The research study involved using the modified FEMWATER code to investigate the impact of total stress changes on groundwater flow in the vicinity of a salt tailings pile. Total stress and pore-pressure data observed at the Lanigan and Rocanville potash-mine sites were used to assist the development of a generic FEMWATER model. The original 3-D mesh considered for model study covers a region of 7.6 km x 7.6 km x 60 m. The simulated pile itself covers a surface area of 1.6 km x 1.6 km within the region. Symmetry of the idealized system allowed half of the system to be modelled to reduce the size of the mesh. The model was layered to facilitate different materials representing different hydrostratigraphic scenarios. The GMS-release of the FEMWATER code (version 2.1) was modified to simulate the pore-pressure response to total stress changes caused by tailings pile loading at the ground surface to be modelled. The modified code was verified before applying to present study.<p>Long-term pore pressure generation and dissipation due to pile construction was investigated for eleven hydrostratigraphic scenarios consisting of plastic clays, stiff till and dense sand layers commonly found in Saskatchewan potash mining regions. The model was run for two distinctive pile loading patterns. Model results indicated that the loading pattern has a significant influence on pore pressure generation beneath the pile. The model was initially run for 30 year pile construction period and later simulated for 15, 25 and 35 year construction periods to investigate the impact of loading rate. These results showed that, as expected, the peak pore water pressure head is proportional to the pile construction rate. A sensitivity analysis, which was carried out by changing hydraulic conductivity of stiff till, revealed that the lower the hydraulic conductivity, the greater the pore pressure generation beneath the pile.<p>Overall, the research study helped to understand and predict the influence of pile construction and hydrostratigraphy on pore-pressure changes beneath salt tailing piles. Low K/Ss or cv materials (compressible tills) demonstrate a slow dissipation rate and high excess pressures. Compared to dense sand which has very high K/Ss, till has very low K/Ss which causes in high excess pore pressure generation. Sand layers act as drains, rapidly dissipating pore pressures. Thicker low K/Ss units result in slower dissipation and higher pressures. As the thickness of the low K/Ss layer increases, the peak pressures increase as the drainage path lengthens. Thin plastic clay layers give rise to the highest pressures.<p>The model study showed that hydrostratigraphic scenarios similar to those found at Saskatchewan potash mine sites can generate the high pore pressures observed in the vicinity of salt tailings piles as a result of pile loading. Peak pressures are very sensitive to pile construction rates, loading patterns and hydrostratiagraphy of the region. Peak pressures can reach levels that would be of concern for pile stability on the presence of adverse geological conditions.

The research study involved using the modified FEMWATER code to investigate the impact of total stress changes on groundwater flow in the vicinity of a salt tailings pile. Total stress and pore-pressure data observed at the Lanigan and Rocanville potash-mine sites were used to assist the development of a generic FEMWATER model. The original 3-D mesh considered for model study covers a region of 7.6 km x 7.6 km x 60 m. The simulated pile itself covers a surface area of 1.6 km x 1.6 km within the region. Symmetry of the idealized system allowed half of the system to be modelled to reduce the size of the mesh. The model was layered to facilitate different materials representing different hydrostratigraphic scenarios. The GMS-release of the FEMWATER code (version 2.1) was modified to simulate the pore-pressure response to total stress changes caused by tailings pile loading at the ground surface to be modelled. The modified code was verified before applying to present study.<p>Long-term pore pressure generation and dissipation due to pile construction was investigated for eleven hydrostratigraphic scenarios consisting of plastic clays, stiff till and dense sand layers commonly found in Saskatchewan potash mining regions. The model was run for two distinctive pile loading patterns. Model results indicated that the loading pattern has a significant influence on pore pressure generation beneath the pile. The model was initially run for 30 year pile construction period and later simulated for 15, 25 and 35 year construction periods to investigate the impact of loading rate. These results showed that, as expected, the peak pore water pressure head is proportional to the pile construction rate. A sensitivity analysis, which was carried out by changing hydraulic conductivity of stiff till, revealed that the lower the hydraulic conductivity, the greater the pore pressure generation beneath the pile.<p>Overall, the research study helped to understand and predict the influence of pile construction and hydrostratigraphy on pore-pressure changes beneath salt tailing piles. Low K/Ss or cv materials (compressible tills) demonstrate a slow dissipation rate and high excess pressures. Compared to dense sand which has very high K/Ss, till has very low K/Ss which causes in high excess pore pressure generation. Sand layers act as drains, rapidly dissipating pore pressures. Thicker low K/Ss units result in slower dissipation and higher pressures. As the thickness of the low K/Ss layer increases, the peak pressures increase as the drainage path lengthens. Thin plastic clay layers give rise to the highest pressures.<p>The model study showed that hydrostratigraphic scenarios similar to those found at Saskatchewan potash mine sites can generate the high pore pressures observed in the vicinity of salt tailings piles as a result of pile loading. Peak pressures are very sensitive to pile construction rates, loading patterns and hydrostratiagraphy of the region. Peak pressures can reach levels that would be of concern for pile stability on the presence of adverse geological conditions.

