Water is one of the most important and limited resources in regions with little rainfall. As populations continue to grow, so does the need for water. Individuals in water management positions need to be well informed in order to avoid potential negative effects concerning the overall quality and amount of water available for both people and the environment. In order to provide better information for these individuals, computer models and mathematical relationships are commonly developed to estimate the outcome of different situations regarding surface water and groundwater. Along these lines, this study focused on two modeling studies that provide information to managers regarding either stream restoration techniques or the amount of groundwater available. The first study investigated the effects that beaver dams have on streams. In order to do this, a computer model was developed to represent a section of stream with beaver dams and a section without. The model provided information regarding changes in the average depth, width, and velocity of the stream as a result of having beaver dams. We also measured changes in sediment size distributions between the two stream sections to confirm that beaver dams additionally impact sediment movement and channel shape. Results indicated that only a few dams are actually needed to achieve many of the desired changes in stream restoration. The second study involved testing an equation that was used to predict how much precipitation would become groundwater in a Midwestern watershed. Variables in the equation included measurements of natural or developed land, movement of water through soil, the depth of the water table, and hillslope steepness. We tested the equation in two western watersheds to determine if variables used in the earlier study remain relevant when applied under different conditions. The independent application of the method to each western watershed stressed the importance of meeting simplifying assumptions and developing more complete datasets. We also found that the application of existing simplified empirical relationships may not be suitable in estimating groundwater recharge in mountain watersheds.

Geophysical imaging methods significantly enhance our knowledge of subsurface characteristics and their use has become prevalent over a range of subsurface investigations. These methods facilitate the detection and characterization of both metallic and nonmetallic subsurface targets, and can provide spatially extensive information on subsurface structure and characteristics that is often impractical to obtain using standard drilling and sampling procedures alone. Electrical imaging methods such as electrical resistivity tomography (ERT) have proven to be particularly useful in hydrogeologic and geotechnical investigations because of the strong dependence of the electrical properties of soils to water saturation, soil texture, and solute concentration. Given the available geophysical tools as well as their applications, the selection of the appropriate geophysical survey design is an essential part of every subsurface geophysical investigation. Where investigations are located in an area with subsurface information already available, this information may be used as a guide for the design of a geophysical survey. In some instances, no subsurface information is available and a survey must be designed to cover a range of possible circumstances. Yet, in other instances, there may be significant subsurface information available, but because of subsurface complexities, a geophysical survey must still be designed to cover a broad range of possibilities. Demonstrating the application and limitations of ERT in a specific field application, the first investigation presented in this document provides guidance for developing methods to improve the design and implementation of ERT surveys in a complex subsurface environment. The two investigations that follow present the development of a relatively simple optimization approach based on limited forward modeling of the geophysical response for both static and mobile surveys. This process is demonstrated through examples of selecting a limited number of ERT surveys to identify and discriminate subsurface target tunnels (with a simple cylindrical geometry). These examples provide insights into the practical application of the optimization process for improved ERT survey design for subsurface target detection. Because of their relative simplicity, the optimization procedures developed here may be used to rapidly identify optimal array configurations without the need for computationally expensive inversion techniques.

