A engenharia hidrológica visa quantificar os parâmetros que envolvem um balanço híbrido. Nesse domínio, a avaliação da taxa de recarga de aqüíferos subterrâneos torna-se relevante, devido ao uso indiscriminado desse recurso híbrido. Com o auxílio de um lisímetro e a aplicação de conceitos teóricos da infiltração, estimou-se a taxa de recarga potencial do Aqüífero Guarani para a região de São Carlos. O lisímetro, instalado na Estação Hidrometereológica do CRHEA, possui uma área de exposição de 3,6 m2 e profundidade de 1,50 m. Para a coleta do volume infiltrado utilizou-se um sistema de drenagem, com destino em um tanque coletor graduado. O lisímetro foi preenchido com solo da zona de afloramento do Aqüífero Guarani (solo arenoso). Houve monitoramento de umidade do solo, dentro do lisímetro e em campo aberto, nas proximidades do local de retirada do solo. Coletaram-se dados de infiltração no período de janeiro de 2002 a janeiro de 2003. A taxa de recarga direta potencial foi estimada em 55,6% da precipitação, para o período em estudo. Análises do comportamento da água no solo demonstraram que a recarga em aqüíferos subterrâneos ocorre somente em períodos de chuva (novembro a março). Para o período seco (abril a outubro) as precipitações esparsas não são suficientes para suprir a deficiência de umidade do solo. O trabalho permitiu, ainda, concluir que os métodos teóricos para estimar evapotranspiração potencial não são adequados em regiões caracterizadas por períodos secos e chuvosos. / Hydrologic Engineering quantifies the parameters involving water balance. Thus, the evaluation of aquifers recharge rates is considered a relevant matter due to the uncontrolled use of this type of water resource. The potential recharge rate of Guarani Aquifer for São Carlos area was estimated based on data measured on lysimeter and through the analysis of theoretical infiltration concepts. The lysimeter, assembled at the Hydrometereological Station of CRHEA, is 1.50 m deep and has 3.6 m2 of exposure area. A drainage was used to collect the infiltrated volume, leading it to a graduate collection tank. The lysimeter was filled with soil from the recharge zone of Guarani Aquifer (sandy soil). Soil humidity was monitored inside the lysimeter and at open field, around the area from where the soil was extracted. Infiltration data was recorded between January 2002 and January 2003. Potential direct recharge rate was calculated to 55.6% of the precipitation, for the studied period. Analyses of water behavior in the soil have shown that aquifers recharge occurs only in rainy periods (from november to march). Throughout the droughts (from april to october), sparse precipitations are not enough to compensate the humidity deficiency in the soil. It was also possible to conclude that the theoretical methods for estimation of potential evapotranspiration are not suitable for regions characterized by droughts and rainy periods.

>Magister Scientiae - MSc / Previous studies have shown that the use of chloride mass balance (CMB) method is a suitable and practical approach to estimate groundwater recharge. This enables the prediction of groundwater availability to inform practical strategies for managing groundwater resources. However, such studies have largely applied the chloride mass balance method on national and catchment scales with limited focus on quaternary catchment level (QCL). Neglecting the chloride mass balance method at quaternary catchment level limits practical management and utilization of water resources at quaternary catchment level. The goal of the current study was to prove that 1) the chloride mass balance method should be applied at quaternary catchment level to ensure practical assessment of groundwater availability and that 2) chloride mass balance assessment should be accompanied with supplementary methods for its application in quaternary catchments of similar physiographic and hydrogeologic conditions. To achieve these goals, the present study assessed the application of chloride mass balance method on a pilot scale used alongside rainwater infiltration breakthrough (RIB) and water table fluctuation (WTF) methods to estimate the groundwater recharge as an indicator of groundwater availability. The pilot area (PA) was in the upper Berg River catchment in Western Cape in South Africa. Chloride concentrations were determined in groundwater samples collected from boreholes and rain water in rain gauges in the pilot area. Rainfall and borehole water levels in the pilot area were used in water table fluctuation and rainwater infiltration breakthrough analyses. As quality assurance, the specific yield data obtained from the pumping test were compared to those determined with the linear regression model. This established the reliability of the analysis i.e. the relationship between groundwater level and rainfall. Mean groundwater recharge values calculated using the chloride mass balance, rainwater infiltration breakthrough and water table fluctuation methods were 27.6 %, 23.67 %, and 22.7 % of the total precipitation received in the catchment, respectively. These results indicate that the use of these three methods have potential to estimate groundwater recharge at quaternary level which is the basic unit of water management in South Africa. These findings agree with previous studies conducted in the same catchment that indicate that mean groundwater recharge ranges between 18.6 % and 28 % of the total precipitation. In the future, these methods could be tested in catchments which have physiographic and hydrogeologic conditions similar to those of the current pilot area. / African Union (AU)

