Hydrogeology of Wisconsin Karst Landscapes: What’s a Protective Soil Cover?
Dr. Maureen Muldoon UW-Oshkosh Geology Department Presentation to NR151 TAC 11/15/2016 Outline • Wisconsin’s Carbonate Aquifers – Eastern Dolomite Aquifer – SW Wisconsin • Flow Characteristics of Eastern Dolomite Aquifer • Water Cycle and Recharge • Existing Data on Pathogens • What Soil Depth is Protective? WI Bedrock Geology Stratigraphy and Aquifers Wisconsin Aquifers
• Sand & gravel aquifer
• Eastern dolomite aquifer
• Sandstone & dolomite aquifer
• Crystalline bedrock aquifer What is Karst? • A type of topography that is formed on limestone (& dolostone) gypsum, and other rocks, primarily by dissolution, and is characterized by sinkholes, caves, and underground drainage (Glossary of Geology) • Spectrum of landscapes -- Door Co. to tower karst of China • Significant land area - 20% of U.S., 40% of area east of Mississippi River Eastern Dolomite Aquifer
Eastern Dolomite Aquifer
• Calumet and Brown Counties Eastern Dolomite Aquifer
Flow Patterns in Eastern Dolomite Aquifer • Regional divide between flow to Lake Michigan and flow to Fox Valley • Groundwater discharge to surrounding surface water features • Long flow paths • Vertical flow through relatively uniform aquifer
SW Wisconsin Geology • Lithology (rock type) is quite variable – shale, dolomite, limestone • Sinnipee carbonates – Decorah-Platteville can act as a “perching” layer – Decorah-Platteville are weathered and fractured when uppermost bedrock unit • Prairie du Chien – Was karstified prior to deposition of St. Peter sandstone – Often quite karstified if it is uppermost bedrock unit • Domestic wells completed in both carbonate units and sandstone units Flow Patterns in Southwestern WI • Greater topographic relief WI Springs database • Short flow paths from ridgetop to adjacent creek or river • Lithologic variability can cause perching & significant lateral movement of water Outline • Wisconsin’s Carbonate Aquifers – Eastern Dolomite Aquifer – SW Wisconsin • Flow Characteristics of Eastern Dolomite Aquifer • Water Cycle and Recharge • Existing Data on Pathogens • What Soil Depth is Protective? Flow Characteristics of Eastern Dolomite Aquifer • Dense and ubiquitous fracture network – little surface runoff – water easily infiltrates to subsurface • Recharge – exceedingly rapid – carries surface contaminants to the water table • Flow within the aquifer occurs primarily along bedding plane fractures – Little to no attenuation of contaminants within the aquifer • Flow rates vary from 10’s to 100’s of ft/day
Bedding-plane Fractures Groundwater Velocities
Bissen quarry, Door Co, WI (Muldoon, 1999; Muldoon & Bradbury, 2005) Groundwater Velocities • Bissen Tracer Tests – Detailed site characterization to locate vertical and horizontal fractures – Monitoring system designed to sample specific bedding plane fractures – Injected “salty water” into the subsurface and “traced” how it moved – Can use results to determine flow velocities Groundwater Velocities 0.04 10-2 peak conc 13.7, 188.3 hrs • Bissen Tracer Tests 0.02
– Calculated velocities using 0.00
peak arrival times 0.30 10-3 0.20 peak conc 193, 7.0 hr velocity 74.7 ft/day – Mix of fracture and matrix 0.10 velocities 0.00 0.30 – Range 1.54 – 388.1 ft/day 10-4 0.20 peak conc 216, 5.5 hrs – Mean 41.7 ft/day 0.10 velocity 115 ft/day 0.00
– Median 19.4 ft/day 0.005 10-5 peak conc 3.41, 16.1 • Inadvertent Tracer Tests velocity 32.0 ft/day – 100’s of ft/day 0.000 0.04 10-6 peak conc 42.3, 55.2 hrs velocity 9.5 ft/day
0.00 0 50 100 150 200 Elapsed Time (hours) Outline • Wisconsin’s Carbonate Aquifers • Flow Characteristics of Eastern Dolomite Aquifer • Water Cycle and Recharge – Timing of Recharge – Rate of Recharge • Existing Data on Pathogens • What Soil Depth is Protective? Water Cycle • Processes – Evaporation – Transpiration – Precipitation – Infiltration – Groundwater flow – Overland flow – Stream runoff • Groundwater Recharge -- water that seeps past the root zone and makes it to the water table (top of the saturated zone) • Indictors of recharge • Water level in well rises • Change in water temperature or chemistry Water levels fluctuations at a research site in Door County (~monthly measurements)
800 MW3 MW3
MW1
750 MW6A MW6A MW2D
MW2D MW7C 700 MW7C MW1 650 MW2A Head (ft above Headabove (ft msl) 600 MW2A wells open intervals of
550 J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O 1987 1988 1989 1990
(from Bradbury and Muldoon, 1992) Recharge in Areas of Thin Soils
measurements every 15 minutes 0 1 2 3 4 miles locations of wells and rain gauge used in this study other municipal wells Assessing Seasonal Variations in Recharge and Water Quality in the Silurian Aquifer in Areas with 10 to 20 ft of Soil Cover
Maureen A. Muldoon, UW-Oshkosh Geology Dept. Kenneth R. Bradbury WI Geological & Natural History Survey Site Selection
Kewaunee
Brown
Calumet
Manitowoc
• Depth to rock ~10 to 20 ft • Depth to water <50 feet • Downgradient of agricultural fields Kewaunee Well Characteristics
Brown • Completed geophysical logs to identify Manitowoc high-permeability bedding plane fractures Calumet
Well County Soil Avg Water thickness (ft) Depth (ft) BN420 Brown 10 28.06
CA1143 Calumet 18 54.21
KW183 Kewaunee 7 8.52
MN544 Manitowoc 18 33.06 Recharge Events ‘07-’08
21 3 ) ) t t f f ( (
23 5 e r e r 0 a t a t 25 7 1 8 3 4 2 W W - -
o o N W t t 27 9 B K h h p t e e p t 29 11 D D 31 13 50 30 ) ) t t f f ( (
52 31 r e r e t 54 32 a t 1 4 3 5 4 W W a - 1
- o o t t A
56 33 M N C h h p t e e p t 58 34 D D 60 35 ) 2 40 e e s ) v h i e s a t n c l i h (
1 20 c n p i i ( u m
e c C r
P 0 0 2 1 1 1 1 1 1 1 9 9 9 1 2 3 3 4 5 6 6 7 7 8 8 3 4 5 8 / 1 1 2 2 / / 0 0 / / / / / / / / / / / / / / / / / / 2 5 1 1 2 1 1 1 2 2 1 7 2 5 1 2 3 1 1 2 1 / / / / / / / 5 1 2 1 2 8 2 / 9 9 6 / / 9 6 0 / 1 / 9 / 0 5 2 4 6 0 0 0 0 0 0 0 / 3 7 0 4 / 2 / / / / / / / / / / / / / 8 0 0 8 7 0 0 0 8 0 0 0 8 0 8 0 8 0 0 0 0 0 / / / / / 7 0 0 0 0 7 0 7 8 8 8 8 8 8 8 8 8 8 8 8 7 7 7 7 7 Conductivity Variations during a
Recharge Event ) t f
700 10 (
y t e r v i 3 i 650 11 a t c t 1 8 W d u o W t n K 600 12 o h C p t
October to December, 2007 e s 550 13 D p e c i e
c h 1 n P r i 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 2 1 1 2 0 2 0 2 0 0 0 1 1 / / / / / / / / / / / / / / 3 2 5 1 1 2 1 2 3 1 8 1 2 1 1 4 / 0 2 7 9 0 2 / / 0 / 0 5 6 9 0 / / / / / / / / / / 0 0 0 0 0 7 0 0 7 0 0 7 7 0 7 7 7 7 7 7 7 7 7 7
• Sharp change in conductivity within 24 hrs of recharge event – Rise in conductivity as soil moisture drains – Drop in conductivity as low-conductivity recharge enters saturated zone Recharge to the Silurian Aquifer – Studies in NE WI demonstrate that recharge reaches the aquifer within 1 to 2 days, even with sediment thicknesses up to 18 ft and depth to water > 50 ft – Review of Midwestern and national literature suggests that cohesive soils frequently contain fractures and macropores to significant depths – Dodge County: Manure through 15+ feet of clay via cracks and pathways
Soil Macropores Outline • Wisconsin’s Carbonate Aquifers • Flow Characteristics of Eastern Dolomite Aquifer • Water Cycle and Recharge • Existing Data on Pathogen Contamination – Karst Task Force Report – UWSP Data Viewer – Kewaunee County • What Soil Depth is Protective? Regional Water Quality Data Calumet Nitrate Data
Data from Danielle Santry Calumet Co LWCD Calumet E. Coli Data
Data from Danielle Santry Calumet Co LWCD
Calumet County Private Well Data; 2005-2016 Percentage of Wells Unsafe by Year in Groundwater Protection Area 100%
90%
80%
70%
60%
Bacteria and/or Nitrate
50% Nitrate ≥ 10 mg/L Total Coliform Bacteria E. coli 40%
30% Percent Wells Exceeding Safe Drinking Standard Water Drinking Safe Exceeding Wells Percent 20%
10%
0% 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 Brown County • Morrison Township, Brown County – Brown water event Feb- March 2006 – 86 wells tested unsafe for Coliform and/or E.Coli. Private Well Data
• UW Stevens Point Center for Watershed Science – Interactive program that allows you to view groundwater quality data at a variety of scales – Example percent of wells with bacteria detections at county scale https://www.uwsp.edu/cnr-ap/watershed/Pages/wellwaterviewer.aspx Issues with some web browsers. Use Microsoft Explorer or Edge
Private Well Data
• Township Scale • Section Scale
Percent of wells with bacteria detections
Private Well Data
• Township Scale • Section Scale
Average nitrate-N concentration
Virus Sampling (May 2014)
• Sampled 10 household wells in Kewaunee County – 6 bovine-specific viruses plus bovine bacteroides – 7 human-specific viruses plus human bacteroides – pepper mild mottled virus – zoonotic pathogens • pump ~800 L through • enterohemorrhagic E. coli • Salmonella species hemodialysis filters • Campylobacter jejuni • qPCR methods except • Cryptosporidium species protozoa by IFA • Giardia lamblia • Coliforms by Quanti-Tray
Virus Sampling (May 2014) • 7 of 10 wells were positive for fecal contamination • Human and bovine fecal
sources contaminated 3 wells each; 1 well had both sources • 6 wells were negative for total coliform or E. coli indicators even though pathogens were present • 4 wells had evidence of of Salmonella bacteria • One well was positive for the bacterium Campylobacter jejuni County-wide Sampling (Nov 2015) • County-wide randomized sampling of private wells stratified by depth-to- bedrock – <5 ft – 5-20 ft – > 20 ft • Participation – 800 solicitation letters – 407 willing participants – 327 samples • One week “Synoptic” sample, November 2015
October 2016 Brown Water Event • Manure applied to nearby field on Tuesday, Oct 25 • 1.06-inch rain event on Wednesday, Oct 26 • Brown water arrived on Wednesday evening October 2016 Brown Water Event • We have an autosampler capable of collecting samples for pathogens installed on a well five miles north of the newsworthy brown water well • Collected continuous samples from Oct 25 - Nov 2 Outline • Wisconsin’s Carbonate Aquifers • Flow Characteristics of Eastern Dolomite Aquifer • Water Cycle and Recharge • Existing Data on Pathogens • What Soil Depth is Protective? Column Studies are not Representative of Field Conditions NE WI Karst Task Force • Broad membership – Researchers – County conservationists – Farmers – Crop consultants – DNR, DATCP • Two sub-commitees – Vulnerability ranking – BMPs • Recommendations – primarily intended to minimize groundwater contamination from pathogens and “brown water” – secondarily intended to minimize groundwater contamination from nitrate What Soil Depth is Protective?
Level Relative of protection Landscape criteria vulnerability required to contamination
Less than 5 ft (60 inches) to carbonate bedrock, and/or closed depressions or Extreme 1 any drainage areas that contribute water to sinkholes/bedrock openings
2 5-15 feet to carbonate rock High
3 >15-50 feet to carbonate rock Significant
Greater than 50 feet to carbonate Moderate 4 bedrock What Soil Depth Is Protective? • Recharge reaches the aquifer within 1 to 2 days, even with sediment thicknesses up to 18 ft and depth to water up to 54 ft • Kewaunee County Spreading ordinance – No spreading from Jan 1 to April 15 in areas with less than 20 ft of soil
What Soil Depth Is Protective? • Kewaunee County Virus Sampling – Fecal pathogens have been detected in many wells that were negative for coliform bacteria and E. coli • County-wide randomized sampling of private wells in November 2015, Kewaunee County – See differences in contamination rates based on the different depth-to-bedrock categories – Additional statistical analysis will look for the “break point” to explore where contamination drops off – Depth-to-bedrock data are being compiled for the July 2016 sampling event Kewaunee County November 2015 Sampling
To t a l Sampled To t a l E.coli Nitrate-N Wells Wells Coliform >10 mg/l County 4896 323 < 5 ft 318 116 31% 3% 17% Raw Data 5-20 ft 557 105 29% 2% 10% >20 ft 4021 96 19% 0% 6% unknown 6
Weighted Analysis, Validated Depth to Bedrock
Summary • WI Carbonate Aquifers – Hydrogeology of the Eastern Dolomite aquifer is well understood – SW WI aquifer has different hydrogeology – May require different approaches • Recharge – Is episodic and most recharge occurs in early spring – Significant recharge events also occur in fall (after plants go dormant) and winter – Water-levels respond rapidly (within 24 to 48 hours) to significant recharge events
Summary • What Soil Depth is Protective? – Current codes are not protective and are based on a sand column study that does not represent field conditions • Farmers believe that if they “follow the rules” they won’t cause groundwater contamination • NE WI Karst Force vulnerability rankings have been supported by subsequent research – <5 ft extreme vulnerability – 5-15 ft high vulnerability