The main goal of this research is to develop and test a groundwater recharge estimation method that can address some of the key research priorities in groundwater. In this context use is made of various modelling tools including ArcGIS, field data (in situ observations of soil temperature and soil moisture), and soil physics as represented by a physically based vadose zone hydrologic model (HYDRUS-1D). The research is conducted in a pilot watershed in north Okanagan, Canada. The public version of HYDUS-1D and another version with detailed freezing and thawing module are first used to investigate seasonal distribution of heat and water movement in the vadose zone. Model performance is evaluated in different scales by using field data, the gradient-based optimization algorithm of HYDRUS-1D, and ROSETTA derived prior information about soil hydraulic parameters. The latter are fitted to statistical distributions and used in Monte-Carlo experiments to assess the potential uncertainty in groundwater recharge due to model parameters. Next, the significance of the recharge estimation method for catchment scale transient groundwater modelling is demonstrated by applying uniform and variable flux boundary condition to a saturated zone transient groundwater model, MIKESHE. The results showed that the traditional uniform recharge assumption can lead to misleading decisions related to water resources management and pumping well network design. The effect of pumping well network and the provincial Water Act on water resources sustainability are further examined in an evolving climate. The results suggest potential water resource problem in the basin, which can possibly be attributed to the previously installed pumping well network (depth and screen level), and the provincial water use policy. The findings of this study demonstrate that such problems related to inappropriate well network and water resource management can greatly be minimised with the use of the recharge estimation method developed in this study.

<p>In this dissertation, I explored the effects of vegetation type on ecosystem services, focusing on services with significant potential to mitigate global environmental challenges: carbon sequestration and groundwater recharge. I analyzed >600 estimates of groundwater recharge to obtain the first global combined analysis of groundwater recharge and vegetation type. Using a regression model, I found that vegetation was the second best predictor of recharge after precipitation. Recharge rates were lowest under forests, intermediate in grasslands, and highest under croplands. The differences between vegetation types were higher in more humid climates and sandy soils but proportionately, the differences between vegetation types were higher in more arid climates and clayey soils. My extensive field estimates of recharge under paired vegetation types in central Argentina and southwestern United States provided a more direct test of the relationships between vegetation and recharge. The field data confirmed the strong influences of vegetation and its interactions with abiotic factors on recharge observed in the synthesis. The results indicate that vegetation shifts have a proportionately larger potential to affect recharge in more arid climates and clayey soils.</p><p>At the same study systems, I compared my field estimates of recharge to organic carbon stocks (in biomass, litter and soil) under the different vegetation types to evaluate tradeoffs between carbon sequestration and groundwater recharge as affected by vegetation shifts. To determine net values of vegetation shifts, I combined the changes in carbon and water with reported economic values of the ecosystem services. Based on physiological tradeoffs between photosynthesis and transpiration in plants, I hypothesized that vegetation promoting carbon storage would reduce recharge and vice versa. Changes in water and carbon services were inversely proportional, with rain-fed cultivation increasing groundwater recharge but decreasing carbon storage compared to the grasslands they replaced whereas woody encroachment did the opposite. In contrast, cultivated plots irrigated with ground water decreased both ecosystem services. Higher precipitation and clay content both exacerbated changes in carbon storage with grassland conversions, whereas higher precipitation accentuated, but higher clay content diminished, those in recharge. Regardless of the nature of vegetation shift, most of the net values of grassland conversions were negative, with the shifts representing increasing costs in the following order: woody encroachment, rain-fed cultivation and irrigated cultivation. Values of changes in carbon were greater in magnitude than those of recharge, indicating that establishment of carbon markets may drive land-use changes in grasslands over water markets.</p><p>Lastly, I examined the effects of changes in subsurface hydrology resulting from grassland conversion to croplands on soil inorganic carbon stocks in the same U.S. study system. I observed significantly lower inorganic carbon stocks under both rain-fed and irrigated croplands compared to the grasslands they replaced. The losses were visible to past 6 m depth in the soil profile and were uncharacteristically rapid for the carbon pool that is considered to be relatively inert. Based on the negative relationship between the inorganic carbon stocks and recharge rates and higher estimated exports of bicarbonates in recharge under croplands, I concluded that increased recharge with cultivation resulted in dissolution and leaching of grassland soil carbonates. Ecosystem services and their relationships to biotic and abiotic factors quantified here will further our understanding of the tradeoffs and interactions between the two services through vegetation shifts.</p> / Dissertation