Philosophiae Doctor - PhD / The thesis addresses sustainability of groundwater utilization in arid and semiarid regions of Namibia. Recharge in this hydrogeological setting occurs as discrete events to aquifers that are bounded in extent. Case studies involving fractured hardrock and alluvial aquifers with aquifer-ephemeral river interaction were considered. The nature of recharge to arid region bounded aquifers was explored. In arid region aquifers, roundwater storage is depleted during extended dry periods due to pumping and natural discharge. Steady state conditions are rarely achieved. With lowering of the water table, evapotranspiration is reduced thus decreasing aquifer discharge. However, depletion of ephemeral river flow is the primary source of water to boreholes. Physical constraints such as river bed and aquifer hydraulic properties set a limit to the degree of natural replenishment possible during flow events. An approach to assessing sustainable yield of a fractured rock aquifer associated with ephemeral river flow is discussed using a case study from rural semi-arid Namibia. Limited data required the simulation results to be verified against geological and hydrogeological constraints. The aquifer’s gain in storage is estimated through numerical simulation. It provides a basis for groundwater scheme management that rely on limited data in semi-arid conditions in sub-Saharan Africa. Aspects related to ephemeral river flow and groundwater recharge to strip alluvial aquifers was addressed in the second case study. The processes controlling infiltration, significance of surface water and groundwater losses, and possible artificial recharge options were investigated through numerical simulation. It was concluded that recharge processes in arid alluvial aquifers differ significantly from those in humid systems. Conjunctive use of surface and groundwater resources require artificial augmentation of aquifer recharge due to constrains in natural infiltration rates. The study provides a reference for sustainable management of alluvial aquifer systems in similar regions. It is seen from the study that high rates of groundwater exploitation deplete surface water resources needed downstream while failure to capture surface flow during flood events cause loss of potential recharge. It is concluded that as water demand in Namibia increases, basin wide combined surface water and groundwater resource evaluation and management have become a necessity.

Master of Science / Department of Civil Engineering / David R. Steward / Konza Prairie is one of the few areas in the United States were natural landscape of the area is still intact. Human action on changing the landscapes in this area is limited and much of the land remains as native grassland. In spite of its natural existence, this area is not completely isolated from the rest of the world. Changes that are taking place in climate will eventually have the same effect to this region as well as other human populated areas. Increase in carbon concentration in the air has resulted to increase in temperature, this increase in temperature increases the evaporation from the sea, oceans and the ice capes. As the atmospheric water vapor changes the precipitation pattern also change. Changes in precipitation due to climate change will result to change in hydrology and hydraulics of the streams and groundwater flow regime. Precipitation provides surface runoff and groundwater infiltration, which recharge the cracked limestone aquifer present in the Konza area. The infiltration water moves trough the cracked rocks and eventually reach the creeks such as Kings Creek and flow to the Kansas River. Increase in precipitation will result to increase in surface runoffs and more groundwater recharge. Decrease in precipitation will result to decrease in both surface and groundwater. To examine changes in groundwater elevation as recharge change in Konza, a groundwater model was developed based on erosion impact calculator (EPIC) ecological model and SLIT groundwater model. EPIC model estimates the deep percolation (recharge) as 12% and total runoff to about 24% of the annual average precipitation. The annual average recharge values from EPIC were used in SPLIT to simulate results for the groundwater elevation at Konza prairie. Field wells elevation were use to calibrate the SPLIT results. By estimating the hydraulic permeability value to 0.546m/d the field well measurements and SPLIT simulated groundwater elevation results provide a good match. After calibration max and min recharge together with a 5-years moving average were used to examine the changes in groundwater elevation as recharge changes. Future study intends to use the calibrated Konza groundwater model and the forecasted climate data to simulate result for groundwater elevation as climate changes.

