No description available.

The Waipara – Kowai groundwater allocation zones (referred to as zones) are located 50 kilometers north of Christchurch. Land use in the Waipara zone has evolved from dry land farming towards horticultural and irrigated pastoral farming, and as such the demand for groundwater resources has increased significantly. Recent 14C age dating has shown that deep wells tap >1000 years old water, raising concerns about possible resource mining. The Kowai groundwater allocation zone has had minimal regional hydrogeological investigations and previously little is known about the groundwater resources here. The Waipara – Kowai groundwater allocation zones are located near obliquely convergent plate margin and the Porters Pass Fault System. Recent (early Quaternary) deformation has been noted by workers along margins and associated with emerging structures within basins. These emerging faults and folds within the basin are acting as hydrological barriers, hindering the passage of groundwater within the basin. A geomorphic map was constructed for this study based on existing soils maps, limited field soil surveys and morphometric analysis. Nine geomorphic surfaces are described, with inferred ages of modern to >73 ka. The geomorphic investigation revealed that the Kowai groundwater allocation zone surface is stepped, with increasing thickness of loess up gradient on the downlands. Near the coast there is intercalated terrestrial and marine sediments, to the west overlying the Kowai Formation are small alluvial fans. In the Waipara Basin the Waipara fan dominates the central portion of the basin, with smaller fluvial and alluvial fans building out from the margins. Groundwater recharge was investigated using chemical, isotopic, water level observations and a simple water balance. It was found that in the Kowai zone the major recharge sources were the rainfall, losses from the rivers and streams. The southern region of the Waipara zone is recharged by rainfall with small contributions from the Kowai River (North Branch). In the South region of the Waipara Basin groundwater recharge is derived from rainfall and losses from streams. The groundwater systems are conceptualized as being topographically driven, with slope – basin floors interactions being an important source of groundwater recharge.

No description available.

The need to renew and expand civil infrastructure, combined with an increased acknowledgement of a changing climate, has highlighted the need to incorporate the influence of climatic factors into the design of infrastructure. In geotechnical engineering, this includes understanding how climate influences the performance of slopes associated with engineered cuttings in pre- existing natural landforms. This understanding extends to both hydrological and hydrogeological conditions, both of which are often analyzed using numerical modeling of surface water and groundwater. Climate change predictions for Northern Ireland indicate that the amount and intensity of rainfall and extreme weather events will increase. This has raised concerns regarding the stability of existing engineered cut-slopes and the design of future highway and railway infrastructure. Recent studies have indicated that there is a link between pore pressure cycles and softening of slope structures, especially in clay rich materials typical of glacial till drumlins in Northern Ireland. These pore pressure fluctuations are caused by seasonal changes in the rate of recharge which then propagate through the deeper hydrogeologic system. As a consequence, the design of these cuttings requires that the hydrogeological response of these landforms to seasonal climate variations be incorporated into geotechnical designs. Two dimensional hydrogeological simulations are typically used in engineering practice. The main objective of this study was to evaluate the sensitivity of these simulations to dimensionality (two- and three-dimensions). The primary focus was on steady state groundwater flow within two drumlins with large slope cuts. Two- and three-dimensional groundwater models were developed using available information for a highway and a railway study site. The performance of each of these models was then compared to field monitoring from each site. A series of sensitivity studies were undertaken to evaluate the influence of key material properties and boundary conditions. Estimated recharge rates were found to range from 21 to 31 mm year-1 for both the railway (Craigmore) and highway (Loughbrickland) study sites. The hydraulic head distribution at the Craigmore site was similar for both dimensional simulations with a “best-fit” recharge rate of 50 to 60 mm year-1. At the Loughbrickland site, similar hydraulic head distributions with the “best-fit” recharge rate of 80 mm year-1 were reached in both dimensions. Overall, the research completed here emphasized the importance of gathering appropriate data prior to conducting development of hydrogeological models. As more data is made available, the overall complexity of the system can be better understood. As the complexity of the problem increases, the requirements for understanding the hydrogeological system in all three-dimensions becomes more important.

