Single well forced gradient tracer tests are a potential cost-effective approach to estimate in situ aquifer contaminant fate and transport parameters for use in natural attenuation assessments and remediation schemes. To date dipole flow tracer tests have been used to measure the conservative and hydraulic parameters of an aquifer, while push-pull tests are well characterised for use with biodegrading tracers. The effect of typical aquifer physical heterogeneity on the ability of single well tests to successfully estimate parameters has not yet been characterised. Also, the ability of single well tests to accurately and quickly measure aquifer parameters using tracer mixtures should be analysed. To investigate the effect of physical heterogeneity on single well tests scaled down ultraviolet imaging experiments were performed in a low profile box. Potential tracers for use in mixtures were investigated through column and batch experiments: Inorganic anions and fluorescein, inorganic cations, acetate and trichlorofluoroethene were considered to measure conservative transport parameters, cation exchange capacity, biodegradation potential and hydrophobic sorption respectively. Numerical modelling was used to simulate reactive tracer signals in single well forced gradient tests. Results suggest that dipole flow tracer tests are appropriate for measuring conservative transport parameters and the sorption of lowly retarded tracers, but are not highly suitable for biodegrading tracers. Tests could be performed with non-recirculating flow, allowing simpler modelling, if equal injection and extraction flow rates could be ensured. Push-pull tests are suitable for biodegrading tracers and moderate to highly retarded tracers. This limits the potential to use reactive tracer mixtures in these tests. Dipole flow tracer test breakthrough curves are highly susceptible to heterogeneity, and could be used to identify discrete permeability variations in aquifers. The effect of heterogeneity is not significant on push-pull test breakthrough curves, but seriously affects tracer plume migration. Inorganic anions provided the most reliable conservative tracer. Trichlorofluoroethene was found to be a suitable tracer to measure hydrophobic sorption. The biodegradation surrogate chosen for a field test should biodegrade similarly to the contaminant under study.

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There is increasing pressure to understand the pathways of potential contaminants In the subsurface environment. Such an understanding relies on the development of a reliable conceptual model of subsurface flow pathways. In this thesis, a combination of geophysical and conventional hydrological techniques was used to characterise the hydrogeology of the Pow sub-catchment, which is part of the River Eden catchment in Cumbria, United Kingdom. Field geophysical investigations of the subsurface are typically performed through the delineation/imaging of its physical properties. Information gathered from such geophysical methods can then be used to differentiate and characterise lithological units and, in some cases, related hydrological properties and processes. Despite some considerable advances in the use of geophysics for hydrogeological studies, hydrological quantification of the geophysical responses under field conditions has often remained challenging. The main focus of this study is on improving the hydrological conceptual model of the Pow sub-catchment, using multiple geophysical datasets as a means of assessing the vulnerability of the regional sandstone aquifer. Specifically, this thesis explores the potential of electrical properties to differentiate hydrological units at the site, with a specific focus on saturated hydraulic conductivity. This leads to the establishment of electrical-lithological and electrical-hydraulic conductivity relationships, which are used to improve the conceptual model of subsurface hydrology within the Pow sub-catchment. Such approaches could enable lithological and hydraulic characterisation of heterogeneous subsurface in a way that is currently prohibitively expensive across anything other than small spatial areas. The field geophysical investigations successfully revealed a three-layered model structure and.3 'channel' feature reflect to the lithological variations. The joint application of multiple geophysical datasets combined with borehole information allowed the development of an initial conceptual model of the site. The resulted conceptual model illustrates the potential importance of superficial deposits for controlling the hydrogeology of the Pow sub­catchment. Using synthetic studies to constrain the interpretation of the field datasets, limitations in the geoelectrical inversion were identified. The approach of using a priori information in an inversion routine significantly improved the inversion results. The link between electrical properties and hydraulic conductivity were investigated and evaluated using three induced polarisation-based electrical models and a surface conductivity model for hydraulic conductivity estimation. It was found that knowledge of the formation factor, cation exchange capacity and porosity was necessary to constrain electrical-hydraulic conductivity estimation models. Two approaches were used to produce a field-scale hydraulic conductivity estimation map: induced polarisation-based models for hydraulic conductivity estimation and an empirical relationship between the real part of complex conductivity and hydraulic conductivity. The mapping of low and high hydraulic conductivity zones helps to improve the conceptualisation of the Pow sub-catchment, which includes: (1) infiltration to the overburden unit through a network of zones comprising of sand and gravel-rich material, (2) possible flow pathways through a network of fractures, fissures and laminated sand features, and (3) preferential flow pathways through the paleo-channel and the occurrence of 'breaks' in the clayey till unit above the regional sandstone aquifer. This study shows the value of multiple geophysical datasets in providing comprehensive insights into the connection between the ground surface and the regional aquifer, and thus the pathways of potential contaminants from the surface to the aquifer in the sub­catchment. The ability to predict subsurface hydraulic properties from geophysics could provide important supporting information, help to reduce the cost of more conventional hydrogeological investigations and increases the confidence level in geophysical interpretations.

