Dissertations / Theses on the topic 'Recharge estimation'

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.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2009.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 153-161).
Quantifying and characterizing groundwater recharge are critical for water resources management. Unfortunately, low recharge rates are difficult to resolve in dry environments, where groundwater is often most important. Motivated by such concerns, this thesis presents a new probabilistic approach for analyzing diffuse recharge in semiarid environments and demonstrates it for the Southern High Plains (SHP) in Texas. Diffuse recharge in semi-arid and arid regions is likely to be episodic, which could have important implications for groundwater. Our approach makes it possible to assess how episodic recharge can occur and to investigate the control mechanisms behind it. Of the common recharge analysis methods, numerical modeling is best suited for considering control mechanisms and is the only option for predicting future recharge. However, it is overly sensitive to model errors in dry environments. Natural chloride tracer measurements provide more robust indicators of low flux rates, yet traditional chloride-based estimation methods only produce recharge at coarse time scales that mask most control mechanisms. We present a data assimilation approach based on importance sampling that combines modeling and data-based estimation methods in a consistent probabilistic manner. Our estimates of historical recharge time series indicate that at the SHP data sites, deep percolation (potential recharge) is indeed highly episodic and shows significant interannual variability. Conditions that allow major percolation events are high intensity rains, moist antecedent soil conditions, and below-maximum root density. El Niño events can contribute to interannual variability of percolation by bringing wetter winters, which produce modest percolation events and provide wet antecedent conditions that trigger spring episodic recharge.
(cont.) Our data assimilation approach also generates conditional parameter distributions, which are used to examine sensitivity of recharge to potential climate changes. A range of global circulation model predictions are considered, including wetter and drier futures. Relative changes in recharge are generally more pronounced than relative changes in rainfall, demonstrating high susceptibility to climate change impacts. The temporal distribution of rainfall changes is critical for recharge. Our results suggest that increased total precipitation or higher rain intensity during key months could make strong percolation peaks more common.
by Gene-Hua Crystal Ng.
Ph.D.

Quantification of groundwater recharge is a crucial prerequisite for sustainable groundwater resource management, particularly in semi-arid areas where there are large demands for groundwater supplies. This research presents an alternative approach for recharge estimation based on the soil water balance technique. The purpose is to develop a model which provides a suitable balance between physical credibility and data which realistically can be gathered. A spreadsheet model was written based on the conceptual representation of the principal physical processes which actually affect recharge in a semi-arid area. Alternative procedures were included in order to represent: (a) the estimation of runoff, (b) the inclusion of the period with predominant bare soil evaporation and (c) the accounting for evapotranspiration following rainfall on dry soil. The model was tested using real data from a semi-arid region (Northeast Nigeria) making use of selected periods of days and years in order to illustrate the principal model characteristics. The results were presented in the form of diagrams and graphs helping to visualise the interactions between the physical components and the effect of the additional procedures on recharge estimation. The credibility of the model was investigated using an alternative concept of 'analysis of plausibility'. This concept makes use of as wide as possible a range of quantitative and qualitative information from the hydrological system in order to verify the robustness of the model when extensive datasets required by conventional validation techniques are not available. The results suggested that the modelled recharge is physically sound and it is in line with the overall determination of recharge in semi-arid areas by a range of methods. The soil water balance model was utilised to explore important aspects of recharge in semi-arid regions showing the effect of the field variability on the model's output. The preliminary results show that the developed concept reasonably represents the inherent field variability, thus corroborating the strength of the approach for recharge estimation in semi-arid regions.

This dissertation reports on the methods and results of a three-phased investigation to estimate the annual volume of ephemeral-channel-focused groundwater recharge attributable to urbanization (urban-enhanced groundwater recharge) in the Sierra Vista subwatershed of southeastern Arizona, USA. Results were used to assess a prior estimate.

The first research phase focused on establishment of a study area, installation of a distributed network of runoff gages, gaging for stage, and transforming 2008 stage data into time series of volumetric discharge, using the continuous slope-area method. Stage data were collected for water years 2008 - 2011.

The second research phase used 2008 distributed runoff data with NWS DOPPLER RADAR data to optimize a rainfall-runoff computational model, with the aim of identifying optimal site-specific distributed hydraulic conductivity values and model-predicted infiltration.

The third research phase used the period-of-record runoff stage data to identify study-area ephemeral flow characteristics and to estimate channel-bed infiltration of flow events. Design-storm modeling was used to identify study-area predevelopment ephemeral flow characteristics, given the same storm event. The difference between infiltration volumes calculated for the two cases was attributed to urbanization. Estimated evapotranspiration was abstracted and the final result was equated with study-area-scale urban-enhanced groundwater recharge. These results were scaled up to the Sierra Vista subwatershed: the urban-enhanced contribution to groundwater recharge is estimated to range between 3270 and 3635 cubic decameters (between 2650 and 2945 acre-feet) per year for the period of study. Evapotranspirational losses were developed from estimates made elsewhere in the subwatershed. This, and other sources of uncertainty in the estimates, are discussed and quantified if possible.

The focus of this study was on recharge mechanisms and recharge estimation within the Table Mountain Group area. The study evaluated recharge processes and recharge estimation methods in the Table Mountain Group aquifer systems.

This aim of this study was to improve the understanding and functioning of the Table Mountain Group aquifer system and contribute to the sustainable development of this potential source for water supply in the Montagu area.

Il seguente elaborato è frutto del lavoro di ricerca, della durata di cinque mesi, svolto presso il Department of Catchment Hydrology del centro di ricerca UFZ (Helmholtz-Zentrum für Umweltforschung) con sede in Halle an der Saale, Germania. L’obiettivo della Tesi è la stima della ricarica della falda acquifera in un bacino idrografico sprovvisto di serie di osservazioni idrometriche di lunghezza significativa e caratterizzato da clima arido. Il lavoro di Tesi è stato svolto utilizzando un modello afflussi-deflussi concettualmente basato e spazialmente distribuito. La modellistica idrologica in regioni aride è un tema a cui la comunità scientifica sta dedicando numerosi sforzi di ricerca, presentando infatti ancora numerosi problemi aperti dal punto di vista tecnico-scientifico, ed è di primaria importanza per il sostentamento delle popolazioni che vi abitano. Le condizioni climatiche in queste regioni fanno sì che la falda acquifera superficiale sia la principale fonte di approvvigionamento; una stima affidabile della sua ricarica, nel tempo e nello spazio, permette un corretta gestione delle risorse idriche, senza la quale il fabbisogno idrico di queste popolazioni non potrebbe essere soddisfatto. L’area oggetto di studio è il bacino idrografico Darga, una striscia di terra di circa 74 km2, situata in Cisgiordania, la cui sezione di chiusura si trova a circa 4 kilometri dalla costa del Mar Morto, mentre lo spartiacque a monte, ubicato a Nord-ovest, dista circa 3 kilometri dalla città di Gerusalemme.

A exploração acelerada das águas subterrâneas pode acarretar em problemas de disponibilidade de água. Esse problema tende a ser acentuado devido as mudanças no clima previstas para as próximas décadas. Nesse contexto, este trabalho buscou avaliar os possíveis impactos das mudanças climáticas e do uso do solo sobre níveis de água subterrânea em zona de afloramento do Sistema Aquífero Guarani. Foram utilizadas simulações de Modelos de Circulação Global (MCG) como dados de entrada para um modelo transiente de fluxo hídrico subterrâneo, visando avaliar o comportamento dos nveis de água sob diferentes condições climáticas. Este modelo foi calibrado utilizando dados de níveis freáticos em seis poços localizados na bacia do Ribeirão da Onça (BRO). A partir de dados climáticos observados, estimou-se a recarga, usada como input no modelo matematico, em diversos tipos de cultura por meio do balanço hídrico. As maiores alterações nas médias pluviométricas mensais foram projetadas, pela maioria dos modelos climáticos, para ocorrer no perodo seco. No perodo chuvoso, as previsões indicaram que essas médias devem diminuir em torno de 50%. Quase 70% dos cenários climáticos geraram, no modelo transiente, variações dos nveis freáticos abaixo daqueles medidos no monitoramento entre 2004 e 2011. Em setores da área de estudo, o rebaixamento da superfície potenciométrica, simulada sob condições climáticas mais extremas previstas por alguns modelos, ultrapassou 10 m. Os cenários mais otimistas, embora tenham resultado em elevações dos níveis de água em mais metade da BRO, também geraram rebaixamentos de até 5 m. Os resultados reforçam a necessidade do contínuo monitoramento hidrogeológico, principalmente em áreas de recarga do SAG, e do desenvolvimento de outros trabalhos que quantiquem os impactos das mudanças climáticas, aplicando diferentes métodos de estimativa de recarga e downscaling.
The unsustainable use groundwater in many countries might cause water availability restrictions. Such issues are likely to worsen due to changes in climate, predicted for the incoming decades. In this context, the objective of this work was to assess possible climate and land use changes impacts on groundwater levels in the Guarani Aquifer System\'s (GAS) outcrop zone. Global Climate Models\' (GCM) outputs were used as inputs in a transient ux groundwater model. Thus, groundwater table uctuation could be evaluated under distinct climatic conditions. Six monitoring wells, located in the Ribeir~ao da Onca basin (ROB), provided water table measurements to calibrate the groundwater model. Using observed climatic data, a water budget method was applied to estimate recharge in dierent types of land uses. Statistically downscaled future climate scenarios were used as inputs in that same recharge model, which provided the inputs for SPA. Most of the GCMs used here predict temperature arises over 2°C. Major monthly rainfall mean changes are projected by the GCM great majority to take place in the dry season. During wet seasons, the predictions indicate those means might experience around 50% decrease. Water table variations, derived from the transient model under almost 70% of the climate scenarios, were below of those measured between 2004 and 2011. Few GCM predicted more extreme climate scenarios. In some regions of the study area and under these conditions, groundwater surface would decline more than 10 m. Although more optimistic scenarios resulted in an increase of groundwater levels in more than half of ROB, these would cause up to 5 m water table decline. The results reinforce the need for a permanent hydrogeological monitoring, mainly in the GAS recharge areas, along with the development of other climate change impacts assessment works using dierent downscaling and recharge estimates methods.