Accurately characterizing the distribution of hydraulic parameters is critical for any site investigation, particularly those dealing with solute or contaminant transport. Despite the fact that many tools are currently available for both characterizing (e.g. soil core analysis, slug and pumping tests, direct push techniques, etc.,) and modeling (e.g. geostatistical interpolators, construction of geological models, etc.,) heterogeneous aquifers, this still remains a challenge. In this thesis, hydraulic tomography (HT), a recently developed tool for characterizing and modeling heterogeneous aquifers is evaluated under both laboratory and field conditions. To date, both steady state hydraulic tomography (SSHT) and transient hydraulic tomography (THT) have been demonstrated at the laboratory scale, however, only SSHT has been rigorously validated through the prediction of independent tests (those not used for estimating the distribution of hydraulic parameters), and comparison to other characterization/modeling techniques. Additionally, laboratory and field validations of HT using comparisons other than the prediction of independent pumping tests (e.g. prediction of solute transport) are lacking. The laboratory studies performed in this thesis address some of these gaps by: i) rigorously validating THT through the prediction of independent pumping tests, and comparison to other characterization techniques; ii) using HT estimated parameter distributions to predict the migration of a conservative tracer in a heterogeneous sandbox aquifer; and, iii) predicting the flow of water to a well in a heterogeneous, unconfined, sandbox aquifer. For all three cases, HT was compared to more traditional characterization/modeling approaches, such as; the calculation of homogeneous effective parameters, kriging of point data, or the creation and calibration of a geological model. For each study the performance of HT was superior to the other characterization methods. These laboratory experiments demonstrated both the ability of HT to map aquifer heterogeneity, and the critical need for accurately understanding heterogeneity in order to make accurate predictions about a system. In this regard, HT is a powerful tool at the laboratory scale where the forcing functions (i.e., boundary conditions, flow rates, etc.,) are accurately known. While several field scale HT studies have been reported in the literature, none attempt to validate 3D THT through the prediction of independent pumping tests, or through comparison to known geology. The application of THT at the field scale presents unique challenges not faced in the laboratory setting. For example, boundary conditions are not accurately known and it is not possible to instrument a field site as densely as a sandbox aquifer. In the field studies conducted as part of this thesis, THT was validated by comparing estimated hydraulic parameter fields to known geology (borehole data) and simulating 9 pumping tests that were performed at the site. The THT analysis was able to capture the salient features of the aquifer (the presence of a double aquifer separated by an aquitard), and was able to reasonably reproduce most of the pumping tests. For comparison purposes, a homogeneous model and three additional heterogeneous models were created: i) permeameter estimates of hydraulic conductivity from soil cores were interpolated via kriging; ii) the transition probability/Markov Chain approach was used to interpret material classifications from borehole logs; and iii) a stratigraphic model was created and calibrated to pumping test data. Of these cases, THT and the calibrated stratigraphic model performed best, with THT performing slightly better. This work indicates that it is possible to interpret multiple pumping tests using hydraulic tomography to estimate the 3D distribution of hydraulic parameters in heterogeneous aquifer systems. Also, since hydraulic tomography does not require the collection and analysis of a large number of point samples, it is likely comparable in cost to other characterization/modeling approaches.

The Grand River Watershed, in southern Ontario, is home to approximately 900,000 people and one of the fastest growing regions in Canada; specifically, in the urban areas of Guelph, Cambridge, Kitchener, and Waterloo. This growth strains the watershed’s capacity to supply adequate water resources to these municipalities, as well as manage the waste-water treatment effluent discharged from them. Nowhere in the watershed is this juxtaposition in water resource function more apparent than at the city of Brantford, with a population of approximately 100,000 people. Located forty-two kilometers downstream from the major urban areas, Brantford is unique in the watershed in that it obtains its entire municipal water supply directly from the Grand River, into which the upstream municipalities discharge 77% of the total waste-water treatment plant effluent emitted to the watershed. One contaminant of concern is nitrate, which, for decades, has been linked to numerous human and aquatic health complications. The input of nitrate from these upstream WWTP’s is considerable; the WWTP’s have a combined flow rate of 2.3 m3s-1, and a mean nitrate concentration of 10.4 mg N·L-1 (data from Anderson, 2012). As a comparison, the Nith River, the largest tributary to the Grand River between Cambridge and Brantford, has a summer baseflow of 2.9 m3s-1 and, from 2000 to 2004, had a mean nitrate concentration of 4.4 mg N·L-1 (Cooke, 2006). Brantford, in addition to treating their water supply, relies on the dilution of in-stream nitrate from groundwater that is thought to discharge along the Grand between Cambridge and the Brantford municipal water intake. This 40-km reach of the Grand River is colloquially referred to as either the discharge reach or the recovery reach. Recent data from various authors indicate that groundwater may not always act to dilute in-stream nitrate from upstream WWTPs (Encalata, 2008; Pastora, 2009; Rosamond 2009). The main objective of the research completed in this thesis was to refine the conceptual model of groundwater/surface water interaction along the Grand River between Cambridge and Brantford. Refinement of this conceptual model was accomplished in two parts. First, groundwater discharge, from bank seepage and direct discharge through the riverbed, was located using a variety of methods; a simple reconnaissance survey by canoe, a FLIR thermography survey, drag probe surveys, and a temperature profiling method. Then domestic wells, seeps, tributaries, riverbed discharge, and WWTP effluent were sampled to geochemically characterize inputs to the Grand River.