No description available.

The overall aim of this thesis has been to develop a pragmatic strategy to aid decisionmaking concerning the management of raised bogs for future sustainability, and specifically to provide a tool to identify the extents and locations of those areas around the bog margins within which water tables need to be managed. Undesirable water losses resulting from damage to peripheral lagg fens that would once have surrounded intact mire systems will be associated with a steepening change in hydraulic gradient. Although steep hydraulic gradients are frequently cited as a problematic threat to a raised bog there has been a lack of previous attempts to quantify a suite of indicative gradients to form a predictive model. This thesis has considered the possibility of identifying key areas of threatened lagg fen from analysis of topographic and hydraulic gradient data across the mire surface of surviving peat domes and their adjacent landscapes. These marginal lagg areas are important to the overall sustainable hydrology of raised bogs, but the identification of land judged necessary to the hydrological integrity of these habitats has received little attention in the scientific literature. Acquisition of the necessary indicative data, carried out at the landscape scale at a range of raised mires, was made feasible by the use of differential Global Positioning Systems (dGPS) for accurate and rapid surveying of transects across a suite of UK raised mires. It may be that developments in dGPS and remote sensing methods such as LiDAR will offer opportunities for future development of this approach. An early product of the strategy was the development of a methodology for carrying out rapid assessments of the condition or "health" of the sites. Profiles of the raised bogs were computed and a database of gradient results was generated for each profile. This involved the identification of generic slope features within the profile of the bogs. An attempt to identify characteristic values associated with generic profiles was then made. A simple data model has been derived, which is indicative of gradient thresholds between characteristic groups. Significant values for hydraulic gradient of between 0.0063-0.0082 across the raised bog dome, and 0.02 for the Rand or steeper shoulders of the bog are suggested for thresholds between relatively intact and damaged systems. These results may be used to compute target water levels at the edges of a mire, and to predict where in the surrounding land this needs to be achieved in order to help sustain the raised water table of the core peat dome. Following a verification process the indicative model was used to predict a preferred hydrological boundary at a further raised bog site (Swarth Moor in North Yorkshire; SD806695). Whilst the results relate to raised n-iires within the UK, and it would be useful therefore to now carry out a comparative study elsewhere, the results of this thesis strongly suggest that quantified gradient data provide a surrogate for judging where the hydrology of peripheral land may influence the condition of the core site. This may offer advantages to conservation agencies in their attempts to maximise the potential for sustainable restoration of this rare and valued habitat.

An analysis of ground-water movement based on the individual components of Darcy's Law has been undertaken with reference to aquifers in England˙ Variations in hydraulic gradient, in the parameters defining the physical and mechanical characteristics of an aquifer, in geological structure and in physical properties of ground water will modify fluid velocities. Although the hydraulic conductivity of porous media can be stated in terms of these parameters, complexities of geology prevent an adequate statement other than under restricted conditions Around a discharging or recharging well, non-steady and steady state flow has been analysed for the determination (in situ) of the formation constants of an aquifer, both real and apparent values being derived. Critical analysis of data in relationship to rate of abstraction, time since discharge commenced or ceased and distance to observation well has been carried out, variations in the formation constants usually occurring in defined trends. The inter-relationship of the formation constants and their importance in hydrological surveys has been discussed. Real variations in transmissibility have been determined and diagrams compiled to indicate regional trends. Analysis of yield-depression curves has led to the assemblage of type and breakaway curves" from which the formation constants of the aquifer can be derived within defined statistical probability levels. Factual data relating to ground-water movement have been analysed and the results presented on a probability basis, wherever possible. This method is considered to be important in hydrogeological studies, Particular emphasis has been placed on ground-water conditions in the Chalk due to its importance as a source of water supply. The significance of fluid movement in relationship to exploitation of ground-water resources and to problems of overdevelopment has been considered. Progressive changes in ground-water chemistry, under both natural and artificial conditions, have been established.