My deepest respect and appreciation are extended to Dr. L. Gray Wilson for providing the opportunity to conduct this research, for his advice and assistance during the course of the research, and for his review of and suggestions for improving this manuscript. I would also like to thank Michael Osborn for his assistance. This research was funded by the City of Tucson. The assistance and direction provided by Mt. Bruce Johnson and Mt. Joe Babcock at Tucson Water are gratefully acknowledged. My thanks are also extended to Dr. Daniel D. Evans, Dr. L.G. Wilson, and Dr. Stanley N. Davis for serving on my thesis committee. Bruce Smith's assistance is gratefully acknowledged. Bruce spent two long days with 110-degree temperatures In a parking lot describing the lithology of sediment samples collected during the drilling phase of this research. He also determined the moisture content and particle size distribution on samples collected from the borehole. The assistance of Ralph Marra and Steve Brooks is also gratefully acknowledged. Ralph waded through city and county bureaucracies to determine zoning at each dry-well site. Steve assisted with collecting dry-well settling chamber sediment samples.

>Magister Scientiae - MSc / In the Kruger National Park (KNP) which is the flagship conservation area in South Africa, the impact on groundwater should be kept to a minimum as groundwater plays a vital role in sustaining ecosystem functioning and sustaining baseflow to streams and rivers. For this reason groundwater has been recognized as one of the environmental indicators that need to be monitored. The KNP has adopted a Strategic Adaptive Management (SAM) approach with clear ecosystem management goals. The achievement of these goals is evaluated by using environmental indicators. These indicators are evaluated against thresholds of potential concern (TPC). TPCs are a set of boundaries that together define the spatiotemporal conditions for which the KNP ecosystem is managed. TPCs are essentially upper and lower limits along a continuum of change in selected environmental indicators. Historically, groundwater recharge and surface water interaction with rivers has tended to be overlooked in the KNP. This study proposes a conceptual model of groundwater recharge processes in the KNP, defining when and how groundwater recharge occurs. Two methods were used, the Cumulative Rainfall Departure (CRD) and stable isotopes of ²H and ¹⁸O. An adapted version of the CRD which incorporates a long and short term memory of the system was used to identify possible recharge processes. Further, using the CRD method a reliable reconstruction of the long term groundwater level trends are simulated using monthly rainfall totals with reference to the average rainfall over the entire time series 1936-2009. The stable isotope of ²H and ¹⁸O samples from cumulative rainfall samplers, surfacewater (streams and rivers) and groundwater from boreholes were collected monthly for approximately one year (May 2010 to July 2011). The isotope composition of the groundwater was used to establish whether recharge was immediate or delayed. Additionally, the isotopic composition of surface-water from rivers and streams were compared to that of groundwater to identify surface-water interactions. Groundwater recharge in KNP occurs during the rainy summer months (December to March) and very little to none during the dry winter season (April to September). Recharge takes place during rainfall sequences 100mm or more. The stable isotope records collected from cumulative rainfall, groundwater and surface water (streams and rivers) indicate that groundwater experiences evaporation prior to infiltration. As the KNP experiences high evaporation rates, insignificant rainfall sequences contribute little or zero to recharge. The CRD analysis of groundwater level fluctuations shows that recharge to the aquifers respond to dry and wet cycles that last for 6 to 14 years. The KNP experienced several periods of below-average rainfall and hence no significant recharge took place to the basement aquifers. During a normal rainy season the water levels rise somewhat then starts receding again. It is only during major rainfall events that may occur every 100yrs to 200yrs causing the aquifers to fully recharge. This was perfectly illustrated by the high groundwater levels after the 2000 major rainfall event that recharged the aquifers fully. During below average rainfall years the overall water level trend is drastically declining. The system experiences higher natural losses than gains due to outflow of groundwater to streams and rivers. The KNP is divided down the center by two geological formations, granites along the west and basalts along the east. The combination of the CRD model and the stable isotopic analysis suggest that the dominant recharge processes that occur in the southern region of the KNP are direct recharge via piston flow and indirect recharge via preferred pathways particularly streams and rivers. Along the eastern half of the KNP on the Basalts and Rhyolite direct recharge via piston flow are dominant. Groundwater is not recharged via small streams and rivers (Sweni and Mnondozi Rivers) as it was found that at these particular sites these rivers are detached and do not interact with groundwater. Along the western granitic areas the dominant recharge process are indirect recharge. Recharge takes place via preferred pathways particularly streams and rivers. It was found that ephemeral rivers (Nwatsisonto River) act as sinks for groundwater recharge and influent-effluent conditions are experienced along seasonal rivers (Mbyamiti River). The large perennial Sabie and its tributary the Sand River are consistently fed by groundwater, above all maintaining base flow during the dry season. These rivers act as basin sinks receiving groundwater discharge all year round. Using the stable isotope composition of rainfall, surface-water and groundwater to act as a natural tracer, in combination with the CRD method proved invaluable to confirm the plausible recharge processes. The study provided a conceptual understanding of the groundwater system in the KNP forming the foundation to developing acceptable limits (TPCs) of the groundwater levels in the KNP. The model will serve as a guide for the recharge processes and for deciding on the location and time frames for data collection to ultimately set TPCs for groundwater in the KNP to sustainably manage the resource.

