No full-text available
To read the full-text of this research,
you can request a copy directly from the author.
Quaternary geology Stratford-Conestogo area
... The diamicton has an average composition of 13% sand, 74% silt and 13% clay (Table 3), an average carbonate content of 41% and calcite to dolomite ratios of 2.2 (Table 3). These deposits are correlated with a stone-free, clay-rich diamicton, formally named Maryhill Till (Karrow 1974;1993), interbedded with laminated clay and silt, collectively referred to as Maryhill drift (Bajc and For personal use only. This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. ...
... Oscillations of ice lobes from the northwest, northeast and southwest during the Port Bruce Phase (Bajc et al. this volume) deposited up to 45 m of diamicton, typically described and interpreted as till (Cowan 1976(Cowan , 1979Karrow 1968Karrow , 1974Karrow , 1993) that comprise aquitard ATB1 (Figs. 7i, 8i, 9b-9d; Table 3). These sediments partially bury the edges of the Orangeville Moraine (Figs. 7h and 8h). ...
... A thin sandy silt facies (Fig. 9b) with an average matrix composition of 42% sand, 52% silt and 5% clay was observed in several boreholes in the far northwest of the area (Fig. 9a, Table 3). While this could simply be local variations within Tavistock Till (Cowan 1976), mapping to the southwest raises the possibility of correlating this coarser facies with Stirton Till (Karrow 1993;Karrow and Paloschi 1996). ...
Regional-scale three-dimensional modelling of Quaternary sediments in the Orangeville Moraine area of southwestern Ontario has been completed as part of the Ontario Geological Survey groundwater initiative and provides an improved understanding of the glacial history and conceptual hydrostratigraphic framework for that region. Older (Marine Isotope Stage (MIS) 3-5) diamicton, glaciolacustrine, glaciofluvial and rare non-glacial deposits forming regional aquitards and local aquifers are found in the northwestern part of the area. Catfish Creek Till, deposited during the late glacial maximum (LGM) (MIS 2), forms a key aquitard and stratigraphic marker at depth. Diamicton, fine-textured glaciolacustrine sediments, and the gravel, sand and silt conduit and subaqueous fan sediments that comprise the overlying Orangeville Moraine were deposited in an ice walled lake formed between ice lobes during retreat from the LGM. Diamicton deposited during late glacial ice margin fluctuations forms the upper aquitard unit and buries the edges of the moraine. The Orangeville Moraine is the largest aquifer in the area, and is partially confined by the upper tills. Thick fine-textured glaciolacustrine deposits, Catfish Creek Till and older aquitards separate the moraine from bedrock aquifers across most of the area. Depending on hydraulic gradients, buried bedrock valleys with gravel and sand fills have the potential to recharge the bedrock aquifer.
... Bay ice lobes (Karrow 1993) and the sandy to clayey Port Stanley Till of similar age deposited 202 by the Erie-Ontario ice lobes (Karrow 1987, Cowan 1972) to the southeast . These tills onlap the 203 Waterloo moraine around its peripheries and prevent the rapid infiltration of surface waters into 204 the subsurface. ...
... We look forward to the continued evolution of understanding of this 737 interesting geologic feature as new data are acquired, mapping methods improve and 738 groundwater resource exploration continues in the region. Karrow (1987Karrow ( , 1993) provided for comparison. ...
... Karrow (1987,1993) This Study Karrow (1987Karrow ( , 1993 This Study Karrow (1987Karrow ( , 1993 This Study Karrow (1987Karrow ( , 1993 This Study Wentworth Till Mean 37 48 58 42 5 10 25 41 1.5 n=1 Range -----Port Stanley Till Mean 41 24 52 52 7 24 38 Erie basin glaciolacustrine deposits n/a n/a Erie basin glaciolacustrine deposits n/a n/a ...
Population growth in the groundwater-dependent municipalities of southwestern Ontario has prompted interest in the exploration for new, previously untapped, groundwater resources. In this study, the groundwater resource potential of the sediments infilling a deeply buried bedrock valley network centred beneath the Region of Waterloo and the counties of Brant and Hamilton–Wentworth are explored. The objectives of this study are to further refine valley location and geometry, understand infilling sediments and their hydrogeological properties, and characterize waters contained within the aquifers to inform future water management decisions. Results of a regional ground gravity survey were instrumental in locating buried bedrock valleys and guided follow-up drilling. Continuous sediment coring and monitoring well installations were completed to target thick and coarse-grained sediment packages that, based on existing borehole data, showed aquifer potential. Hydraulic testing and groundwater sampling results provided valuable insights into groundwater quantity and quality. Highly transmissive aquifers, some worth investigating further, have been identified within portions of the valley network. The aquifers appear to occur at a number of stratigraphic positions and do not necessarily occur as the deepest unit overlying bedrock. Bedrock topography likely played a role, however, in their preferential preservation. They are commonly overlain by thick sequences of relatively impermeable sediments, providing excellent protection from anthropogenic contamination. Information from water chemistry, however, does suggest hydraulic connection to the surface at some locations. Groundwater quality and quantity information combined with a conceptual three-dimensional geologic model aids in the selection of groundwater resource exploration targets within the untapped resources of the deep, Dundas buried valley sediments.
... Geological knowledge of many of these moraines is limited to surficial geological mapping at a 1:50,000 scale (e.g. Karrow, 1993). ...
... The moraine consists of a main southeast-northwest elongate ridge and a number of associated ridges that are orientated radial to the main moraine (e.g. Crosshill, Hawkesville; Karrow, 1993). The Waterloo Moraine sediment stratigraphically overlies Catfish Creek and lower till (Fig. 3, Bajc and Karrow, 2004). ...
... Detailed descriptions of the Hawkesville Spur indicate that it is predominantly gravel (Bowes, 1976). Depending upon the stratigraphic position of the diamicton, it has been correlated on the basis of matrix texture, clast lithology and matrix chemistry with upper and middle Maryhill, Tavistock, Mornington and Port Stanley tills (Karrow, 1993). ...
The Waterloo Moraine is a stratified moraine with an area of ∼400 km2 and thickness of 60 m. Its sedimentary record contains evidence of high-magnitude meltwater discharge and rapid sedimentation. Sedimentary structures and sediment architecture are presented from several sites that record depositional events of subcritical flows, supercritical flows and hydraulic jumps. The sedimentological signature of these events is: (i) a variety of large scale cross-strata, (ii) climbing cross-stratification, (iii) antidune cross-stratification and (iv) steep-walled scours with diffusely graded fills. These depositional signatures can be attributed to two depositional environments. A conduit or esker setting is interpreted for the observed large-scale cross-beds with bimodal and openwork gravel, whereas a subaqueous fan setting is inferred for the remainder of the studied deposits. The subaqueous fan setting is interpreted in terms of the jet-efflux model where rapid streamwise deceleration of the inertia-dominated jet is recorded by antidunes produced by supercritical flow; steep-walled scours and diffusely graded fills formed beneath hydraulic jump processes; and climbing dunes record subcritical flow. The paper demonstrates that stratified deposits of the Waterloo Moraine consist of organized deposits that can be interpreted within the current understanding of flow dynamics and depositional sedimentary facies models. This provides a step toward improved understanding of the spatial heterogeneity of the moraine sediment and development of predictive models for improved understanding of the hydrogeological character of the Waterloo Moraine.
... The Grand River floodplain, containing glacial fluvial sand and gravel deposits, is adjacent to the Moraine. Topographically, the Waterloo Moraine is the dominant feature within the Region, extending in a general undulating northwest-southeast direction, and ranging in thickness from 20 to over 100 m (Karrow 1993). The surface is composed of sandy hills, with some ridges of sandy till, and kames or kame moraines with outwash sands occupying the intervening hollows (Karrow 1993). ...
... Topographically, the Waterloo Moraine is the dominant feature within the Region, extending in a general undulating northwest-southeast direction, and ranging in thickness from 20 to over 100 m (Karrow 1993). The surface is composed of sandy hills, with some ridges of sandy till, and kames or kame moraines with outwash sands occupying the intervening hollows (Karrow 1993). ...
... The Waterloo Moraine is a large, ice-contact sediment complex formed primarily through Quaternary glaciation. As a result of various ice advances and retreats throughout the Wisconsinan, the stratigraphy of the Moraine is heterogeneous, featuring sand, gravel, diamict and fine-grained discontinuous sediments units, with sediment contributions from the Ontario-Erie, Huron and Georgian Bay glacial lobes (Figure 1) (Chapman and Putnam 1984;Karrow 1993;Gautrey 1996;Bajc and Karrow 2004;Bajc and Shirota 2007;Weaver and Arnaud 2011). Meltwater associated with the Wisconsinan glaciation resulted in deposition of several recognizable tills: the Port Stanley/ Tavistock, Maryhill and Catfish Creek Tills (Chapman and Putnam 1984;Karrow 1993;Bajc and Newton 2007). ...
The Waterloo Moraine is a historic and continuing groundwater resource for the growing Region of Waterloo in southern Ontario, Canada, providing hundreds of thousands of litres of fresh water daily to the regional water supply. The complex stratigraphy of the Moraine is characterized by a system of multiple aquifers separated by regionally discontinuous aquitards, complicating resource assessments. The Region’s extensive monitoring and production well network has been sampled repeatedly over the last four decades, providing insights into how long-term pumping and urban development have affected aquifer geochemistry. Various environmental tracers were used to identify groundwater residence time and mixing including 3H, 3H/3He, CFCs, SF6, 14C, and 4He. Studies on the Waterloo Moraine provided important contributions to the application of these environmental tracers by validating unsaturated zone transport theory and documenting the effects of localized atmospheric CFC contamination. These studies have also provided important information about groundwater flow and mixing in the Moraine. Both historical and recent hydrogeological studies identified urban applications of road deicers (salt) and rural agricultural practices (nitrate loadings) as potential problems for future use of groundwater as a domestic water supply for the region, with Cl and NO3-N concentrations in some areas approaching 900 and 17 mg/L, respectively. The effects of these urban and rural contaminant issues are explored, and efforts to mitigate and reduce the impact, including the effects of best (beneficial) management practices, are discussed. The potential impacts of these non-point source contaminants on the public water supply should be considered when planning new residential developments.
... Ensuing revisions, including those of Taylor (1939) and Chapman and Putnam (1951) as well as 1:50,000 scale surficial geological mapping (e.g. Karrow 1993) resulted in a refined definition. This mapping depicted areas of hummocky terrain, including genetically related radiating spurs of sand and gravel attributed to the Waterloo Moraine. ...
... The subsurface geological information, in conjunction with the surficial geology maps (Karrow 1968(Karrow , 1993Cowan 1975), was the basis for developing an initial conceptual geological model for the Waterloo Region that consisted of 18 stratigraphic units and bedrock (Bajc and Shirota 2007). Many of these units, however, have a Canadian Water Resources Journal / Revue canadienne des ressources hydriques 5 limited spatial extent, their boundaries pinching out at inferred ice margins, meltwater channels and limits of glaciolacustrine inundation. ...
... The till often has a red to grey-mauve colour suggesting a possible Erie-Ontario lobe source, possibly from shale below the Niagara Escarpment. The fine-grained texture of this till is attributed to the incorporation of clast-poor silty to clayey glaciolacustrine sediment (Karrow 1993). Interbeds of rhythmically laminated silt and clay associated with subglacial and proglacial facies of the unit suggest a predominant glaciolacustrine depositional environment. ...
Aquifers of the Waterloo Moraine play a key role as the main source of drinking water for the Region of Waterloo. For the effective management of this water source, a sound understanding of the aquifers contained within and below the Moraine is essential. Critical knowledge required for this understanding includes the definition of the sediment facies distribution, architectural elements and geological origin of the Quaternary-aged deposits. A basin analysis approach has been applied to geologic data collection and interpretation to unravel the paleogeographic history of the study area and to provide a predictive framework for understanding its geological variability. Coarse (sand and gravel) sediment within the Waterloo Moraine was deposited during a series of high-energy meltwater discharge events from several sediment input corridors (eskers), into a deep, large, ice-supported glacial lake. This depositional setting led to a complex three-dimensional architecture comprising sand-gravel and mud units that are increasingly interbedded away from the multi-directional influx sources around the perimeter of the Moraine. A recently completed digital, three-dimensional geologic model of the area provides details of the various geological units that help refine the understanding of the hydrostratigraphy. This information has improved the understanding of groundwater flow (including interaction between surface and groundwaters) and has provided valuable information critical for source water protection. Information on the distribution, thickness, geometry and properties of these units has resulted in a better understanding of the potential linkages between near-surface recharge areas and deep aquifers across the region. This geological information is important in developing predictive models, for example, determining the location of high transmissivity zones within the moraine. Derivative products such as aquifer vulnerability and recharge maps may help inform policy makers in developing land use and nutrient management plans in the vicinity of well fields and sensitive lands.
... The Waterloo Moraine is well characterized hydrogeologically because of its value as a water source to the local communities. The Waterloo Moraine is predominantly of hummocky relief, mainly composed of sand and gravel with intervening till layers and has been interpreted to be an interlobate kame moraine (Karrow, 1993). ...
... The underlying bedrock consists of the Salina Formation, a Silurian dolomitic limestone (Karrow, 1993 Groups of boreholes were linked into 317 local-scale cross sections to allow continuous interpretation of the stratigraphy [ Figure 9]. A typical cross section is depicted in Figure 10 showing ...
This study extends the methodology for the delineation of capture zones to base flow contribution areas for stream reaches under the assumption of constant average annual base flow in the stream. The methodology is applied to the Alder Creek watershed in southwestern Ontario, using three different numerical models. The three numerical models chosen for this research were Visual Modflow, Watflow and HydroGeoSphere. Capture zones were delineated for three different stream segments with reverse particle tracking and reverse transport.
The modelling results showed that capture zones delineated for streams are sensitive to the discretization scheme and the different processes considered (i.e. unsaturated zone, surface flow). It is impossible to predict the size, shape and direction of the capture zones delineated based on the model selected. Also, capture zones for different stream segments will reach steady-state at different times. In addition, capture zones are highly sensitive to differences in hydraulic conductivity due to calibration. It was found that finite element based integrated groundwater - surface water models such as HydroGeoSphere are advantageous for the delineation of capture zones for streams.
Capture zones created for streams are subject to greater uncertainty than capture zones created for extraction wells. This is because the hydraulic gradients for natural features are very small compared to those for wells. Therefore, numerical and calibration errors can be the same order of magnitude as the gradients that are being modelled.
Because of this greater uncertainty, it is recommended that particle tracking and reverse transport always be used together when delineating capture zones for stream reaches. It is uncertain which probability contour to choose when the capture zone is delineated by reverse transport alone. The reverse particle tracks help choose the appropriate probability contour to represent the stream capture zone.
... Dreimanis' work established a second reference Quaternary stratigraphic sequence, after Toronto, for all other studies in southern Ontario. The mapping program led to further discoveries of buried organic deposits, such as Woodbridge (White 1975), Innerkip (Cowan 1975), Clarksburg (Warner et al. 1988), and Glen Allan (Karrow 1993). Workers in the region adopted the general and informal term "subtill organics" to refer to fossil occurrences below and between glacial deposits. ...
... Areally extensive windows of Nissouri Phase Catfish Creek Till, the deposit of the main Late Wisconsin (OIS2), have been recognized and mapped in the vicinity of the interlobate zone (Karrow 1993;Cowan 1975), and confirmed by recent drilling (Bajc and Dodge 2011). This unit generally accounts for a significant proportion of the stratigraphic sequence observed within this region with thicknesses ranging between 7 and 25 m in the vicinity of the quarry. ...
Nonglacial deposits of Middle Wisconsin age are being discovered with increased frequency across a broad region of southern Ontario, Canada, and provide strong evidence for a time of significant ice withdrawal from the lower Great Lakes region. With each new discovery, a refined understanding of regional climatic and paleoecological environments is emerging. In this paper, we present the results of a sedimentological and paleoecological study of a subtill organic deposit in Zorra Township, southwestern Ontario. The organic deposit, which lies beneath Nissouri Phase Catfish Creek Till (Late Wisconsin), has been dated by accelerator mass spectrometry at between 50.5 and 42.914C ka BP. The organic remains are contained within slack water pond deposits infilling a channel incised into till either of Early Wisconsin or Illinoian age. The fossil assemblage appears to be strongly influenced by taphonomic processes, including degradation due to oxidation, bacterial and fungal decay, and glacial overriding. Reworking and (or) recycling and selective sorting as well as long-distance transport has also influenced the composition of the fossil assemblage preserved. Nonetheless, meaningful paleoecological information is still obtained from this record. Collectively, the pollen and plant macrofossils indicate a boreal-type pine–spruce forest with temperatures cooler than present. The absence of arctic tundra plants, as are found in many other deposits of similar age in the lower Great Lakes basin, is notable. A pond or wetland inhabited by shoreline herbs, shrubs, and trees was present at or proximal to the site. The freshwater mollusc and ostracode assemblages are consistent with a shallow water habitat with dense submerged vegetation. The terrestrial mollusc assemblage suggests a taiga or transitional taiga–tundra fauna. Together, these fossil groups provide one of the most comprehensive environmental reconstructions of Middle Wisconsin time (oxygen isotope stage 3 or OIS3) in southern Ontario and serve to build on the ever-increasing database of paleoecological information accumulating for this episode of the late Quaternary. © 2015, National Research Council of Canada. All Rights Reserved.
... The Waterloo Moraine is a prominent topographic feature with an elevation of 400 m asl and a relief of ~50 m (Fig. 1). It consists of a main southeast-northwest elongate ridge (Bajc & Karrow, 2004) and a number of associated ridges that are orientated radially to the main moraine (Karrow, 1993). Associated ridges, informally named spurs, are from south to north referred to as the Washington, Phillipsburg, Crosshill and, Hawkesville spurs. ...
... The surficial geology consists primarily of fine sand, silt and silt-sand to clay-silt diamictons. The diamictons have been correlated with Maryhill, Tavistock, and Port Stanley tills (Karrow, 1993). ...
Many moraines in Ontario are important areas of groundwater recharge. Moraine topography and structure controls the transmission of water from surface to groundwater and regional aquifers. An improved understanding of moraines in southern Ontario is of particular interest due to increased concern over source water protection (TEC, 2004). The Waterloo Moraine provides ~60 % of the water supply to Waterloo region (Frind et al., 2002). It is the focus of short term artificial recharge and storage (Wootton et al., 1997), is the site of municipal landfills, has increasing urban encroachment (Sanderson, 1995), and is the headwaters for many stream in the area. Thus, improved information on sediment extent, composition and variability is needed to sustain these vital watershed activities. One, well developed, and little-applied research method in southern Ontario moraines, is sedimentological analogue studies of outcrop and subsurface core for improved understanding of reservoir-aquifer geometry and character (e. g. North and Prosser, 1993; Galloway and Hobday, 1996)
... The Mannheim East wellfield is located within the core area of the Waterloo Moraine, which is classified as a kame deposit with three main aquifers separated by two glacial tills (Karrow, 1993). To mimic the multi-aquifer/aquitard system of the study site, a layer-cake geological model was constructed for this synthetic study, as shown in Fig. 1a and b. ...
This study proposes the utilization of municipal well records as an alternative dataset for large-scale heterogeneity characterization of hydraulic conductivity (K) and specific storage (Ss) using hydraulic tomography (HT). To investigate the performance of HT and the feasibility of utilizing municipal well records, a three-dimensional aquifer/aquitard system is constructed and synthetic groundwater flow and solute transport experiments are conducted to generate data for inverse modeling and validation of results. In particular, we simultaneously calibrate four groundwater models with varying parameterization complexity using five datasets consisting of different time durations and periods. Calibration and validation results are qualitatively and quantitatively assessed to evaluate the performance of investigated models. The estimated K and Ss tomograms from different model cases are also validated through the simulation of independently conducted pumping tests and conservative solute transport. Our study reveals that: 1) the HT analysis of municipal well records is feasible and yields reliable heterogeneous K and Ss distributions where drawdown records are available; 2) accurate geological information is of critical importance when data density is low and should be incorporated for geostatistical inversions; 3) the estimated K and Ss tomograms from the geostatistical model with geological information are capable in providing robust predictions of both groundwater flow and solute transport. Overall, this synthetic study provides a general framework for large-scale heterogeneity characterization using HT through the interpretation of municipal well records, and provides guidance for applying this concept to field problems.
... Based on the geological investigation of the Waterloo Moraine by Karrow (1993), four major glacial tills considered to be aquitards, have been identified throughout the moraine (from youngest to oldest, they are Tavistock/Port Stanley Till, Maryhill Till, Catfish Creek Till, and Pre-Catfish Creek). Coarse grain deposits are found above, in-between, and below Maryhill Till and Catfish Creek Till. ...
Analyses are presented of long-term hydrographs perturbed by variable pumping/injection events in a confined aquifer at a municipal water-supply well field in the Region of Waterloo, Ontario (Canada). Such records are typically not considered for aquifer test analysis. Here, the water-level variations are fingerprinted to pumping/injection rate changes using the Theis model implemented in the WELLS code coupled with PEST. Analyses of these records yield a set of transmissivity (T) and storativity (S) estimates between each monitoring and production borehole. These individual estimates are found to poorly predict water-level variations at nearby monitoring boreholes not used in the calibration effort. On the other hand, the geometric means of the individual T and S estimates are similar to those obtained from previous pumping tests conducted at the same site and adequately predict water-level variations in other boreholes. The analyses reveal that long-term municipal water-level records are amenable to analyses using a simple analytical solution to estimate aquifer parameters. However, uniform parameters estimated with analytical solutions should be considered as first rough estimates. More accurate hydraulic parameters should be obtained by calibrating a three-dimensional numerical model that rigorously captures the complexities of the site with these data.
... The main aquifers in the study area are part of the Waterloo Moraine. Stratigraphy within the moraine is heterogeneous, correlated with various ice advances and retreats throughout the Wisconsinan (Karrow, 1993). Sediments consist of several recognizable tills in a complex interfingering arrangement, often separated by glaciofluvial sediments consisting of outwash sand and gravel, and reworked older tills. ...
Currently, the Regional Municipality of Waterloo (RMOW), Canada, derives about 90% of its water supply from groundwater. During the last five years, the population has grown by 8% per year, with development occurring on formerly agricultural land. Over the last 10 years, geochemical sampling in production, domestic, and monitoring wells across the RMOW, focusing on nitrate and chloride, has provided a background data set to evaluate changes to groundwater quality as development encroaches rural watersheds. Samples were taken in rural, urban, and rural residential (areas with relatively dense concentrations of both individual domestic wells and septic systems) environments. Typically, chloride levels are highest in urban areas and along highways in rural areas; nitrate levels are highest in rural and rural residential areas. Results in some recently urbanized sections indicate a reduction in nitrate concentrations, with little impact yet observed from road salt, but additional sampling is needed to assess long-term trends.
... The first site selected for the study was Ellice Swamp, near Stratford in southern Ontario (Fig. 1). The bog has developed on the eastern flank of Milverton Moraine (Karrow, 1971). Shortly after deglaciation, drainage was impeded, which led to local ponding during which lacustrine silts and clay were deposited. ...
... Ellice Swamp is typical of basin bogs described by Glooschenko and Grondin (1988) in the eastern temperate wetland region of Canada, and is one of the two largest bogs of this type in southwestern Ontario. The bog is developed on the eastern and southeastern flanks of the Milverton Moraine (Karrow 1986). During deglaciation, drainage was impeded, which led to local ponding and deposition of lacustrine silt '~llice Swamp is the official name on topographic maps, but it is a bog according to the Canadian wetland classification system (Tarnocai etal. ...
Ground penetrating radar (GPR) has been applied to the mapping of stratigraphy and peat thickness of a large bog in southwestern Ontario. The GPR survey was undertaken in conjunction with a conventional coring survey and measurement of peat physical properties. The results indicate that GPR responds to peat moisture content and bulk density, which vary with stratigraphic changes. In particular, the acrotelm–catotelm boundary and the basal clay are GPR reflectors. The presence of gyttja above the clay is indicated by complex basal reflections. Ground penetrating radar is a viable alternative to an intensive coring survey for evaluating peat depth and extent.
... A buoyant (quaking) peatvegetation mat covers a substantial portion of the peatland, but shallow water is often present over unvegetated peat (muck) at its centre (Figure 2). Beneath Spongy Lake, 5 m of highly decomposed peat is underlain by a clay layer of undetermined thickness (Karrow 1993). Spongy Lake lies above the regional watertable. ...
Links between local hydrology and vegetation type exist in wetlands, yet it is unclear what role peat volume change plays in these interactions. We measured peat volume change and hydraulic conductivity (Kfield) at three contrasting sites located on the quaking vegetation mat of a kettle-hole peatland in southern Ontario. The three sites had visibly different plant communities and were named, according to their dominant vegetation, Sedge (Carex spp.), Typha (Typha angustifolia) and Carr (Cornus stolonifera). Peat was also collected for laboratory studies of peat volume change, vertical (Kv) and horizontal (Kh) hydraulic conductivity and the effect of compression on hydraulic conductivity (Kc).In the field, the water table rose throughout the study period, resulting in swelling of the peat. Peat volume change above the -100 cm layer was 11.2%, 6.0% and 3.8% at the Sedge, Typha, and Carr sites respectively. In laboratory samples, a falling water table caused compression of the peat below the structured surface mat, and relative peat volume change between the sites followed the same pattern as in the field. Kfield, Kv and Kh generally decreased with depth from ca. 10-2 to 10-6 cm s-1. In the surface layers (0 to -50cm) K trended Carr>Typha>Sedge, whereas the reverse trend was observed in deeper peat. Artificial compression affected K only in the uppermost layers (0 to -15cm). The decline in Kc with compression also trended Sedge>Typha>Carr. Differences in peat volume change and K are probably related to differences in vegetation and soil structure, and may be important for maintaining suitable growing conditions within each community.
Hydraulic tomography (HT) has been shown to be a robust approach for the high‐resolution characterization of subsurface heterogeneity. However, HT can yield smooth estimates of hydraulic parameters when pumping tests and drawdown measurements are sparse, thus limiting the utility of characterization results in predicting groundwater flow and solute transport. To overcome this issue, this study integrates cross‐hole flowmeter measurements with HT analysis of steady‐state pumping/injection test data for the three‐dimensional (3‐D) characterization of hydraulic conductivity (K) at a highly heterogeneous glaciofluvial deposit site, which has not been previously attempted. Geostatistical inverse analyses of cross‐hole flowmeter data are conducted to yield preliminary estimates of K distribution, which are then utilized as initial K fields for steady‐state HT analysis of head data. Four cases combining three data types (geological information, cross‐hole flowmeter measurements, and steady‐state head data) for inverse modeling are performed. Model calibration and validation results from all cases are compared qualitatively and quantitatively to evaluate their performances. Results from this study show that (a) geostatistical inverse analysis of cross‐hole flowmeter data is capable in revealing vertical distributions of K at well locations and major high/low K zones between wells, (b) cross‐hole flowmeter data carry non‐redundant information of K heterogeneity compared to geological information and steady‐state head data, and (c) integration of flowmeter data improves characterization results in terms of revealing K heterogeneity details and predicting independent hydraulic test data. Therefore, this study demonstrates the usefulness of cross‐hole flowmeter data in augmenting HT surveys for improved K characterization in 3‐D.
Hydraulic tomography (HT) has been evaluated as an effective approach for subsurface heterogeneity characterization. However, only a few HT studies have been performed for large-scale field problems due to the difficulty in conducting dedicated HT surveys at large-scale sites, as well as the uncertainty regarding estimated initial and boundary conditions for inverse modeling. To overcome these issues, this study advocates the utilization of existing long-term municipal well records as alternative datasets for large-scale heterogeneity characterization, along with novel data processing and analyses strategies that are proposed to minimize the effect of uncertain initial and boundary conditions on inverse modeling. Specifically, geology-based zonation and geostatistical models are adopted for site heterogeneity characterization through HT analyses of municipal well records, and the estimated hydraulic parameters from both models are validated through the prediction of head response data that have not been used for calibration efforts. Our results reveal that existing field municipal well records could be utilized for large-scale subsurface heterogeneity characterization using the approach of HT when uncertainties regarding initial and boundary conditions are well addressed for inverse modeling. In comparison to geology-based zonation model, the geostatistical model reveals greater details of intralayer heterogeneity where head response data are available, yielding significantly improved calibration and validation results. Overall, this study provides a general framework of using existing hydrographs for large-scale heterogeneity characterization through HT, and advocates the utilization of geostatistical inverse modeling as the second step over traditional zonation modeling approach to reveal intralayer heterogeneity details of hydraulic parameters.
A study of the interaction between groundwater and surface water was undertaken within a small agricultural watershed at Mannheim, southern Ontario, Canada. The study was conducted in a test site managed by the University of Waterloo. Groundwater contribution to the stream was measured along a section of Alder Creek during a rainfall event. After a general characterization by water stable isotopes, the hydrograph separation has been conducted using 18O/16O isotopic ratios before, during and after the rainfall event recorded the fourteenth of July 2015. The elaboration showed that pre-event water (corresponding to groundwater contribution) dominated the streamflow, accounting for 82% of discharge, respect with 18% of event water (precipitation) recorded during the storm flow peak.
The Waterloo Moraine has been a drinking water source for the people of Waterloo Region for over a century and, as such, it has been the subject of numerous geologic and hydrogeologic studies for over five decades. Two of the companion papers in this Special Issue describe the evolution of the hydrogeological conceptualization of the Moraine sediments and the history of groundwater modelling of the Moraine groundwater flow system, respectively. This paper builds on those findings and describes the development and calibration of a three-dimensional finite-element groundwater flow model. A key aspect in the development was the implementation of a spatial geodatabase that links the conceptual hydrogeological framework with the numerical groundwater flow model. The model was based on a detailed characterization of the groundwater and surface water systems, and calibrated to available data under average (steady-state) and variable (transient) pumping and climate conditions. Following model development and calibration, the model was used to conduct a detailed water budget and risk assessment study that compared groundwater demands to available supplies within the Central Grand River Watershed, a subwatershed of the main Grand River Watershed. Several scenarios involving future municipal water demands and potential reductions in groundwater recharge due to planned land-use development were simulated, leading to the conclusion that the projected municipal water demand to 2031 can be supplied by the existing system of wells without causing a significant reduction in groundwater discharge to ecologically sensitive streams and wetlands. The model was also applied to delineate the capture zone for a well field in the Region under conditions of uncertainty, demonstrating a methodology that could be applied to other well fields. The model provides an effective and efficient tool for Regional water managers for the long-term sustainable management of the groundwater resources of the Waterloo Moraine.
The Waterloo Moraine provides a major source of drinking water to the Region of Waterloo and supports many important ecological features throughout the area. As such, the structure of the multi-aquifer system of the Waterloo Moraine has been the topic of technical and scientific studies over the last 50 years. As additional data were collected and investigative tools were developed, the conceptual stratigraphic and hydrogeologic models were updated and refined. A strong correlation exists between the stratigraphy and the hydrostratigraphy within the Waterloo Moraine, and stratigraphic models have largely provided the framework for hydrogeological investigations. The current hydrostratigraphic framework within the Waterloo Moraine was developed through refinement of a stratigraphic framework using water level data, hydraulic response data, geochemical data and geophysical data collected in boreholes and monitoring wells located across the Region of Waterloo. Water supply aquifers are found throughout the stratigraphic sequence, including coarse-grained sediments within, and beneath, the Waterloo Moraine. Shallow coarse-grained unsaturated deposits and hummocky terrain of the central core area of the Waterloo Moraine allow large volumes of recharge to infiltrate, and this water is subsequently transmitted to deeper aquifer aquifer units through erosional windows in the aquitards. One of the most productive aquifers within the Region is located in the basal sediments of the Waterloo Moraine, while other thick and transmissive aquifer units underlie these moraine sediments. This paper describes the past and current studies that contributed to a refined understanding of the hydrogeology of the Waterloo Moraine and its underlying sediments. Discussion focuses on the municipal water supply aquifers and the potential linkages between municipal aquifers and environmental features, such as cold-water streams and wetlands that are reliant on groundwater discharge for ecosystem health. Understanding these linkages is particularly important given the forecasted population growth and increased municipal demand in the Region of Waterloo in the coming decades, and the need to protect the municipal water supply aquifers and sensitive surface water features.La moraine de Waterloo est une source importante d’eau potable pour la région de Waterloo et elle assure de nombreuses fonctions écologiques dans toute la région. Par conséquent, la structure du système multi-aquifère de la moraine de Waterloo a fait l’objet de nombreuses études techniques et scientifiques au cours des 50 dernières années. Avec la collecte de données additionnelles et le développement d’outils d’analyse, les modèles hydrogéologiques et stratigraphiques conceptuels ont été actualisés et raffinés. Il existe une forte corrélation entre la stratigraphie et l’hydrostratigraphie de la moraine de Waterloo, et les modèles stratigraphiques ont largement fourni le cadre des études hydrogéologiques. Le développement de l’actuel cadre hydrostratigraphique de la moraine de Waterloo a consisté à raffiner le cadre stratigraphique grâce à des données sur les niveaux d’eau, des données sur la réponse d’essais hydrauliques, des données géochimiques et des données géophysiques recueillies dans des forages et des puits de surveillance dans la région de Waterloo. Les aquifères utilisés pour l’approvisionnement en eau potable sont répartis dans toute la séquence stratigraphique, dont les des sédiments à grains grossiers à l’intérieur de la moraine de Waterloo et sous celle-ci. Des sédiments non saturés et peu profonds à grains grossiers et du terrain bosselé dans la partie centrale de la moraine de Waterloo permettent l’infiltration d’importants volumes d’eau de recharge qui s’infiltre subséquemment vers les unités aquifères plus profondes par des fenêtres d’érosion dans les aquitards. Un des aquifères les plus productifs dans la région se trouve dans les sédiments à la base de la moraine de Waterloo alors que d’autres unités aquifères épaisses et transmissives se trouvent sous ces sédiments morainiques. Dans cet article, nous décrivons les études passées et actuelles qui ont contribué à mieux comprendre l’hydrogéologie de la moraine de Waterloo et ses sédiments sous jacents. L’article décrit les aquifères servant à l’approvisionnement municipal en eau potable et les liens possibles entre ces aquifères et les entités environnementales, comme les cours d’eau et les zones humides qui sont alimentés par la décharge des eaux souterraines assurerant ainsi la santé des écosystèmes. Comprendre ces liens est de la première importance, compte tenu des prévisions de croissance démographique et de demande municipale accrue dans la région de Waterloo au cours des prochaines décennies, et de la nécessité de protéger les aquifères servant à l’alimentation municipale en eau, ainsi que les eaux de surface sensibles.