Bribie Island is a large, heterogeneous, sand barrier island that contains groundwater aquifers of commercial and environmental significance. Population growth has resulted in expanding residential developments and consequently increased demand for water. Caboolture Shire Council (CSC) has proposed to increase groundwater extraction by a new borefield. Two aquifers exist within the Quaternary sandmass which are separated by an indurated sand layer that is ubiquitous in the area. A shallow aquifer occurs in the surficial, clean sands and is perched on the indurated sands. Water levels in the shallow water table aquifer follow the topography and groundwater occurs under unconfined conditions in this system. A basal aquifer occurs beneath the indurated sands, which act as a semi-confining layer in the island system. The potentiometric surface of the basal aquifer occurs as a gentle groundwater mound. The shallow groundwater system supports water-dependent ecosystems including wetlands, native woodlands and commercial pine plantations. Excessive groundwater extraction could lower the water table in the shallow aquifer to below the root depth of vegetation on the island. Groundwater discharge along the coastline is essential to maintain the position of the saline water - fresh groundwater boundary in this island aquifer system. Any activity that changes the volume of fresh water discharge or lowers the water table or potentiometric surface below sea level will result in a consequent change in the saline water – freshwater interface and could lead to saline water intrusion. Groundwater level data was compared with the residual rainfall mass curve (RRMC) on hydrographs, which revealed that the major trends in groundwater levels are related to rainfall. Bribie Island has a sub-tropical climate, with a mean annual rainfall of around 1358mm/year (Bongaree station). Mean annual pan evaporation is around 1679mm/year and estimates of the potential evapotranspiration rates range from 1003 to 1293mm/year. Flows from creeks, the central swale and groundwater discharged from the area have the potential to affect water quality within the tidal estuary, Pumicestone Passage. Groundwater within the island aquifer system is fresh with electrical conductivity ranging from 61 to 1018ìS/cm while water near the coast, canals or tidal creeks is brackish to saline (1596 to 34800ìS/cm). Measurements of pH show that all groundwater is acidic to slightly acidic (3.3-6.6), the lower values are attributed to the breakdown of plant material into organic acids. Groundwater is dominated by Na-Cl type water, which is expected in a coastal island environment with Na-Cl rainfall. Some groundwater samples possess higher concentrations of calcium and bicarbonate ions, which could be due to chemical interactions with buried shell beds while water is infiltrating to depth and due to the longer residence times of groundwater in the basal aquifer. A steady-state, sub-regional groundwater flow model was developed using the Visual MODFLOW computer package. The 4 layer, flow model simulated the existing hydrogeological system and the dominant groundwater processes controlling groundwater flow. The numerical model was calibrated against existing data and returned reasonable estimates of groundwater levels and hydraulic parameters. The model illustrated that: .. The primary source of groundwater recharge is infiltration of rainfall for the upper, perched aquifer (Layer 1). Recharge for the lower sand layers is via vertical leakage from the upper, perched aquifer, through the indurated sands (Layers 2 and 3) to the semi-confined, basal aquifer (Layer 4). .. The dominant drainage processes on Bribie Island are evapotranspiration (15070m3/day) and groundwater seepage from the coast, canals and tidal creeks (9512m3/day). Analytical calculations using Darcy’s Law estimated that approximately 8000m3/day of groundwater discharges from central Bribie Island, approximately 16% less than the model. .. As groundwater flows preferentially toward the steepest hydraulic gradient, the main direction of horizontal groundwater flow is expected to be along an eastwest axis, towards either the central swale or the coastline. The central swale was found to act as a groundwater sink in the project area.