Simple models that require little input data and are easy to use is the ideal case within hydrology. Basic water balance principles often represent such approaches as the method on rainfall-runoff relationship developed by Sutcliffe et al. in India in 1981. That was tested for the Kilombero Valley in Tanzania in order to estimate the recharge to the soil and sub-surface systems. Measured annual runoff in the streams was compared to the seasonal net rainfall to give the difference as potential recharge. This was done for five separate sub-catchment where the hillslope catchments gave a smaller proportion of the net rainfall to occur as surface runoff compared to the valley-catchments. Due to the difference in hydrologic setting from the original model site in India to the Kilombero Valley (e.g. a wetland and stream type), the soil moisture recharge could not be estimated. Also, corrections are needed to the data preparation process and the state of the original stream flow data is questionable. Thus, the results were interpreted as an indication on how the water resources could be moving in the system. An explaining theory that captured the difference between the landform types is mountain system recharge. That implied that all surplus rainfall generated in the mountains has a potential to eventually recharge the groundwater. The method tested, though its simple general concepts, could not alone give satisfying results for the Kilombero Valley system. However, this study convey the importance of continuous exploration of methods to describe the environment in a simplified way.

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.

La dégradation croissante de la qualité des eaux de la nappe phréatique de petite Beauce a conduit à l'élaboration de plusieurs programmes de lutte contre la pollution d'origine principalement agricole. Le nitrate constitue l'un des principaux facteurs de la détérioration de la qualité des eaux souterraines et le seuil de 50 mg/l est aujourd'hui très largement dépassé dans de nombreux forages AEP. De plus, cette nappe phréatique étant essentiellement réalimentée par le drainage hivernal de la couverture de sol, l'accroissement des prélèvements estivaux pour l'irrigation et plusieurs hivers successifs largement déficitaires en précipitations, ont fortement affecté son niveau piézométrique. Dans ce contexte, l'objectif de cette étude est d'analyser les variations de nature de la couverture de sol et celles de son état hydrique au début de l'hiver afin de mieux connaitre la recharge hivernale de la nappe phréatique des calcaires de Beauce. Dans une première partie le milieu naturel est décrit et le secteur d'étude d'une superficie de 100 ha est présenté en détail. L’analyse se poursuit par l'étude des différents types de sols présents sur le secteur et la mise en évidence de plusieurs caractéristiques essentielles de la couverture de sol. La deuxième partie traite de la variation de l'épaisseur de la couverture de sols, caractéristique essentielle pour la recharge hivernale de l'aquifère. Les résultats acquis à partir de sondages mécaniques a la tarière et notamment ceux obtenus par krigeage pour la cartographie de l'épaisseur de la couverture de sol sont présentés ainsi que ceux obtenus par des méthodes géophysiques (résistivité électrique). La troisième partie concerne le fonctionnement hydrique hivernal de la couverture de sol du secteur étudié. Elle traite des termes du bilan hydrique et du choix d'un modèle adapte compte tenu des données disponibles. Une spatialisation de ce modèle est tentée à l'aide d'une SIG, sur la base d'une prise en considération des situations en sols nus ou emblaves, irrigues ou non. Une estimation des lames d'eau écoulées à la base de la couverture de sol est effectuée pour les hivers 91-92 et 92-93. La recharge hivernale apparait être essentiellement liée aux conditions météorologiques et a l'état hydrique initial (rémanence de l'irrigation) et secondairement à l'épaisseur et au mode d'occupation du sol

>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)

Ephemeral streams with spatially and temporally variable flow are important ecological settings in semi-arid desert environments that until now have been poorly characterized. Our quantitative analysis explores how intermittent stream hydrology varies across geomorphic (mountain streams to desert washes) and climatic gradients (150-400 mm precipitation) in Southern Arizona. Stream channels were instrumented for the first time with a co-deployment of vertical profiles of subsurface temperature sensors, and electrical resistance (ER) sensors on the bed surface. HYDRUS 1-D was used to simulate vertical unsaturated flow, and differences along hydrologic, topographic, and climatic gradients were compared. Annual surface water presence varied < 1%-82% of the year, and reach-normalized infiltration water volumes were 20,000-2,500,000 m³/(km y). Surface water presence was correlated with geomorphic gradient, and infiltration volumes were correlated with surface water presence. This sensor co-deployment method has shown that ER sensors alone are necessary to estimate infiltration in semi-arid, poorly-sorted, coarse desert channels.

Dans cette thèse, nous proposons une démarche méthodologique permettant de simuler le besoin en équipement de rechange pour une flotte de véhicules. Les systèmes se dégradent avec l’âge ou l’usage, et sont défaillants lorsqu’ils ne remplissent plus leur mission. L’usager a alors besoin d’une assurance que le système soit opérationnel pendant sa durée de vie utile. Un contrat de soutien oblige ainsi l’industriel à remédier à une défaillance et à maintenir le système en condition opérationnelle durant la durée du contrat. Ces dernières années, la mondialisation et l’évolution rapide des technologies obligent les constructeurs à proposer des offres de contrat de maintenance bien au-delà de la vie utile des équipements. La gestion de contrat de soutien ou d’extension de soutien requiert la connaissance de la durée de vie des équipements, mais aussi des conditions d’usages des véhicules, dépendant du client. L’analyse des retours clientèle ou des RetEx est alors un outil important d’aide à la décision pour l’industriel. Cependant ces données ne sont pas homogènes et sont très fortement censurées, ce qui rend les estimations difficiles. La plupart du temps, cette variabilité n’est pas observée mais doit cependant être prise en compte sous peine d’erreur de décision. Nous proposons dans cette thèse de modéliser l’hétérogénéité des durées de vie par un modèle de mélange et de concurrence de deux lois de Weibull. On propose une méthode d’estimation des paramètres capable d’être performante malgré la forte présence de données censurées.Puis, nous faisons appel à une méthode de classification non supervisée afin d’identifier des profils d’utilisation des véhicules. Cela nous permet alors de simuler les besoins en pièces de rechange pour une flotte de véhicules pour la durée du contrat ou pour une extension de contrat
This thesis gathers methodologicals contributions to simulate the need of replacement equipment for a vehile fleet. Systems degrade with age or use, and fail when they do not fulfill their mission. The user needs an assurance that the system is operational during its useful life. A support contract obliges the manufacturer to remedy a failure and to keep the system in operational condition for the duration of the MCO contract.The management of support contracts or the extension of support requires knowledge of the equipment lifetime and also the uses condition of vehicles, which depends on the customer. The analysis of customer returns or RetEx is then an important tool to help support the decision of the industrial. In reliability or warranty analysis, engineers must often deal with lifetimes data that are non-homogeneous. Most of the time, this variability is unobserved but has to be taken into account for reliability or warranty cost analysis.A further problem is that in reliability analysis, the data is heavily censored which makes estimations more difficult. We propose to consider the heterogeneity of lifetimes by a mixture and competition model of two Weibull laws. Unfortunately, the performance of classical estimation methods (maximum of likelihood via EM, Bayes approach via MCMC) is jeopardized due to the high number of parameters and the heavy censoring.To overcome the problem of heavy censoring for Weibull mixture parameters estimation, we propose a Bayesian bootstrap method, called Bayesian RestorationMaximization.We use an unsupervised clustering method to identify the profiles of vehicle uses. Our method allows to simulate the needs of spare parts for a vehicles fleet for the duration of the contract or for a contract extension

