a new MAR facility requires cost and time investment, modeling is used to minimize hazard risks and assess possible constraints of the system such as low recovery efficiency, clogging and geochemical processes.

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Preliminary information on urban runoff from selected small watersheds in the Tucson area indicates that average annual runoff from the urbanized areas is more than four times as much as that of a comparable undeveloped desert area, and may be ten times as much in some individual years. The urban runoff contains relatively high concentrations of bacterial loading and dissolved organics; although it is not now known to be a seriously hazardous source of pollutants in ground water, urban runoff should be monitored with increasing urban growth, especially for content of organics, microorganisms, and trace metals. Additional study also should be given to the travel-time regime of runoff from the small tributary urban watershed to the major stream channels where recharge mainly occurs. Deep percolation from irrigation return flows was evaluated during a one -year study for the U.S. Geological Survey's "Southwest Alluvial Basin, Regional Aquifer System Assessment Program". Objectives of the study included (1) identifying sources of recharge information, (2) collecting and summarizing available recharge information, (3) identifying methods for interbasin transference of recharge values, (4) characterizing deep percolation models, and (5) itemizing methods for overcoming data gaps. Apparently there is a difference in opinion among irrigation experts on the extent to which recharge from deep percolation occurs. One reason for the difference of opinion is that field measurements of the flux and velocity components of deep percolation through the vadose zone are scarce, particularly for deep alluvial basins. Similarly, there is a need for a simple, theoretically-based model of deep percolation /recharge. Many of the data deficiencies could be overcome by conducting lumped and site-specific field studies. Such studies, although expensive, would be timely in light of the current interest in ground-water management.

Results of chemical analyses revealed elevated levels of organic surrogate parameters which included dissolved organic carbon, trihalomethanes, total organic halides, and UV absorbance in Tucson groundwater impacted by artificial recharge activity. Inorganic parameters associated with recharge water were also elevated in Tucson groundwater impacted by artificial recharge. The mobility of organochlorine during deep well injection of chlorinated Colorado River Water into the Las Vegas Valley aquifer was also investigated. The Las Vegas Valley aquifer was found to have little sorptive capacity for organo-chlorine.

Increased demand for freshwater in combination with a drying climate has led to water table decline on the Gnangara Groundwater Mound north of Perth, Western Australia. For sustainable groundwater management, a regional-scale modelling system has been developed. Accurate groundwater modelling requires good estimates of aquifer recharge, which in the case of the Superficial Aquifer may be achieved by a Vertical Flux Model. Recharge studies provide this model with input parameters such as unsaturated hydraulic conductivity, soil moisture content and water retention potential. Another key component of sustainable water resource management is to understand the biophysical processes that are involved in surface- and groundwater and plant interaction in order to conserve the natural ecosystem.Hydrogeophysical measurements have the potential to provide non-invasive, in-situ physical parameter estimation for the near-surface. As such it provides a tool to quantify and monitor unsaturated zone dynamics. From hydrogeophysical observations, hydrogeologic parameters can be deduced and then used as constraints for the numerical modelling. Geophysical monitoring further provides field evidence to corroborate or reject modelling results. Some subsurface physical properties are invariable over long time-scales (e.g. depositional features, porosity) and can be mapped with geophysical measurements. Other subsurface components are subject to temporal variations. They are determined by environmental factors, for example the water content changes during the hydrogeologic cycle. Capturing those seasonal variations requires time lapse investigation..The groundwater recharge rates at the Gnangara Mound are dominated by winter rainfall in a Mediterranean climate setting. Rainwater infiltrates through a sandy soil profile that contains water retentive soil horizons. In this thesis, the physical properties of the soil and their temporal variations are explored using Ground-Penetrating Radar (GPR) and neutron logging to delineate the influence of water retentive soil horizons.The spatial distribution of indurated, friably cemented sand layers varies spatially. To delineate these layers, large-scale surface 2D common offset GPR reflection profiles that span the entire groundwater mound are examined. It is found that these layers produce strong reflections in the radargrams that suggest a strong contrast in water content; indicating water retentiveness is present. An analysis scheme is developed that allows large-scale classification of water retention potential based on spatial reflector configuration and reflection strength. The results from spatial investigation indicate that the distribution of potentially water retentive layers is patchy. Where pronounced layers exist, they commonly show dip, which in combination with pipe structures (dissolution and root channels) is likely to result in preferential flow.Laboratory dielectric experiments on samples with variable water saturation demonstrate that retentive and non-retentive soil horizons have a similar dielectric permittivity versus water content relationship which corroborates that high reflectivity indicates elevated water content.Six test sites were selected for time lapse investigation based on soil properties and hydrogeologic setting. A range of surveys were performed before, during and after the annual rainfall cycle in 2011 to capture the temporal variability of vertical water content distribution. Time-lapse crosswell- and surface-to-hole borehole radar datasets were acquired. To obtain high certainty moisture content profiles from those data, a new processing scheme is proposed based on a combined use of zero-offset profiling and vertical radar profiling. Sequential and baseline difference curves are calculated and reveal infiltration scenarios ranging from simple wetting and unsaturated flow regime, to delayed wetting and impeded flow. While some impact on infiltration can be attributed to retentive soil layers, it was found that vegetation appears to play a crucial role in determining soil moisture depletion between wetting cycles. The results from the time-lapse GPR were validated by analysis of long-term time-lapse neutron logging. Neutron logging reinforces the view that retention horizons are unlikely to store additional plant available water compared to the clean sand intervals.Very near-surface water content measurements are a challenge with commercial common offset GPR systems. I develop a new analysis methodology that enables estimation of water content as part of the spatial and temporal characterization of shallow moisture distribution. Dispersion curves are derived from shallow diffracted wavefields that appear in common offset GPR due to a waveguide structure. Inversion based on modal wave propagation in a waveguide allows derivation of waveguide parameters. Dispersion curves are demonstrated to be sensitive to small changes in waveguide properties, which are strongly dependent upon water content. Field examples illustrate the full potential of this technique in lateral near-surface water content quantification.The small- and large scale surveys presented in this thesis form the basis for examination and advancement of the radar methodology in a sandy environment as well as providing field evidence for hydrogeologic significance and distribution of water retentive soil horizons in the unsaturated zone of the Swan Coastal Plain, Western Australia.

