Geologic Controls on Groundwater and Surface Water Nitrate Concentrations in the Paleozoic Bedrock-Dominated Landscape of Southeastern Minnesota

Runkel, Anthony C.; Steenberg, Julia R.; Tipping, Robert G.; Retzler, Andrew J.

doi:10.1130/abs/2018nc-312588

Cited by 5 publications

(7 citation statements)

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“…Freiheit Spring emerges from the Stewartville Formation, which is subhorizontally overlain and underlain by Dubuque-Maquoketa and Prosser-Cummingsville Formations, respectively (Steenberg and Runkel 2018). These formations are partially or entirely comprised of karstified limestone and dolostone with ubiquitous karst features such as sinkholes, sinking streams, caves, and springs-for details see Runkel et al (2003); Mossler (2008); Steenberg (2014). Based on several qualitative and quantitative tracer tests, the areas of the Freiheit surface watershed and groundwater springshed were estimated as ~6.51 and ~0.91 km 2 , respectively (Fig.…”

Section: Hydrogeological Settingmentioning

confidence: 99%

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Joint inversion of groundwater flow, heat, and solute state variables: a multipurpose approach for characterization and forecast of karst systems

et al. 2023

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Characterization of karst systems and forecast of their state variables are essential for groundwater management and engineering in karst regions. These objectives can be met by the use of process-based discrete-continuum models (DCMs). However, results of DCMs may suffer from inversion nonuniqueness. It has been demonstrated that the joint inversion of observations regulated by different natural processes can tackle the nonuniqueness issue in groundwater modeling. However, this has not been tested for DCMs thus far. This research proposes a methodology for the joint inversion of hydro-thermo-chemo-graphs, applying to two small-scale sink-to-spring experiments at Freiheit Spring, Minnesota, USA. In order to address conceptual uncertainty, a multimodel approach was implemented, featuring seven mutually exclusive variants. Spring hydro-thermo-chemo-graphs, for all the variants simulated by MODFLOW-CFPv2, were jointly inverted using a weighted least squares algorithm. Subsequently, models were compared in terms of inversion and forecast performances, as well as parameter uncertainties. Results reveal the suitability of the DCM approach for simultaneous inversion and forecast of hydro-physico-chemical behavior of karst systems, even at a scale of meters and seconds. The estimated volume of the tracer conduit passage ranges from approximately 46–51 m3, which is comparable to the estimate from the flood-pulse method. Moreover, it was demonstrated that the thermograph and hydrograph contain more information about aquifer characteristics than the chemograph. However, this finding can be site-specific and should depend on the analysis scale, the considered conceptual models, and the hydrological state, which are potentially affected by minor unaccountable processes and features.

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Section: Hydrogeological Settingmentioning

confidence: 99%

“…1. Secondary solutional porosity in the geological formations is well developed (Runkel et al (2003).…”

Section: Hydrogeological Settingmentioning

confidence: 99%

Joint inversion of groundwater flow, heat, and solute state variables: a multipurpose approach for characterization and forecast of karst systems

et al. 2023

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“…Secondary pore networks are common and play an important role in both siliciclastic and carbonate bedrock aquifers (e.g., Alexander Jr and Lively 1995; Muldoon et al 2001;Runkel et al 2003Runkel et al , 2006Swanson et al 2006;Tipping et al 2006;Meyer et al 2008;Anderson et al 2011;Green et al 2012;Runkel et al 2018). These fractures and solution features allow water to move rapidly within the bedrock aquifers, particularly within the karstic Prairie du Chien Group.…”

Section: Hydrogeologic Contextmentioning

confidence: 99%

“…Most individual formations are subhorizontal layers dominated by sandstone, shale, and/or carbonate from 15 to 60 m thick. The hydrogeologic framework delineates six major regional bedrock aquifers (Figure 1a; Runkel et al 2003). Aquifer layers are dominated by fine‐ to coarse‐grained sandstone or pervasively fractured and karstified carbonate rock.…”

Section: Introductionmentioning

confidence: 99%

Documentation and Prediction of Increasing Groundwater Chloride in the Twin Cities, Minnesota

et al. 2022

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We provide a comprehensive overview of historic chloride concentrations in the groundwater of the Twin Cities metropolitan area (TCMA) in Minnesota, in order to define the extent of chloride contamination, due primarily to the seasonal application of deicing salt to roadways. Data collected from 1278 wells between 1965 and 2020 are representative of the major aquifers underlying the TCMA and establish a regional natural background chloride concentration of less than 10 mg/L. However, 55% of all measurements (1616 of 2943) are above 10 mg/L, with the highest concentrations found within the uppermost Quaternary aquifers. Chloride concentrations in underlying bedrock aquifers are negatively correlated with the thickness and clay composition of overlying materials. Most chloride measurements (92%) remain below chronic exposure limits set by state and federal authorities. Historical trends indicate that, if the current imbalance between chloride inputs and outflows persists, chloride concentrations in TCMA aquifers will surpass regulatory thresholds by midcentury as surface waters and Quaternary aquifer waters migrate into underlying bedrock aquifers. Most wells in this study are monitored annually, making it impossible to detect important sub-annual fluctuations of chloride concentration that can exceed 40%.

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“…Hydrogeological characteristics and karst evolution have been described in numerous publications in both fractured and/or folded telogenetic and young eogenetic highpercentage carbonates [3]. Less information is available on karst in evaporites [4], quartzites [5], and especially for lithologies at the transition between carbonates and siliciclastics [6][7][8][9][10]. Ghost-rock karst is a specific type of karstification.…”

Section: Introductionmentioning

confidence: 99%

Origin of Fracture-Controlled Conduits in Calcite-Rich Highly Productive Aquifers Impregnated with Diagenetic Silica

Starý,

Bruthans,

Schweigstillová

et al. 2024

Water

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The origin of highly permeable flow paths in carbonate-siliciclastic rocks, such as large-aperture fractures in aquifers in the Eastern Bohemian Cretaceous Basin (EBCB), is poorly understood. The karst potential was assessed from the rock carbonate content and the degree of disintegration after leaching in HCl. Surprisingly, dissolution of calcite in EBCB usually did not lead to rock disintegration until calcite > 78%. Instead, porosity increased significantly. High-porosity rock is held together by microns-thick secondary silica cement with a foam-like structure and considerable tensile strength. Three types of conduits occur in the EBCB: (i) bedding-parallel conduits associated with calcite-rich layers, (ii) subvertical fracture swarm conduits that develop on damaged zones of fracture swarms, and (iii) conduits formed by dissolution of calcite veins by groundwater flow. These are ghost-rock karst features where calcite is leached from the rock in the first phase and the residue is washed out by conduits under steep hydraulic gradients in the second phase. Very similar features have been described in Minnesota and Wisconsin, USA. Research has shown that fractures with sharp-edged walls that give the impression of an extensional tectonics origin may actually be ghost-rock karst features in which dissolution and piping have played an important role in their enlargement.

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Geologic Controls on Groundwater and Surface Water Nitrate Concentrations in the Paleozoic Bedrock-Dominated Landscape of Southeastern Minnesota

Cited by 5 publications

References 0 publications

Joint inversion of groundwater flow, heat, and solute state variables: a multipurpose approach for characterization and forecast of karst systems

Joint inversion of groundwater flow, heat, and solute state variables: a multipurpose approach for characterization and forecast of karst systems

Documentation and Prediction of Increasing Groundwater Chloride in the Twin Cities, Minnesota

Origin of Fracture-Controlled Conduits in Calcite-Rich Highly Productive Aquifers Impregnated with Diagenetic Silica

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