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
This study aimed at assessing the direct recharge of the river Gramame basin aquifer, located in the south region of Paraiba state, through the application of the method WTF (water table fluctuation). Moreover, the study aimed at understanding the behavior of static level variation of the unconfined aquifer, in terms of space and time. For that, a monitoring program was carried out in the unconfined aquifer. Static levels of 27 wells were measured as well as rainfall data. During the period of static level monitoring, three different types of behavior were detected. Investigations have sought to correlate these variations with different behaviors, including: rainfall, thickness of the unsaturated soil, digital terrain model, land use, geology and hydraulic conductivity. This last property was obtained using Beerkan methodology. Most of the factors have influence on the fluctuation of static level, except the geology, most likely due to the low level of detail of this information. The direct calculated recharge for the monitored hydrological year (2009/2010) ranged between 53 and 105 mm, which represents between 5 and 10% of average rainfall in the basin during the study. These values were lower than expected for a humid region, probably due to the low values of rainfall during the survey, which was about 42% lower than average annual basin. According to the results, a systematic monitoring of the aquifer for a longer period is recommended, in order to provide better input data to decision making regarding the use of the groundwater basin.
Este trabalho teve como objetivo a determinação da recarga direta na bacia hidrográfica do rio Gramame, porção sul do Estado da Paraíba, através da aplicação do método WTF (water table fluctuation). Para tanto, foi realizado o monitoramento do aqüífero livre da bacia, através de freqüentes medições do nível estático de 27 poços e tratamento de dados de precipitação. Durante o período do monitoramento do nível do lençol freático dos poços, três tipos diferentes de variação foram detectados. Investigações realizadas buscaram correlacionar as variações com alguns fatores, entre eles: precipitação, espessura da camada não-saturada do solo, elevação do terreno, uso do solo, geologia e condutividade hidráulica, que foi obtida a partir da utilização da metodologia Beerkan. A maioria dos fatores exerceu grande influência no comportamento do aqüífero, com exceção da geologia, provavelmente pelo baixo nível de detalhes destas informações. A recarga direta calculada para o ano hidrológico do monitoramento (2009/2010) variou entre 53 e 105 mm, o que representa entre 5 e 10% da precipitação média na bacia durante o estudo. Estes valores ficaram abaixo do esperado para uma região úmida, muito provavelmente pelos baixos índices pluviométricos registrados durante a pesquisa, que foi cerca de 42% menor do que média anual da bacia. Recomenda-se o monitoramento sistemático do aqüífero por um período mais longo, a fim de dar subsídios na tomada de decisões quanto à utilização da água subterrânea da bacia.

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.

In arid regions, mountain catchments are the major contributor to the total natural water yield. Due to generally low groundwater tables, subsurface underflow - referred to as mountain-front recharge - is important in distinction to the surface runoff at the mountain front. The extent of the groundwater basin is hereby often vague. Approaches to assess mountain-front recharge are mostly based on groundwater data and integrate over time and space. This, however, cannot provide prognostic and time-dependent estimates of subsurface inflow to the adjacent alluvial basin aquifer. Consequently, the proposed strategy builds on rainfall based approaches. Temporal and spatial resolution is in this case mostly limited by data scarcity regarding hydrological characteristics of the catchment area and high-resolution rainfall data. The proposed novel strategy combines three approaches to tackle these challenges. A newly developed conceptual hydrologic model provides time-dependent estimates based on fully distributed monthly rainfall. For distinct response units and seasons, non-linear relationships between rainfall and recharge describe the hydrogeologic response. The derivation of the response functions is based on a mass balance and considers the principal recharge mechanisms. Parameterisation makes use of available expert knowledge on geomorphology and seasonal rainfall characteristics. As an efficient tool to assess uncertainties, fuzzy arithmetic is used for complementary long-term average water balance estimates. This technique allows considering fuzziness in rainfall input, crop water use in mountain oases, and best available assumptions on recharge as portion of rainfall. Uncertainty regarding the potential, albeit unknown extent of groundwater basins is portrayed based on continuous surfaces which represent the degree of membership to a distinct geographical entity (termed as fuzzy regions). Distinct subsets of these fuzzy regions represent potential groundwater basins for water balance assessment. The proposed strategy was applied on the large scale in an arid karst mountain range in northern Oman. The two complementary assessment approaches result in similar ranges of values. They are in good agreement with inversely computed inflow to a steady state groundwater model for the adjacent basin aquifer. The results of the conceptual hydrologic model are confirmed by the plausibility of average recharge rates for distinct response units and seasons. This shows that less intense winter rainfall contributes mainly to groundwater recharge. Uncertainties due to the vague extent of the groundwater basin are about 30 % of the total mean annual value. An option to mitigate this uncertainty is the complementary consideration of adjacent aquifer systems in future studies. Hydrogeologic survey and observation of groundwater levels in the alluvial basin aquifer in near distance to the mountains is a way to underpin these findings in future studies. This recommenddation applies not only to the discussed study area, but also to mountain block systems in general
In ariden Gebieten haben Gebirgseinzugsgebiete einen wesentlichen Anteil am gesamten natürlichen Wasserdargebot. Aufgrund i. Allg. tief liegender Grundwasserspiegel ist - in Abgrenzung zum Oberflächenabfluss am Gebirgsrand - auch der unterirdische Abstrom (mountain-front recharge) von besonderer Bedeutung. Die Ausdehnung des unterirdischen Einzugsgebiets ist dabei oft vage. Ansätze zur Abschätzung des mountain-front recharge basieren meist auf Grundwasserdaten und integrieren in Zeit und Raum. Damit können allerdings keine prognostischen oder zeitabhängigen Schätzungen für den Zustrom zur benachbarten alluvialen Aquifer gemacht werden. Daher wird im folgenden ein niederschlagsbasierter Ansatz vorgeschlagen. Das vorgeschlagene neue Konzept kombiniert drei Ansätze, um den genannten Herausforderungen zu begegnen. Mit einem neu entwickelten konzeptionellen hydrologischen Modell auf Basis verteilter Niederschläge werden monatliche Werte für die Grundwasserneubildung bereitgestellt. Es basiert auf nicht-linearen Beziehungen zwischen Niederschlag und Grundwasserneubildung für definierte hydrologisch homogene Einheiten und Jahreszeiten. Deren Ableitung basiert auf einer Massenbilanz und berücksichtigt die wesentlichen Neubildungsmechanismen. Die Parametrisierung basiert auf Expertenwissen zu Geomorphologie und Niederschlagscharakteristika. Fuzzy Arithmetik wird zur Berücksichtigung von Unsicherheiten in einer ergänzenden mittleren jährlichen Wasserbilanz verwendet. Damit können Unschärfen im Niederschlagsinput, beim Pflanzenwasserbedarf in Gebirgsoasen und best verfügbaren Schätzungen der Neubildung als Bruchteil des Niederschlags effizient berücksichtigt werden. Mittels kontinuierlicher Oberflächen, die den Grad der Zugehörigkeit zu einer bestimmten geographischen Entität anzeigen (fuzzy regions) werden Unsicherheiten in der räumlichen Ausdehnung der unterirdischen Einzugsgebiete beschrieben. Definierte Teilmengen dieser fuzzy regions werden dann bei den Wasserhaushaltsbetrachtungen als potentielle Grundwassereinzugsgebiete verwendet. Der vorgeschlagene Ansatz wurde in einer ariden, teils verkarsteten Gebirgsregion im Norden des Sultanats Oman angewendet. Die beiden sich ergänzenden Ansätze zur Abschätzung der Grundwasserneubildung ergaben im langjährigen Mittel vergleichbare Werte. Diese stimmten auch gut mit den Ergebnissen einer inversen Grundwassermodellierung überein. Die Plausibilität der Neubildungsraten für bestimmte hydrologisch homogene Einheiten und Jahreszeiten spricht für die Verlässlichkeit der Ergebnisse des konzeptionellen hydrologischen Modells. Offensichtlich tragen insbesondere die weniger intensiven Winterniederschläge wesentlich zur Grundwasserneubildung bei. Die Unsicherheiten bezüglich der Ausdehnung des Grundwassereinzugsgebiets belaufen sich auf ca. 30 % des mittleren jährlichen Dargebots. Die komplementäre Betrachtung benachbarter Grundwassereinzugsgebiete ist ein denkbarer Weg, diese Unsicherheit in Zukunft zu reduzieren. Ein wesentlicher Beitrag um die Ergebnisse dieser Studie zukünftig weiter zu untermauern wären hydrogeologische Erkundung und Beobachtung von Grundwasserständen im alluvialen Aquifer, insbesondere nahe dem Gebirgsrand. Diese Empfehlung gilt über dieses Fallbeispiel hinaus für vergleichbare Systeme, in denen ein Gebirgseinzugsgebiet den Aquifer in der angrenzende Ebene speist