Die vorliegende Arbeit umfasst im ersten Teil eine Literaturrecherche zu Aquifer Storage and Recovery (ASR) im Allgemeinen und den Einfluss physikalisch-chemischer Prozesse auf ASR. Aus dieser konnte abgeleitet werden, dass durch standortbedingte Untergrundeigenschaften stark unterschiedliche physikalische und chemische Prozesse ablaufen und eine eindeutige Vorhersage zum Verhalten und zur Effizienz von ASR an einem neuen oder bereits genutzten Standort ohne spezifische Informationen nicht möglich ist. Des Weiteren wurde eine Literaturstudie zum Einfluss der transversalen Dispersivität, als Maß für die Vermischung von transportierten Stoffen quer zu einer (natürlichen) Fließrichtung, auf den (reaktiven) Transport durchgeführt. Letztlich wurde im Rahmen einer betreuten Masterarbeit (M. Sc. Chang Liu) eine Bewertung aus der Literatur entnommener transversaler Dispersivitäten durchgeführt. In den weiteren Teilen der Arbeit wurden Fallstudien mit unterschiedlichen Fragestellungen für die Planung und den Betrieb von künstlichen Grundwasseranreicherungen und speziell ASR numerisch modelliert und bewertet. Zuerst wurden numerische Simulationen zum konservativen Transport am Testfeld „Lauswiesen“, Tübingen, Baden-Württemberg durchgeführt. Diese beinhalteten über Direct-Push(DP)-Erkundungsmethoden gewonnene Informationen zur Untergrundstruktur. Die Ergebnisse zeigen, dass zur Vorhersage des standortspezifischen Transports in den „Lauswiesen“ und für vergleichbare hydraulische Situationen, auch in Hinsicht auf ASR, deterministische hydrogeologische Einheiten und ihre situationsgerechte Berücksichtigung in numerischen Modellen höchst relevant sind. Aufbauend auf den genannten Ergebnissen wurde eine Masterarbeit durch Herrn M. Sc. Tsegaye Abera Sereche durchgeführt. Diese Masterarbeit zeigte für diesen Fall erneut die hohe Relevanz deterministischer Strukturen gegenüber kleinskaligen, dreidimensionalen Heterogenitäten für ASR. Weiterführende numerische Simulationen zu einem möglichen ASR-Feldtest am Standort „Lauswiesen“ ergaben, dass dieser unter den gegebenen Untergrundbedingungen nur bei Abweichungen von einem vertretbaren Konzept für einen Ein-Brunnen-Test, z. B. bei sehr großen Infiltrationsmengen, oder durch Umwandlung in einen Zwei-Brunnen-Test durchführbar ist. Während dieser Arbeit wurden gemeinsame Forschungsarbeiten mit dem Kansas Geological Survey, Kansas, USA durchgeführt, welche die Bewertung der Verwendbarkeit von DP-Brunnen als alternative Infiltrationsmethode zu Oberflächenmethoden beinhalteten. Als Teil der gemeinsamen Arbeiten wurde im Rahmen der vorliegenden Arbeit eine synthetisierte, numerische Bewertung der neuen DP-Infiltrationsbrunnen sowie einen Vergleich mit einer herkömmlichen Oberflächeninfiltrationsmethode übernommen. Im Einklang mit der Zielstellung der Arbeit wurde ebenfalls eine numerische Bewertung natürlicher und anthropogener Heterogenitäten auf die Infiltration durchgeführt. Aus den Ergebnissen konnten für die neue Infiltrationsmethode signifikante Vorteile abgeleitet werden. Weitere numerische Modellierungen wurden durchgeführt, um die wesentlichen Ergebnisse auf einen Feldstandort in der Südlichen Steiermark, Österreich, anzuwenden, welcher: a) bereits ein horizontales Versickerungssystem besitzt, b) weitere Systeme erhalten soll und c) letztlich eine besondere Herausforderung für vertikale Versickerungssysteme darstellt. Die Modellierung des vorhandenen Systems zeigt die hohe Komplexität der Infiltrationsprozesse. Jedoch konnten hydraulische Parameter bestätigt und in weitere planerische Simulationen zu Verwendung von DP-basierten Infiltrationsbrunnen eingefügt werden. Diese zeigen, dass ein Brunnenfeld am Standort auf relativ geringem Raum installiert werden kann. Zusätzlich zeigt ein Feldversuch an einem weiteren Standort (Pirna, Sachsen), dass hohe Infiltrationsraten unter Nutzung von DP-Brunnen möglich sind. / The works presented in the thesis include in the first part a literature research on Aquifer Storage and Recovery (ASR) in general and the impacts of different physico-chemical processes on ASR. This research concludes that site-specific subsurface conditions lead to varying physical and chemical processes and that a conclusive prediction of function and efficiency of ASR at any site, in-operation or new site design, is not possible without site-specific information. Additionally, a literature study was conducted that focused on the impacts of transverse dispersivity, as a measure for mixing of transported species perpendicular to the (natural) flow direction, on (reactive) transport. Finally, evaluation of transverse dispersivity data available in the literature was performed, which included a supervision of a master thesis (of M. Sc. Chang Liu). Numerical simulations of case studies for different questions of planning and operation of artificial recharge systems and more specifically ASR were realized for the other parts of the thesis. The first evaluated case was the “Lauswiesen” test site, Tübingen, Baden-Wuerttemberg. This study used new insights into the subsurface structure gained by Direct-Push(DP) exploration methods. The results obtained show that for further works at the site and for comparable hydraulic conditions, also in the view of ASR, deterministic hydrogeological subunits and their consideration in numerical models are critical for prediction of site-specific transport. Based on the previous findings, a master thesis was conducted by M. Sc. Tsegaye Abera Sereche. The master thesis yet again revealed for this case the high relevance of deterministic subunits compared to small-scale, three-dimensional heterogeneities for ASR. Further, numerical simulations of a possible ASR field test at “Lauswiesen” site showed that under the prevailing subsurface conditions, a field test can only be realized when the set-up of a single-well-test is impracticably changed, by e.g. very high infiltration volumes, or by transformation into a two-well-test. During the thesis joint research works were performed with the Kansas Geological Survey, Kansas, USA, which contained the evaluation of the applicability of DP wells as an alternative to surface infiltration methods. As part of the joint work, this thesis presents a synthesized numerical evaluation of the new DP well infiltration as well as a comparison to a common surface infiltration system. Furthermore, in accordance with the main objective of the work, numerical evaluation of natural and anthropogenic heterogeneities was performed. The results concluded the advantages for the DP wells for infiltration process. Further numerical models were implemented to convey the important results to a field site at Southern Styria, Austria, where: a) an existing infiltration system is already in operation, b) further infiltration systems are planned and c) the subsurface conditions are rather challenging for vertical infiltration systems. Modeling of the existent system revealed the high complexity of the infiltration processes. However, hydraulic parameters could be verified and included into planning simulations for DP-based infiltration wells. The findings show, that a well field can be installed at a comparably small land. Additionally, a field test at a further test site (Pirna, Sachsen) indicates that high infiltrations rates are possible when DP wells are used.