No description available.

Orientador: Didier Gastmans / Resumo: A compreensão dos processos de geração de escoamento nos rios torna necessário o entendimento das interações existentes entre as águas superficiais e subterrâneas, identificando a importância do fluxo de base (FB), e consequentemente dos processos de recarga, para as estimativas de balanço hídrico. A recarga representa a entrada da água na zona saturada e o FB representa a fração do escoamento produto da conexão entre o canal e o aquífero. Em épocas de estiagem a água subterrânea é considerada como a principal componente do FB, e em regiões úmidas é possível se associar a recarga com o FB. No presente estudo foram realizadas as estimativas do FB para 17 sub-bacias localizadas na bacia do rio Atrato (Colômbia). A partir da análise do comportamento temporal da descarga, e considerando o Q90 como parâmetro comparativo do FB, foi identificada uma estreita relação com as variáveis fisiográficas. As bacias com Q90 entre 5,3 e 10,0 mm/dia correspondem as menores declividades médias no curso do rio e Q90 inferiores (1,0 e 5,2 mm/dia) correspondem as maiores declividades. Não foi identificada uma correlação forte entre o FB e a litologia, a partir do qual ressalta-se a importância de categorizar as unidades hidrogeológicas de uma maneira mais detalhada. Posteriormente, foi realizada uma análise de recessão, que definiu a recessão característica (12,8<K[dia]<28,0) e o coeficiente de recessão das bacias (0,92<c<0,96), e consequentemente a separação do hidrograma implementando os seguint... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Comprehension about runoff generation process in rivers becomes necessary to understand interactions between surface and groundwater, identifying the importance of base flow (BF) and recharge processes in water balance applications. Recharge represents the water entrance into the saturated zone and the BF shows the fraction of the runoff result from the connection between the river and the aquifer. On dry periods groundwater is the main component of the BF, which in wet regions is associated with the recharge. In this study, the BFs were estimated for the 17 subbasins, located in the Atrato River basin (Colombia). Through the analysis of the temporal behavior of the river discharge and considering the Q90 as a comparative parameter of the BF, a close relationship between the Q90 and the physical variables was identified. Basins with Q90 between 5.3 and 10.0 mm/day correspond to rivers with higher slopes and lower Q90 (between 1.0 and 5.2 mm/day) correspond to basins with lower river slopes. A correlation between BF and lithology was not identified, which proves the importance of the detailed classification of the hydrogeological units. Subsequently, a recession analysis was performed, which allowed for the definition of the characteristic recession (12.8<K[day]<28.0) and the recession coefficient of the basins (0.92<c<0.96). Finally, the separation of hydrographs was done using the flowing digital filters: Lyne and Hollick filter (FLH), Chapman and Maxwell filter (FCM), Eckha... (Complete abstract click electronic access below) / Resumen: La comprensión de los procesos de generación de escorrentía en los ríos hace necesario el entendimiento de las interacciones existentes entre las aguas superficiales y subterráneas, identificando la importancia del flujo base (FB) y de los procesos de recarga en aplicaciones de balance hídrico. La recarga representa la entrada de agua en la zona saturada y el FB representa la fracción de la escorrentía producto de la conexión con el acuífero. En periodos secos el agua subterránea es la principal componente del FB, que en regiones húmedas es asociado con la recarga. En este estudio fueron estimados los FB para 17 subcuencas, ubicadas dentro de la cuenca del río Atrato (Colombia). A partir del análisis del comportamiento temporal de la descarga del río y considerando el Q90 como parámetro comparativo del FB, fue identificada la estrecha relación entre el Q90 y las variables físicas. Cuencas con Q90 entre 5,3 y 10,0 mm/día corresponden a ríos con mayores pendientes y Q90 inferiores (entre 1,0 y 5,2 mm/día) corresponden a cuencas con menores pendientes del río. No fue identificada una correlación entre o FB y la litología, por lo que se resalta la importancia de una clasificación detallada de las unidades hidrogeológicas. A continuación, fue realizado un análisis de recesión, que permitió la definición de la recesión característica (12,8 <K[día] < 28,0) y el coeficiente de recesión de las cuencas (0,92 <c< 0,96), y posteriormente la separación del hidrograma usando los siguientes... (Resumen completo clicar acceso eletrônico abajo) / Mestre