A hydraulic trap in the form of a purge well is proposed for the Forwell collector well K-71. The trap, which will protect well K-71 from contamination by contaminants migrating downgradient from the old Breslube waste disposal site, is based on a qualitative flow net obtained from a finite-element model of the Forwell Aquifer. The trap constitutes pumping at the position of observation well OW 9-80 at a continuous rate of at least 6.1 X 10-3 m3/s. The uniqueness of the trap lies in its simplicity and relatively low cost.
To examine nitrate persistence, detailed geochemical profiling, using core-squeezed water and piezometer samples, was carried out at five sites in southern Ontario where groundwater is moving downward in silt-rich aquitard sediments at rates of 16 to more than 20 cm year−1. Elevated levels of NO3−-N (5–50 mg 1−1) that occur in the shallow groundwater as a result of agricultural activity, were found to be consistently attenuated, generally to very low levels (< 0.05 mg 1−1-N), at the ‘redoxcline’, the horizon marking the boundary between the surficial weathered (brown) sediments and the underlying unweathered (grey) sediments. Tritium dating suggests that groundwater at the redoxcline depths (3–5 m) was recharged between 1970 and 1980, thus the N03 depletion appears to result from biodegradation reactions since no major landuse changes have occurred during this period. The close association of the nitrate depletion zones with the redoxcline, where, in particular, sediment sulphur contents increase abruptly, and where also porewater SO42− levels increase, suggests that the dominant attenuation reaction is autotrophic denitrification using reduced sulphur compounds present in the unweathered sediment as the electron donor. Mass balance calculations suggest that the increase in the downward rate of migration of the redoxcline, owing to added sulphur consumption from NO3− contamination, is only about 1 mm year−1 at these sites. Review of the literature indicates that most silt- and clay-rich sediments have S contents in the same range, or higher, than those investigated here, thus, in most cases where aquifers are overlain by several metres or more of unweathered confining sediments, it is likely that a high degree of protection is afforded from surficial NO3− contamination.
The Huron-Erie interlobate zone passes near Woodstock, Ontario. Three large limestone quarries (Zorra, Beachville West, Beachville East) provide exposures up to 30 m high of the drift stratigraphy. Grain size, matrix carbonate, color, structure, fabric, lithology, and sequence, along with continuous tracing of contacts and facies changes, allowed recognition of ten tills and related water-laid sediments correlated with the known stratigraphy in surrounding areas. Four major glacial events are recognized, three of Late Wisconsinan age. Three tongues of red, Erie lobe Canning Till (unknown age) are overlain by a Nissouri Stadial (22-17 ka) Catfish Creek Drift complex (two till tongues, regional southwest ice flow). Similar, apparently correlative, glacial and non-glacial sediment sequences within Catfish Creek Drift at Zorra and Beachville West (Centreville Member) suggest a northwest-southeast-trending ice margin. Overlying this are Erie Interstadial (16 ka) glaciolacustrine sediments (Rayside beds), Port Bruce Stadial (15-14 ka) Erie lobe Port Stanley Till, glaciolacustrine Zorra beds, and final Port Bruce Stadial Huron lobe Tavistock Till (three tongues), and deglacial outwash (Dunn's Corner gravels). Repeated glaciolacustrine sedimentation between tills may relate to glacioisostatically reduced gradients and nearby Ice lobe margins. There is little evidence of Catfish Creek interlobate conditions and only independent lobal glacial advances later.
The origin of micro-relief on till sheets of the Conestogo lake area, Ontario, is discussed. The micro-relief constitutes an extensive, integrated system of swales that represents a drainage network which functioned under periglacial conditions in the late Wisconsinan. At many locations within the study area, this drainage exploited the micro-relief of polygonal patterned ground. The present low-order stream system has resulted from contraction of this Pleistocene system. A qualitative modification of Devries' Groundwater Outcrop Erosion Model is developed to explain drainage evolution at the Pleistocene-Holocene transition. Today, the swales are routes for surface and shallow sub-surface flow from the gently sloping interfluves of the study area.
L'origine du microrelief des dépôts de moraines de fond dans la région du lac Conestogo, Ontario, est discutée. Le microrelief constitue un système de bas-fonds extensif et intégrè qui représente un réseau de drainage qui fonctionnait sous des conditions périglaciaires pendant le Wisconsinien supérieur. Ce drainage a emprunté le microrelief des sols polygonaux à plusieurs endroits à l'intérieur de la région d'éude. le système actuel de rivières de bas ordre est le résultat de la contraction de cet ancien système du Pléistocène. Une modification qualitative du modèle de Devries d'érosion par affleurement de la nappe souterraine (Groundwater Outcrop Erosion Model) est développée pour expliquer 1'évolution du drainage pendant la transition Pléistocene-Holocène dans cette région. Aujourd'hui, les bas-fonds forment des routes pour le ruissellement et I'écoulement hypodermique des interiluves à pentes douces de la région d'étude.
Buried bedrock valleys are of economic interest for groundwater and engineering studies, and of scientific interest for the sedimentary sequences they may contain. Two buried valleys, about 60 m deep, north and northeast of Guelph, Ontario, are tributary to the major Dundas Valley southwest of Guelph. Located initially from water well data, their locations and geometry were refined with surface geophysics, including very low frequency resistivity, terrain conductivity, resistivity, transient electromagnetic, gravity, and seismic methods. Useful data are obtained roughly in proportion to cost. Cored and rotary holes in the two valleys were followed by geophysical downhole logging with normal electric, spontaneous potential, single-point resistance, calliper, neutron – epithermal neutron, gamma–gamma, and natural gamma methods. Cores revealed multi-till sequences in the upper parts of the holes and, together with geophysical logs and their interpreted electrofacies, indicate the presence of underlying uniform, pollen-bearing (pine and spruce dominate) lacustrine fills. These fills and the buried valleys containing them are interpreted to be perhaps as old as the last interglacial. Buried valleys are fruitful targets for the discovery of older Quaternary sequences.
The overburden of Essex and Kent counties, southwestern Ontario, has been described as consisting of a clayey silt to silty clay till overlying a gravelly unit resting on bedrock. Recent Quaternary geology mapping has identified additional materials and redefined the origin of others by determining the stratigraphic position and physical and geochemical properties of materials encountered in a sonic drilling program and field mapping. Catfish Creek Till was deposited on the bedrock surface during the Nissouri Stadial as ice advanced south over the area. As ice retreated during the Erie Interstade, fine-grained glaciolacustrine material was deposited in glacial Lake Leverett and overlay Catfish Creek Till. Tavistock Till was deposited over glacial Lake Leverett material as the Huron lobe readvanced south during the Port Bruce Stadial. As the Huron lobe retreated north, coarse-grained glaciolacustrine materials were deposited in the Leamington area. Ice from the Erie lobe deposited the Port Stanley Till along the north shore of Lake Erie in Kent County and deflected meltwater southward from the Huron lobe in the Blenheim area. A series of recessional moraines were deposited by the Huron lobe as it retreated north. The area is capped by a fine-grained glaciolacustrine deposit.