Contaminant fate and transport are two of the most important issues project officers have to deal with when developing a sound remediation strategy for a subsurface contamination site. To accurately assess these issues, knowledge of possible pathways, travel times and groundwater receptors are required. A groundwater flow model of a site facilitates the assessment process by determining flow paths, discharge areas and travel time from a contaminant source to a potential receptor. The resulting model can also be used to show potential impacts on drinking water sources and surface habitats. This project is Phase II of the proposed three phase project, Groundwater Flow Modeling of the Aquifer System at Ft. Belvoir (Widdowson, 1998). Phase I consisted of developing a conceptual model of the aquifer system, recommending a modeling strategy and developing a data collection strategy. The objectives of this phase are to design and construct a computer simulation of the groundwater flow system in the aquifers below Ft. Belvoir and to develop a strategy for improved data collection using the results of the model. Steps in this phase included creation of the numerical model, calibration to known water surface elevations, and a sensitivity analysis of the boundary conditions. The numerical model was created in the Department of Defense Groundwater Modeling System environment using MODFLOW. The model was calibrated to pre-1970 wells for the deep aquifer and recent site characterization wells for the upper aquifer. The head distribution was influenced the greatest by topography and the major creeks. Accuracy of the well surface elevations played a major role in the calibration process, as well as tidal influences. A sensitivity analysis showed that adjusting the recharge and the seepage face parameters affected the model results (head and groundwater flow rates) the greatest. While adjusting the constant head and general head boundaries affected the model results the least. / Master of Science

The study focuses on an alluvial plain situated within a large meander of the Logan River at Josephville near Beaudesert which supports a factory that processes gelatine. The plant draws water from on site bores, as well as the Logan River, for its production processes and produces approximately 1.5 ML per day (Douglas Partners, 2004) of waste water containing high levels of dissolved ions. At present a series of treatment ponds are used to aerate the waste water reducing the level of organic matter; the water is then used to irrigate grazing land around the site. Within the study the hydrogeology is investigated, a conceptual groundwater model is produced and a numerical groundwater flow model is developed from this. On the site are several bores that access groundwater, plus a network of monitoring bores. Assessment of drilling logs shows the area is formed from a mixture of poorly sorted Quaternary alluvial sediments with a laterally continuous aquifer comprised of coarse sands and fine gravels that is in contact with the river. This aquifer occurs at a depth of between 11 and 15 metres and is overlain by a heterogeneous mixture of silts, sands and clays. The study investigates the degree of interaction between the river and the groundwater within the fluvially derived sediments for reasons of both environmental monitoring and sustainability of the potential local groundwater resource. A conceptual hydrogeological model of the site proposes two hydrostratigraphic units, a basal aquifer of coarse-grained materials overlain by a thick semi-confining unit of finer materials. From this, a two-layer groundwater flow model and hydraulic conductivity distribution was developed based on bore monitoring and rainfall data using MODFLOW (McDonald and Harbaugh, 1988) and PEST (Doherty, 2004) based on GMS 6.5 software (EMSI, 2008). A second model was also considered with the alluvium represented as a single hydrogeological unit. Both models were calibrated to steady state conditions and sensitivity analyses of the parameters has demonstrated that both models are very stable for changes in the range of ± 10% for all parameters and still reasonably stable for changes up to ± 20% with RMS errors in the model always less that 10%. The preferred two-layer model was found to give the more realistic representation of the site, where water level variations and the numerical modeling showed that the basal layer of coarse sands and fine gravels is hydraulically connected to the river and the upper layer comprising a poorly sorted mixture of silt-rich clays and sands of very low permeability limits infiltration from the surface to the lower layer. The paucity of historical data has limited the numerical modelling to a steady state one based on groundwater levels during a drought period and forecasts for varying hydrological conditions (e.g. short term as well as prolonged dry and wet conditions) cannot reasonably be made from such a model. If future modelling is to be undertaken it is necessary to establish a regular program of groundwater monitoring and maintain a long term database of water levels to enable a transient model to be developed at a later stage. This will require a valid monitoring network to be designed with additional bores required for adequate coverage of the hydrogeological conditions at the Josephville site. Further investigations would also be enhanced by undertaking pump testing to investigate hydrogeological properties in the aquifer.

