Hydrogeologic setting and the potentiometric surfaces of regional aquifers in the Hollandale Embayment, southeastern Minnesota, 1970-80

Abstract

Introduction 1.1 Purpose and scope 2 1.2 Previous investigations 4 1.3 Methods of investigation 6 2.0 Hydrogeologic setting 2.1 Structural geology 10 2.2 Hydrogeologic relationships 14 2.3 Drift hydrogeology 16 2.4 Bedrock hydrogeology 18 2.5 Precipitation 22 3.0 Horizontal groundwater movement 3.1 Potentiometric surfaces 24 3.2 Undifferentiated drift aquifer 26 3.3 Upper Carbonate aquifer 30 3.4 St. Peter aquifer 34 3.5 Prairie du Chien-Jordan aquifer 38 3.6 Ironton-Galesville aquifer 42 3.7 Mount Simon-Hinckley aquifer 46 4.0 Vertical groundwater movement 50 References 54 Conversion factors 56 III GLOSSARY The geologic and hydrologic terms pertinent to this report are defined as follows: Alluvium sedimentary material deposited by modern rivers, including sediments laid down in river beds, flood plains, and in-stream lakes. Aquifer a formation, group of formations, or part of a formation that contains sufficient saturated permeable material to yield significant quantities of water to wells or springs. Confining bed a body of material with low vertical permeability stratigraphically adjacent to one or more aquifers. Replaces the terms "aquiclude," "aquitard," and "aquifuge." Drift all deposits resulting from glacial activity. Equipotential line line connecting points of equal static head. (Head is a measure of the potential.) Evapotranspiration water withdrawn by evaporation from water surfaces and moist soil and by transpiration from plants. Ground water that part of subsurface water that is in the saturated zone. Groundwater divide a ridge in the potentiometric surface from which ground water represented by that surface moves away in both directions. Head, static the height above a standard datum of the surface of a column of water that can be supported by the static pressure at a given point. Hydraulic conductivity capacity of a rock to transmit water under pressure. It is the rate of flow of water at the prevailing kinematic viscosity passing through a unit section of area, measured at right angles to the direction of flow, under a unit hydraulic gradient. Ice contact stratified drift deposited in contact with melting glacier ice; includes eskers, kames, kame terraces, and features marked by numerous kettles, some being ice-block lakes. Karst a type of topography that is formed over limestone, dolomite, or gypsum by dissolution and that is characterized by closed depressions or sinkholes, caves, and underground drainage. Loess a sediment, commonly unstratified and unconsolidated, composed mainly of silt-size particles, ordinarily with accessory clay and sand, deposited primarily by the wind. Outwash sorted, stratified drift deposited beyond the ice front by melt-water streams. Paleozoic an era of geologic time that comprises the Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian, and Permian systems; commonly thought to have occurred from 225 to 570 million years ago. Potentiometric surface a surface that represents the static head of water in an aquifer; defined by the levels to which wat...

Groundwater-quality and select quality-control data from the National Water-Quality Assessment Project, January 2017 through December 2019

“…The Prairie du Chien-Jordan aquifer consists of as much as 335 ft of fractured sandy dolomite of the Ordovician-age Prairie du Chien Group and the underlying quartz sandstone of the Cambrian-age Jordan Sandstone. The aquifer in the Prairie du Chien Group and the Jordan Sandstone are hydraulically connected and have traditionally been considered a single aquifer (Delin and Woodward, 1984;Young, 1992a, b). The Prairie du Chien-Jordan aquifer is the principal source of water for public-supply wells in suburban areas of the Twin Cities metropolitan area and also is the primary source of water for domestic wells inside and outside of the Twin Cities metropolitan area in the study area.…”