Paleozoic Karst Aquifers in the Mid-Continent

Topics Overview Conceptual model Aquifer Properties Dynamics Water quality Karst Geomorphology Modeling difficulties

Floridan Edwards Roswell Paleozoic carbonates in mid-continent

Mississippi embayment Illinois basin Michigan basin Mississippi embayment Wisconsin arch Ozark plateau Finlay arch Cincinnati arch Lexington dome Nashville dome

Biscayne Aquifer (Pleistocene) Floridan Aquifer (Tertiary) Edwards Aquifer (Cretaceous) Permian (Roswell in NM and Blaine in TX) Mississippian Silurian Cambrian-Ordovician (Nashville and Lexington, Ozarks, Arbuckle Mtns in OK) Paleozoic Karst in the Appalachians

Conceptual Models

Mechanism for cave development Flow through small fractures, diffuse flow, similar to porous media Mechanism for cave development Conduit development and migration of the water table

Conceptual model for Paleozoic Karst Aquifer, Based on Mammoth Cave Area, KY Topo divide Watershed divide

Erosion of base level stream causing multiple levels of caves Erosion of base level stream causing multiple levels of caves. Based on Mammoth Cave area

Properties Intact Limestone: Low K and S Karstified LS: High K, Low S Epikarst (surface): Low K, High S Hydraulic diffusivity: T/S

Water level response to rainfall Well in Big Clifty Sandstone Water level in well and local rainfall, Ozark Plateau Well in St. Louis LS Rainfall in Mammoth Cave Area Water level response to rainfall Large Kb/S = fast response (rise and fall) Small Sy = large magnitude

Water Quality

Depth to saline ground water

Vulnerability of Karst Aquifers to Contamination Sinkholes funnel surface contamination into cave conduits. Rapid transport in caves (km+/day) moves contaminants away from source Thin soils provide minor sorption/retention Turbulent flow transports clay. Increase tubidity and contaminants sorbed to clay

Important Hydro-Geomorphic Features in Karst Aquifers Sinkholes: Recharge, ground stability Estevelles: Recharge and discharge Vertical fractures w/dissolution: Recharge/discharge Epikarst: Storage Solution channels: water pathways; high velocity flow Springs: Focused discharge

Porosity

Sinkholes and Estevelles

Sinkhole collapse related to hydrogeology

Flooding caused by sinkholes

                                                                                           . Sinkhole risk evaluation. Controlled largely by underlying formation. Mississippian produces most sinkholes

First-order spring. Discharge > 100 cfs Springs

Discharge from springs Percent of days when discharge equaled or exceeded 2 springs in Ordovician rocks 2 springs in Silurian rocks Discharge Probability Plots Discharge from springs Hydrograph for karst spring Discharge as function of time recharge recession recharge recession recharge recession

Vertical fractures and faults

Karst systems and biodiversity

Blind Salamander Blind Cave Fish Cave Ecosystems

Modeling Flow in Karst Conduits Porous Aquifer, Darcy: Conduit, Manning: Fundamental difference in physics of flow Hr: hydraulic radius=x-section area/wetted perimeter n = wall roughness Conduit geometry and wall roughness highly variable —how to determine in the field for an aquifer?

Ozark Plateau Aquifer System

Stratigraphy of the St. Francois and Ozark Aquifers caves typically underlie sandstone Pb-Zn

Geology

Thickness of Springfield Aquifer Ozark Aquifer

Regional potentiometric surface on Ozark Plateau and Western Interior Aquifer System

Cross-section on NW side of Ozark Plateau Cross-section on NW side of Ozark Plateau. Fresh water mixes with saline water in laterally equivalent units deeper in basin.

Potentiometric surface in Ozark Plateau in Missouri

330 Mgpd

Lead and zinc mining districts in Ozark Plateau Biggest producer of Pb,Zn in the world in 1920s Viburnum Trend Active

Pb and Zn concentrations in water, sediment and tissue Site Mining area Lead Zinc Water (µg/L) Bed sediment (µg/g) Tissue (µg/g) Center Creek Tri-State <1 370 0.3 67-270 5,600 770 Big River Old Lead Belt 2,300 134 8-19 670 514 Meramec River -- 180 12.2 140 296 West Fork of Black River Viburnum Trend <1-11 10-95 0.5-8.3 13-33 12-46 70-110 Strother Creek <1-3 20 0.7 33-148 120 150 Background <1-20 15-28 <0.1-0.6 <1-44 43-140 57-230