A Bacia do Alto Tietê (BAT) abriga uma população de 19,5 milhões de pessoas numa área de 5.985 km2, correspondendo aproximadamente ao contorno da região Metropolitana de São Paulo (RMSP). A BAT é composta por dois sistemas aqüíferos principais: o Sistema Aqüífero Sedimentar (SAS) (1.452 km2) e o Sistema Aqüífero Cristalino (CAS) (4.238 km2). A importância da água subterrânea na RMSP tem crescido significativamente nos últimos 20 anos. Diversas indústrias e condomínios têm utilizado a água subterrânea como fonte complementar e muitas vezes exclusive de abastecimento de água, extraindo um volume que corresponde a cerca de 13% do volume total de água distribuído pelas companhias de abastecimento público. Apesar de sua importância, pouco se sabe sobre a qualidade e quantidade de água que abastece esses sistemas aqüíferos. Além disso, em áreas urbanas, a influência antrópica causa mudanças aos padrões de recarga natural dos sistemas aqüíferos. Este estudo teve os seguintes objetivos: i) estimar a recarga no SAS em duas áreas com diferentes padrões de ocupação urbana (alta e baixa densidade de impermeabilização), utilizando diferentes métodos (flutuação dos níveis de água, aproximações darcinianas, hidroquímica, isótopos estáveis); e ii) determinar a origem da água de recarga (vazamentos do sistema de água e esgoto ou infiltração natural de chuva). Os períodos mais chuvosos e mais secos para ambas as áreas foi janeiro e agosto, respectivamente, e a precipitação total para a área menos urbanizada. O método de flutuação dos níveis de água estimou um valor de recarga natural para a área menos urbanizada de 246 mm/a e 183 mm/a para a área densamente urbanizada. Um valor de 481 mm/a foi obtido pelas aproximações darcinianas para a área mais urbanizada e 311 mm/a para a área menos urbanizada e, se as estimativas forem precisas, a diferença entre os resultados dos diferentes métodos indica a soma das fontes de recarga antrópicas (respectivamente 298 mm/a e 65 mm/a). A análise dos dados químicos de Na+, Cl-, NO3 -, NH4 + e SO42- demonstrou a presença de vazamentos extensivos do sistema de esgoto em ambas as áreas. Os resultados dos isótopos em NO3 - para a área urbanizada (enriquecimento de ?15N e ?18O) e dados químicos (DOC, HCO3-) indicam que a desnitrificação tem papel importante na atenuação do nitrato no aqüífero. Os dados de níveis de água, da zona não saturada e isótopos ambientais indicam que chuvas menores que 20 mm/dia ou 100 mm/mês não são capazes de recarregar o aqüífero. Os dados de ?18O e ? 2H coletados em ambas as áreas apresentam-se sobre uma linha de mistura entre as assinaturas da chuva (maior que 100 mm/mês) e água do sistema de abastecimento público, indicando a contribuição destas fontes distintas na recarga dos aqüíferos (contribuição urbana de 14% na recarga da área menos urbanizada e 67% na área mais urbanizada, corroborando os resultados dos outros métodos). Os dados obtidos neste estudo indicam que vazamentos do sistema de esgoto e de água de abastecimento têm papel fundamental na recarga do aqüífero e na qualidade da água subterrânea.
The Upper Tiete Watershed (UTW) has a population of 19.5 million in an area of 5,985 km2, which corresponds approximately to the contour of the Metropolitan Region of Sao Paulo (MRSP), Brazil. The UTW is comprised of two major aquifer systems: the Sedimentary Aquifer System (SAS) (1,452 km2) and the Crystalline Aquifer System (CAS) (4,238 km2). The importance of groundwater in the MRSP has increased substantially during the last 20 years. Several industries and condominiums are using groundwater as a complementary and often exclusive source of water supply, extracting a volume that corresponds to approximately 13% of the total volume of water distributed by the public supply companies. Despite their importance, not much is known about the quality and quantity of the water that recharge these aquifer systems. Besides, in urban areas, the anthropogenic influence causes changes to the natural water recharge patterns of the aquifer systems. This study had the following objectives: i) estimating the recharge of the SAS in two areas with different land use patterns (high and low density of paved surfaces), using different methods (water table fluctuation, Darcyan approach, hydrochemistry, environmental isotopes); and ii) determining the origin of the recharge water (leakage of supply water and sewerage system or natural infiltration of rainfall). The rainiest and driest months for both areas were January and August, respectively, and the total precipitation for the densely paved area was 1,193 mm and 1,407 mm for the least-paved area. The water table fluctuation methodology estimated that natural recharge for the poorly urbanized area is 246 mm/a and 183 mm/a for the densely urbanized area. A value of 481 mm/a was obtained through the Darcyan approach for the more urbanized area and 311 mm/a for the less urbanized area and, if the estimations are accurate, the difference between the results of the different methods indicates the sum of the anthropogenic recharge sources (respectively 298 mm/a and 65 mm/a). Analysis of chemical data for Na+, Cl-, NO3 -, NH4 + and SO42- showed the presence of extensive sewerage leakage in both areas. Results from isotopes in NO3- for the urbanized area (enrichment of ?15N and ?18O) and chemical data (DOC, HCO3-) indicated that denitrification plays an important role in attenuating the nitrate in the aquifer. The data from water levels, the unsaturated zone and environmental isotopes indicate that rainfall volumes lower than 20 mm/day or 100 mm/month are not able to recharge the aquifer. Data from ?18O and ? 2H collected in both areas lie on a mixing line between the fingerprints of precipitation water (higher than 100 mm/month) and water from the public supply system, indicating the contribution of these distinct sources to the recharge of the aquifers (urban contribution of 14% for the recharge of the less urbanized area and 67% in the more urbanized area, corroborating the results of other methods). The data obtained in this study indicates that leakage of the sewage and water distribution system plays a major role in the recharge of the aquifer and groundwater quality.

Os aquíferos da região do Canal do Jurubatuba são importantes no abastecimento industrial, comercial e residencial. Em 2001, foi detectada contaminação por solventes organoclorados nos solos e nas águas subterrâneas da região, atingindo o aquífero fraturado profundo, caracterizando risco para a população local e acarretando na paralisação de diversos poços de produção. Tratando-se de um aquífero fraturado, a contaminação apresentou-se complexa, devido a dificuldades na previsão de fluxos nesses sistemas. Este trabalho, inserido no projeto \"Bases técnicas para a gestão de áreas contaminadas por solventes clorados\" (GESOL), objetiva estimar a recarga dos aquíferos na região do Canal do Jurubatuba, por meio dos métodos de balanço hídrico, da variação do nível d\'água do aquífero e isotópico; realizar as caracterizações hidroquímica e isotópica (O, H, e Sr) das águas subterrâneas e das potenciais fontes de recarga (água da chuva rede de abastecimento de água e de esgoto); e integrar os resultados para avaliar a atuação dos processos naturais e das possíveis influências antrópica e da dinâmica das águas subterrâneas na sua composição. Os trabalhos incluíram o monitoramento de dados meteorológicos e da variação do nível d\'água subterrânea; e coleta de amostras de água para análises químicas e isotópicas. O acumulado de chuvas mensal e a respectiva variação do nível d\'água dos poços monitorados, evidenciaram que a recarga dos aquíferos está sendo efetiva sob pluviometria média acima de 100 mm, confirmada pelo monitoramento da zona não saturada. As análises isotópicas da chuva permitiram elaborar a reta meteórica local, que apresentou boa correlação com a reta meteórica global, além de evidenciarem haver relação entre a quantidade de precipitação mensal e a variação no enriquecimento de isótopos estáveis. O enriquecimento isotópico nos resultados das amostras e água e de fontes, observado durante o período prolongado de seca de 2013/2014, apresentou correlação com poços com maior contribuição de fonte antrópica na recarga naquele período, indicando influência de diferentes comportamentos do clima na composição das fontes de recarga e das águas subterrâneas. Os isótopos de Sr apresentaram razoável eficácia na identificação de fontes antrópicas da recarga, mas não permitiram a distinção entre essas fontes. As caracterizações hidroquímica e isotópica mostraram que os aquíferos avaliados apresentaram alteração na qualidade de suas águas, em maior ou menor grau, em diferentes níveis, em decorrência de contribuição de fontes de recarga antrópica. O amônio se mostrou o indicador mais eficaz na determinação de contribuição antrópica na recarga por esgoto, e a presença de nitrato reflete a potencial atuação de processos de nitrificação nas águas subterrâneas. Os resultados dos métodos físicos utilizados para o cálculo de recarga, considerando-se as limitações de cada método, indicaram valores muito próximos. A recarga potencial pelo método do balanço hídrico apresentou média anual de 18,84% e a estimativa de recarga média pelo método da variação do nível d\'água de 16,27% do total de precipitação. O método isotópico indicou média geral de 51,7% de contribuição antrópica na mistura das águas subterrâneas. A influência de fluxos ascendentes, identificada pelas cargas hidráulicas dos poços monitorados e pelas semelhanças hidroquímica e isotópica entre as águas dos poços profundos e rasos, está contribuindo para a mistura das águas subterrâneas dos aquíferos de porosidade intergranular.
The aquifers in the Jurubatuba Canal region are important for the industrial, commercial and residential supply. In 2001, a contamination by organochlorine solvents was detected in the soils and groundwater in the region, reaching the deep fractured aquifer, posing risk for the local population and causing the interruption in several production wells. As the aquifer is fractured, the contamination was found to be complex, due to the difficulty to predict the flows in these systems. This study, part of the project called \"Technical base for the management of areas contaminated by chlorine solventes (1)\", aims at estimating the recharge of the aquifers in the Jurubatuba Canal region using water balance, water table flutuation and isotopic methods; developing the hydrochemical and (O, H and Sr) isotopic studies about the groundwater and the potential recharge sources (rainwater, water and sewage supply networks); and integrating the results in order to assess the action of natural processes and possible anthropic and dynamic influences in the groundwater composition. The studies have included monitoring meteorological data and groundwater level variation; and also collecting water samples for chemical and isotopic analyses. The total monthly rainfall and the correspondent variation of the water levels in the monitored wells have shown that the aquifers recharge has been effective, with an average rainfall above 100 mm, confirmed by the monitoring of the unsaturated zone. The isotopic analyses of the rainfall have enabled the elaboration of the local meteoric water line, which has presented a good correlation with the global meteoric water line, and they have also pointed out a relation between the monthly precipitation quantity and the variation in the enrichment of stable isotopes. The isotopic enrichment in the results of water and recharge sources samples, observed during the long dry period in 2013/2014, has presented a correlation with the wells that have a bigger contribution of anthropic source in the recharge of that period, indicating an influence of climate changes in the composition of the recharge sources and the groundwater. The Sr isotopes have presented a reasonable efficacy in the identification of anthropic recharge sources, but they have not allowed the distinction between these sources. The hydrochemical and isotopic characterizations have shown that the evaluated aquifers have presented a bigger or smaler alteration in their water quality in different levels, due to the contribution of anthropic recharge sources. Ammonium was found to be the most efficient index to determine the anthropic contribution for the sewage recharge and the presence of nitrate reflects the potential action of nitrification processes in the groundwaters. The results of the physical methods used for the recharge calculation, considering the limitations of each method, indicated very close values. The potential recharge by the water balance method has presented an annual average of 18.84% and the average recharge estimate of the water table flutuation was 16.27% of the total precipitation. The isotopic method has shown a general average of 51.7% of anthropic contribution in the groundwater mixing. The influence of upward flows, identified by the hydraulic charges in the monitored wells and by the hydrochemical and isotopic similarities between the waters in the deep and shallow wells, is contributing for the mixing of the groundwaters of the intergranular porosity aquifers.