In 1998, a permeable reactive barrier system was installed at the Atomic Energy of Canada Ltd. (AECL) Chalk River Laboratories in Chalk River, Ontario, to prevent the discharge of a 90Sr plume into a nearby swamp. The system known as the “Wall and Curtain” contains clinoptilolite, a zeolite, as a reactive material to sorb 90Sr. The overall objective of this study was to provide refined estimates of the efficiency and longevity of the system. To better understand the flow in the aquifer and through the Wall and Curtain, a detailed physical field characterization of the site was performed. Borehole-dilution tests were performed in 19 mm (¾ inch) drive-point piezometers. The results indicate that the Wall and Curtain system intercepted deeper, contaminated groundwater as intended. Hydraulic conductivities (K) determined through slug tests indicate that the aquifer was relatively homogeneous. Average linear groundwater velocities determined through borehole dilution compared well with velocities determined through the Darcy equation based on slug-test K estimates. The measurements from the field study were used to develop a three dimensional physical flow model. The numerical computer code HydroGeoSphere was used to provide an approximate representation of groundwater flow in the aquifer and through the Wall and Curtain. The model was calibrated by comparing simulated and observed hydraulic head values across the site. The model showed good agreement with the observed heads and acceptable agreement with the field estimates of groundwater velocities. A detailed geochemical characterization of the aquifer and the reactive material, clinoptilolite, was performed through field and laboratory work. Pore-water samples were taken from multiple locations in the aquifer. Solid and pore-water samples from the reactive material were used to determine distribution coefficients for 90Sr and competing cations. Sequential leach tests were performed on small amounts of the radioactive solid samples. Results indicate that the system was highly efficient in treating an average mass flux of > 17,000 Bq/m2day-1. The leading edge of the plume was found to have only reached 40 cm into the 2 m thick Curtain of clinoptilolite after nearly 14 years of operation. The reactive material readily sorbed 90Sr, with a distribution coefficient of > 76,000 mL/g for beta activity. Kinetically controlled ion exchange was the main mechanism of sorption onto the clinoptilolite for most cations. The results indicate that the system was highly efficient. Reactive transport models of the site using two different numerical codes, HydroGeoSphere and MIN3P, were constructed to provide refined estimates of the longevity of the system. The model constructed in HydroGeoSphere included five solutes. Zoned distribution coefficients were specified for the transported solutes. In MIN3P, only the reactive material was used as a model domain. Typical concentrations of the plume were specified. Ion exchange was considered in the simulation, as well as radioactive decay of Sr. An updated version of MIN3P was used which also considers kinetic sorption of Sr. Longevity estimates of the different simulations ranged between 30 years and over 200 years for the Wall and Curtain system. Based on field and laboratory experiments, longevity estimates of 80 years to 100 years seemed more reasonable. Results of the numerical simulation indicate that by that time, the system would have remediated 1200 MBq of 90Sr. Continuous monitoring of the outflow will ensure that the time-to-replacement of the system will be met.

The Palm Valley oasis in arid central Australia is characterised by stands of palm trees (Livistona mariae). How these unique plants, separated by nearly a 1000 kilometres of arid country from their nearest relatives persist, has long fascinated visitors. Defining the hydrogeology of the Hermannsburg Sandstone, a regionally extensive and thick Devonian sequence of the Amadeus Basin that underlies Palm Valley, is the major thrust of investigation. Appraisal of drilling data shows this aquifer to be a dual porosity fractured rock aquifer which, on a regional scale, behaves as a low permeability, hydraulically continuous resource. Groundwater is low salinity (TDS &lt1000 mg/L) and bicarbonate rich. Slight variations in cation chemistry indicate different flow paths with separate geochemical histories have been sampled. Stable isotope (????H, ???????O) results from Palm Valley show groundwater to have a uniform composition that plots on or near a local meteoric water line. Radiocarbon results are observed to vary from effectively dead (&lt 4%) to 87 % modern carbon. To resolve groundwater age beyond the radiocarbon window the long lived radioisotope 36Cl was also used. Ratios of 36Cl/Cl range from 130 to 290 x 10-15. In this region atmospheric 36Cl/Cl ratio is around 300 x 10-15. Thus an age range of around 300 ka is indicated if, as is apparent, radioactive decay is the only significant cause of 36Cl/Cl variation within the aquifer. A review of previous, often controversial, 36Cl decay studies shows results are usually ambiguous due to lack of certainty when factoring subsurface Cl- addition into decay calculations. Apparently, due to the thickness of the Hermannsburg Sandstone, no subsurface sources of Cl- such as aquitards or halites, are encountered along groundwater flow paths, hence the clear 36Cl decay trend seen. The classic homogenous aquifer with varying surface topography, the &quotToth&quot flow model, is the simplest conceptual model that need be invoked to explain these isotope data. Complexities, associated with local topography flow cells superimposed on the regional gradient, signify groundwater with markedly different flow path lengths has been sampled. The long travel times (&gt 100 ka) indicate groundwater discharge would endure through arid phases associated with Quaternary climate oscillations. Such a flow system can explain the persistence of this arid zone groundwater-dependent ecosystem and highlight the possibility that Palm Valley has acted as a flora refuge since at least the mid- Pleistocene.

