Conventional methods of groundwater modeling are based on applying laminar flow condition in the aquifer and assuming primary porosity to be present in the aquifer. But in cases where conduits, caves, springs and sinks characterize the aquifer as in karst, this assumption is inappropriate. In addition to Darcian flow condition in matrix portion of aquifer there should be consideration for dealing with non-Darcian flow in the conduits where high velocity of flow occurs. Presence of conduit network in the aquifer greatly affects the potentiometric heads within the aquifer. Hence the necessity of different modeling method has long been realized for karst aquifers. MODFLOW-Conduit Flow Process (CFP) has the capability to simulate both turbulent and laminar groundwater flow condition present in caves and conduits portion of karst aquifers. This study examined the cases where a sub-regional model was used to simulate discharge of springs and heads both with and without considering the presence of conduit network in the aquifer using MODFLOW-CFP 2005 and MODFLOW 2005 respectively. Comparison of results showed that the potentiometric head in the area consisting conduit network were unrealistically low when conduit network was not considered to be present in the matrix. This study also introduces and uses a program called CONGEN to generate conduit flow process file for CFP Mode 1. Furthermore this study also carried out the benchmark testing to examine the capability of MODFLOW-CFP to simulate both laminar and turbulent pipe flow in the conduits for a sub-regional scale. Results from transient state simulation indicate that, although MODFLOW-CFP considers both laminar and turbulent flow conditions in the pipe like conduits in the karst, it underestimated the peak discharge of the springs in this study.

Made available in DSpace on 2014-06-11T19:26:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-07-12Bitstream added on 2014-06-13T18:54:14Z : No. of bitstreams: 1 stradioto_mr_me_rcla.pdf: 2953628 bytes, checksum: 6040f85bad204d9e807f0b3ddd58c5bd (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O presente trabalho tem como objetivos estudos petrológicos e hidroquímicos em área de ocorrência dos sedimentos do Grupo Bauru, na região sudoeste paulista. A análise petrográfica e a evolução diagenética foram realizadas com a utilização de microscopia óptica, microscopia eletrônica de varredura e difratometria de Raios X. Para caracterização hidroquímica foram realizadas análises físico-químicas. A análise hidroquímica apontou o predomínio das águas bicarbonatadas cálcicas e sódicas e, secundariamente aparecem as clorosulfatadas cálcicas e as cloretadas sódicas. As águas bicarbonatadas sódicas concentram-se na porção leste, nordeste e central da área, enquanto as bicarbonatadas cálcicas distribuem-se por toda a área, com discreto predomínio na porção central. Quanto à composição detrítica, os arenitos do Grupo Bauru são constituídos essencialmente por quartzo e feldspatos e em menor quantidades aparecem os fragmentos líticos e os minerais acessórios. Os principais processos diagenéticos identificados nos arenitos analisados foram dissoluções de minerais pesados, fragmentos líticos e aluminossilicatos; cimentação por calcita microcristalina, formação de argilominerais, cimentação por calcita em mosaico e tardia e cimentação por zeólitas. / The present research has as objective petrologic and hydrochemical studies in area of occurrence of the sediments of the Bauru Group, in the São Paulo southwestern region. Optical microscopy, scanning electron microscopy and X-ray diffraction were applied in the petrographic analysis and the diagenetic evolution. To the hydrochemical characterization was used physical-chemical analyses. The hydrochemical analysis revealed the predominance of bicarbonated calcic and sodic waters and secundarily appear chlorosulphated calcic and the sodic chlorinated. The bicarbonated sodic waters concentrate in the east, northeast and central portion of the area, while the bicarbonated calcic are distribute for all the area, with discrete predominance in the central portion. How much to the detritic composition, the sandstone of Bauru Group are constituted essentially by quartz and feldspars and in minor amounts appear the lytic fragments and the accessory minerals. The main diagenetic processes identified in the sandstone analyzed had been heavy mineral, lytic fragments and aluminossilicate dissolutions, cementation by microcrystalline calcite, formation by clay minerais, cimentation by recrystallized calcite and cimentation by zeolite.