碩士
國立成功大學
資源工程學系碩博士班
97
Characterization of the hydrogeological parameters of an aquifer is an essential task. Traditional approaches of mapping the subsurface with surface geophysics or the recently emerging field-scale data fusion and tomographic approaches are either too expensive for basin coverage or provide information that does not directly address issues related to groundwater. The purpose of this study is to apply tomographic approach to imaging the subsurface at the basin scale, and perform MODFLOW model with homogeneous and heterogeneous method, and stream-flow estimation model to estimated the stream infiltration under consideration at the variation of stream water level in Hsinhuwei stream. The sensitivity analysis had provided. Several cases are investigated and analyzed. The results indicate that assessment of the stream infiltrations obtained with stream-flow estimation model are 2,642,000 tons/year, and MODFLOW model with homogeneous and heterogeneous method are 1,709,000 and 2,054,000 tons/year, respectively. As the stream water level raised about 2.5 meters, the amounts of stream infiltration estimated from the Ferris analytical model are significant increments of 316,000 tons/year and MODFLOW with homogeneous and heterogeneous model are 264,000 and 343,000 tons/year, respectively. Consequently, an increase stream storage will result in an increase groundwater recharge between 10.0％ and 18.5％.

博士
國立成功大學
資源工程學系碩博士班
99
In groundwater hydrology, transmissivity (T) and storativity (S) are important parameters in groundwater recharge estimation. This study develops an analytical approach to estimating T in basins with the use of the stream hydrographs of water level and flow records. Our physical model describes T values in unconfined aquifers as large-scale basin T averages. The proposed analytical approach is useful when data on basins are scarce. In Taiwan, precipitation varies across locations and seasons. The annual mean rainfall is approximately 2,500 mm, 80% of which falls during the wet season (May–October) and 20% falls during the dry season (November–April). Therefore, this study combines the instantaneous recharge theory, the master recession curve (MRC), and the recession-curve-displacement method to verify estimates of mean basin values. We use stream hydrographic records obtained during the wet and dry seasons. Moreover, statistical methods are applied to estimate groundwater recharge. We select hydrographic data on daily mean streamflow and water table obtained from three streamflow gauging stations in southern Taiwan. Mean absolute error (MAE) evaluation criteria are used to select the most appropriate season for T estimation. MAE values in the Kaoping, Dongkang, and Linbian basins during the wet (dry) season are 0.48 (0.82), 0.41 (0.61), and 1.08 (1.71), respectively. Three case studies, which compare field records obtained from a pumping test, demonstrate the feasibility of the proposed analytical approach to estimating T. The MRC of the wet season is appropriate in three basins, indicating that a recharge episode can evaluate aquifer reliably based on stream hydrographic records. However, using the recession index formula of Rorabaugh and Simons (1966), some S estimates seem too small. In the groundwater recharge study, the case of the Kaoping River is classified as an all-basin case; the Kaoping River basin holds groundwater recharge from the Chishan River basin, Laonong River basin, Ailiao River basin, and Kaoping River. The null hypothesis of normal distribution cannot be rejected at a significance level of 0.05. Furthermore, through the method of moments estimation, we estimate the annual groundwater recharge for the all-basin case and the Kaoping basin at 54.7±13.6 and 46.6±16.9 hundred million m3, respectively. Moreover, a comparison of the error percentages of annual groundwater recharge between the all-basin case and the Kaoping basin reveals that 34% of all samples have 20% or more errors. The analytical results demonstrate that the annual groundwater recharge estimates differ between the all-basin case and the Kaoping basin. The analytical results show a positive correlation between basin area and recession index. The recession index and the recharge associated with a single rainfall recharge episode are positively related to the basin area. Specifically, larger basins usually have higher recession indices and recharge from a single rainfall recharge episode. Additionally, in estimating groundwater recharge, we must multiply the recharge depth with the basin area using the recession-curve-displacement method. Integration with a larger area and a higher recession index results in a multiplication effect on groundwater recharge. Thus, groundwater recharge is overestimated in the present research cases.

碩士
臺灣大學
生物環境系統工程學研究所
98
The groundwater resource is abundant in Taiwan and it is making a critical issue to exploit groundwater resource properly. Groundwater resources could be well managed and utilized if the storage and movement of groundwater is rationally evaluated. The continually declining groundwater level in Chou-shui river alluvial fan is mainly caused by the unregistered pumping by private wells due to enormous water demand from agriculture and aquaculture, in turn leading to land subsidence and soil salination. In addition, the construction of Taiwan High Speed Rail (THRS) has caused serious land subsidence in Tuku and Yuan-Chang township. This research estimated ground water storage, recharge, and withdraw rate in Chou-Shui river alluvial fan by developing numerical model with MODFLOW and SWAT. Unregistered withdraw by private wells in this area are investigated through comparing registered groundwater rights from Water Resources Agency with simulated discharge. Finally, the recharge efficiency of artificial lakes with radii of 3 km and 1.5 km along the THRS were addressed. Results show that, during 1999 to 2002, averaged recharge in the Chou-Shui river alluvial fan is 1.24 billion tons/year, side-stream recharge is 895.7 million tons/year, and unregistered pumping from private wells is 1.1941 billion tons/year. Scenarios with different elevation, soil, and land use type lead to diverse recharge rate. Highest recharge rate is found at the proximal fan, which is 1 million tons/year/km2. Moreover, recharge rate is 940 thousand tons/year/km2 at Gu-Keng and Dou-Liu, and 532 thousand tons/year/km2 near the Pei-Kang river, the worst case. The locations of two THSR recharge scenarios are close, result in similar recharge rates, which are 807.8 thousand tons/year/km2 for the 3 km lake and 797.2 thousand tons/year/km2 for the 1.5 km lake.

碩士
中原大學
土木工程研究所
101
Both soil infiltration volume and evaporation play an important role during the hydrological cycle process, and it is indispensable especially when it comes to water balance calculation. As subjected to geographic and climatic affects, Taiwan is experiencing unevenly distribution of rainfalls in time and space. Coupled with the undulating topography, short and rapid river flows, and difficulty in storing and using the rainfalls have caused most rainwater to flow directly into the sea, causing more limits in using the water resources in Taiwan. This study aims to conduct estimation on rainfall infiltration in different types of soils, evaporation volume, runoff volume and groundwater recharge volume in common red clay and sandy clay loam found in Taoyuan area. The estimated soil moisture contents were then compared with the measured data of on-site TDR soil water content, and verification was finally made to appraise the reliability. The study discovers that the undulating curve of TDR moisture volume in winter was not great and the variation of estimated value of moisture content was greater. However, when the rain falling time had gone through long period of estimation and calculation, both of them had the tendency to coincide. The reason may be due to insufficient depth of rainfall intensity, resulting in inability for water amount to penetrate the soil surface. Based on the estimated results conducted in 2003-2007, groundwater recharge volume of red clay accounted for approximately 8.15-9.46% of total annual rainfall volume, and that of annual runoff volume was approximately 61.94-67.73%; whereas, the groundwater recharge volume of sandy clay loam was approximately 15.03-16.34% of total annual rainfall volume, and that of annual runoff volume was approximately 36-38.33%. We also understand that groundwater recharge volume of sandy clay loam is higher than that of red soil recharge volume. Meanwhile, the estimated groundwater recharge volume is generally conformed to the estimated values conducted by other literatures. However, as this study was able to consider different rainfall patterns, it is thus possible to apply the estimation method of this study to perform monthly estimation of recharge volume.

碩士
國立屏東科技大學
土木工程系所
98
The main two objectives of reconnaissance Estimation of Groundwater Recharge and Exploitation using Groundwater Hydrograph Analysis method for Pingtung Plain, Taiwan, can be summarized as: The first objective is to adjust the method to set up of the slope of exploitation rate in term of the primitive Groundwater-Hydrograph Analysis. From the adjusted Groundwater-Hydrograph Analysis to estimate groundwater recharge, exploitation and groundwater loss are 1844 MM3, 1347 MM3, and 15.62 MM3 of the years 2001, 2002 and 2003 respectively for Pingtung Plain, Taiwan. The second objective is to investigate the characteristic, application and limited conditions using Groundwater -Hydrograph Analysis method. The results from the study show the groundwater recharge amounts of the years 2001, 2002 and 2003 are 1844 MM3, 1347 MM3and 1562 MM3 respectively. The groundwater exploitations of the years 2001, 2002 and 2003 are 1305 MM3, 1298 MM3 and 1228 MM3 respectively. The groundwater losses of the years 2001, 2002 and 2003 are 5.17 MM3, 2.61 MM3 and 2.14 MM3 respectively. The Groundwater Safe Yield of the years 2001, 2002 and 2003 are 13.27 MM3, 10.86 MM3 and 13.48 MM3 respectively. In addition, the Groundwater-Hydrograph Analysis method is easily used to estimate groundwater recharge and groundwater exploitation for the clearly demarcated area of wet and dry seasons. It is reliable for referenced value to easily estimate the result of groundwater recharge or exploitation. Furthermore, this method is quite suitable to estimate the area where have not detailed groundwater exploitation information.