The Thornton Well Field, located in an area of dominantly (~80%) agricultural land-use, produces ~50% of the drinking water for the city of Woodstock. Since the mid 1990?s nitrate concentrations in some of the supply wells are above the Maximum Allowable Concentration (MAC) of 10mg-N/L. The source of the nitrate is believed to be from agricultural fertilizing practices. As response to this problem, the County of Oxford purchased 111 hectares of farmland within the capture zone of the Thornton Well Field. This land is rented back to farmers with restrictions placed on the amount of nitrate fertilizer that can be applied in an attempt to sustainably reduce the nitrate concentrations in the ThorntonWell Field below MAC. <br /><br /> The objective of this thesis is to improve the site conceptual hydrogeologic model, both at a spatial scale suitable for numerical analysis through regional groundwater flow modelling (representative distance ~9km) and at a smaller scale (representative distance ~2km) for nitrate transport modelling in the vicinity of the Thornton Well Field and the purchased land. Field investigations aimed to support the site hydrogeologic model involved drilling, geologic logging, and instrumentation of a 72m deep borehole completed to bedrock in the center of the nitrate plume, at the border of the farmland under consideration. The shallow subsurface features encountered during this initial drilling operation were tracked below the farm fields with geophysical tools and additional drilling and core logging throughout the field site. Transient hydraulic head observations in combination with on-site precipitation measurements were used to indicate where a hydraulic connection between ground surface and deeper layers exists, which allow rapid infiltration to occur into a glaciofluvial outwash channel which was identified as one important pathway for nitrate transport to the Thornton Well Field. One receptor at the end of that pathway, the screen of the supply Well 01, was depth-discrete profiled for water inflow and nitrate concentrations to obtain better characteristics of the receptor. <br /><br /> A method was developed to estimate the nitrate mass stored in the unsaturated zone below Parcel B, permitting an estimation of the time frame required for flushing the nitrate out of this zone, and the anticipated effects on nitrate concentrations in the supply wells. The spatial distribution of nitrate concentrations in the unsaturated zone and in the aquifer units was analyzed. It was found that the nitrate concentration within the unsaturated zone below Parcel B is ~16mg-N/L, resulting in a total nitrogen mass of ~20t within that zone. It was shown that significant reductions (~10%) in nitrate concentrations in the supply wells of the Thornton Well Field can be achieved, assuming zero nitrate mass influx into the domain from Parcel B. <br /><br /> A comprehensive data base was developed to organize, manage, and analyze all site measured data for that purpose, and regional hydrogeologic data from the MOE Water Well Record Database. The contents of this database in conjunction with the MOE Water Well Record Database were used to construct a three-dimensional digital representation of the hydrostratigraphic units at a regional and at a local scale. This three-dimensional hydrostratigraphic unit spatial distribution along with surface watershed information and potentiometric surfaces of the various aquifer units will be used to define a suitable spatial domain and associated boundary conditions for future modelling efforts. This hydrostratigraphic model will serve as basis for predicting the effects of agricultural land-use changes within the capture zone of the Thornton Well Field (Parcel B) on the nitrate concentrations in the supply wells of the Thornton Well Field.

The Thornton Well Field, located in an area of dominantly (~80%) agricultural land-use, produces ~50% of the drinking water for the city of Woodstock. Since the mid 1990?s nitrate concentrations in some of the supply wells are above the Maximum Allowable Concentration (MAC) of 10mg-N/L. The source of the nitrate is believed to be from agricultural fertilizing practices. As response to this problem, the County of Oxford purchased 111 hectares of farmland within the capture zone of the Thornton Well Field. This land is rented back to farmers with restrictions placed on the amount of nitrate fertilizer that can be applied in an attempt to sustainably reduce the nitrate concentrations in the ThorntonWell Field below MAC. <br /><br /> The objective of this thesis is to improve the site conceptual hydrogeologic model, both at a spatial scale suitable for numerical analysis through regional groundwater flow modelling (representative distance ~9km) and at a smaller scale (representative distance ~2km) for nitrate transport modelling in the vicinity of the Thornton Well Field and the purchased land. Field investigations aimed to support the site hydrogeologic model involved drilling, geologic logging, and instrumentation of a 72m deep borehole completed to bedrock in the center of the nitrate plume, at the border of the farmland under consideration. The shallow subsurface features encountered during this initial drilling operation were tracked below the farm fields with geophysical tools and additional drilling and core logging throughout the field site. Transient hydraulic head observations in combination with on-site precipitation measurements were used to indicate where a hydraulic connection between ground surface and deeper layers exists, which allow rapid infiltration to occur into a glaciofluvial outwash channel which was identified as one important pathway for nitrate transport to the Thornton Well Field. One receptor at the end of that pathway, the screen of the supply Well 01, was depth-discrete profiled for water inflow and nitrate concentrations to obtain better characteristics of the receptor. <br /><br /> A method was developed to estimate the nitrate mass stored in the unsaturated zone below Parcel B, permitting an estimation of the time frame required for flushing the nitrate out of this zone, and the anticipated effects on nitrate concentrations in the supply wells. The spatial distribution of nitrate concentrations in the unsaturated zone and in the aquifer units was analyzed. It was found that the nitrate concentration within the unsaturated zone below Parcel B is ~16mg-N/L, resulting in a total nitrogen mass of ~20t within that zone. It was shown that significant reductions (~10%) in nitrate concentrations in the supply wells of the Thornton Well Field can be achieved, assuming zero nitrate mass influx into the domain from Parcel B. <br /><br /> A comprehensive data base was developed to organize, manage, and analyze all site measured data for that purpose, and regional hydrogeologic data from the MOE Water Well Record Database. The contents of this database in conjunction with the MOE Water Well Record Database were used to construct a three-dimensional digital representation of the hydrostratigraphic units at a regional and at a local scale. This three-dimensional hydrostratigraphic unit spatial distribution along with surface watershed information and potentiometric surfaces of the various aquifer units will be used to define a suitable spatial domain and associated boundary conditions for future modelling efforts. This hydrostratigraphic model will serve as basis for predicting the effects of agricultural land-use changes within the capture zone of the Thornton Well Field (Parcel B) on the nitrate concentrations in the supply wells of the Thornton Well Field.

