Buried Valley Aquifer Research Articles

Can small buried-valley aquifers be an emergency water source on the Canadian Prairies?

Can small buried-valley aquifers be an emergency water source on the Canadian Prairies?

Investigating the hydraulic role of a large buried valley network on regional groundwater flow

An understanding of the three-dimensional hydrostratigraphic architecture of a buried valley network, in particular the continuity of permeable units within their fill, is needed to evaluate the resource potential and role of buried valley aquifers in regional groundwater flow. In this study, a facies modeling algorithm within the exploration and production software Petrel was used to construct a geological model of a buried valley network located in the central Peace Region in Northeast British Columbia, Canada. Facies were interpreted using resistivity inversion results from an airborne electromagnetic survey (SkyTEM) and borehole gamma-ray and lithology logs. This detailed geological model and a simplified geological model of the buried valley network were used to develop two interpretive numerical groundwater flow models in MODFLOW. Calibration was performed using baseflow estimates derived using a novel approach whereby upper and lower bounds for baseflow indices were combined with streamflow estimates from the Northeast Water Tool (NEWT), a hydrological modeling tool developed for water allocation for industrial use by the British Columbia Oil and Gas Commission. The modeling results suggest that permeable deposits exist within the buried valleys, but are not regionally connected throughout the whole network, and thus do not play a significant role in the regional groundwater flow regime. However, locally extensive permeable deposits occur within the buried valleys and may offer viable water sources for domestic use or to replace existing surface-water licenses for industrial use.

Characterizing the Spiritwood Valley Aquifer, North Dakota, using helicopter time-domain EM

Buried valley aquifers, consisting of permeable sand and gravel deposits in eroded bedrock valleys, are important sources of groundwater supply in many regions of the United States and Canada. Investigations of the Spiritwood aquifer in southern Manitoba by the Geological Survey of Canada and other workers, have demonstrated the value of helicopter time domain electromagnetic (HTEM) surveys in aquifer mapping and characterization using the contrasts between Quaternary glacio-lacustrine sand-gravels (high resistivity) that are relatively permeable and clay-tills (low resistivity) that are relatively impermeable, as well as the deeper, much less resistive Cretaceous Pierre Formation Shale basement rocks. This success provided the impetus for the North Dakota State Water Commission to fly a VTEM helicopter EM survey in the Jamestown, ND region in October, 2016. The VTEM data collected over the Spiritwood-JT block allowed for geological mapping from near surface to depth, in spite of relatively weak resistivity contrasts (<10X). These data were inverted with a layered-earth algorithm to produce resistivity-depth models. These models were able to resolve the location and depths to the top and bottom of the Spiritwood aquifer throughout the central portion of the block providing more detailed pictures of the aquifer’s geometry. In addition to resolving the main aquifer as well as its deeper channels, the VTEM data and models highlighted several smaller, previously undiscovered aquifers that cross-cut/branch-off from the main Spiritwood channel. These are interpreted as probable transverse low-K barriers that were apparent from the existing test drilling and aquifer testing.

Bedrock mapping of buried valley networks using seismic reflection and airborne electromagnetic data

In glaciated terrain, buried valleys often host aquifers that are significant groundwater resources. However, given the range of scales, spatial complexity and depth of burial, buried valleys often remain undetected or insufficiently mapped. Accurate and thorough mapping of bedrock topography is a crucial step in detecting and delineating buried valleys and understanding formative valley processes. We develop a bedrock mapping procedure supported by the combination of seismic reflection data and helicopter time-domain electromagnetic data with water well records for the Spiritwood buried valley aquifer system in Manitoba, Canada. The limited spatial density of water well bedrock observations precludes complete depiction of the buried valley bedrock topography and renders the water well records alone inadequate for accurate hydrogeological model building. Instead, we leverage the complementary strengths of seismic reflection and airborne electromagnetic data for accurate local detection of the sediment-bedrock interface and for spatially extensive coverage, respectively. Seismic reflection data are used to define buried valley morphology in cross-section beneath survey lines distributed over a regional area. A 3D model of electrical conductivity is derived from inversion of the airborne electromagnetic data and used to extrapolate buried valley morphology over the entire survey area. A spatially variable assignment of the electrical conductivity at the bedrock surface is applied to different features of the buried valley morphology identified in the seismic cross-sections. Electrical conductivity is then used to guide construction of buried valley shapes between seismic sections. The 3D locus of points defining each morphological valley feature is constructed using a path optimization routine that utilizes deviation from the assigned electrical conductivities as the cost function. Our resulting map represents a bedrock surface of unprecedented detail with more complexity than has been suggested by previous investigations. Our procedure is largely data-driven with an adaptable degree of expert user input that provides a clear protocol for incorporating different types of geophysical data into the bedrock mapping procedure.