Through the application of downhole logging techniques an innovative assessment of density dependent groundwater flow has been undertaken that highlights the limitations of water level measurements for assessing groundwater flow in coastal environments. The method utilises an EM39 bulk conductivity log to calculate fluid conductivity/fluid density that was then used to convert measured point water head to freshwater head/environmental head to improve the understanding of groundwater flow at the creek. This method of assessing density dependent flow is unique and has not previously been demonstrated. The converted water levels showed that interpretation of groundwater flow is critically dependent on a detailed knowledge of both head and density. An assessment of the potential error in the conversion process indicated that, for the low gradients at the study site, misinterpretation of flow could occur due to errors inherent in the process. As a result, it is recommended that pressure transducers and loggers be used to monitor pressure in variable density systems so that Darcy???s equation can be used directly to calculate groundwater flow and direction. The thesis also presents the results of high-resolution geophysical mapping of the distribution of saline groundwater beneath a tidal creek. The mapping was used to develop a detailed conceptual model of the salinity distribution at a tidal creek that included: the presence of saline intrusion beneath the creek; saline groundwater overlying fresh groundwater due to surface flooding in extreme tide events; concentrated discharge of groundwater (comprised of brackish water due to mixing in the aquifer) at the creek banks; and, significant changes in the distribution of saline groundwater according to rainfall events and only minor changes over a tidal cycle. The conceptual model, geophysical site assessment, water level analysis and numerical modelling represents a multi-disciplinary approach to the assessment of the interaction of saline and fresh groundwater that has not previously been undertaken. Significant anisotropy was inferred from geophysical observations that indicated vertical flow in the borehole annulus. This observation is particularly significant and implies that even relatively short (1.0 to 2.0 m) screened wells may not yield accurate fluid conductivity and head values in variable density systems.

The intermontane Mackenzie Basin is located within the central South Island of New Zealand. The glacial basin contains three glacial lakes which are used for hydroelectric power generation via a canal system that links the lakes. The basin is an area of climate extremes, low rainfall, high summer temperatures, and snowy winters. The area is predominantly used for pastoral farming, however farming practices are changing and, combined with an increasing population, there is a need to define the groundwater resources to enable sustainable resource management. Little is currently known about the hydrogeological system within the Mackenzie Basin, and what is known is from investigations carried out during the construction of the canal system from 1935 to 1985. There are four glacial formations that overlie Tertiary sequences and Torlesse bedrock. However, due to the glacial processes that have been ongoing over at least the last 300 ka, determining the occurrence and extent of groundwater within the outwash gravels is difficult. It is suggested that the permeability of the formations decreases with depth, therefore horizontal and vertical hydraulic conductivity decrease with depth. A shallow groundwater table is present within the Post Glacial Alluvial Gravels which is recharged directly from fast flowing streams and rivers as well as rainfall. It appears that this shallow system moves rapidly through the system and it is unlikely that the water infiltrates downwards to recharge the deeper groundwater system. It is thought that a deep groundwater system flows preferentially through the Mt John Outwash Gravels, being the second youngest glacial formation. Water chemistry and age dating tracer analysis indicate that the deeper groundwater is over 80 years old and that the groundwater system is recharging slowly. The shallow groundwater in the Post Glacial Alluvial Gravels and within the major fans to the east of the basin is 10 to 20 years in age. Baseline data such as water chemistry, groundwater levels, and surface water gaugings have been collected which can be used for future investigations. More data needs to be collected to create a long term record to further define the hydrogeological system and to determine the best way to manage the resource for long term sustainable use in the future.