Hydraulic tomography has been proposed as an alternative site characterization method, however, relatively few field scale studies have been attempted. In this paper, we characterize the highly heterogeneous glaciofluvial aquifer-aquitard system at the North Campus Research Site, located at the University of Waterloo, Waterloo, Ontario, Canada using transient hydraulic tomography (THT). In particular, we performed 9 pumping tests in a network of wells to image the hydraulic conductivity (K) and specific storage (S s) distributions (or tomograms) as well as their uncertainties in three-dimensions using the THT code of J. Zhu and T.-C. J. Yeh (2005). We first performed stochastic inverse modeling of the 9 pumping tests individually to gain insight into the level of detail that can be imaged. Then, we sequentially included 4 of the pumping tests in a THT analysis. The resulting K and S s tomograms were then validated visually by comparing them to stratigraphy and permeameter K estimates. The K and S s tomograms were also rigorously assessed through the simulation of all 9 pumping tests and comparing the simulated and observed drawdowns. We find that performing the inversion with multiple pumping tests (i.e., hydraulic tomography) yields improved results when compared to the analysis of individual pumping tests.
Commercial borings to a depth of 36 m encountered organic sediments under till. A continuously cored borehole was subsequently put down to 42 m and revealed a succession of sand and silt, over clayey Maryhill hill, over sandy Catfish Creek Till, over fossiliferous sand. Pollen, plant macrofossils, and a few ostracodes, molluscs, and insects provide a coherent picture of interstadial conditions. Two pollen zones are represented. The older zone is characterized by Picea and ThujalJuniperus pollen, and Dryopteris-type and Sphagnum spores, which suggest a lowland, forested peatland. Reduction of peatland, and transition to a wetland with more open water associated with a stream is indicated by an increase in Cyperaceae pollen, Pediastrum algae, and a diversity of aquatic plant macrofossils during the later zone. Fossil plant assemblages are similar to modern southern boreal associations in Ontario, which implies that the climate was cooler and possibly drier than the present. Phytogeographically, Picea needles and wood, and seeds of Brasenia schreberi and Potamogetan spirillus are noteworthy among the plant macrofossils. The sequence of Late Wisconsinan tills overlying the fossiliferous zone implies a Middle Wisconsinan age for the interstadial. This is supported by an accelerator radiocarbon date on small wood pieces of 40,080 + 1,200 years B.P.
Geophysical surveys and chemical analyses on cores were carried out in three Ontario peatlands, from which we have gained a better understanding of the peat properties that control the geophysical responses. The electrical conductivity depends linearly on the concentration of total dissolved solids in the peat pore waters and the pore waters in turn bear the ionic signatures of the underlying mineral sediments. The ionic concentration, and thus the electrical conductivity, increase linearly from the surface to basement. The average bulk electrical conductivity of peatlands at Ellice Marsh, near Stratford, and at Wally Creek Area Forest Drainage Project, near Cochrane, are of the order of 25 mS/m. The Mer Bleue peatland, near Ottawa, has extremely high electrical conductivity, reaching levels of up to 380 mS/m near the base of the peat. The Mer Bleue peatland water has correspondingly high values of total dissolved solids, which originate from the underlying Champlain Sea glaciomarine clays. The dielectric permittivity in peats is largely controlled by the bulk water content. Ground penetrating radar can detect changes in water content greater than 3%, occurring within a depth interval less than 15 cm. The principal peatland interfaces detected are the near-surface aerobic to anaerobic transition and the peat to mineral basement contact. The potential for the successful detection of the basement contact using the radar can be predicted using the radar instrument specifications, estimates of the peatland depth, and either the bulk peat or the peat pore water electrical conductivities. Predicted depths of penetration of up to 10 m for Ellice Marsh and Wally Creek exceed the observed depths of 1 to 2 m. At Mer Bleue, on the other hand, we observe that, as predicted, a 100 MHz signal will penetrate to the base of a 2 m thick peat but a 200 MHz signal will not.
The amplitude spectrum of ground penetrating radar (GPR) reflection data acquired with a particular antenna set is normally concentrated over a spectral bandwidth of a single octave, limiting the resolving power of the GPR wavelet. Where variously-sized GPR targets are located at numerous depths in the ground, it is often necessary to acquire several profiles of GPR data using antennas of different nominal frequencies. The most complete understanding of the subsurface is obtained when those frequency-limited radargrams are jointly interpreted, since each frequency yields a particular response to subsurface reflectivity. The application of deconvolution to GPR data could improve image quality, but is often hindered by limited spectral bandwidth.
Excavation below the Lake Algonquin gravel beach bar near Clarksburg, Ontario, exposed mollusc-bearing clay over a lens of plant debris. This is the northernmost and most deeply buried Lake Algonquin fossil site found thus far in Ontario. It is the first site to provide dates from directly below the Algonquin beach bar. Two radiocarbon dates of about 11 200 years confirm the age of isostatically transgressing Lake Algonquin. Plant macrofossils (21 taxa), pollen (39 taxa), molluscs (12 taxa), and ostracodes (18 taxa) indicate that the climate was colder than present by several degrees and the forest-tundra ecotone was nearby initially but retreated northward rather quickly. Upward increases in abundances and diversity of molluscs and ostracodes suggest it was a time of rapid migration and colonization of species.
Mollusc assemblages were studied in two marl deposits at Kitchener and Cambridge, in southwestern Ontario. Lacking datable terrestrial plant material, a chronology was determined by pollen analysis. Similarities in mollusc assemblages and changes allowed five equivalent mollusc assemblage zones to be identified in the two deposits, spanning approximately 12 to 7 ka. In total, 34 mollusc taxa were identified, with 19 common to both sites. Overall, the most abundant taxa were Valvata spp., Gyraulus parvus, Pisidium casertanum, and P. ferrugineum. Terrestrial molluscs (four taxa) were rare. Overall, cool, shallow water with abundant vegetation and quiet conditions were indicated. At around 9 ka, a marked decrease in mollusc abundance and diversity, but relatively stable percentages, is noted at both sites. We speculate this was caused by an increase in sedimentation rate, perhaps caused by a brief warming.
Inconsistencies in assemblages at marl sites may be partly attributable to sampling, but a chance factor in dispersal is also suggested. A minimum of two sampling sites at a given sedimentation basin, nearshore and mid-basin, are recommended to maximize assessment of assemblages. More detailed data from living molluscs are needed to enhance paleoenvironmental interpretations.