abstract: Stable isotopes were measured in the groundwaters of the Salt River Valley basin in central Arizona to explore the utility of stable isotopes for sourcing recharge waters and engineering better well designs. Delta values for the sampled groundwaters range from -7.6‰ to -10‰ in 18O and -60‰ to -91‰ in D and display displacements off the global meteoric water line indicative of surficial evaporation during river transport into the area. Groundwater in the basin is all derived from top-down river recharge; there is no evidence of ancient playa waters even in the playa deposits. The Salt and Verde Rivers are the dominant source of groundwater for the East Salt River valley- the Agua Fria River also contributes significantly to the West Salt River Valley. Groundwater isotopic compositions are generally more depleted in 18O and D with depth, indicating past recharge in cooler climates, and vary within subsurface aquifer layers as sampled during well drilling. When isotopic data were evaluated together with geologic and chemical analyses and compared with data from the final well production water it was often possible to identify: 1) which horizons are the primary producers of groundwater flow and how that might change with time, 2) the chemical exchange of cations and anions via water-rock interaction during top-down mixing of recharge water with older waters, 3) how much well production might be lost if arsenic-contributing horizons were sealed off, and 4) the extent to which replacement wells tap different subsurface water sources. In addition to identifying sources of recharge, stable isotopes offer a new and powerful approach for engineering better and more productive water wells. / M.S. Geological Sciences 2010

Magister Scientiae - MSc / The focus of this work was to monitor and evaluate the hydrochemical characteristics of the groundwater in the Incomati Estuary for a period of one year. The aims of this work were to evaluate the groundwater chemistry data for any spatial and temporal variations and to evaluate the suitability of the groundwater for drinking and irrigation purposes. / South Africa

South Florida has transformed from a natural to a managed ecosystem upon channelization of Kissimmee River and the wetlands in the 1960’s. The drainage has resulted in fast transport of water and nutrient, and subsequently eutrophication of the downstream water bodies. The intervention required: intensive management of the shallow groundwater to balance ecological water requirement; and nutrient removal, namely phosphorus, to minimize eutrophication. The study was set to examine and develop an operational prediction method for groundwater-phosphorus interactions to support the wetlands management. Accordingly, a point scale and a spatio-temporal groundwater level was simulated using sequence based Markovian stochastic analysis and dynamic factor analysis methods respectively. A root mean square error of 0.12m and 0.15m was observed for a point and spatio-temporal groundwater prediction. Soluble and sequestered phosphorus were also simulated at 13% error using a watershed based model called ArcWAM. A spatial analysis on simulated soluble phosphorus and groundwater level indicated similarity of patterns (spatial correlation) 99% of the time. A geographically weighted multivariate analysis of soluble phosphorus using predictors of groundwater level, total phosphorus of surficial water, and distance from Kissimmee River showed a goodness of fit (R2 ) of 0.2 – 0.7. Amongst the factors, the groundwater explained 70% of the soluble phosphorus variability. In summary, an increase in soluble phosphorus was observed with groundwater rise and a decrease during groundwater recession. A reversed relationship was identified for the total phosphorus. Presumably, organic matter in the root zone has contributed to increased soluble phosphorus with the rise in groundwater. On the other hand, solubility of calcium carbonate from the karst aquifers seems to fix and precipitate phosphorus during recession of groundwater. The least sequestration of phosphorus, observed in oversaturated wetlands also suggested that nutrient removal on karst hydrogeology could be risky unless a check is made using vegetation strip to enhance phosphorus uptake. The study concluded that phosphorus could be operationally predicted associated with forecasting of groundwater fluctuation. Further research is recommended to explore factors that could be derived either empirically or from satellite data for prediction of soluble phosphorus at minimum cost.

