[gentle music]
- Jennifer Detra: Welcome, my name is Jen Detra.
I am the McCoy Public Library Director
here in Shullsburg, Wisconsin.
We are in Lafayette County down here.
The library's been here since the 1930s, I wanna say.
And we are hosting this program tonight
mostly because of a Discovery grant
that our Main Street got.
And we were just curious what the community is curious about,
if that makes sense.
We wanna know, the community has expressed an interest
in learning more about what's underneath us.
So this is just one part of that.
And Maureen here is gonna teach us about our water.
[audience applauds]
- Maureen Muldoon: So, as Jen said, I'm Maureen Muldoon.
I work for the
Wisconsin Geological and Natural History Survey.
And we are basically the state agency
that is responsible for all the subsurface information,
so the things under your feet.
Personally, I'm a groundwater scientist,
or also called a hydrogeologist.
But we have people who map bedrock geology.
We have people who map surficial sediments.
I have focused on the groundwater.
And so, that's gonna be the focus of today's talk,
is the groundwater part of what's under your feet.
Wisconsin Karst aquifers--
Somebody said, "Why are we talking about aquifers?
Well, 'cause that's what holds groundwater.
And karst aquifers are exceedingly productive aquifers.
They yield a lot of water.
But they're also very vulnerable aquifers.
And we're gonna talk about sort of
what makes them vulnerable.
And one of the things is the bedrock geology.
Just what are the rocks that make up that aquifer?
And so, everybody knows what limestone is, right?
You've seen limestone.
Another really similar rock is dolomite.
And the feature about limestones and dolomites
that's important for karst is that they dissolve, right?
These are the rocks that have caves in 'em,
which are basically just big, dissolved holes underground.
These are the rocks that get sinkholes.
And so, that's kind of what we mean by karst.
So, we're gonna go into a little detail
about bedrock geology a little bit.
The water cycle is, of course, very important for aquifers
because the water has to come from the sky
to get into the aquifer.
And we'll talk a little bit about the process
of what we call groundwater recharge.
Another thing that affects vulnerability
is the soils, right?
So, what kind of material do you have on top of those rocks?
How thick is it?
Does it let water through easily or not?
That's gonna affect vulnerability.
'Cause basically, we count on soils to do some stuff for it.
Like, think of all the things
that happen at the ground surface.
We count on soils to sort of filter and treat that water
as it moves from the ground surface
and into the aquifer.
And then, finally, the last thing
that sort of matters is what is the land use?
What are we doing on top of the surface of the ground
that might or might not affect that aquifer?
So I'm just gonna show you a quick outline.
The first topic is gonna be geology and karst.
We're gonna talk about the bedrock geology of the state.
What do we mean by karst, and where do we have karst aquifers?
And then we'll go into some of the other parts,
like the water cycle
and "Why worry about karst?" and those things.
But just in terms of bedrock geology,
so, there's all these really brightly-colored rocks
in northern Wisconsin.
And these are very old, like a billion years-plus,
crystalline rocks.
And by that, I mean things like granites
or, like, if you've been up to Devil's Lake
and seen the quartzite, right?
And it's all these intergrown crystals.
They do not move water well.
They are not good aquifers, right?
But if you look at this line
that goes from here over to here,
that's this cross section, okay?
So, it's as if you took a knife
and kind of sliced into Wisconsin
and you could look at it on the side.
And what you see is you've got these old rocks on the bottom,
but then you have this package of rocks on top
that are like nice, little layers, right?
And those are our sedimentary aquifers.
There's, we'll go into a little more detail later,
but the kind of tanny one is a Cambrian sandstone,
and then there's the Prairie du Chien dolomite,
and then there's the St. Peter sandstone,
which a lot of people around here use for water supply.
And then there's the Sinnipee Group,
which another stack of dolomites.
This pinky one is the Maquoketa shale,
and then, this one way in the east is the Silurian dolomite.
And so, I'm gonna be talking a lot about the Silurian dolomite,
and then, also talking about the Sinnipee
and the Prairie du Chien dolomites
that you have down here.
Okay, so, karst, it's kind of an odd word, right?
Like, what is it?
And basically, it's a landscape.
It's a landscape that forms by dissolving rock.
So, this is just straight--
There's a book called The Glossary of Geology.
This is just straight from that.
"Type of topography
"that's formed on limestone, dolomite, gypsum,
and other rocks," that can dissolve.