Thesis (M.S. - Soil, Water and Environmental Sciences)--University of Arizona. / Includes bibliographical references (leaves 107-111)

Thesis (Ph. D.)--University of Hawaii at Manoa, 2004. / Includes bibliographical references.

Thesis (Ph.D.)--University of Western Australia, 2008.

Thesis (M.S.)--University of Southern California, 2007. / Includes bibliographical references (leaves 92-96).

Thesis supervisor: You-Kuan Zhang. Includes bibliographic references (p. 158-172).

Arid and semi-arid basins in the Western United States (US) have been significantly impacted by human alterations to the water cycle and are among the most susceptible to water stress from urbanization and climate change. The climate of the Western US is projected to change in response to rising greenhouse gas concentrations. Combined with land use/land cover (LULC) change, it can influence both surface and groundwater resources, both of which are a significant source of water in the US. Responding to this challenge requires an improved understanding of how we are vulnerable and the development of strategies for managing future risk. In this dissertation, I explored how hydrology of semi-arid regions responds to LULC and climate change and how hydrologic projections are influenced by the choice and calibration of models. The three main questions I addressed with this dissertation are: 1. Is it important to calibrate models for forecasting absolute/relative changes in streamflow from LULC and climate changes? 2. Do LSMs make reasonable estimates of groundwater recharge in the western US? 3. How might recharge change under projected climate change in the western US? Results from this study suggested that it is important to calibrate the model spatially to analyze the effect of LULC change but not as important for analyzing the relative change in streamflow due to climate change. Our results also highlighted that LSMs have the potential to capture the spatial and temporal patterns as well as seasonality of recharge at large scales. Therefore, LSMs (specifically VIC and Noah) can be used as a tool for estimating current and future recharge in data limited regions. Average annual recharge is projected to increase in about 62% of the region and decrease in about 38% of the western US in future and varies significantly based on location (-50% - +94 for near future and -90% to >100% for far future). Recharge is expected to decrease significantly (-13%) in the South region in the far future. The Northern Rockies region is expected to get more recharge in both in the near (+5.1%) and far (+9.0%) future. Overall, this study suggested that land use/land cover (LULC) change and climate change significantly impacts hydrology in semi-arid regions. Model choice and model calibrations also influence the hydrological predictions. Hydrological projections from models have associated uncertainty, but still provide valuable information for water managers with long term water management planning.