Les facteurs qui régissent l'intensité et la répartition de la recharge naturelle et artificielle dans les aquifères cristallins altérés et fracturés sont mal connus. Ce sont cependant les caractéristiques déterminantes de ce type de roche—ces roches sont très hétérogènes—qui rendent difficile l’estimation des flux dans ces milieux ainsi que des propriétés hydrauliques qui les contrôlent. La première partie de ce manuscrit fournit un état des connaissances sur la recharge des eaux souterraines et ses méthodes d’estimation, permettant de comprendre les défis scientifiques et sociétaux abordés dans cette thèse. La deuxième partie présente les travaux numériques et expérimentaux menés pour approfondir notre compréhension de la dynamique des flux d’eaux souterraines dans ces milieux hétérogènes à plusieurs échelles. Le premier axe de recherche porte sur les processus de recharge naturelle à l’échelle du bassin versant. La recharge diffuse a été modélisée avec un modèle physique simple d’infiltration et comparée à des estimations préalables de recharge totale. Nos résultats illustrent la forte dépendance de la recharge aux précipitations et à l’irrigation, et l’importance de la recharge focalisée. Les facteurs responsables de la distribution spatiale de la recharge sont aussi étudiés. Le deuxième axe est basé sur le suivi de la mise en eau d’un bassin de recharge artificielle dans un site hautement monitoré et bien équipé. Ces observations ont été interprétées avec des modèles analytiques et numériques. Ces modèles ont mis en évidence l’existence de flux préférentiels horizontaux, mais aussi d’une compartimentation latérale qui entrave la propagation des intrants de recharge
The factors governing the intensity and distribution of natural and artificial recharge in weathered and fractured crystalline aquifers are poorly understood. However, it is the defining characteristics of this type of rock—these rocks are very heterogeneous—that make the estimation of fluxes and the hydraulic properties controlling them difficult. The first of its two parts provides the theoretical framework on groundwater recharge processes and its estimation methods for comprehending the scientific and societal challenges discussed in this thesis. The second part presents the numerical and experimental work carried out to deepen our understanding of the dynamics of groundwater flows in these heterogeneous underground environments at several scales. The first line of research focuses on natural recharge processes at the watershed scale. Diffuse recharge was modeled with a simple physical infiltration model and compared to previous estimates of total recharge. Our results highlight the strong dependence of recharge on rainfall and irrigation, and the importance of focused recharge. The factors responsible for the spatial distribution of recharge are also studied. The second axis is based on the monitoring of the filling of an artificial recharge basin at a highly monitored and well-equipped site. These observations were interpreted with analytical and numerical models to improve our knowledge of flow dynamics in fractured crystalline rocks at the medium scale. These models illustrated the existence of preferential horizontal flows, but also of a lateral compartmentalization that hinders the propagation of recharge inputs