In energy harvesting communications, the transmitters have to adapt transmission to the availability of energy harvested during communication. The performance of the transmission depends on the channel conditions which vary randomly due to mobility and environmental changes. During this work, we consider the problem of power allocation taking into account the energy arrivals over time and the quality of channel state information (CSI) available at the transmitter, in order to maximize the throughput. Differently from previous work, the CSI at the transmitter is not perfect and may include estimation errors. We solve this problem with respect to the energy harvesting constraints. Assuming a perfect knowledge of the CSI at the receiver, we determine the optimal power policy for different models of the energy arrival process (offline and online model). Indeed, we obtain the power allocation scheme when the transmitter has either perfect CSI or no CSI. We also investigate of utmost interest the case of fading channels with imperfect CSI. Moreover, a study of the asymptotic behavior of the communication system is proposed. Specifically, we analyze of the average throughput in a system where the average recharge rate goes asymptotically to zero and when it is very high.

Philosophiae Doctor - PhD / The study addressed the groundwater assessment and sustainable management of the coastal alluvial aquifers in Namib Desert, the Omaruru River Delta Aquifer (Omdel Aquifer) was used as a case study. Sustainable utilization of groundwater in parts of hyper-arid Sub-Saharan Africa, like the Namib Desert, is always a challenge due to lack of resources and data. Understanding of hydrogeological characteristics of the Omaruru Delta Aquifer System is a pre-requisite for the management of groundwater supply in the Central Namib area (Namib Desert). For the Omdel Aquifer in the Omaruru catchment, Namibia, issues to investigate include the lack of information on the geology and hydrogeological setting, the hydraulic properties and geometry of the aquifer at the inflow and outflow sections, groundwater recharge conditions upstream of the aquifer, and the impact of artificial recharge. Omdel Aquifer occurs in a desert environment with less than 20 mm of rainfall per annum, it’s regarded to receive no direct groundwater recharge from rainfall, only from occasional (inconsistent) flooding of the Omaruru River, due to periodic thunderstorms in the upstream catchment. Since the Omdel Aquifer does not receive direct recharge from rainfall, an artificial recharge scheme was implemented to augment the water supply. One of the objectives of the study is to integrate artificial recharge with hydrogeological understanding of the Omdel Aquifer to establish a conceptual framework for assessment of groundwater recharge and discharge, water chemistry and balanced water supply.