Fundação de Amparo a Pesquisa no Estado do Rio Grande do Sul / The Campus of UFSM (Universidade Federal de Santa Maria) is supplied mainly by groundwater, captured at outcrop zones (ZA) of the Guarani Aquifer System (GAS). In this sense, the present study aimed to fill the lack of quantitative information of groundwater in the UFSM Basin Campus School. The aims of this study were: 1) Perform recharge estimation of water table in single-well, using the Water Table Fluctuation method. 2) Execute statistical analysis on weekly data levels, monitored since May 2010, identifying possible correlations with rainfall data s and analysis on weekly data levels, and 3) Quantify the areas sealed in bowl using ArcGIS software and Google Earth images of 2007 to 2010. The results of the study indicated a 17.0% to 48.0% infiltration rate of the total precipitation in FATEC old well, whereas an average of 36.0% of rainfall contributes to aquifer recharge. The investigation of soil sealing, performed with data from 2007 to 2014 showed an increase of 24.32 ha in the sealed area during the study period. In the static analysis of correlation of weekly levels with volumes of rain, it was observed that the rains recorded in the measurement date were those of major influences on monitored levels, indicating the replacement level. Regarding the fluctuating levels trends from a total of eight wells monitored, two had drawdown trend. The seasonal analysis showed that levels of the seasons of winter and autumn were those with more water stored in the aquifer, while in summer and spring the opposite happened. As a conclusion, despite the sealed areas had a significant and rapid growth for the Basin, wherein this growth has not specified losses in volumes of recharges groundwater. Once the correlation data between rain and water levels were positive, the level variation trends indicated two of the eight wells with loss of water volume during the monitoring. / O Campus da UFSM (Universidade Federal de Santa Maria) é abastecido principalmente por águas subterrâneas, captadas em Zona de Afloramentos (ZA) do Sistema Aquífero Guarani (SAG). Nesse sentido, o presente estudo objetivou analisar quantitativamente às águas subterrâneas na Bacia Escola do Campus da UFSM. Para tanto, os objetivos específicos desse trabalho foram: 1) Elaborar estimativas de recarga do lençol freático em poço único, utilizando o método da flutuação do nível da água/WTF (Water Table Fluctuation). 2) Realizar análises estatísticas em dados de medições semanais de níveis da água (NA), monitorados no Campus da UFSM desde maio de 2010, identificando-se possíveis correlações com os dados de precipitações e as flutuações do nível da água. Ainda analisou-se a sazonalidade de variação desses níveis e, 3) Mapear a variação das áreas impermeabilizadas na Bacia com uso do programa ArcGIS e de imagens do Google Earth do ano de 2007 a 2010. Os resultados do trabalho apontaram para uma taxa de infiltração na área da Bacia de 17,0 a 48,0% da precipitação total, em média 36% das chuvas contribuem para a recarga do aquífero. As modificações no uso da terra mostrou que houve um crescimento de 24,32 ha, na área impermeabilizada no período avaliado. Na análise da correlação dos níveis da água semanais com os volumes de chuvas, evidenciou-se que as chuvas registradas na data da aferição foram aquelas de maiores influências nos níveis monitorados, acusando reposição no nível. Quanto à tendência de flutuação dos níveis, de um total de oito poços monitorados, dois apresentaram tendência de rebaixamento. A análise sazonal dos níveis mostrou que as estações do inverno e outono são aquelas que recarregam o aquífero, enquanto que no verão e na primavera acontece o contrário. Conclui-se que apesar das áreas impermeabilizadas apresentarem um crescimento significativo e rápido para a Bacia, esse crescimento ainda não forneceu prejuízos nos volumes das recargas das águas subterrâneas. Uma vez que os dados de correlação entre a chuva e os níveis da água foram positivos e as tendências de variação de nível indicaram dois dos oitos poços com perda de volume de água ao longo do monitoramento..