Groundwater resources is the major source of potable water in Mchinji District of Central Malawi and globally. Although the total amount of water on and under the earth‟s surface is generally assumed to have remained constant, the rapid population boom coupled with extension of agricultural farmland and industrial development are putting pressure and stress on the quality and quantity of water resources. In principal therefore, „use and discard‟ philosophy in water resources cannot be subscribed (Lloyd, 1999). The situation ultimately calls for rational management of water resources to ensure its sustainability. Water intended for human consumption must be free from organisms that are the causative agents of diseases and must not contain chemical substances at concentrations that may be hazardous to human health. In addition drinking water should be aesthetically acceptable, free from unpleasant taste, color, odor and turbidity. Drinking water should also be free from bacteria and viruses whose presence would indicate fecal contamination. Some are known to be toxic and their concentrations must be below acceptable value, taking into account that drinking water is but one of the several pathways by which substances enters the body. ix Due to perceived concerns of over extraction and rapid water resources depletion, optimal management of groundwater resources are now receiving much attention. Their associated literatures have taken quite different approaches both philosophically and operationally to the analysis of how groundwater should be managed, allocated and cared for spatially and temporally. This study investigated the spatial and temporal fluctuations of concentrations of chemical and biological substances in groundwater such as pH, electrical conductivity, total dissolved solids, iron, fluoride, manganese, chloride, sulfates, sodium and fecal coliform in Mchinji District of Central Malawi. Through examination and analysis of static water levels as an indicator of water table fluctuations, groundwater availability was also measured. It was found that anthropogenic activities on the landscape can impact the quality and quantity of the water resources in this area and this impact on the various sectors of the inhabitant‟s livelihoods. Groundwater in Mchinji is composed of a number of chemical and biological elements whose origin is either from the material in which it percolates through, or stored before exploitation. Anthropogenic activities in this area plays a role in the quality and quantity of groundwater through land use and land cover change as evidenced by comparisons of Landsat Thematic x Mapper™ satellite images over different time scales. In Mchinji no regular groundwater monitoring is being done indicating a deficiency in sustainability interventions of the resource. This study calls for integrated and sustainable water resources management and coordinated efforts amongst water users, local councils, regulatory authorities and environmental policy makers. Of far greater importance in groundwater sustainability analysis is the issue of groundwater monitoring. It is imperative therefore to preserve the resource while preservation is still possible. Groundwater is now turning into „blue gold‟ and becoming a highly sought-after commodity. It should, however, be utilized sustainably to meet the needs of the present without compromising the ability of future generations to meet their own needs.

No description available.

The contamination of groundwater by naturally occurring arsenic (As) in South and South East Asia has resulted in the exposure of an estimated 100 million people to hazardously high concentrations of this known carcinogen. Whilst the biogeochemical processes and mechanisms responsible for releasing As to groundwater are now understood, the fundamental controls on these processes have yet to be resolved. In particular, the role of different sources of organic matter (OM) in controlling the rate and extent of As release and how the contributions of these different sources may be influenced by groundwater abstraction practices, remains poorly constrained. Indeed, it is the absence of such key information which currently limits our capability to accurately predict both where and when As will be released in to the groundwaters of this region. Elucidation of the controls of these processes is therefore of vital importance for aiding policy makers and those responsible for mitigating the effects of the current catastrophe in providing a sustainable source of As free drinking water to millions of people in the countries impacted.We conducted investigations at two known As hotspots in West Bengal and Cambodia to assess the impact of groundwater abstraction practices on the composition of dissolved organic carbon (DOC) and As release. The radiocarbon age of DOC at both sites requires a contribution of young surface or near surface derived OM as well as contributions from older, sedimentary sourced OM. Mixing profiles at the Cambodian study site suggest this subsurface OM end member to have an age of between 1000 and 6000 years. A clear association is observed between high As concentrations in shallow groundwaters containing young DOC, with lower concentrations of As being associated with older DOC in deeper groundwater. This provides the first direct confirmation that younger, more labile sources of OM are able to support more extensive As release in these aquifers. Perhaps more importantly, it is shown that modern surface derived OM can be drawn into As contaminated groundwaters. Comparison of the residence times of groundwaters suggests that the extent of ground-surface water interaction is more extensive and extends to greater depths in aquifers that have been subjected to massive groundwater abstraction. Indeed, it is suggested thatgroundwater abstraction practices may be responsible for driving the downward transport of As contaminated shallow groundwater into deeper groundwater, and may potentially be driving changes in the composition of organic carbon within the groundwater. This could give rise to a more reactive, bioavailable organic carbon pool which has the potential to further influence As mobility in these groundwaters. The potential for secular changes in the groundwater As hazard in these regions must therefore consider the impact that changes in the DOC composition may have on the biogeochemical evolution of these aquifers.