碩士
國立中興大學
水土保持學系
88
Groundwater accounts for an important portion of usable water resources. In the past, groundwater investigations often focus on regional characteristics and relationships between groundwater recharge and discharge. The objective of this study is to utilize appropriate methods for estimating the groundwater recharge and discharge that only requires streamflow data without considering the geological influences. This study applied the base-flow-record estimation method and the recession-curve displacement method to streamflow data from Lien-Hwa-Chi #3、#4 and #5 watersheds and Pi-Lu-Chi #11 and #12 watersheds in central Taiwan. The results show that base flow index of watershed increase with increasing area and slope. The area of watershed is more important than slope in influencing stored groundwater volume in the watershed. The base-flow-record estimation method and the recession-curve displacement method appear to underestimate groundwater discharge from hydrographs governed by first rainfall of a long dry season. The type of rainfall is therefore important in applying the two methods used in this study.

博士
國立臺灣大學
農業工程學系
85
Abstract Groundwater is one of the vital water resources on Taiwan. A lot of Water have been withdrawn, and some adverse effects such as land subsidence and sea- water intrusion have been developed. Therefore, the determination of the safety pumping yield is an important task. The precipitation may infiltrate into the subsurface and become the supplement of ground-water. Therefore, the estimation of the amount of precipitation recharge to ground water is the priority work for the ground-water management planning. The quality and quanity of ground-water are equally important for ground-water recharge. If the oil leaks from the storage tank, it will migrate into ground- water aquifer. The oil is compound of hydrocarbon that does not readily dissolve in water and behaves as a separate fluid phase is known as Non-Aqueous Phase Liquid (NAPL). The interface of two immiscible, flowing fluids of oil and water in porous media may behave in unstable fashion. The velocity at tip of interface may be higher than the mean velocity, which causes the aquifer contaminant moves much faster and consequently increases the risk of contaminating ground water aquifers. Therefore, it is also important to inestigate the controlling factors of an unstable wetting front to act in the prevention and remediation of ground water contamination. The thesis is divieded into two parts, the one is to investigate the controlling factors of unstable wetting front; the other is to develop an estimation method for evaluating the quanity of rainfall recharge to ground-water. The stochastic analysis method is adopted for the study due to the parameter such as hydraulic conductivity and precipitation are varied with space and time. The development of the two-phase flow equation is based on the mass balance principle with the boundary conditions such as the velocity continuity and capillary pressure bamance at the interface. By assuming the two-phase fluids in porous media are saturated, a covariance function of the wetting front position is derived by the stochastic appeoach. The result shows the unstable interface between two immiscible fluids is governed by the fluid velocity and properties such as viscosity and desity. The fluid properties which affect the interface instability are expressed as dimensionless parameters, such as mobility ratio, capillary number and Bond number. If the fluid flow is driven by gravity force, whether the interface is upward displacement or downward displacement, the variance of unstable interface decreases with increasing of mobility ratio, increases with increasing of capillary number and decreases with increasing of Bond number. For the case of a horizontal flow, the result shows that the generation of unstable interface is not affected by capillary number. The tainfall recharge coefficient is investigated based on an unconfined aquifer with unbound infinite boundary condition. A spectrum''s relation between the precipitation and ground-water level is derived. The rainfall recharge coefficient can be obtained from the solution of the spectrum equation. The estimation of rainfall recharge coefficient will be affected by the location of observation well if the rainfall recharge and ground-water level is applied to CHho-Shui-River alluvial tip for the estimation the rainfall recharge coefficient. The results show that the rainfall recharge coefficient is about 0.03 and the amount

Cette étude a été réalisée sur le mont Covey Hill (Québec, Canada) afin de quantifier les échanges entre l'eau souterraine et trois cours d'eau (Outardes, bassin versant : 23 km2 ; Allen, bassin versant : 26 km2 ; Schulman, bassin versant : 9,5 km2) et d'estimer la recharge vers l'aquifère régional. L'analyse des séries temporelles de débits, de précipitations et de niveaux de la nappe phréatique a été utilisée afin de déterminer la dynamique hydrologique de la zone d'étude. Un bilan hydrique a été calculé et un modèle d'infiltration verticale a été construit afin de calculer les différents flux d'eau sur les bassins versant des rivières Allen et Outardes. Les résultats montrent que le débit de base représente 32, 40 et 4% du débit total des rivières Allen, Outardes et Schulman respectivement. Les analyses corrélatoires et spectrales montrent que les cours d'eau ont un effet mémoire de moins de 10 jours i.e. que le système hydrologique est très dynamique et peu influencé par l'aquifère. Les niveaux piézométriques montrent quant à eux un cycle annuel. Des liens précipitations-débits très clairs, mais de courte durée ont été mis en évidence, de même que des liens précipitations-niveaux piézométriques plus diffus. Ces analyses n'ont pas permis de confirmer la présence d'un lien aquifère-cours d'eau. Un échantillonnage hebdomadaire d'eau de surface a permis l'analyse géochimique de l'eau pendant les saisons estivales de 2007 et 2008. Cette analyse montre que durant l'étiage, la rivière Outardes et le ruisseau Schulman sont alimentés par l'eau provenant du roc fracturé des grès du Potsdam tandis que la rivière Allen est alimentée par l'eau contenue dans les sédiments. Par ailleurs, l'utilisation du 222Rn a montré que la contribution de l'aquifère est faible et très localisée sur les trois bassins. Le calcul du bilan hydrique indique que la rivière Allen est caractérisée par une prépondérance de l'infiltration tandis que la rivière Outardes est surtout alimentée par le ruissellement de surface. Les milieux humides présents sur le bassin de la rivière Allen jouent un rôle important pour ralentir les écoulements et favoriser ainsi la recharge tandis que la présence de grès peu perméable verticalement (Flat Rock) semble favoriser le ruissellement sur le bassin Outardes. La recharge modélisée au moyen du Modèle d'infiltration verticale (MIV) est de 227 ± 73 mm pour la rivière Allen et de 240 ± 79 mm pour la rivière Outardes, mais cette dernière valeur est probablement surestimée en raison du manque de précision du MIV pour simuler le ruissellement. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : échanges nappe-rivière, recharge, séries temporelles, Covey-Hill.

碩士
嘉南藥理科技大學
觀光事業管理系暨溫泉產業研究所
101
There are over a hundred hot spring outcrops in Taiwan and about 20 are commercialized. In recent years the hot spring industries experience rapid growths that dramatically increase the withdrawals of hot spring thermal water. First collected from 2011 to 2012 between the in situ data and monitoring data and to analyze and construct the Hot springs area hydrogeological conceptual model using MODFLOW software on groundwater flow model three-dimensional simulations, in order to meet situ hydrogeological structure and hydraulic parameters model.Spa monitoring wells by the field data, in 2012 the water level and water temperature compared with 2011, there is no significant change in spa water should be used in a balanced state, from 100 to 101 years level measurements indicate changes in the level point ± 0.2 cm, no subsidence potential.The investigation is now estimated Hot springs after about 16,318 ~ 23,539 cubic meters using / day, by the numerical simulation to estimate the water balance analysis showed that spa water recharge is about 18,448 ~ 25,669 cubic meters / day, compared compared with the results in the present investigation to estimate more than 13%.

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.