Rapid development and growth of industrialization has brought immense enrichments in living standards of humans, however, improper planned development also brings along several environmental problems such as pollution of environment and excessive consumption of natural resources. Among all the others, uncontrolled utilization of water poses a severe threat to the coming generations. Past decades have witnessed water shortage in various countries of the world. Although about 80% of the earth’s surface is covered with water, around 97.2% of water is salty making it inappropriate for general usage. Among the rest of the 2.8%, which is present as fresh water on surface, a large proportion of it has been found to be severely polluted. The increasing demand of fresh water both for industrial and domestic usage adds great demand on the available groundwater. Moreover, the severe pollution of fresh water on the surface adds more stress on the available groundwater. In Australia, approximately 20% of water supply is from groundwater and in the case of Western Australia groundwater provides two thirds of its water supply needs. Thus, it is important to manage groundwater sources in Western Australia to achieve the optimum water utilization and maintain the water table and it is also essential to decide on an appropriate water budget. Groundwater flow modelling is an effective tool to get appropriate water distribution and, to examine effects from pumping on water levels and direction of groundwater flow paths, thereby helping in its proper management and utilization. Apart from monitoring the flow and utilization, groundwater flow modeling is also vital to keep the track of pollutant in the groundwater. Increasing surface pollution and landfill sites tend to pollute the groundwater due to leaching. / The above mentioned aspects formed the basis of the present research. A groundwater flow model was developed in Visual MODFLOW Premium to study the effect of three different types of soil in and around Perth region. This study also shows the hypothetical contaminated site model for benzene, toluene, ethylbenzene and xylene (BTEX) transport in Perth Superficial unconfined aquifer which includes three major aquifer sediments namely Bassendean Sand, Safety Bay Sand and Tamala Limestone. Among the four different contaminants it was observed that benzene is able to migrate quickly as compared to the other contaminants due to its smaller distribution coefficient. / This study also explored the major soil parameters such as effect of sorption, effective porosity and hydraulic conductivity on contaminant plume configuration and contaminants concentration for the three types of aquifer sediments. A critical comparison of the behaviour of the three different types of soils was also conducted. / Simulation results of sensitivity analysis have shown that sorption and hydraulic conductivity greatly affected the contaminant plume length and concentration of contaminants with much lesser effect shown by the effective porosity. The simulated results also showed that the movement of contaminant in Tamala Limestone is most rapid by comparing these three types of aquifer sediments together. Thus, it can be said that contaminated sites found in Tamala Limestone needs immediate remediation of contaminants to bring down the contaminants concentration in groundwater. / In brief, the thesis explores the current groundwater scenario in and around Perth region. Based on the information a hypothetical scenario simulation has critically analyzed the various parameters affecting the water and contaminant flow for the various soil parameters. The study is considered as a building block for further research on developing a remediation technique for groundwater contaminant treatment.

No description available.