It is widely recognized that topographically-driven groundwater flow can perturb conductive thermal regimes. High-relief topography amplifies the impact of factors controlling groundwater flow and advective heat transfer. A finite element method is developed to model the influence of geology, climate, surface topography and regional heat flux on steady groundwater flow and heat transfer. Because fluid viscosity (hence fluid flux) depends upon temperature, groundwater flow is influenced by the regional heat flux. As a consequence, isothermal approaches to modeling deep groundwater flow in mountains may be inappropriate. Using a free-surface approach, the water table is represented as an internal characteristic of the groundwater flow system, rather than the upper boundary for fluid flow. Thick unsaturated zones are expected in high-permeability terrain (greater than 10⁻¹⁵ m²) with arid climate, or where groundwater recharge is restricted by extensive alpine glaciers. Only vertical fluid flow is assumed to occur in the unsaturated zone, therefore, heat transfer above the water table is represented by one-dimensional advection and two-dimensional conduction. Simulation results indicate that water table elevations are highly sensitive to changes in the controlling factors, but have little impact on the thermal regime. Conductive thermal regimes are predicted in low-permeability terrain (less than 10⁻¹⁸ m²) or in high-permeability terrain with arid climate (recharge rates less than 10⁻¹¹ m/sec). Strong advective heat transfer masks the regional heat flux when permeability exceeds 10⁻¹⁶ m² in terrain with relief of 2 km over a horizontal distance of 6 km. Less than one percent of typical mean annual precipitation is transmitted through deep groundwater flow systems under these conditions. Asymmetric surface topography complicates efforts to interpret chemical and thermal data collected near the valley floor. Fracture zones outcropping at the valley floor can capture a large percentage of groundwater flowing through the system and a significant percentage of the basal heat flux. Maximum spring temperatures are indicated when bulk permeability is between 10⁻¹⁷ m² and 10⁻¹⁵ m². Outside this range, spring temperatures approach ambient air temperature. Topographically driven groundwater flow can distort and obliterate free-convection cells that might otherwise develop within a mountain massif. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The evaluation of groundwater quality has become increasingly important as more industrial waste and solid domestic refuse comes into contact with groundwater. Often the quantity and extent of contamination is determined by direct sampling of the groundwater and soil. An alternative method of detecting contaminated groundwater is by noting the electrical resistivity of the contaminated soil. The feasibility of logging resistivity while conducting cone penetrometer testing has been investigated in this research. To this end a two stage program was devised, consisting of lab testing and then field tests of a working tool. Lab testing was carried out using a prototype probe designed to evaluate the feasibility of the project. The lab testing consisted of determining the resistivity of a number of different soil, electrolyte, and organic contaminant mixtures while varying the configuration of the probe. On the basis of lab testing the necessary requirements for the module dimensions and electronics were chosen and were fine tuned by field tests. The module itself consists of an insulated four electrode array and is mounted behind a standard 15 sq cm piezo-cone (CPTU). Upon completion of the development phase the instrument was tested at four different sites. From field testing it was determined that the resistivity cone (RCPTU) was able to accurately map changes in groundwater chemistry on the basis of resistivity measurements. The results of the resistivity testing were verified by groundwater sampling. It was also found that changes in lithological properties, as determined by the cone penetration test (CPT), could influence the resistivity. Basic guidelines for the use of the RCPTU in contaminant investigations are presented. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate