KARST HYDROGEOLOGY OF BIG CREEK BASIN

Van Brahana, Ph.D., P.G

Professor Emeritus, U of A Research Hydrologist Emeritus, USGS

Concerns Associated with Karst

1. Complex flow is typical in karst aquifers; 2. Fast flow zones dominate karst aquifers, thereby enhancing sediment transport as well as rapid advection; 3. Variation in hydraulic conductivity in karst aquifers is greater than in other rock types; 4. Water levels in karst aquifers require a thorough understanding of the flow zones —typically WL are not good indicators of flow directions; 5. There is little or no contaminant attenuation in karst; 6. Interaction of surface- and groundwater is profound in karst; 7. Flow systems are continually evolving, and must be considered ephemeral; 8. Each karst aquifer is a unique combination of more than 60 controlling influences, and thereby assessment of environmental risk requires a thorough study prior to action .

Scientific Justification

6 7 8 1 2 3 4 5 Mass of animal waste from 6500 hogs = ~30,000 humans ; No treatment of waste; stored in open lagoons; Untreated waste spread on < 1 mile 2 of fields overlying karst ; Thin soils typically overlie karst; Only cursory geology was described in the notice of intent (NOI); No mention of karst was addressed in NOI; No mention of groundwater was covered in NOI; No background groundwater quality was established in the NOI; 9 This study was undertaken to fill the void of missing, relevant, essential science.

Acknowledgements

Dr. Joe Nix , Ph.D., Ouachita Baptist University, Chemistry ; Retired Ray Quick, M.S., P.G., Operations Manager, Woodward-Clyde Consultants and URS Corporation ; Retired; ADEQ-Water & Hazardous Waste ; Retired John Murdoch, B.S., Division of Agriculture-Instrumentation, U of A ; Retired Brian Thompson, B.S., Tyson, Inc .; Retired Teresa Turk, M.S., NOAA, Ecology ; Retired Carol Bitting, Newton County liason; Field Coordinator Chuck Bitting, B.S., National Park Service, Karst Specialist Victor Roland, M.S., Environmental Dynamics Ph.D. Student Katarina Kosic, M.S., Political Science and Karst Ph.D. Student Sarah Robertson, B.S., Student Volunteer Vanya North, B.S., Student Volunteer Tyler Wright, B.S., Work-Study Student

In karst, the groundwater component is much greater than in other settings.

Hydrologic Budget

KARST HYDROGEOLOGY COMPONENTS DESCRIBED HEREIN

1. Illustrate field inventory of karst features, including groundwater attributes; 2. Briefly describe existing water quality; 3. Synthesize dye tracing to date; 4. Propose two changes to further science.

Location

Physiographic regions

Ozark Highlands

Graphic modified from Rob Jacobson, USGS

Big Creek Basin and areas of karst near the Buffalo National River

CAFO Modified from Chuck Bitting, National Park Service

Mountain outcrops Sedimentary rock layers of Big Creek Basin—nearly flat lying, significant erosion; Boone dominantly mantled karst, with significant underdraining to springs Valley outcrops Source: Braden and Ausbrooks, 2003

Location of data-collection sites

KARST FEATURES OBSERVED IN BIG CREEK BASIN

1. Dry stream reaches downstream from flowing reaches; losing stream reaches; 2. Sinkholes, swallets, estavelles, internally-drained depressions, shafts; 3. Caves and cave streams; 4. Numerous springs; 5. Bedding-plane anastamoses; significant dissolution along joints; 6. Rapid groundwater flow; 7. Significant surface- & groundwater interaction 8. Presence of karst-forming formations

Dry stream reaches below flowing reaches

White, evaporative crust (smells like a poultry house) coating dry-stream reach. This is also indicative of existing impacts on water quality in Big Creek.

Sinkholes and swallets capture surface streamflow

Thick limestones develop large caves

Photo courtesy of Chuck Bitting

Fast-flow provides little or no attenuation of contamination

High discharge springs integrate flow from large areas

Bedding plane anastamoses are fast-flow mini-caves

chert above acts as pressure confining layer dissolved limestone (bedding-plane anastamoses) are fast-flow and high K chert below acts as perching layer

3 cm

Dissolution along bedding planes and joints creates significant porosity and permeability in the rock mass

Throughout its area of occurrence, the Boone Formation is known for its karst development

Source: Braden and Ausbrooks, 2003

Greater dissolved solids; Restricted flow and recharge; Calcium and bicarbonate are dominant ions; Very low nutrients & pathogens Lower dissolved solids; less dissolution; Mixed major ions; Low nutrients & pathogens Modified from: Braden and Ausbrooks, 2003

Sampling nutrient-rich spring covered in duckweed

Photo courtesy of Carol Bitting

Synthesis of Dye Tracing

1. Flow velocities are extremely fast —1500 to 2500 feet per day by conservative estimate; 2. Flow is dispersive, and difficult to predict; 3. Point-to-point flow documents that groundwater moves underneath surface water divides; 4. Subtle structural differences in tilt and lithologic variations control most flow; 5. Faults generally act as groundwater dams, and divert flow to regional resurgences; 6. Regional resurgences are appropriate sites for expanded sampling.

Dye injection into shallow dug wells with excellent hydraulic connection to aquifer

Dye injection into sinkhole that captures the entire flow of a stream during recession

Substream springs reflect fast flow from dye input sources

3.5 miles/7 days CAFO Caves are purple; springs are blue.

Preliminary tracing results

Big Creek Watershed boundary Spreading fields for waste Base-map source: Chuck Bitting, National Park Service

CAFO school

2200 feet/30.5 hours

Summary

These data indicate that it is essential to incorporate karst science into our permitting process for CAFOs on karst if we intend to preserve these environments and their contained water resources. Likewise, open communication with all stakeholders, with an emphasis on facts and science –this needs to be one of our guiding principles.

We all live downstream

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