Incorporating ancillary data into the inversion of airborne time-domain electromagnetic data for hydrogeological applications

Abstract Helicopter time-domain electromagnetic (HTEM) surveys often suffer from significant inaccuracies in the early-time or near-surface data—a problem that can lead to errors in the inverse model or limited near-surface resolution in the event that early time gates are removed. We present an example illustrating the use of seismic data to constrain the model recovered from an HTEM survey over the Spiritwood buried valley aquifer in Manitoba, Canada. The incorporation of seismic reflection surfaces results in improved near-surface resistivity in addition to a more continuous bedrock interface with a sharper contact. The seismic constraints reduce uncertainty in the resistivity values of the overlying layers, although no a priori information is added directly to those layers. Subsequently, we use electrical resistivity tomography (ERT) and borehole data to verify the constrained HTEM models. Treating the ERT and borehole logs as reference information, we perform an iterative time-shift calibration of the HTEM soundings to achieve regional-scale consistency between the recovered HTEM models and the reference information. Given the relatively small time-shifts employed, this calibration procedure most significantly affects the early-time data and brings the first useable time gate to a time earlier than the nominal first gate after ramp off. Although time shifts are small, changes in the model are observed from the near-surface to depths of 100 m. Calibration is combined with seismic constraints to achieve a model with the greatest level of consistency between data sets and, thus, the greatest degree of confidence. For the Spiritwood buried valley, calibrated and constrained models reveal more structure in the valley-fill sediments and increased continuity of the bedrock contact.

Buried-valley aquifers in the Canadian Prairies: geology, hydrogeology, and origin1Earth Science Sector (ESS) Contribution 20120131.

We review over 100 years of literature on Prairie buried valleys to provide a platform for future research and policy development. Prairie buried-valley fills commonly function as aquifers that yield abundant groundwater. They have distinct geologies and a distinct stratigraphic setting, which imparts them with distinct hydrogeological properties and gives clues as to how they formed and filled. Prairie buried-valley aquifers are commonly encased in low-permeability strata: Cretaceous shale commonly underlies them, and thick (10–300 m) low-permeability Quaternary till tends to overlie them. This reduces recharge, in rare cases nearly completely, while protecting groundwater resources from contamination and drought. It also tends to lead to highly mineralized groundwater chemistries. The stratigraphic position of Prairie buried valleys also speaks to their origin: those that subtend (“hang”) from the bedrock unconformity were likely eroded by preglacial fluvial systems during late Tertiary uplift of the Rocky Mountains, whereas those that subtend from surfaces within the till package are likely glaciofluvial valleys eroded in proglacial spillway or tunnel-valley settings. Another key trait of Prairie buried valleys is that their fills tend to be heterogeneous and architecturally complex. Sand, gravel, mud, and diamicton are common; any one can dominate the fill at a given location. This heterogeneity, in conjunction with irregularity common to buried-valley bedrock floors, commonly causes aquifer compartmentalization and makes prediction of aquifer potential difficult prior to drilling. It also suggests that most Prairie buried valleys filled over time, and likely over multiple glaciations, in multiple depositional environments.