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k Menderes River Basin located in western Turkey has been facing continuous groundwater level decreases for the past 30 years. In dry periods, irrigation demand is completely met by pumping from groundwater system, which reduces water levels significantly. This provides enough storage to be recharged in wet seasons when streams are running. However, increased runoff in wet season are not utilized neither for irrigation nor for recharge and lost to the Aegean Sea without being infiltrated. Hence, surface artificial recharge methods can be useful to collect excess water in recharge basins, thus allowing infiltration to increase groundwater storage in wet seasons to be later utilized in dry seasons. A 2-D groundwater model is set up by using SEEP/W software. The material functions and parameters used in the model for saturated/ unsaturated conditions are taken from previous studies. Calibration was done to check the accuracy of input data and to control the validity of model. The amount of excess water that will be collected in recharge basins was estimated from flood frequency analysis. Concerning different probabilities, different scenarios were simulated to observe the increase in groundwater levels. Simulation results suggest that significant increase in groundwater storage could be achieved by applying artificial recharge methods. In addition to recharge basins, to reinforce the effect of artificial recharge, simulations were repeated with the addition of an underground dam at downstream side of the basin. Simulation results indicate that the increase in groundwater storage is not sufficient to warrant construction of the underground dam.

This thesis presents a novel analytical solution strategy for the zero-inertia (ZI) equations of free surface flow. These equations are utilized herein for routing flood flow in open channels and for simulating excess rainfall runoff on overland planes. The novel solution approach is shown to be both accurate and robust, especially under the complicated and intricate conditions of infiltrating flow on initially dry river beds or soils, e.g., as present in arid and semiarid areas. This is underlain by comparing modeling results of the novel analytical procedure with those of validated numerical solutions. Furthermore, it is shown that the analytical ZI model can deliver a process-oriented portrayal of runoff concentration in the flood-generating parts of the catchment. Subsequently, the novel analytical ZI model is applied for a real-world water management problem in the Sultanate of Oman, Arabian Peninsula. Within an integrated flash flood routing model—which is also presented in this thesis—the novel analytical routing approach helps in accurately matching the dynamics of advancing and infiltrating ephemeral river flow, established as a consequence of release from a groundwater recharge dam. The integrated modeling system houses the aforementioned analytical downstream model and tailor-made, state-of-the-art modeling components to portray the upstream flow processes, dam operation (including evaporation), and spillway release flow. The proposed modeling system can aid in rendering a realistic image of transient transmission losses and dependent flow dynamics. This is of extremely high importance for water resources assessment, as well as for optimizing recharge dam operation strategies in order to maximize downstream transmission losses and, thus, groundwater recharge
Diese Dissertation präsentiert einen neuartigen analytischen Lösungsansatz für das beschleunigungsfreie Wellenmodell (bzw. „Zero-Inertia-Modell“, „ZI-Modell“, oder „diffusives Wellenmodell“). Im Rahmen der Arbeit wird das hergeleitete hydrodynamische Modell sowohl zur Simulation von Freispiegelabflüssen in nichtprismatischen und durchlässigen Gerinnen, als auch für die Beschreibung von auf der Landoberfläche abfließendem Infiltrationsüberschuss eingesetzt. Es wird gezeigt, dass der neuartige analytische Ansatz — im Hinblick auf Massenerhaltung und die exakte Abbildung der Abflussdynamik — akkurate Ergebnisse liefert und gleichzeitig unter komplexen und verwickelten Prozessbedingungen anwendbar ist. So belegt eine vergleichende Analyse mit validierten numerischen Lösungsansätzen die Robustheit des analytischen ZI-Modells. Insbesondere die im Sinne der numerischen Mathematik stabile und genaue Modellierung der gekoppelten Abfluss- und Infiltrationsvorgänge in anfänglich trockenen Gerinnen ist dabei ein Novum. Weiterhin wird die Eignung und Anwendbarkeit des neuartigen Modellansatzes zur Beschreibung der Abflusskonzentrationsprozesse gezeigt. Der neuartige Lösungsansatz wird im Folgenden für ein reales Wassermanagementproblem im Sultanat Oman, Arabische Halbinsel eingesetzt. Als Bestandteil eines integrierten Modellsystems, welches ebenfalls im Rahmen der Dissertation vorgestellt wird, dient das analytische ZI-Modell zur Simulation von infiltrierendem Wadiabfluss, welcher unterstrom von Grundwasseranreicherungsdämmen starke Verluste von Masse und Impuls erfährt. Zusammen mit maßgeschneiderten und dem Stand der Technik entsprechenden Komponenten für die Betriebssimulation des Anreicherungsdammes (inklusive Verdunstung von der freien Seefläche) sowie für die Abbildung der oberstromigen hydrodynamischen Prozesse (ebenfalls inklusive Infiltration) wird der neuartige analytische Ansatz in einem Modellsystem zusammengefasst. Das Modellsystem ist in der Lage ein realistisches Bild der raumzeitlichen Dynamik des Abflusses sowie der Grundwasserneubildung aus infiltrierendem Wadiabfluss zu liefern. Damit stellt das Modellsystem ein wertvolles Werkzeug sowohl zur Wasserdargebotsermittlung, als auch für die Optimierung des Betriebes von Grundwasseranreicherungsdämmen dar