L’aquifère molassique du Bas-Dauphiné est situé le long de la vallée du Rhône, dans le Sud-Est de la France. Cet aquifère d’une superficie proche de3000 km², et d’une épaisseur moyenne de 400m renferme une eau d’excellente qualité, utilisée par de nombreuses collectivités pour l’alimentation en eau potable. Cependant certains secteurs montrent une forte vulnérabilité de la nappe aux activités agricoles. L’utilisation d’outils géochimiques etisotopiques a permis de préciser le fonctionnement hydrodynamique de l’aquifère. Dans un premier temps, nous avons montré que la stratification des écoulements décrite par De La Vaissière (2006) sur la partie drômoise de l’aquifère s’étend au secteur isérois. Les eaux les plus profondes ont des vitesses de circulation de l’ordre du mètre par an alors que les flux superficiels ont des vitesses de circulations d’une centaine de mètres par an. D’autre part, le marquage des nappes superficielles et des rivières par des teneurs faibles en tritium (de 3 à 4 UT) et forte en magnésium (jusqu’à 18 mg/L)indique un apport d’eaux anciennes, issues de l’aquifère molassique vers ces eaux superficielles. La définition de deux pôles d’eaux et l’application d’une équation de mélange couplés à la réalisation de bilans hydrogéologique a permis d’appréhender les volumes échangés. Il apparaît finalement que les réservoirs d’eaux superficiels constituent l’exutoire principal de l’aquifère molassique. L’utilisation des éléments traces a mis en avant le rôleessentiel du temps de séjour des eaux dans l’aquifère ainsi que des conditions d’oxydo-réduction dans l’acquisition de la minéralisation. L’évaluation de la qualité naturelle des eaux de la nappe a montré l’impact des activités agricoles sur l’aquifère, avec prés de 80% des échantillons ayant une teneur en nitrates supérieure à la concentration naturelle supposée. L’étude des teneurs en pesticides conforte ce constat. De plus l’étude de l’évolution des concentrations en polluants montre une dégradation de la ressource. / The molassic basin of Bas-Dauphiné is located in south-eastern France, in the Rhône valley. With an averagethickness of about 400 m, and a surface area of about 2900 km², this aquifer is an important groundwaterresource for freshwater supply and agriculture. However, this resource is also vulnerable and is impacted byhuman activities. The use of geochemical and isotopic analyses made it possible to understand the hydrodynamicsurvey of the aquifer. Firstly, we showed the stratification of the groundwater previously described in thesouthern part of the molassic aquifer could be extended to the north. The groundwater flow velocity is about onemeter / year for the deepest flow and around 100-200 meter /year for the shallowest flow. Secondly, superficialaquifers and rivers are marked by low tritium activities (3 to 4 UT) and high magnesium concentrations (until 18mg/L), which indicate ancient molassic water contribution. The definition of two water types and the applicationof a mixing equation combined with hydrogeological balances lead to an estimation of the contribution of thedeep aquifer to the shallow aquifer. It is finally established that surface water (aquifers and rivers) constitute themain outlet of the molassic aquifer. The use of trace elements shows the importance of the groundwaterresidence time and of redox conditions in the water mineralization. The assessment of baseline quality shows theimpact of agricultural activities upon the aquifer, with nearly 80 % of samples showing higher nitrateconcentration than the maximal natural concentration. This is confirmed by the study of pesticidesconcentrations. Furthermore, the evolution of pollutants concentrations points out a deterioration of the resource.