博士
國立成功大學
資源工程學系碩博士班
94
The purpose of this research is to estimate groundwater recharge by using streamflow hydrograph models. There are two case studies in this research. Case Study 1: Four methods include, Recession-Curve -Displacement Method (RCDM), Constant Recharge Method (CRM), Base-Flow-Record Estimation (BFRE), and Mathematical Digital Filtering Method (MDFM), are adopted to estimate groundwater recharge in Cho-Shui Shi Basin. Case Study 2: Water Balance Model (WBM) in this research is coupled with Base-Flow-Record Estimation and Stable-Base-Flow Analysis (SBFA) to estimate groundwater recharge in Taiwan. In this research, mapping is achieved by using Geographic Information Systems (GIS) and geostatistics. In the case study of Cho-shui Shi Basin, RCDM is constructed to calculate groundwater recharge when evident events occur. However, the inconsequent result that base flow is grater than streamflow is caused by the instantaneous injection given sometimes. CRM is developed to eliminate the inconsequent result in RCDM. Besides, CRM also provides analyzable procedure when continuous recharge events occur. Two baseflow separation methods, BFRE and MDFM, provide a more convenient and faster analytic procedure compared with RCDM and CRM. Although the increment of groundwater recharge is hard to be obtained by BFRE or MDFM in the periods when recharge events occur, it is suggested to adopt BFRE and MDFM in the applications of large scale study area. The results obtained from the case study of Taiwan are as followed. The spatial distribution of the long-term mean SBFI is: mountain areas express a rate of 40~60%, the areas of hills and terraces express a rate of 20~40%, and the areas of alluvial plains receive an SBFI between 10~20%, the avearage SBFI obtained by stable-base-flow analysis is about 34.5%; The spatial distribution of long-term mean annual runoff is about 0-1000 mm in the western area, and above 3000 mm in the northeastern corner. The long-term mean runoff ratio for Taiwan is about 55.5%; The spatial distribution of the naturally occurring long-term mean annual groundwater recharge is: The highest rates occur in the northeastern part and the central-eastern part of Taiwan, mountain areas express a rate of 800-2000 mm/year annually, the areas of hills and terraces express a rate of 200-600 mm/year annually, and the areas of alluvial plains receive an annual groundwater recharge below 200 mm. Note that the mean annual groundwater recharge is approach 0 mm in the western edge of Taiwan, which is the most serious land subsidence area in Taiwan; The total groundwater recharge of Taiwan is about 18 billion tons per year, and the groundwater recharge rate is about 0.21. The advantages of water balance model estimated in this study are the rapid analytic processes and the low data requirement. At present, stable-base-flow analysis developed in this study still contains subjectivity when determines the stable-base-flow period. But with the analyzed results of 191 streamflow gauging stations by stable-base-flow analysis, it is shown that the low-flow period differs by the position of the gauging station. The low-flow period can be neglected in the downstream area, while the low-flow period presents obviously in the upstream area. This discovery could be the direction to eliminate the uncertainty caused by subjectivity in the further research.

碩士
國立屏東科技大學
土木工程研究所
83
Groundwater forms an essential component of the total available resources in many areas. Knowledge of the processes and amount of groundwater recharge are therefore of fundamental importance in establishing an adequate water resources development plan. The Pingtung Plain is an important agricultural area in southern Taiwan and, due to rapid economic development, use of the groundwater resource has changed dramatically in recent years; groundwater overdraft and aquifer pollution have become serious problems in many areas of this coastal plain. Three phases are included in this study to describe groundwater recharge in the Pingtung Plain. First, investigations of cores are performed to determine the hydraulic conductivity, using a falling-head permeameter. Sedimentary samples are taken form two main river beds, i.e. Kaoping River and Tungkang River, applying different models for quantifying the hydraulic conductivity. Secondly, a chloride mass balance method is employed to obtain groundwater recharge in four divisions of the plain. Finally, the experimental data are incorporated in a groundwater computer simulation model in order to verify the assumed hydrogeological parameters. The results indicate that the chloride mass balance is a simple and effective method to estimate groundwater recharge. Further, numerical simulation is shown to provide the additional information required to improve the accuracy of future groundwater management models.

"June 2001"
Bibliography: p. 165-183.
xxviii, 250 p. : ill., plates (col.), maps (col.) ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
The aims of this study were to develop models for predicting groundwater recharge from alley farming systems in the Murray Basin and for designing alley farms that will result in a prescribed recharge reduction. --p. 158.
Thesis (Ph.D.)--University of Adelaide, Dept. of Agronomy and Farming Systems, 2002

碩士
國立屏東科技大學
土壤與水工程國際碩士學位學程
105
The objective of this thesis is to study the relationship of daily rainfall, daily recharge inflow, and daily groundwater table fluctuation, by using artificial neural networks (ANNs) and multiple linear regression (MLR) in Pingtung of Southern Taiwan. Daily hydro-meteorological data, which include rainfall (mm/day) and groundwater table (m/day), have been collected over a five-year period. Besides, for study artificial recharge, 3 months inflow data (m/day) was also collected. In the process of modeling, all data were normalized prior to analysis, rainfall and recharge water level were selected as input variables while the differences of groundwater table were used as dependent variable. Three difference ANN models naming as multiple linear regression (MLR), Time-Lag Recurrent Network (TLRN), and Time-Delay Network (TDNN) are studied for establishing the relationship of rainfall, the level of recharge water intake and groundwater variation. Compared findings, the results highlighted the coefficient of determination (R2) for MLP is higher than other models. It means MLP is appropriate for estimating the variable on groundwater variation in this study site.