The Santa Rosa Creek Watershed is an approximately 48 mi2 large watershed located on the central coast of California. This watershed drains to the Pacific Ocean through Santa Rosa Creek as it passes through agricultural land and the town of Cambria. Historically the groundwater within the Santa Rosa Creek Watershed has been used for irrigation, municipal and domestic uses, and the creek is critical habitat steelhead trout. During dry years, there is less water for all uses. When low groundwater levels occur, water can be drawn out of the creek and into the soil, drying out steelhead habitat. Seven agricultural operators within the Santa Rosa Creek Watershed are working with a local non-profit to improve sustainability of the aquifer through artificial groundwater recharge. One of these projects includes the use of a recharge basin. This study was conducted to understand the impacts of that recharge basin on the groundwater surrounding it as well as to evaluate the site’s potential for other recharge methods. The groundwater within the site of interest was modeled using GMS to calculate head values, to determine flow directions, and to determine timings. Three different hydrogeologic layers were used to simulate an upper unconfined zone, a clay confining layer, and a confined zone. The model was calibrated to known groundwater head values throughout the site. ArcMap was used to organize and preprocess data that went into the GMS model. Elevation, hydrologic soil characteristics, boundary heads, recharge rates, evapotranspiration rates, and well locations and pumping rates datasets were all preprocessed and imported into GMS. The model showed that the water from the recharge basin does not percolate into the underlying groundwater aquifer, but it flows out of the upper unconfined layer and into the creek over time. This is caused primarily by a low hydrologic conductivity confined aquifer in the northern section of the site as well as a confining clay layer underneath the unconfined top layer. According to the model, the site may not be feasible for artificial groundwater recharge in the northern portion, but there is potential for recharge in the southern area. Further data collection could improve the model to support or dispute these findings.

Almost 90% of the treated sewage effluent processed by the two treatment plants serving the greater Tucson area is available for passive recharge through the Santa Cruz River streambed north of Tucson. In the absence of any major disturbance of the effluent channel, the recharge capacity of the streambed materials decreases over time as microbial activity, and possibly suspended sediments settling out of solution, act to clog the surficial sediments under the effluent stream. Effluent stream transmission-loss measurements made over the period from November 1994 to August 1995 provided data used to determine the average vertical hydraulic conductivity of the low-flow channel in the study reach through simulations using the computer model known as KINEROS2. Saturated hydraulic conductivity (KSAT) served as the calibration parameter in the model. The appropriate KSAT value was chosen for each set of field data by matching the observed and simulated downstream hydrographs for the study reach. KSAT values were corrected for viscosity changes resulting from changing average daily surface water temperatures over the study period. Saturated hydraulic conductivity values for the effluent stream channel ranged from a maximum of 37 mm/hr in January, 1995, following several major winter storms, to a minimum of 11 mm/hr in August, 1995, after a nearly six-month interstorm period. The saturated hydraulic conductivity values decay exponentially with time after the last major winter storm. The mathematical model describing this decay may be used to estimate effluent recharge rates under similar future meteorological and climatological conditions.