Airborne time‐domain electromagnetics, electrical resistivity and seismic reflection for regional three‐dimensional mapping and characterization of the Spiritwood Valley Aquifer, Manitoba, Canada

The Geological Survey of Canada commissioned a helicopter‐borne time‐domain electromagnetic (HTEM) survey over a 1062 km2 area of the Spiritwood Valley in southern Manitoba in order to test the effectiveness of airborne time‐domain electromagnetics for mapping and characterizing buried valley aquifers in the Canadian Prairies. The data exhibit rich information content and clearly indicate the broader Spiritwood Valley in addition to a continuous incised valley along the broader valley bottom. We detect complex valley morphology with nested scales of valleys including at least three distinct valley features and multiple possible tributaries. Conductivity‐depth images (CDI) derived from the HTEM decays indicate that the fill materials within the incised valleys are more resistive than the broader valley fill, consistent with an interpretation of sand and gravel. Comparison of ground‐based electrical resistivity and seismic reflection data allow for the evaluation of CDI models. Lateral spatial information is in excellent agreement between data sets. However, CDI results tend to underestimate the dynamic range of electrical conductivity while overestimating depths to valley bottoms; these issues may be associated with system limitations, algorithm limitations or differences between data types. The integrated data sets illustrate that HTEM surveys have the potential to map complicated buried valley aquifers at a level of detail required for groundwater prospecting, modelling and management.

Variable infiltration and river flooding resulting in changing groundwater quality – A case study from Central Europe

Summary The changes in groundwater quality occurring in a buried valley aquifer following a reduction in groundwater exploitation and enhanced infiltration due to extensive flooding of the Odra River in 1997 were investigated. Long-time series data for the chemical composition of groundwater in a large well field for drinking water supply indicated the deterioration of groundwater quality in the wells capturing water from the flooded area, which had been intensively cultivated since the 1960s. Infiltration of flooded river water into the aquifer is suggested by an elevated chloride concentration, although salt flushing from the rewatered unsaturated zone due to the enhanced recharge event is much more feasible. Concomitantly with chloride increases in the concentrations of sulphate, ferrous iron, manganese, and nickel imply the oxidation of pyrite (FeS 2 ) which is abundant in the aquifer. The proton production resulting from pyrite oxidation is buffered by the dissolution of calcite, while the Ca:SO 4 stoichiometry of the groundwater indicates that pyrite oxidation coupled with nitrate reduction is the dominant process occurring in the aquifer. The pyritic origin of SO 4 2 - is confirmed by the sulphur isotopic composition. The resultant Fe 2+ increase induces Mn-oxide dissolution and the mobilisation of Ni 2+ previously adsorbed to Mn-oxide surfaces. The study has a major implication for groundwater quality prediction studies where there are considerable variations in water level associated with groundwater management and climate change issues.

The changes of groundwater chemistry of semi-confined buried valley aquifer during one decade of water exploitation

This article presents the analysis of the temporal changes in water chemistry in a semi-confined aquifer (Wielkopolska Buried Valley aquifer, Poland) during one decade of water exploitation. It is shown that the groundwater contamination, as documented in a previous work, still persists and has lead to steady groundwater quality deterioration. The most intensive changes in water chemistry due to contamination are observed in the regions recognized earlier as the most vulnerable parts of the aquifer. The influence of contamination is effective despite implementation of groundwater protection activities. The travails of groundwater quality protection of the confined or semi-confined aquifers were accented.

The Unusual and Large Drawdown Response of Buried‐Valley Aquifers to Pumping

The buried-valley aquifers that are common in the glacial deposits of the northern hemisphere are a typical case of the strip aquifers that occur in many parts of the world. Pumping from a narrow strip aquifer leads to much greater drawdown and much more distant drawdown effects then would occur in a sheet aquifer with a similar transmissivity and storage coefficient. Widely used theories for radial flow to wells, such as the Theis equation, are not appropriate for narrow strip aquifers. Previously published theory for flow to wells in semiconfined strip aquifers is reviewed and a practical format of the type curves for pumping-test analysis is described. The drawdown response of strip aquifers to pumping tests is distinctive, especially for observation wells near the pumped well. A case study is presented, based on extensive pumping test experience for the Estevan Valley Aquifer in southern Saskatchewan, Canada. Evaluation of groundwater resources in such buried-valley aquifers needs to take into account the unusually large drawdowns in response to pumping.