Made available in DSpace on 2014-06-11T19:32:18Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-05-18Bitstream added on 2014-06-13T19:21:50Z : No. of bitstreams: 1 leite_cbb_dr_rcla.pdf: 7311558 bytes, checksum: 5bdbab506865068f3f86a6c0dea7b45a (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Ipt / Reservatórios formados pela construção de barragens causam impactos significativos sobre diversos aspectos ambientais de uma bacia hidrográfica. Durante o enchimento do reservatório um sistema de fluxo transitório é induzido em suas áreas marginais. Como as cargas hidráulicas nas bordas do reservatório sofrem elevação, ocorrem inversões nas direções de fluxo e temporariamente se estabelece um fluxo do reservatório para o sistema aqüífero. O resultado final do reajuste transitório inicial é uma alteração permanente, a longo prazo, do regime hidrogeológico regional. Os níveis d'água são elevados, as cargas hidráulicas do aqüífero são aumentadas, porém os gradientes hidráulicos são suavizados, provocando a elevação e o aplainamento da superfície potenciométrica, com redução das descargas de base nos exutórios naturais em relação à situação original. É objeto deste trabalho o desenvolvimento de procedimentos para avaliação dos impactos da formação do reservatório sobre a superfície potenciométrica do aqüífero livre, utilizando modelos numéricos com a introdução de uma abordagem geoestatística, tanto por krigagem como por simulação estocástica, no tratamento dos dados de campo. O local escolhido para a realização deste trabalho foi a cidade de Pereira Barreto (SP), situado na margem do atual reservatório da Usina Hidrelétrica de Três Irmãos, no baixo Rio Tiête, considerando informações e dados do monitoramento sistemático (poços e piezômetros) realizados na área, durante os anos de 1987 a 2001. Do ponto de vista metodológico a execução do presente estudo comprovou a viabilidade e a adequação da Geoestatística associada à modelagem matemática com fins previsionais, em escala local, para a avaliação das modificações induzidas na superfície potenciométrica do aqüífero livre após a implantação de reservatórios. / Hydropower reservoirs result in significant environmental impacts in the context of hydrographic basins. During the infillment of the reservoir, a transient flow system is induced in its surroundings. Also the hydraulic heads are raised in the edges of the reservoir resulting in a change of the flow direction, in such a way that after the complete fulfillment, the underground water will flow from the reservoir to the aquifer. The outcome of this inicial transient readjustment is a long-run permanent change in the hydrogeologic regional system. This way, the water levels are raised and the hydraulic heads of the aquifer are increased. On the other hand, the hydraulic gradients are alleviated resulting in an elevation followed by a flattening of the potentiometric surface as the basement discharge of the natural exutories reduce as compared to the original situation. This study aims to develop procedures to assess the impacts of the Três Irmãos' hydropower reservoir on the potentiometric surface of the free aquifer in the flooded area in the lower Tietê river valley using numerical model with a geostatistical approach of the data. Both krigiage and stochastic simulation of the underground water circulation system were applied in this context. Data and information generated by the systematic monitoring of both well and piezometers, gathered from 1987 to 2001, were taken into account in this geostatistical analyses. From the methodological standpoint, the undertaking of this study showed the adequacy and viability of using geostatistics coupled with mathematical modelling as tools for local level assessments of induced changes in the potentiometric surfaces of the free aquifers after the fulfillment of the reservoirs.