The variably saturated flow model Unsat 2 was used for three case study simulations of dry well recharge in the Tucson Basin, Arizona. Dry well design, and rainfall/runoff and vadose zone conditions representative of the locality were assumed in the simulations to address travel time to the regional aquifer, rates and extent of radial flow, and relative degree of solute attenuation by sorption and dilution with regional groundwater. Soil specific surface was used to estimate relative degree of sorption among the three cases. One case of uniform soil composition and two cases of layered soil composition were simulated. Clay content had the greatest influence on specific surface. Hydraulic conductivity had the greatest influence on soil water velocities and degree of radial flow. The presence of layered subsurface conditions that included strata of low hydraulic conductivity enhanced the degree of subsurface solute attenuation by sorption and dilution.

>Magister Scientiae - MSc
This study is part of the current investigation of the Elandsfontein aquifer to assist with the management of the system and to ensure the protection of the associated Langebaan Lagoon RAMSAR listed site. The Elandsfontein aquifer unit is situated adjacent to the Langebaan Road aquifer in the Lower Berg River Region. The aquifer unit is bordered by the Langebaan Lagoon (west), possible boundary toward the Langebaan Road aquifer (north), the Groen River bedrock high (southeast) and the Darling batholith (south).

Groundwater response to climate variability and land cover change is important for sustainable management of water resources in the Southwest US. Global Climate Models (GCM) project that the region will dry in the 21st century and the transition to a more arid climate may be under way. In semiarid Basin and Range systems, this impact is likely to be most pronounced in Mountain System Recharge (MSR), a process which constitutes a significant component of recharge in these basins. Despite the importance of MSR the physical processes that control MSR, and hence the climate change impacts, have not been fully investigated because of the complexity of recharge processes in mountainous catchments and limited observations. In this study, methodologies were developed to provide process-based understanding of MSR based on empirical and data-driven approaches. For the empirical approach, a hydrologically-based seasonal ratio the Normalized Seasonal Wetness Index (NSWI) was developed. It incorporates seasonal precipitation variability and temperature regimes to seasonal MSR estimation using existing empirical equations. Stable isotopic data was used to verify recharge partitioning. Using the NSWI and statistically downscaled monthly GCM precipitation and temperature data, climate change impacts on seasonal MSR are evaluated. Second, a novel data-based approach was developed to quantify mountain block recharge based on the catchment storage-discharge (S-Q) relationships and informed by isotopic data. Development of S-Q relationships across the Sabino Creek catchment, Arizona, allowed understanding of MBR dynamics across scale.Two ArcGIS desktop applications were developed for ArcGIS 9.2 to enhance recharge and evapotranspiration (ET) estimation: Arc-Recharge and RIPGIS-NET. Arc-Recharge was developed to quantify and distribute recharge along MODFLOW cells using spatially explicit precipitation data and a digital elevation model. RIPGIS-NET was developed to provide parameters for the RIP-ET package and to visualize MODFLOW results. RIP-ET is an improved MODFLOW ET module for simulating ET. RIPGIS-NET improves alluvial recharge estimation by providing spatially explicit riparian ET estimates. Using such tools and the above methods improves recharge and ET estimation in groundwater models by incorporating temporally and spatially explicit data and hence the assessment of climate variability and land cover change on groundwater resources can be improved.