Joining multiple AEM datasets to improve accuracy, cross calibration and derived products: The Spiritwood VTEM and AeroTEM case study

ABSTRACTAirborne time‐domain electromagnetic methods (AEM) are useful for hydrogeological mapping due to their rapid and extensive spatial coverage and high correlation between measured magnetic fields, electrical conductivity, and relevant hydrogeological parameters. However, AEM data, preprocessing and modelling procedures can suffer from inaccuracies that may dramatically affect the final interpretation. We demonstrate the importance and the benefits of advanced data processing for two AEM datasets (AeroTEM III and VTEM) collected over the Spiritwood buried valley aquifer in southern Manitoba, Canada. Early‐time data gates are identified as having significant flight‐dependent signal bias that reflects survey flights and flight lines. These data are removed from inversions along with late time data gates contaminated by apparently random noise. In conjunction with supporting information, the less‐extensive, but broader‐band VTEM data are used to construct an electrical reference model. The reference model is subsequently used to calibrate the AeroTEM dataset via forward modelling for coincident soundings. The procedure produces calibration factors that we apply to AeroTEM data over the entire survey domain. Inversion of the calibrated data results in improved data fits, particularly at early times, but some flight‐line artefacts remain. Residual striping between adjacent flights is corrected by including a mean empirical amplitude correction factor within the spatially constrained inversion scheme. Finally, the AeroTEM and VTEM data are combined in a joint inversion. Results confirm consistency between the two different AEM datasets and the recovered models. On the contrary, joint inversion of unprocessed or uncalibrated AEM datasets results in erroneous resistivity models which, in turn, can result in an inappropriate hydrogeological interpretation of the study area.

Use of mathematical modeling to investigate inter-aquifer contamination by organic-rich water through an unplugged well (central Wielkopolska, Poland)

Hydrogeological research was performed to establish the origin of organic-rich water in a Quaternary aquifer (Wielkopolska Buried Valley aquifer, Poland). The spatial distribution of such water was determined by means of multilevel sampling with a packer. The nature, spatial distribution and chemistry of the organic-rich water suggest hydraulic connection between the Quaternary aquifer and the underlying Neogene aquifer. This connection may be enabled by an old abandoned, improperly plugged well, and must therefore be considered as an artificial hydraulic connection between hydrogeologically separated aquifers. For the verification of this hypothesis, a groundwater contaminant transport model was constructed. The results of contaminant transport modeling allow the contaminant transport parameters (transverse and longitudinal dispersivity) to be identified in the field. The numerical groundwater model was used for the prognosis of organic-rich water remediation, and for specification of water-resource management principles in the region where organic-rich water occurs. The results of this research enable the verification of assumptions regarding complex groundwater flow conditions in the boundary zone of a buried valley.

The Influence of Anthropogenic Contamination on the Groundwater Chemistry of a Semi-confined Aquifer (The Wielkopolska Buried Valley Aquifer, Poland)

The problem of the identification of the influence of anthropogenic contamination on the groundwater chemistry of a semi-confined buried valley aquifer is presented. It has been shown that the symptoms of groundwater chemistry transformation due to anthropogenic contamination appear, even though confined conditions occur. Statistical techniques have been used for the identification of this problem. Factor analysis has been used to recognize the most vulnerable parts of the aquifer. Based on the factor scores, data sets characterizing natural and pollutant groundwater chemistry were distinguished. The comparison of the “natural” groundwater chemistry with the whole data set (by means of the correlation analysis and regression analysis) enabled the identification of the components which are the most sensitive to anthropogenic impact. The changes of groundwater chemistry over time identify the intensity of the anthropogenic impact.

Application of factor analysis to study contamination of a semi-confined aquifer (Wielkopolska Buried Valley aquifer, Poland)

Groundwater chemistry is controlled by many natural processes as well as anthropogenic processes. The identification of the influence of anthropogenic processes on groundwater chemistry is difficult particularly in cases of early phase of groundwater anthropogenic transformation. The present study shows the application of factor analyses (FA) for the identification of anthropogenic processes affecting groundwater chemistry of a semi-confined aquifer (Wielkopolska Buried Valley aquifer, Poland). The results of this study clearly demonstrate that FA is a reliable method for differentiation of natural and anthropogenic processes affecting groundwater chemistry, particularly during the early phase of anthropogenic groundwater chemistry transformations.