Based on the physics of flow through porous media, on the dynamic equations of De Saint-Venant and on the kinematic wave approach a numerical model which links groundwater motion through an unconfined aquifer to stream and overland flows has been developed. Galerkin's method has been used to discretize the partial differential equations over the space domain, whereas finite difference schemes have been utilized to approximate the set of nonlinear ordinary differential equations into a set of difference equations which have been solved iteratively by Newton-Raphson's method by means of Gauss substitution of each time step. It has been suggested that the use of two-dimensional models to simulate nonlinear aquifer motions by means of Dupuit's assumption has been the main cause of senseless numerical transient fluctuations on the water table levels. The fact that the accuracy of the solutions near the sinks is constrained to the magnitude of the pumping rates has been shown to be another consequence of having assumed the hydraulic gradient to be equal to the slope of the free surface. A new approach to solve complex channel networks by means of penalty functions over the depths of flow in order to simulate abrupt cross-section width augmentation at the junctions has been presented. Stage-discharge rating functions which take the slope of free surface into account have been used as open downstream boundary conditions to allow the simulation of hysteresis even in these boundaries of the channel networks. It has been shown that approximation of natural cross-sections to asymmetric trapezia can minimize the errors of the main geometric elements of these natural channel cross-sections. Several unsuccessful attempts to model surface runoff as shallow two-dimensional flow have led to the conclusion that it cannot be modelled using fixed boundaries.

Predicting contaminant movement in aquifers is essential for the protection of groundwater resources. Contaminant movement is strongly influenced by hydraulic property heterogeneity. The aim of this project has been to determine if hydraulic property values are correlated with geological structures, even if the aquifer is a cemented sandstone: if they are, the correlations could be used in gaining insight into, and quantitatively estimating, solute transport. Example Permo-Triassic sandstone lithofacies associations across England were examined in order to determine common lithofacies geometries. Several thousand measurements of permeability and several hundred measurements of porosity were determined on a core from northern England and two outcrops from the Midlands in order to examine correlations with lithofacies. Two types of synthetic fluvial multiple channel systems with flow a long and across channels were then numerically simulated to determine the significance of the correlations found. Results indicate that the Permo-Triassic sandstones have a wide range of lithologies and permeabilities, varying between and within sequences and regions. Permeability is generally greater for aeolian sandstone than for fluvial sandstone. The borehole core stud y shows that lithofacies correlate with porosity, permeability, and permeability to porosity ratio, though some significant overlaps occur for permeabilities of the three coarser lithofacies. Mudclasts can reduce sandstone permeability of the two coarser lithofacies by up to 6 % and 8% respectively. Markov chain analysis indicates that the sequences of lithofacies are structured, and hence the permeability is also similarly structured. The two outcrop studies confirm that permeability structures vary more between than within beds. Solute transport modelling indicates that differing solute breakthrough patterns will occur with different types of hydraulic property distributions based on lithofacies geometry. Thus lithofacies correlations can be used to help predict solute movement, but transverse dispersion, not explicitly studied here, also appears particularly important. Generally, the heterogeneous porous medium can be reasonably represented by an equivalent homogeneous medium for prediction purposes, however determining appropriate properties for the equivalent homogeneous medium is challenging.

Urban groundwater needs proper management since it is potentially susceptible to both hydraulic and chemical stresses. To manage an aquifer well, an understanding is needed of how the aquifer works. Much research has been done on urban aquifers but relatively little on hard-rock metasediment aquifers especially in equatorial climates such as Peninsular Malaysia. Therefore, research aim is to understand equatorial climate hard rock metasediment urban aquifers and their susceptibility to hydraulic and chemical impacts using data likely to be available to regulatory authorities. Shah Alam, a city developed over the last 50 years is investigated. Borehole log, meteorological, pumping test, and water quality data were used. The meta sandstone-shale sequence is fractured to at least 100m and covered by a weathering zone that is more clay rich where finer metasediments occur. Permeabilities ranged from 0.01 to 1 m/day. Results show that the abstraction activity has induced recharge into aquifer; which CO2 contents indicate that it had been through a soil zone. Some weathering reactions had occurred. Water quality samples with very low salinity barely above precipitation concentrations. Many of the water samples were polluted by one or more species, and sewer influences were common. It can be concluded that aquifer very susceptible to quality stress with a very limited pollution attenuation capacity. It is quite flashy system when pumping.

Estimating manufactured nanoparticle mobility using fast, simple methods could form a useful part of a risk assessment tool. The aim of this work was to investigate whether zeta potential could be used for this purpose. Using a new surface zeta potential measurement technique, the surface zeta potential of a 50m sandstone sequence was found to vary little with lithofacies when chemical conditions were kept constant. A surface area modified linear mixing model was able to describe the sandstone zeta potential, suggesting that clay minerals are the dominant control on bulk properties. The sandstone and silica nanoparticle zeta potentials were sensitive to the chemical composition and pH of the surrounding fluid, which was influenced by ion exchange and carbonate dissolution. The zeta potential of the sandstone and nanoparticles can be used to qualitatively describe the relative mobility under different chemical conditions. Calculations using DLVO and colloid filtration theory (CFT) can reproduce the equilibrium concentration (C’/C\(_0\)) values observed experimentally, however the significant tailing in the breakthrough curve is not described by this traditional particle transport model. Further work is required to determine whether DLVO and CFT can be used as part of a mobility screening tool, as this initial study suggests.