Thesis (M.S.)--West Virginia University, 2008.
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Access to surface water is limited in Australia and many regions rely on groundwater for all their water needs. Most of aquifers are already fully allocated and there is an increasing demand for more extraction. During drought, drop in rainfall can result in less recharge into groundwater system. Decrease in rainfall can cause direct and indirect impacts on groundwater. Drop in rainfall can result in less recharge into groundwater system. Moreover decreased rainfall can cause limited accessibility to surface water which results in increased demand for extraction. Understanding of groundwater recharge mechanism and quantifying how far climate change can influence groundwater, plays an important role for establishing sustainable extraction without causing any damage into environment. The CoupModel was selected as a tool to simulate groundwater behavior under different Scenarios. Model inputs are derived from actual observations, such as climatic data. Few assumptions were considered to conceptualize drainage system, such as soil hydraulic parameters, drainage system and evaporation procedure. The study period is 30 years between 1979 and 2008. Model was run for two 15-year periods to identify how far climate change can influence groundwater recharge in the study area. Eyre Peninsula area is highly dependent on groundwater for town water supply, Irrigation and industrial development. Therefore any science study would be definitely valuable for groundwater resource management of this area.

Cette thèse a pour objectif d’étudier l’influence de la recharge rapide sur le vieillissement des batteries lithium, et son impact sur les performances des véhicules électriques dans le cadre d’une utilisation postale. La première partie est consacrée à la modélisation de batteries lithium par un modèle à circuit électriques équivalent, dont les paramètres sont identifiables par des tests de caractérisation linéaires. La deuxième partie est dédiée à l’étude du vieillissement, et abouti sur un estimateur de vieillissement par l’exploitation des données des tests de vieillissement accélérés. Ensuite, l’utilisation postale est étudiée, et un profil de courant représentatif de la sollicitation réelle de la batterie est proposé. Ce dernier a permis de valider le modèle de la batterie dans le domaine de l’utilisation postale. Ensuite un modèle de véhicules électriques est présenté, il intègre le modèle de batterie, tout en le faisant vieillir en utilisant l’estimateur de vieillissement. Enfin, les différentes stratégies de recharges possibles sont énumérées et comparées. Pour conclure sur leurs influences sur le vieillissement des batteries, et donc les performances de véhicules
This thesis aims to study the influence of fast charging on the aging of lithium batteries, and its impact on the performances of electric vehicles as part of a postal use. The first part is devoted to the modeling of lithium batteries with an equivalent electric circuit model, whose parameters could be identified using linear characterization tests. The second part is dedicated to the study of aging, and results in an aging estimator using data collected from accelerated aging tests programs. Then the postal usage is studied, and a power profile representative of the actual load on the battery is provided. The latter was used to validate the model of the battery in the field of postal use. Then the postal use is studied, and a current profile representative of the real behavior of the battery is provided. This profile was used to validate the model of the battery in the postal use domain. Then a model of electric vehicles is presented, it integrates the battery model, which can simulates the aging state of the battery using the ageing estimator. Finally, the various possible strategies of recharge are listed and compared, which leads to conclusions about their influences on aging of batteries, and the vehicles performance

The main aim of the project is to investigate the feasibility of artificial recharge of the Bushmans River Mouth Aquifer in the Eastern Cape. The suggested method of recharge is through natural infiltration through a series of wetlands in the back dune area. The proposed site was the Klipfontein Vlei which is located just north of the Bushmans River Mouth. Artificial recharge is defined as augmenting the natural movement of surface water into underground formations by some method of construction, the spreading of water, or by artificially changing natural conditions. A variety of methods have been developed, including water spreading, recharging through pits and wells, and pumping to induce recharge from surface water bodies. The choice of a specific method is controlled by local topography, geology and soil conditions, and the quantity of water to be recharged and ultimate water usage. In special circumstances, land value, water quality, and climate play an important role. Artificial recharge is not a foreign concept to South Africa and this project is to test its feasibility in a back dune wetland area. Augering done in the study area revealed the dominance of sandy loam in the upper layers of the pans, loamy sand in the middle levels and the presence of some sand lenses in the lower reaches. Particle size analysis done by sieving and hydrometer test, showed a dominant 3f fraction. There was variation in modes in pan 1 from unimodal to bimodal to trimodal. Pan 2 showed no variation as all samples were unimodal and moderately well sorted. Infiltration tests were done by a double ring infiltrometer. These results showed that the infiltration rates of the pans became stable after 15 to 20 minutes, thus indicating that the soil had reached its saturation point. The resistivity surveys revealed a stepped water table. The inclination of the water is controlled by the predominately argillaceous horizons of the Bokkeveld Group. Based on the above results, it is recommended that the Klipfontein Vlei be used as an artificial recharge site.