Granville Solvents: growth and remediation of a chemical recycling facility in a small Ohio town

Granville Solvents Inc. (GSI) operated for years on the Raccoon Creek flood plain in the central Ohio town of Granville, handling bulk quantities of fuels and solvents. The site is adjacent to Granville’s public water supply. The water wells of the village draw from a substantial buried-valley aquifer, which is vulnerable to surface influences and contaminants. GSI received a 3-year Resource Conservation and Recovery Act (RCRA) Part A permit without any siting evaluation because of its grandfather status, and was able to expand its operations greatly. During the expansion, continued negotiations involving permit applications and modifications were conducted; with continued disregard for site contamination. Although a Part B permit was never granted, GSI operated for 6 years under RCRA. Today the site is a Superfund operation and more than five million dollars have been spent on cleanup and maintenance of contaminated soil and groundwater. After 15 years of cleanup, the active remediation has been suspended for the present; however, management of the site for the protection of the adjacent well field is likely to continue well into the future.

Quantitative investigations of the hydraulic connection between a large reservoir and a buried valley aquifer in southern Alberta

Quantitative investigations, including two aquifer tests and development of a three-dimensional (3D) groundwater flow model, were required to determine the hydraulic connection between an irrigation reservoir and a buried valley aquifer in southern Alberta. Evidence of seepage was detected in the buried valley aquifer 10 km east of the Pine Coulee reservoir at the onset of filling in 1999, when the reservoir level exceeded an elevation of 1035 m above sea level (a.s.l.). Concern for an increase in the local water table and the creation of artesian conditions in the aquifer prompted this study to determine the approximate location of a seepage window that appeared to be connecting the reservoir and aquifer. Observations of hydraulic head in the aquifer during the pumping tests revealed a barrier boundary when the reservoir level was at an elevation of 1035 m a.s.l. and a recharge boundary condition when the elevation exceeded 1039 m a.s.l. These data were used to calibrate a 3D groundwater flow model, which was needed to determine the hydraulic properties and approximate location of the leakage zone. The quantitative investigation showed that seepage likely occurred through the sideslopes of the flooded coulee, rather than through the low-permeability coulee floor sediments or the embankment dam. Further simulations illustrated the expected seepage rates at various reservoir supply levels and the pumping rates required for relief wells installed in the buried valley aquifer to maintain historic aquifer hydraulic head. A brief postanalysis indicated that the forecasted pumping rates were only 15% lower than have been required to maintain preconstruction water levels in the buried valley aquifer.Key words: dams, seepage analysis, groundwater modelling, buried valley aquifer, pumping test.

Modeling multiscale heterogeneity and aquifer interconnectivity.

A number of methods involving indicator geostatistics were combined in a methodology for characterizing and modeling multiscale heterogeneity. The methodology circumvents sources of bias common in data from borehole logs. We applied this methodology to the complex heterogeneity within a regional system of buried valley aquifers, which occurs in the western glaciated plains of North America and includes the Spiritwood Aquifer. The region is conceptualized as having a hierarchical organization with three facies assemblage types (large-scale heterogeneity) and two facies types within each assemblage (small-scale heterogeneity). We statistically characterized the sedimentary architecture at both scales, formulated indicator correlation models from those characterizations, and used the models to simulate the architecture in a multiscale realization. We focused on the interconnectivity of units creating higher-permeability pathways. Higher-permeability pathways span the realization even though the proportion of higher-permeability facies is less than the percolation threshold. Thus, geologic structures as represented in the indicator correlation models create interconnectivity above that which would occur if the higher-permeability facies were randomly placed. This amount of interconnection among higher-permeability facies within the multiscale realization is consistent with that suggested in prior hydraulic and geochemical studies of the regional system.

