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The hydrogeology of the Tono basin, Japan, is strongly inuenced by the hydraulic properties of faults, especially the main Tsukiyoshi fault, which extends through the centre of the assessment area and has an E-W strike. According to the results of borehole investigations, the fault has N800W strike, 700 dip, 10 ô 30m width and approximately 30m vertical off-set. Hydraulic head discontinuities over the main fault in the basin are about 40 m as a result of the low permeability of the fault acting as a barrier to ow perpendicular to it. The fracture data from the Tono basin was analysed in order to establish a correlation between geologic/geometric attributes of a fracture and associated permeability of the interval that contains the fracture, if any. Pressure response transients to excavation of two shafts that are monitored at various boreholes within the study site show that proximity to a fault is a key attribute that determines the ability of the fracture to conduct water. The responses in boreholes that are close to the fault are vertically invariant, indicating a large vertical permeability. This is not the case in boreholes that are further from the main fault, where there is depth dependence in the pressure responses. Near the fault, the damage zone seems to be equilibrating the heads between otherwise unconnected aquifers. The Tsukiyoshi fault therefore acts as barrier to ow perpendicular to it but also acts as conduit to vertical ow and ow parallel to the fault. A three-dimensional model that simulates groundwater ow in the Tono basin is constructed in order to study the dynamic uid ow before and after it was disturbed by production and the excavation of the shafts. In the steady-state calculation, the model predicts that the hydraulic head at depth in boreholes near the fault is near the land surface. This condition indicates high vertical permeability in those boreholes. This thesis introduces a new approach of using pressure response data to do an inversion calculation for the effective porosity of the granite. Pressure response transients have been analysed using a numerical inversion procedure to estimate the specic storage of the granite. The specic storage was calculated using the pressure response data and ranged from 4:12 10ô7 to 8:93 10ô6mô1. These values of the specic storage were used to do a transport calculation in order to study the impact of the main fault on the transportation of hypothetical contaminants in the basin. Particle tracking was used to investigate and demonstrate the effects of the fault on path lines. The fault was found to have a strong inuence on the transportation of contaminants. The general trend of the transportation of the contaminants follows groundwater ow from the northern high elevations toward the southern low elevation. This shows that the contaminants are transported mainly by advection. However, this trend is interrupted by the Tsukiyoshi fault that blocks horizontal ow and sends water toward the surface. An interesting feature demonstrated by the model is that, within the fault core, no contaminants were found. The contaminants rise through the high-permeability damage zone and cross over the fault through the weathered granite. However, at depths where the water changes direction slowly because of the fault barrier to horizontal ow, the contaminants seem to be able to cross the fault. The explanation is that diffusion becomes the dominant mode of transport at the point where the water moves at slow velocities.

The Institute for Groundwater Studies (IGS) undertook a groundwater surface water interaction project under the funding of Water Research Commission starting July 2010. The Modder River was identified as an appropriate study area since it is located downstream of Krugersdrift Dam and has only been impacted by farming activities. This thesis aims at investigating the hydraulic parameters and flow characteristics of groundwater in the study area aquifer so as to have a preliminary picture of the groundwater systems of the site prior to the groundwater surface water interaction project takeoff. The field procedures were performed starting with site inspection, drilling, water level monitoring, pumping tests, tracer tests, and chemical sampling. Geological classification was performed during site inspection and drilling, while soil cover was analysed for texture analysis in the soil science laboratory. Water level monitoring was performed to study the groundwater fluctuations and flow directions with time. Constant rate tests were performed together with recovery tests to determine the transmissivity of the aquifer in the study area while point dilution tracer tests were done to determine the Darcy velocity of the section of maximum flow in the aquifer. In chemical analysis, micro and macro analysis were performed while tritium 3H, Deuterium 2H, and 18-Oxygen were analysed for in isotope analysis. Chemistry and isotope analysis were done to classify water in terms of its source, fate and age. From all boreholes, at the average depth of 8 meters, an alluvial material was obtained in between the top calcareous soil material and the bottom shale formation. The water level fluctuation trend was similar in all boreholes indicating possibilities of a common aquifer intercepted by all boreholes. Using water level time series, groundwater flow direction was determined to be towards the North-Eastern direction slightly in the direction of local topography while the river flow is westwards. The geometric mean of transmissivity values obtained from a Cooper-Jacob plot is 66 m2/d and the geometric mean for the recharge value from chloride method is 1.7 %. The geometric mean of the Darcy velocity value obtained from different boreholes in the aquifer is 6.9 m/d. These mean values are representative of the whole aquifer. In addition to flow direction being due to topography, it is hypothesized that the unusual flow direction behaviour is due to the seepage that acts like a natural borehole at the river bank such that a semi-cone of depression is formed towards the North East. In hydrochemistry, the most abundant cation is sodium followed by magnesium and the most abundant anion is T.Alk (carbonates). From a Piper diagram, groundwater was characterized to be calcium magnesium bicarbonate type of water. The SAR of groundwater is low and within the recommended value for irrigation agriculture while the EC is so high that the water is recommended strictly for crops that are not sensitive to brackish water. According to the isotope analysis, the water from the boreholes and seepage seem to have the same isotopic fingerprint. Needless to say that, the water that seeps on the banks is the same water as that from the aquifer that is intercepted by the boreholes. Groundwater plots closer to the global meteoric water line than river water which plots on the evaporation water line, needless to say that, river water is evaporation water rich in 18-oxygen while groundwater experiences less evaporation hence high 16-oxygen content. The hydrogeology of the area is therefore characterized by the presence of major flow in the gravel material at the average depth of 8 meters.

Fractures are mechanical ruptures in rocks, form by stress (lithostatic, tectonic, and thermal stresses and high fluid pressures) concentrations around flaws, heterogeneities, and physical discontinuities at a variety of scales. In groundwater reservoirs, mainly in those formed within relatively less permeable or hard rocks, connected fractures may form privileged conduits for fluid flow and solute through the rock, and therefore needs to be located and quantitatively (geometry, permeability, and ability to transport solute) appreciated for a better understanding of water flow and mass transport processes in the subsurface. Many techniques have been adapted from petroleum applications to address these issues and are reviewed in the present study with after an overview on geological and geo-mechanical features that evolve fracturing. Very few existing tools are cost-effective and easy to be performed on the field. The FEC (Fluid Electrical Conductivity) based techniques; mainly the single borehole based ones involve often, relatively cost effective equipments and are simple. The present study focus also on the applicability of âFlowing Fluid Electrical conductivity loggingâ (Tsang et al., 1990; Doughty et al., 2005) and the FEC based dilution test (well dilution) for fracture characterization in the Karoo aquifer. The FFEC is found to be a promising technique for local fracture characterization, mainly in contamination studies (investigation and scenario testing), like in mine environments; and is recommended to be experienced in South-Africa, particularly in the meta-sediments of the Karoo environment. The FEC based dilution test (well dilution) is gaining interest in fracture characterization in South Africa (Mohr Samuel and van Biljon Willem., 2009; Lasher Candice et al., 2009) and has been assessed on two experimental fields in the Karoo Aquifer. The technique is found to constitute a powerful tool for detection of flowing fractures and for qualitative interpretation. The Drost et al (1968) analytical solution suggested for the analysis of the test data (Cook et al., 2001a; Love et al., 2002) have been applied and yielded semi-quantitative values that can be used as first estimation of the groundwater velocity from flowing points into the studied boreholes. However, due to non ideal condition, refinements are still needed mainly for the field procedure and for the consideration of the mass circulation that may be associated with density gradient along the borehole.