Hydrogeology of the Cambrian-Ordovician aquifer system in the northern Midwest, United States with a section on ground-water quality

Young, H. L.; Siegel, Donald I.

doi:10.3133/pp1405b

Cited by 32 publications

(37 citation statements)

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“…They show that transient leakage fluxes from the aquitard to the underlying aquifer system peak at about 0.017 m 3 /d/km 2 , declining to about 0.006 m 3 /d/km 2 at steady state. Intrinsic hydraulic conductivity and leakage fluxes presented here for the Maquoketa aquitard are almost 3 orders of magnitude lower than values previously reported by others, who based estimates on steady‐state flow assumptions (Walton 1960; Young 1992). Results presented here suggest that recent higher estimates based on regional numerical modeling reported by Hart et al (2006) are attributable to numerous cross‐connecting multiaquifer wells rather than through‐going vertical fractures.…”

Section: Resultscontrasting

confidence: 68%

Fracture Control of Ground Water Flow and Water Chemistry in a Rock Aquitard

Eaton

Anderson

Bradbury³

2007

Groundwater

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There are few studies on the hydrogeology of sedimentary rock aquitards although they are important controls in regional ground water flow systems. We formulate and test a three-dimensional (3D) conceptual model of ground water flow and hydrochemistry in a fractured sedimentary rock aquitard to show that flow dynamics within the aquitard are more complex than previously believed. Similar conceptual models, based on regional observations and recently emerging principles of mechanical stratigraphy in heterogeneous sedimentary rocks, have previously been applied only to aquifers, but we show that they are potentially applicable to aquitards. The major elements of this conceptual model, which is based on detailed information from two sites in the Maquoketa Formation in southeastern Wisconsin, include orders of magnitude contrast between hydraulic diffusivity (K/S(s)) of fractured zones and relatively intact aquitard rock matrix, laterally extensive bedding-plane fracture zones extending over distances of over 10 km, very low vertical hydraulic conductivity of thick shale-rich intervals of the aquitard, and a vertical hydraulic head profile controlled by a lateral boundary at the aquitard subcrop, where numerous surface water bodies dominate the shallow aquifer system. Results from a 3D numerical flow model based on this conceptual model are consistent with field observations, which did not fit the typical conceptual model of strictly vertical flow through an aquitard. The 3D flow through an aquitard has implications for predicting ground water flow and for planning and protecting water supplies.

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Section: Resultscontrasting

confidence: 68%

Fracture Control of Ground Water Flow and Water Chemistry in a Rock Aquitard

Eaton

Anderson

Bradbury³

2007

Groundwater

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“…The cause of the reversal lies in the region's complex geology [ Young and Siegel , 1992], and in particular, a sequence of highly permeable carbonate rocks underlying different sections of the basin (Figure 13b). The importing headwater basins of the Cedar River sit over the outcropping Devonian carbonate rocks (dark blue in Figure 13b), the uppermost unit of the “U” shaped basin strata shown in line A–A', known as the Hollandale Embayment.…”

Section: Results and Analysesmentioning

confidence: 99%

River basins as groundwater exporters and importers: Implications for water cycle and climate modeling

2009

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[1] The groundwater reservoir and its interaction with surface water facilitate lateral transport of continental water and energy. Current climate models do not account for long-distance groundwater flow between model cells but route the atmospheric surplus (precipitation (P) minus evapotranspiration (ET)) directly to stream discharge within a model grid cell. We ask how much water exits a river basin without ever passing through its surface outlet? What are the climatologic and geologic factors influencing this flux? To answer these questions, a separation of groundwater flow from river flow is necessary. We use the ratio of stream discharge (Qr) to basin recharge (R = P À ET) for this purpose; where Qr:R < 1, a basin is considered a groundwater exporter; and where Qr:R > 1, a basin is considered a groundwater importer. Here Qr is obtained from 39 years of U.S. Geological Survey Hydro-Climatic Data Network observed stream discharge from 1555 basins across the continental United States, and R (P À ET) is derived from 50 years of hydrologic simulation by the Variable Infiltration Capacity model. It was found that the Qr:R ratio deviates significantly from 1 across the continent. Detailed investigations of individual basins suggest that the deviations are primarily a function of geology, while climate and basin scale influence the magnitude of these deviations. Further, a marked incongruity between the surface and groundwater flow directions is apparent, suggesting that surface drainage is only partially indicative of subsurface flow regimes. The apparent significance of this long-distance groundwater flow component reinforces the need for inclusion of the groundwater reservoir in current water cycle and climate modeling efforts.

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“…Groundwater sampled from beneath the Maquoketa Shale has been shown to have higher average Ra than groundwater from wells completed in the regionally unconfined portion of the MCOAS (Stackelberg, Szabo, & Jurgens, ; Szabo et al, ). However, local confining units in underlying aquifers can also promote geochemical conditions that are associated with elevated Ra in groundwater (Grundl & Cape, ; Mathews, Gotkowitz, & Ginder‐Vogel, ; Stackelberg et al, ; Szabo et al, ; Young & Siegel, ).…”

Section: Introductionmentioning

confidence: 99%

Spatial and temporal variability of radium in the Wisconsin Cambrian–Ordovician aquifer system

et al. 2020

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Compliance monitoring of contaminants in public drinking water supplies results in publicly available data sets that are maintained by state agencies and useful for investigating changes in water quality. In this study, spatial and temporal trends in naturally occurring radium (combined 226Ra + 228Ra) concentrations in groundwater from the Midwestern Cambrian–Ordovician aquifer system were evaluated with a Wisconsin Department of Natural Resources compliance data set. Average combined Ra from 2000 to 2018 in the Midwestern Cambrian–Ordovician aquifer system increased from 5.5 to 7.9 pCi/L in the confined region and from 4.8 to 6.6 pCi/L in the unconfined region. On a local scale, the data demonstrate increasing radium in the communities of Sussex (n = 98) and Brookfield (n = 35), and a decreasing trend in nearby Waukesha (n = 176). This study demonstrates the utility of compliance data sets for investigating water quality trends and the importance of geographic scale in examining such data.

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Hydrogeology of the Cambrian-Ordovician aquifer system in the northern Midwest, United States with a section on ground-water quality

Cited by 32 publications

References 0 publications

Fracture Control of Ground Water Flow and Water Chemistry in a Rock Aquitard

Fracture Control of Ground Water Flow and Water Chemistry in a Rock Aquitard

River basins as groundwater exporters and importers: Implications for water cycle and climate modeling

Spatial and temporal variability of radium in the Wisconsin Cambrian–Ordovician aquifer system

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