Like, granites don't really dissolve,
but limestone does.
And the kind of things you see in these landscapes
are sinkholes, caves, lots of underground drainage,
like, that kind of thing.
It's a big range of landscapes.
The picture that I'm showing you here,
you can kind of see these fractures in this field.
And these are fractures in the rock
that have been enlarged by dissolution.
And so, like, the plants are a little happier over it
'cause there's a little more sediment there, right?
But have you ever seen those pictures
of the tower karst in China,
where there's the river, and there's all these,
just these little pillary things coming up?
That's, like, really advanced karst.
Like, basically, that's just all the rest
of these sinkholes and stuff have dissolved away,
and you're left with a couple sticky-up bits.
It's called the tower karst of China.
And it's a huge range of landscapes,
but it's not rare, right?
It's about 20% of the U.S.
and about 40% of the landscape east of the Mississippi.
So, there's a fair number of people in the Upper Midwest
who live on karst aquifers.
Okay, so where does it happen in Wisconsin?
Basically, if you take the area
where you have dolomite or limestone bedrock,
and then you look at, you know,
if the depth of soil is less than 50 feet,
it's the reddish areas on the map,
and if it's greater than 50 feet,
it's kind of the tanny areas.
So, we have karst kind of in this U-shape,
which if you remember, that's sort of the pattern
of those sedimentary rocks, right?
This is all the old stuff up top,
this is where the Cambrian sandstone was,
and then this is where we have those carbonate rocks.
And the two main areas that we have where this is an issue
is northeast, like in Door and Kewaunee Counties.
And this diagram
is from the Door County Soil and Water Department,
and it's "Protect the Water You Drink" from Door County.
And this is very much what that landscape looks like.
There's lots of vertical fractures, right,
and then there's lots of fractures
that run parallel to the bedding plane.
There's occasional little sinkholes and caves.
But this really well-connected fracture network
is where the water is living and moving up in that area.
This is a picture that I got from Tony Runkel.
He's a geologist with the Minnesota Geological Survey,
sort of our sister agency across the river.
And this is more what the karst is like down here
where you've got a dolomite, but then, you've got a shale,
and then you've got a sandstone underneath it.
In Door, it's pretty much all dolomite.
Here, you've got a bunch of different rock types,
and that's gonna affect the type of karst.
And we'll go into that a little more
in the, like, last third of the talk,
where we talk about the hydrogeology
of southwest Wisconsin.
Okay, so that pretty much is your introduction
to what karst is.
Just a couple quick karst features from this area.
You see here, there's a big sinkhole.
This is from Blue Mounds.
This is when they redid Highway 151 maybe,
I don't know, 20 years ago.
And you see this nice conduit coming into the road.
And then, this is, of course, Cave of the Mounds,
which how many folks have been there, right?
Yeah, pretty dissolved hole
with all this secondary features and deposits in it.
So, the kind of things you see down here
are sinkholes, conduits, and caves.
And at the ground surface, the carbonates weather
to produce this kind of reddish, clay material called terra rosa.
And we'll talk a little bit about that too.
So, northeastern Wisconsin karst
is what we're gonna sort of talk about a little bit now.
This is an area that I've done a ton of work on.
I started working up here
when I first started the survey in, ooh, 1987.
So, and then I went up to UW-Oshkosh for a while,
and now I'm back at the survey.
But this is the outcrop of the Silurian dolomite,
kind of in the Upper Midwest.
How many people have been to Niagara Falls?
Yeah, it's the dolomite over a shale,
and the shale is eroding,
and that's what's making the falls move back.
So it's exactly the same rocks we have here.
We just don't have a big river going over ours.
But anyway, this is the Silurian dolomite outcrop.
And here's a picture of it up in Door County from a quarry.
And what you can see, I hope,
is that there's kind of pretty clear vertical fractures.
There's, like, two sets at right angles.
And then there's all these fractures
that run parallel to the bedding.
Right, and there's this great picture
that we got across from one of our old research sites.
That's an alfalfa field, right?
And you can really, really see the fractures,
'cause there's only about a foot and a half,
two feet of soil in that field.
But where the fractures are bigger
and some soil has washed in,
the alfalfa's a little greener and happier, right,
and looks good.
And over the blocks, it doesn't look so good.
But this field over here, I think it was oats.
I mean, it just doesn't express it,
'cause it's not as deeply taprooted as the alfalfa.
Once somebody said to me, like,
"What's the fracture pattern like in Door County?"
I was like, "This."
They're like, "Everywhere?"
And I'm like, "Yeah, everywhere."
[laughs] We just don't always see it.
Like, the alfalfa shows it really good.
But that's what the land surface looks like
underneath the soil.
This is kind of an odd picture.
This is a well that I drilled as part of my PhD project.
It's about a three-inch diameter core hole
just drilled into the rock.
And we went down with one of those bird's-eye view cameras
that looks all the way around, right?
And so, what you see is a fracture
coming into that borehole.
So, it's a horizontal fracture coming into the borehole.
And it's open about, I don't know, a quarter-inch.
One time when we were drilling,
we actually found a cherry pit in one of the fractures.
Just, like, things move easily through this aquifer.
Okay, so that was your very brief introduction
to geology and karst.
And now, we're gonna spend a little bit of time
on the water cycle and just groundwater basics,
just so that we're all on the same page
when we start talking about aquifers.
And I figure, it's always good
to start with the water cycle, because we all know it.
We all learned it in middle school,
and we all live in it, right?
So, just to sort of think a little bit about how it works.
Okay, so, we're all good with the water cycle, right?
We live in the Upper Midwest.
It rains, precipitation, right?
Water has to evaporate from surface water.
Or it's got to transpire out of plants, right?
So cornfields, trees.
Trees can pump out hundreds of gallons of water a day,
right, through transpiration.
All that water goes up into the atmosphere,
comes along, comes back down as precipitation.
When that water hits the ground, it's got a couple of options.
It can infiltrate.
It can run off and go to, like, a lake or stream.
And that's kind of its options.
But if it infiltrates
and it gets all the way down to the water table,
then it starts to flow as groundwater, right?
And what the groundwater does is it comes in
and there are various what we call discharge points,
natural places where that water comes out of the aquifer.
And that discharge point could be this lake
or this river over here,
or it could be the well that you pump, right?
You lower the water level and make water flow to that well.
Sort of a man-made discharge point.
So, what do I mean by groundwater?
People sometimes envision groundwater
the way surface water is, like lakes and streams.
And so, they're like, "Oh, we hit the underground river."
It's like, no, right?
[laughs] That's not what groundwater is.
It's just the water filling the pores,
the little kind of spaces between the grains
and the cracks in the rock.
It's like, if you go to the beach
and you're kind of near the water's edge
and you dig down,
the hole will fill with water, right?
That's what groundwater is.
It's just the water between the sand grains,
between the little cracks in the rock.
There's not big underground rivers and lakes.
It's just pore spaces, okay?
So that's sort of what groundwater is.
And in Wisconsin, it's pretty important.
About 70% of Wisconsinites
utilize groundwater for drinking water.
And some of that is through municipal supply systems,
and some of that is through people's own private wells.
Okay, but yeah, we're a very groundwater-dependent state,
which is kind of interesting,
since we have so much surface water,
but we use a lot of groundwater.
Okay, so this is, again, a little Groundwater 101.
Just some definitions.
Somebody wanted to know what an aquifer is.
It's just a fancy word for any geologic unit
that can store and transmit water.
That's what an aquifer is.
It's what we pump to get water out
when we want to use groundwater.
Okay, the water table,
and it's sort of shown here in this diagram,
but it's also shown in these kind of blown-up pictures,
basically, it's the boundary between what we call
the unsaturated zone and the saturated zone.
So, in the unsaturated zone,
think back to that lovely summer beach
that you may have been on, right?
When you first start digging in the sand,
it might be moist,
but the water's not flowing into the hole.
And that's because the water is sort of clinging
to those sand grains.
It's unsaturated.
There's both a little bit of moisture and air
in that pore space.
But once you go below the water table,
it is saturated, full up with water, right?
So all the pore spaces are full with water.
So, that's kind of what the water table is.
One of the processes I wanna mention
as part of the water cycle
and being important with groundwater
is the idea of groundwater recharge, right?
How does water get into the system?
And, you know, this water that's coming in
after a rain event, like this time of year,
most of that's being used by plants, right?
It is not getting into the groundwater system.
It's coming in, it's infiltrating into the soil,
and it's getting used.
For water to actually recharge and get down to the water table,
it has to kind of get past that root zone.
And we're gonna just look at
sort of how that varies throughout the year.
And I'm gonna use some data from northeast Wisconsin.
Okay, so this is kind of a busy slide.