Groundwater is the only fresh water resource in the semi-arid to hyper-arid Western Dead Sea catchment. Due to exploitation of groundwater the water level is decreasing in the surrounding Cretaceous aquifer system and sustainable water management is needed in order to prevent the progressive yields and contamination of those water resources. In addition, the water level of the Dead Sea decreases dramatically by at least one meter per year. This is connected to channel off the water from the Jordan River to supply intensive agriculture in the semi-arid to hyper-arid region. Hydrological and hydro-geological analysis and modelling in arid regions, like the study area, frequently suffer from data scarcity and uncertainties regarding rainfall and discharge measurements. The study showed that spatial and temporal interpolations as well as additional methods (e.g. empirical relationships and simultaneous numerical approaches) were suitable tools to overcome data shortage for modelling. Water balances are the result of a calibrated model and are the basis for sustainable management of surface and subsurface water resources. The present study investigates beside the hydrological characterisation of selected sub-catchments (wadis) also the hydro-geology of the Judean limestone aquifer and calculates a comprehensive water balance of the entire western flank of the Dead Sea by the application of two numerical open source codes: OpenGeoSys (OGS) and J2000g. The calibrated two-dimensional hydrological model J2000g provides a 33 years time series of temporal and spatial distributed groundwater recharge for the numerical groundwater flow model of OGS. The mean annual groundwater recharge of 139.9 · 10^6 m^3ˑ a^-1 is nearly completely depleted by abstractions from pumping wells close to the replenishment area in the Judea Mountains.

Groundwater is the only fresh water resource in the semi-arid to hyper-arid Western Dead Sea catchment. Due to exploitation of groundwater the water level is decreasing in the surrounding Cretaceous aquifer system and sustainable water management is needed in order to prevent the progressive yields and contamination of those water resources. In addition, the water level of the Dead Sea decreases dramatically by at least one meter per year. This is connected to channel off the water from the Jordan River to supply intensive agriculture in the semi-arid to hyper-arid region. Hydrological and hydro-geological analysis and modelling in arid regions, like the study area, frequently suffer from data scarcity and uncertainties regarding rainfall and discharge measurements. The study showed that spatial and temporal interpolations as well as additional methods (e.g. empirical relationships and simultaneous numerical approaches) were suitable tools to overcome data shortage for modelling. Water balances are the result of a calibrated model and are the basis for sustainable management of surface and subsurface water resources. The present study investigates beside the hydrological characterisation of selected sub-catchments (wadis) also the hydro-geology of the Judean limestone aquifer and calculates a comprehensive water balance of the entire western flank of the Dead Sea by the application of two numerical open source codes: OpenGeoSys (OGS) and J2000g. The calibrated two-dimensional hydrological model J2000g provides a 33 years time series of temporal and spatial distributed groundwater recharge for the numerical groundwater flow model of OGS. The mean annual groundwater recharge of 139.9 · 10^6 m^3ˑ a^-1 is nearly completely depleted by abstractions from pumping wells close to the replenishment area in the Judea Mountains.:Acknowledgements Abstract Nomenclature Content List of Figures List of Tables 1 Introduction 1.1 Motivation 1.2 State of the Field 1.3 General research questions 1.4 Challenges 1.5 Structure of the Thesis 2 Theory and Methods 2.1 Data analysis 2.2 Governing equations 2.2.1 Surface Flow - Hydrological Model: J2000g 2.2.2 Subsurface Flow - Groundwater Flow Model: OpenGeoSys 2.3 Groundwater recharge 3 Study area 3.1 Study site selection 3.2 Geography 3.2.1 Climate 3.2.2 Soils 3.2.3 Vegetation 3.2.4 Land use 3.3 Hydrology 3.3.1 Wadis 3.3.2 Flashfloods 3.3.3 Dead Sea 3.4 Geology 3.5 Hydro-geology 3.5.1 Springs 3.5.2 Well fields 4 Hydrological Model 4.1 Conceptual Model 4.2 Hydrological Model J2000g 4.2.1 Data base 4.2.2 Simulation results from J2000g 5 Structural geological model 5.1 Stratigraphy 5.2 Database 5.3 Workflow 6 Numerical groundwater flow model 6.1 Work flow of 2D and 3D meshing 6.2 Parametrisation 6.3 Boundary conditions 6.4 Model Set-up 6.5 Calibration of Steady-State model 6.6 Transient Model 6.6.1 Model assumptions 6.6.2 Challenges 6.6.3 Preliminary results 7 Conclusions and Outlook 7.1 Important results from the hydrological model 7.2 Important results from the geological structural model 7.3 Important results from the hydro-geological model 7.4 Deficiencies 7.5 Outlook References 8 Enclosed Publications