Orientador: Paulo Milton Barbosa Landim / Resumo: Reservatórios formados pela construção de barragens causam impactos significativos sobre diversos aspectos ambientais de uma bacia hidrográfica. Durante o enchimento do reservatório um sistema de fluxo transitório é induzido em suas áreas marginais. Como as cargas hidráulicas nas bordas do reservatório sofrem elevação, ocorrem inversões nas direções de fluxo e temporariamente se estabelece um fluxo do reservatório para o sistema aqüífero. O resultado final do reajuste transitório inicial é uma alteração permanente, a longo prazo, do regime hidrogeológico regional. Os níveis d'água são elevados, as cargas hidráulicas do aqüífero são aumentadas, porém os gradientes hidráulicos são suavizados, provocando a elevação e o aplainamento da superfície potenciométrica, com redução das descargas de base nos exutórios naturais em relação à situação original. É objeto deste trabalho o desenvolvimento de procedimentos para avaliação dos impactos da formação do reservatório sobre a superfície potenciométrica do aqüífero livre, utilizando modelos numéricos com a introdução de uma abordagem geoestatística, tanto por krigagem como por simulação estocástica, no tratamento dos dados de campo. O local escolhido para a realização deste trabalho foi a cidade de Pereira Barreto (SP), situado na margem do atual reservatório da Usina Hidrelétrica de Três Irmãos, no baixo Rio Tiête, considerando informações e dados do monitoramento sistemático (poços e piezômetros) realizados na área, durante os anos de 1987 a 2001. Do ponto de vista metodológico a execução do presente estudo comprovou a viabilidade e a adequação da Geoestatística associada à modelagem matemática com fins previsionais, em escala local, para a avaliação das modificações induzidas na superfície potenciométrica do aqüífero livre após a implantação de reservatórios. / Abstract: Hydropower reservoirs result in significant environmental impacts in the context of hydrographic basins. During the infillment of the reservoir, a transient flow system is induced in its surroundings. Also the hydraulic heads are raised in the edges of the reservoir resulting in a change of the flow direction, in such a way that after the complete fulfillment, the underground water will flow from the reservoir to the aquifer. The outcome of this inicial transient readjustment is a long-run permanent change in the hydrogeologic regional system. This way, the water levels are raised and the hydraulic heads of the aquifer are increased. On the other hand, the hydraulic gradients are alleviated resulting in an elevation followed by a flattening of the potentiometric surface as the basement discharge of the natural exutories reduce as compared to the original situation. This study aims to develop procedures to assess the impacts of the Três Irmãos' hydropower reservoir on the potentiometric surface of the free aquifer in the flooded area in the lower Tietê river valley using numerical model with a geostatistical approach of the data. Both krigiage and stochastic simulation of the underground water circulation system were applied in this context. Data and information generated by the systematic monitoring of both well and piezometers, gathered from 1987 to 2001, were taken into account in this geostatistical analyses. From the methodological standpoint, the undertaking of this study showed the adequacy and viability of using geostatistics coupled with mathematical modelling as tools for local level assessments of induced changes in the potentiometric surfaces of the free aquifers after the fulfillment of the reservoirs. / Doutor

Underground coal mining operations induce ground movements, which may impact overlying hydrogeologic systems. Potential impacts mainly include changes in the hydraulic conductivity of overlying strata, decreasing of the hydraulic head and changes in water flow. The present research quantifies potential hydrogeologic impacts caused by underground mining through modeling of pre- and post-mining hydrogeologic systems. Three-dimensional conceptual hydrogeologic models were constructed with the Processing Modflow for Windows software package (PMWiN). The models are based on an actual case study, but were simplified in terms of geometry and material properties. Water flow was simulated under changing hydrogeologic properties. A number of scenarios were investigated including models with horizontal or inclined topography, featuring an aquifer overlying two longwall panels. The hydrogeologic properties of the models were estimated based on empirical relationships between the post-mining hydraulic conductivity and strain in the overburden. The strain regime in the overburden was estimated using the Surface Deformation Prediction System (SDPS) package, which allows calculation of surface deformations due to underground coal mining. The research focuses on changes in hydraulic heads; results indicate that hydraulic heads may decrease over undermined areas and may rebound as mining ceases. Water infiltration may occur from higher located overburden formations to lower formations due to mining induced changes in hydrogeologic properties.

The life of the hydrogeological well is not important only in petroleum geology but also in the water industry. Nowadays, when the demand of water rises, it is necessary to ensure the smooth running of the wells and care as much as possible about their condition. The aim of this thesis is try to apply the methods of production analysis commonly used in oil production in the oil industry for water supply wells. In the thesis I will focus on monitoring the productivity of the well with regard to increasing the hydraulic losses caused by clogging. iv

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