Modeling of flow and contaminant transport in coupled stream–aquifer systems

This paper describes an integrated approach for modeling flow and contaminant transport in hydraulically connected stream–aquifer systems. The code, FTSTREAM, extended the capabilities of the ground-water model, FTWORK, to incorporate chemical fate and transport in streams. Flow in the stream network is modeled as an unsteady, spatially varying flow, while transport modeling is based on a one-dimensional advection–dispersion equation. In addition to sorption and decay during transport in ground water, the model incorporates volatilization, settling and decay during transport in surface water. The interaction between surface water and ground water is accommodated by a leakage term and is implemented in the model using an iterative Picard-type procedure to ensure mass conservation across the interface between the two systems. The modeling approach is used to simulate contaminant transport in the Mad River, Ohio, which is hydraulically connected to a buried valley aquifer of sand and gravel outwash. The river is a receiving stream in the upstream part of the modeled area. Downstream, heavy pumping from a municipal well field causes the river to become a loosing stream. Induced infiltration from the river is responsible for a considerable portion of the well yield. The flow and transport model, developed for this study, simulates coupling between flow in the aquifer and the river. Hypothetical sources of contamination are introduced at selected locations in the upstream portion of the aquifer. The model is then used to simulate the expected transport in both the aquifer and the stream. A series of simulations elucidates the role of the river in facilitating the transport of the hypothetical contaminants in ground water and surface water. Effect of sorption, retardation and volatilization on contaminant transport is also examined for the case of the volatile organic compounds.

Measures of Economic and Environmental Performance for Alternative Agricultural Production Systems

The primary purpose of the reported research was to evaluate the economic and environmental performance of three production systems under study in the Ohio Buried Valley Aquifer Management Systems Evaluation Area (MSEA) project. The three systems studied included a monoculture system-ontinuous corn (Zea mays L.) (chisel plow) with routine fertilizer and pesticide treatments; the typical system-a corn/soybean [Glycine max (L.) Merr.] rotation (chisel plow and no-till) with routine applications of pesticides and fertilizers ; and an alternative system-a corn/soybean/wheat (Triticum aestivum L.)-hairy vetch (Vicia villosa Roth subsp. villosa) rotation (ridge-tilled) with fertilization based on soil tests and strategic applications of pesticides. Enterprise and whole farm budgets were constructed for each system. All sources of receipts and costs arising from production were recognized in the profitability analysis. The typical system was found to have the highest return to management and the monoculture system the lowest return. The alternative system produced net returns of about 50% of those of the typical system. The wheat phase of the alternative system was the primary source of reduced returns. A linear programming analysis was conducted to compare profitability for the three systems with farm size variable (machinery complement capacity was the determinant of farm size). The LP results suggested a widening of the profit differential between typical and alternative systems due to a greater acreage capacity for the typical system. However, results suggested that if wheat yields were increased through spring application of N fertilizer for wheat, the alternative system would be about equal in profits to the typical system. Environmental impact assessment, evaluated through use of the Erosion-Productivity Impact Calculator (EPIC), suggested lesser environmental consequences resulting from the alternative system than from either of the other studied systems. Adjustments in the alternative system to improve profitability brought little environmental downside.

History of the Sole Source Aquifer Program: A Community‐Based Approach for Protecting Aquifers Used for Drinking Water Supply

AbstractThe Sole Source Aquifer Program has helped prevent contamination of many community drinking water supplies. If an aquifer supplies the sole or principal source of a community's drinking water, a local ground water user may petition the Environmental Protection Agency (EPA) under the Safe Drinking Water Act for its designation and protection as a “sole source aquifer.” Since 1974, residents and officials of 65 communities and multi‐community areas have petitioned and received assistance from the EPA to prevent contamination of their local ground water source of drinking water. This designation means that EPA may review federal financially assisted projects to determine if they would contaminate the aquifer and cause a public health hazard. If they could cause contamination, EPA can request that the project be modified or stopped. The significance of this program in terms of population served and funds affected has been substantial, indicating the Sole Source Aquifer Program has been an important local tool for protecting ground water used as a source of drinking water. Information is given on three different examples of sole source aquifer designations protected under this program: the New Jersey Coastal Plain Aquifer System, the Great Miami River Buried Valley Aquifer System (Ohio), and the Eastern Snake River Plain Aquifer (Idaho), serving populations of 543,000, 921,000, and 275,000, respectively. In all three examples, preventing ground water contamination through the Sole Source Aquifer Program has protected the community drinking water supply.