In arid regions, mountain catchments are the major contributor to the total natural water yield. Due to generally low groundwater tables, subsurface underflow - referred to as mountain-front recharge - is important in distinction to the surface runoff at the mountain front. The extent of the groundwater basin is hereby often vague. Approaches to assess mountain-front recharge are mostly based on groundwater data and integrate over time and space. This, however, cannot provide prognostic and time-dependent estimates of subsurface inflow to the adjacent alluvial basin aquifer. Consequently, the proposed strategy builds on rainfall based approaches. Temporal and spatial resolution is in this case mostly limited by data scarcity regarding hydrological characteristics of the catchment area and high-resolution rainfall data. The proposed novel strategy combines three approaches to tackle these challenges. A newly developed conceptual hydrologic model provides time-dependent estimates based on fully distributed monthly rainfall. For distinct response units and seasons, non-linear relationships between rainfall and recharge describe the hydrogeologic response. The derivation of the response functions is based on a mass balance and considers the principal recharge mechanisms. Parameterisation makes use of available expert knowledge on geomorphology and seasonal rainfall characteristics. As an efficient tool to assess uncertainties, fuzzy arithmetic is used for complementary long-term average water balance estimates. This technique allows considering fuzziness in rainfall input, crop water use in mountain oases, and best available assumptions on recharge as portion of rainfall. Uncertainty regarding the potential, albeit unknown extent of groundwater basins is portrayed based on continuous surfaces which represent the degree of membership to a distinct geographical entity (termed as fuzzy regions). Distinct subsets of these fuzzy regions represent potential groundwater basins for water balance assessment. The proposed strategy was applied on the large scale in an arid karst mountain range in northern Oman. The two complementary assessment approaches result in similar ranges of values. They are in good agreement with inversely computed inflow to a steady state groundwater model for the adjacent basin aquifer. The results of the conceptual hydrologic model are confirmed by the plausibility of average recharge rates for distinct response units and seasons. This shows that less intense winter rainfall contributes mainly to groundwater recharge. Uncertainties due to the vague extent of the groundwater basin are about 30 % of the total mean annual value. An option to mitigate this uncertainty is the complementary consideration of adjacent aquifer systems in future studies. Hydrogeologic survey and observation of groundwater levels in the alluvial basin aquifer in near distance to the mountains is a way to underpin these findings in future studies. This recommenddation applies not only to the discussed study area, but also to mountain block systems in general.:1 Mountains - 'water towers' for water resources systems in arid regions 2 Mountain hydrology and water resources assessment 2.1 Mountain hydrology and mountain-front recharge 2.2 Essential aspects to advance mountain hydrology 2.2.1 Rainfall characteristics and options for data acquisition 2.2.2 Groundwater-surface water interactions and availability of reference values 2.3 Approaches to the assessment of mountain-front recharge 2.3.1 Options to assess groundwater recharge 2.3.2 Arid zone water balance modelling - options and limitations 2.3.3 Key components for assessing mountain-front recharge 2.4 Linear reservoir models to describe base flow recession 3 Approaches to deal with uncertainty with a special focus on fuzzy sets 3.1 Probability based uncertainty assessment versus fuzzy reasoning 3.2 Fuzzy sets and related methods 3.3 Ranges of application in hydrology and water resources management 4 A novel strategy for estimating groundwater recharge in arid mountain regions 5 Fuzzy-based tools to portray uncertainties in water balance assessment 5.1 Fuzzy Recharge Areas: From qualitative data to quantitative conclusions 5.1.1 The concept of the Fuzzy Recharge Areas 5.1.2 Consideration of adjacent basins 5.2 Water balance assessment based on fuzzy arithmetic 5.2.1 Outline of the calculation procedure 5.2.2 Implementation of the fuzzy arithmetic operators 5.2.3 Implementation of the regionalisation approach APLIS 6 A conceptual hydrologic model to assess mountain-front recharge 6.1 Basic idea 6.2 Model structure 6.3 Calculation procedure using histograms of rainfall depths 6.4 Non-linear seasonal rainfall-recharge relationships 6.4.1 Derivation of the rainfall-recharge relationships 6.4.2 Sensitivity analysis 6.4.3 Response functions based on extreme parameter sets 6.5 Subsurface routing based on linear reservoir models 7 Case Study: Groundwater recharge assessment for the Barka Region (Oman) 7.1 Study area 7.1.1 Topography 7.1.2 Climate 7.1.3 Evapotranspiration 7.1.4 Rainfall characteristics 7.1.5 Geology and Hydrogeology 7.1.6 Soils 7.1.7 Runoff characteristics 7.1.8 Vegetation and irrigated agriculture in mountain oases 7.2 Recharge mechanisms in the study area 7.3 Assessment of mountain-front recharge - Methodology 7.3.1 Data Processing of Fuzzy Recharge Areas 7.3.2 Determining response units 7.3.3 Water use in mountain oases 7.3.4 Long-term average considerations based on fuzzy arithmetic 7.3.5 Time-dependent assessment using the conceptual hydrologic model 7.4 Assessment of mountain-front recharge - Results 7.4.1 Long-term average considerations 7.4.2 Time-dependent estimates 7.5 Consideration of uncertainties 7.6 Discussion & Conclusions 7.6.1 Water resources assessment in the study area 7.6.2 Modelling approaches 8 Summary 9 Prospects for future work List of Figures List of Tables List of Symbols List of Abbreviations Appendix A: Sensitivity of the response function to variations of the different model parameters B: Histograms of subsurface outflow at the mountain front QMFR based on different parameterisations of the conceptual hydrologic model References
In ariden Gebieten haben Gebirgseinzugsgebiete einen wesentlichen Anteil am gesamten natürlichen Wasserdargebot. Aufgrund i. Allg. tief liegender Grundwasserspiegel ist - in Abgrenzung zum Oberflächenabfluss am Gebirgsrand - auch der unterirdische Abstrom (mountain-front recharge) von besonderer Bedeutung. Die Ausdehnung des unterirdischen Einzugsgebiets ist dabei oft vage. Ansätze zur Abschätzung des mountain-front recharge basieren meist auf Grundwasserdaten und integrieren in Zeit und Raum. Damit können allerdings keine prognostischen oder zeitabhängigen Schätzungen für den Zustrom zur benachbarten alluvialen Aquifer gemacht werden. Daher wird im folgenden ein niederschlagsbasierter Ansatz vorgeschlagen. Das vorgeschlagene neue Konzept kombiniert drei Ansätze, um den genannten Herausforderungen zu begegnen. Mit einem neu entwickelten konzeptionellen hydrologischen Modell auf Basis verteilter Niederschläge werden monatliche Werte für die Grundwasserneubildung bereitgestellt. Es basiert auf nicht-linearen Beziehungen zwischen Niederschlag und Grundwasserneubildung für definierte hydrologisch homogene Einheiten und Jahreszeiten. Deren Ableitung basiert auf einer Massenbilanz und berücksichtigt die wesentlichen Neubildungsmechanismen. Die Parametrisierung basiert auf Expertenwissen zu Geomorphologie und Niederschlagscharakteristika. Fuzzy Arithmetik wird zur Berücksichtigung von Unsicherheiten in einer ergänzenden mittleren jährlichen Wasserbilanz verwendet. Damit können Unschärfen im Niederschlagsinput, beim Pflanzenwasserbedarf in Gebirgsoasen und best verfügbaren Schätzungen der Neubildung als Bruchteil des Niederschlags effizient berücksichtigt werden. Mittels kontinuierlicher Oberflächen, die den Grad der Zugehörigkeit zu einer bestimmten geographischen Entität anzeigen (fuzzy regions) werden Unsicherheiten in der räumlichen Ausdehnung der unterirdischen Einzugsgebiete beschrieben. Definierte Teilmengen dieser fuzzy regions werden dann bei den Wasserhaushaltsbetrachtungen als potentielle Grundwassereinzugsgebiete verwendet. Der vorgeschlagene Ansatz wurde in einer ariden, teils verkarsteten Gebirgsregion im Norden des Sultanats Oman angewendet. Die beiden sich ergänzenden Ansätze zur Abschätzung der Grundwasserneubildung ergaben im langjährigen Mittel vergleichbare Werte. Diese stimmten auch gut mit den Ergebnissen einer inversen Grundwassermodellierung überein. Die Plausibilität der Neubildungsraten für bestimmte hydrologisch homogene Einheiten und Jahreszeiten spricht für die Verlässlichkeit der Ergebnisse des konzeptionellen hydrologischen Modells. Offensichtlich tragen insbesondere die weniger intensiven Winterniederschläge wesentlich zur Grundwasserneubildung bei. Die Unsicherheiten bezüglich der Ausdehnung des Grundwassereinzugsgebiets belaufen sich auf ca. 30 % des mittleren jährlichen Dargebots. Die komplementäre Betrachtung benachbarter Grundwassereinzugsgebiete ist ein denkbarer Weg, diese Unsicherheit in Zukunft zu reduzieren. Ein wesentlicher Beitrag um die Ergebnisse dieser Studie zukünftig weiter zu untermauern wären hydrogeologische Erkundung und Beobachtung von Grundwasserständen im alluvialen Aquifer, insbesondere nahe dem Gebirgsrand. Diese Empfehlung gilt über dieses Fallbeispiel hinaus für vergleichbare Systeme, in denen ein Gebirgseinzugsgebiet den Aquifer in der angrenzende Ebene speist.:1 Mountains - 'water towers' for water resources systems in arid regions 2 Mountain hydrology and water resources assessment 2.1 Mountain hydrology and mountain-front recharge 2.2 Essential aspects to advance mountain hydrology 2.2.1 Rainfall characteristics and options for data acquisition 2.2.2 Groundwater-surface water interactions and availability of reference values 2.3 Approaches to the assessment of mountain-front recharge 2.3.1 Options to assess groundwater recharge 2.3.2 Arid zone water balance modelling - options and limitations 2.3.3 Key components for assessing mountain-front recharge 2.4 Linear reservoir models to describe base flow recession 3 Approaches to deal with uncertainty with a special focus on fuzzy sets 3.1 Probability based uncertainty assessment versus fuzzy reasoning 3.2 Fuzzy sets and related methods 3.3 Ranges of application in hydrology and water resources management 4 A novel strategy for estimating groundwater recharge in arid mountain regions 5 Fuzzy-based tools to portray uncertainties in water balance assessment 5.1 Fuzzy Recharge Areas: From qualitative data to quantitative conclusions 5.1.1 The concept of the Fuzzy Recharge Areas 5.1.2 Consideration of adjacent basins 5.2 Water balance assessment based on fuzzy arithmetic 5.2.1 Outline of the calculation procedure 5.2.2 Implementation of the fuzzy arithmetic operators 5.2.3 Implementation of the regionalisation approach APLIS 6 A conceptual hydrologic model to assess mountain-front recharge 6.1 Basic idea 6.2 Model structure 6.3 Calculation procedure using histograms of rainfall depths 6.4 Non-linear seasonal rainfall-recharge relationships 6.4.1 Derivation of the rainfall-recharge relationships 6.4.2 Sensitivity analysis 6.4.3 Response functions based on extreme parameter sets 6.5 Subsurface routing based on linear reservoir models 7 Case Study: Groundwater recharge assessment for the Barka Region (Oman) 7.1 Study area 7.1.1 Topography 7.1.2 Climate 7.1.3 Evapotranspiration 7.1.4 Rainfall characteristics 7.1.5 Geology and Hydrogeology 7.1.6 Soils 7.1.7 Runoff characteristics 7.1.8 Vegetation and irrigated agriculture in mountain oases 7.2 Recharge mechanisms in the study area 7.3 Assessment of mountain-front recharge - Methodology 7.3.1 Data Processing of Fuzzy Recharge Areas 7.3.2 Determining response units 7.3.3 Water use in mountain oases 7.3.4 Long-term average considerations based on fuzzy arithmetic 7.3.5 Time-dependent assessment using the conceptual hydrologic model 7.4 Assessment of mountain-front recharge - Results 7.4.1 Long-term average considerations 7.4.2 Time-dependent estimates 7.5 Consideration of uncertainties 7.6 Discussion & Conclusions 7.6.1 Water resources assessment in the study area 7.6.2 Modelling approaches 8 Summary 9 Prospects for future work List of Figures List of Tables List of Symbols List of Abbreviations Appendix A: Sensitivity of the response function to variations of the different model parameters B: Histograms of subsurface outflow at the mountain front QMFR based on different parameterisations of the conceptual hydrologic model References

博士
國立中央大學
應用地質研究所
105
Based on global hydrological data, the Center for Environmental Systems Research, University of Kassel, Germany, classified Taiwan as an area of water shortage. Water resources per capita in Taiwan (4,074m3/yr) are only one fifth of the world average (21,796m3/yr). In some regions and particularly during dry periods, groundwater is the only reliable water resource in Taiwan. This is particularly true for mountain regions. Estimating groundwater recharge is a key component in determining the potential yield and sustainable management of groundwater resources. The research presented here consists of three components: (a) groundwater level monitoring and pumping samplings; (b) assessment of groundwater composition and mass-balance based identification of recharge sources; (c) comparison of groundwater composition with surface water (spring and river) in the region. We established a monitoring network for groundwater levels at five wells located at the NCU Research well field near Chien-Shih area, Hsinchu. Moreover, groundwater was sampled at specific time intervals during a pumping sampling. Nearby river and spring water were also collected before and after pumping samplings. Stable oxygen isotopes of water samples were then analyzed. For the purpose of regional groundwater management, knowledge about the residence time of groundwater is an important parameter for planning groundwater protection and improvement measures. According to calculations based on mass-balance equations, the contribution of recharge from precipitation was much higher in spring water (13.7-46.3％) than in river (11.9-16.7％). In rainy season, the springs (71-100%) from the catchment in the study area is the major recharge source of groundwater than river (0-86%) and precipitation (0-32%). In dry season, the springs (44-100%) from the catchment in the study area is the major recharge source of groundwater than river (11-88%) and precipitation (0-31%). Finally, the isotopic data were compared with past geochemical characteristics of aquifer and local meteoric water line (LMWL) in Chien-Shih area. The research results provide insights into the recharge mechanism of the well field, in particular the sources and pathways of recharge.