The Waterloo Moraine is a stratigraphically complex system and is the major water supply to the cities of Kitchener and Waterloo in Ontario, Canada. Despite over 30 years of investigation, no attempt has been made to unify existing geochemical data into a single database. A composite view of the moraine geochemistry has been created using the available geochemical information, and a framework created for geochemical data synthesis of other similar flow systems. Regionally, fluid chemistry is highly heterogeneous, with large variations in both water type and total dissolved solids content. Locally, upper aquifer units are affected by nitrate and chloride from fertilizer and road salt. Typical upper-aquifer fluid chemistry is dominated by calcium, magnesium, and bicarbonate, a result of calcite and dolomite dissolution. Evidence also suggests that ion exchange and diffusion from tills and bedrock units accounts for some elevated sodium concentrations. Locally, hydraulic "windows" cross connect upper and lower aquifer units, which are typically separated by a clay till. Lower aquifer units are also affected by dedolomitization, mixing with bedrock water, and locally, upward diffusion of solutes from the bedrock aquifers. A map of areas where aquifer units are geochemically similar was constructed to highlight areas with potential hydraulic windows.
This paper examines a southern Ontario kettle-hole peatland (Spongy Lake) to determine its hydrogeological linkage with local
and regional water tables. The water table in the peat deposit and lake are perched 6 m above the regional aquifer, and there
are strong lateral and downward hydraulic gradients. The horizontal hydraulic gradient (Δh/Δz) measured at the edge of the
peatland ranged between 0.15 and 0.23 and the vertical gradient reached −1.24 (i.e., downward flow). At depths less than 1.0
m, saturated hydraulic conductivity (Ks) ranged from 10−7 to 10−5 m s−1 and increased in magnitude with proximity to the peat surface. In an intermediate zone (1.0–4.0 m depth), Ks values ranged from 10−8 to 10−7 m s−1, while deeper clay materials had Ks values ranging from 10−9 to 10−8 m s−1. A clay layer directly below the deep peat limits downward seepage of water (one to two orders of magnitude less than evaporation).
During periods of relatively high water, most seepage loss occurs laterally at the interface between mineral sediment and
the peat. Spongy Lake is an important recharge zone for the regional aquifer, and the hydrologic and ecological integrity
of the system should be protected.
A succession of stratigraphic codes (1933, 1961, 1983) has guided attempts to refine classifications and naming of stratigraphic units for Quaternary deposits of the Great Lakes region. The most recent classifications for the late Quaternary of the Lake Michigan lobe (1968) and the eastern Great Lakes (1972) have been widely used, but later work has created the need for revision. An attempt has been made to integrate the two previous classifications following the diachronic system of the 1983 Code of Stratigraphic Nomenclature. A new nomenclature for the higher, more broadly recognized units was presented in 1997. We here present the diachronic nomenclature for finer subdivisions recognized in the eastern and northern Great Lakes. Following the interglacial Sangamon Episode, the three parts of the Wisconsin Episode are further subdivided as follows: the Ontario Subepisode (former Early Wisconsinan) comprises the Greenwood, Willowvale, and Guildwood phases; the Elgin Subepisode (former Middle Wisconsinan) comprises the Port Talbot, Brimley, and Farmdale phases; and the Michigan Subepisode (former Late Wisconsinan) consists of Nissouri, Erie, Port Bruce, Mackinaw, Port Huron, Two Creeks, Onaway, Gribben, Marquette, Abitibi, and Driftwood phases. Succeeding interglacial time to the present is the Hudson Episode.
Remediation of subsurface contamination requires an understanding of the contaminant (history, source location, plume extent and concentration, etc.), and, knowledge of the spatial distribution of hydraulic conductivity (K) that governs groundwater flow and solute transport. Many methods exist for characterizing K heterogeneity, but most if not all methods require the collection of a large number of small-scale data and its interpolation. In this study, we conduct a hydraulic tomography survey at a highly heterogeneous glaciofluvial deposit at the North Campus Research Site (NCRS) located at the University of Waterloo, Waterloo, Ontario, Canada to sequentially interpret four pumping tests using the steady-state form of the Sequential Successive Linear Estimator (SSLE) (Yeh and Liu 2000). The resulting three-dimensional (3D) K distribution (or K-tomogram) is compared against: (1) K distributions obtained through the inverse modeling of individual pumping tests using SSLE, and (2) effective hydraulic conductivity (K(eff) ) estimates obtained by automatically calibrating a groundwater flow model while treating the medium to be homogeneous. Such a K(eff) is often used for designing remediation operations, and thus is used as the basis for comparison with the K-tomogram. Our results clearly show that hydraulic tomography is superior to the inversions of single pumping tests or K(eff) estimates. This is particularly significant for contaminated sites where an accurate representation of the flow field is critical for simulating contaminant transport and injection of chemical and biological agents used for active remediation of contaminant source zones and plumes.
Hydraulic conductivity (K) and specific storage (S(s)) are required parameters when designing transient groundwater flow models. The purpose of this study was to evaluate the ability of commonly used hydrogeologic characterization approaches to accurately delineate the distribution of hydraulic properties in a highly heterogeneous glaciofluvial deposit. The metric used to compare the various approaches was the prediction of drawdown responses from three separate pumping tests. The study was conducted at a field site, where a 15 m × 15 m area was instrumented with four 18-m deep Continuous Multichannel Tubing (CMT) wells. Each CMT well contained seven 17 cm × 1.9 cm monitoring ports equally spaced every 2 m down each CMT system. An 18-m deep pumping well with eight separate 1-m long screens spaced every 2 m was also placed in the center of the square pattern. In each of these boreholes, cores were collected and characterized using the Unified Soil Classification System, grain size analysis, and permeameter tests. To date, 471 K estimates have been obtained through permeameter analyses and 270 K estimates from empirical relationships. Geostatistical analysis of the small-scale K data yielded strongly heterogeneous K fields in three-dimensions. Additional K estimates were obtained through slug tests in 28 ports of the four CMT wells. Several pumping tests were conducted using the multiscreen and CMT wells to obtain larger scale estimates of both K and S(s). The various K and S(s) estimates were then quantitatively evaluated by simulating transient drawdown data from three pumping tests using a 3D forward numerical model constructed using HydroGeoSphere (Therrien et al. 2005). Results showed that, while drawdown predictions generally improved as more complexity was introduced into the model, the ability to make accurate drawdown predictions at all CMT ports was inconsistent.
The delineation of well capture zones is a basic component of ground water protection. The conventional methodology for capture zone delineation is backward advective particle tracking, often applied under the assumption of a two-dimensional aquifer. The suitability of the conventional approach for complex heterogeneous multi-aquifer systems was investigated, using the Waterloo Moraine aquifer system as an example. It was found that the conventional approach produces irregular particle tracks that require judgment to interpret in a meaningful way, and it can raise questions that may affect the credibility of the capture zone delineation. As an alternative, the potentially powerful but little-used backward-in-time advective-dispersive transport approach was investigated. A key advantage of this approach is its capability to represent local heterogeneities through the dispersion term. The dispersion process has a natural smoothing effect that results in unambiguous capture zones without the need for interpretation, thus enhancing credibility. The question of capture zone validation is also addressed. The meaning of a three-dimensional capture zone is considered, and it is shown that a fully three-dimensional representation of the system is crucial for valid results. The distinction between the maximum extent capture zone and the surface capture zone is also explained. In the case of complex heterogeneous systems, advective particle tracking can be used as an initial screening tool, whereas the more realistic backward-transport modeling approach can be used for final capture-zone delineation.
ResearchGate has not been able to resolve any references for this publication.