This is four wells
in Brown, Kewaunee, Manitowoc, and Calumet Counties.
They're color-coded like with the counties, right?
So we're gonna look at this top two,
like this Brown County
and I think it's Calumet County, the red one.
And this time period goes from September of '07
to August of '08,
so it's about a year's worth of data.
And what you're seeing down here are the rain events
in terms of inches of precipitation as the bars
and then cumulative precipitation as the line.
And what's an indication of groundwater recharge
is the water level in the well goes up, right?
There's also sometimes chemistry changes with it.
But look at when that happens, okay?
So, these water-level measurements
are getting taken automatically
by a little thing called a pressure transducer
every 30 minutes.
And what we see is...
...in fall, right, we have a couple big rain events
and the water level goes up.
In the winter,
we didn't used to get a lot of recharge in the winter,
but a lot of times now we're having quick, little melt events
like in December and January and stuff.
And you see, like, the snow melts
and the water levels in the wells go up, right?
The main period of groundwater recharge in Wisconsin
is the spring snowmelt event.
You take all that precipitation
that you've stockpiled up for the winter,
and you melt it, and it goes into the groundwater system.
And this is a time where plants
aren't really pulling it out, right?
In fall, plants kind of die back,
and you lose that transpiration pull on the water.
Does anybody remember--
I don't know if this was as big an event down here
as it was up where I live in Oshkosh,
but in the summer of '08,
we had a really horrendous rain event
where we got something like 13 inches of rain in two days.
I was actually out of town and driving back,
and there was a picture of the intersection of my street
that my brother saw in England,
and it was flooded, and people were canoeing, right?
I mean, it was an insane amount of rain that we got.
It was early June of '08.
So that summer, we had a summer recharge event.
We often don't have-- I mean, most of the time,
water levels fall all summer long,
and then they'll start coming back up in the fall.
But that year, we had a large summer recharge event.
But the reason I'm going into this
is because recharge is the process
that moves things from the ground surface into the aquifer.
But it doesn't do it 24/7, right?
It does it very episodically.
So if we kind of manage what we're doing
in the fall and in the spring,
like, in terms of what we're putting out there
in terms of manure or agricultural chemicals,
that can help us in terms of
whether that's gonna go into our aquifer or not.
So you got to think about,
you're trying to protect that aquifer.
That aquifer's really vulnerable.
And so, you don't want stuff lying around those times of year
that could flush into the aquifer.
Okay, that was your quick introduction
to water cycley stuff.
So now the question, why worry about karst, right?
There's nice caves, they're kind of fun to visit.
They're cool in the summer, right?
Well, there's sinkholes.
This is one in Waukesha County,
and this is one up in Door County,
which basically how those start
is there's a little void underground,
and it keeps dissolving and propagating upward
until eventually, the stuff above it collapses in
and you have this vertical shaft,
which it doesn't take much imagination to figure out,
like, if this opened under your house or a road, right?
It would not be a good thing, right?
'Cause there's these sinkholes that you can't see
until they open up, right?
So that's sort of one thing,
the problem, the possibility of collapse.
The other thing, which is one of the features of the talk,
is aquifer vulnerability.
Right, so, this is not a great map for colorblind people,
and I apologize.
I did not make it.
It was made in the late 1980s by DNR and my agency.
But the green means areas
where groundwater is less vulnerable to contamination,
and the red means areas
where groundwater is vulnerable to contamination.
And the things that went into generating this map
were what type of bedrock is in the area?
How far is it to the bedrock?
How far is it to the water table?
What are the soil characteristics
and the characteristics of the sediment
that overlies the aquifer?
And you can see the karst areas,
like Door and over here, they're pretty red, right?
'Cause we're pretty vulnerable.
There's been sort of historic water quality concerns
in northeast Wisconsin,
primarily in terms of bacterial contamination
and the occasional brown water event.
Have you guys heard of brown water events?
Hopefully you don't really get them as much down here.
Basically, that comes out of somebody's well.
Okay. [laughs]
This is a particular case in Kewaunee County
in October of 2016
where manure had been applied to a field
in the morning and it incorporated,
and then they got an inch and a half of rain
and it just all washed in.
And this was a house right next to that farm field.
Rarely does it get that bad,
but it does mean that there's possibility
of, you know, microbes
and other things from that manure,
even if it doesn't turn brown,
getting into somebody's homeowner well.
Okay, so, let's think about soils, right? [laughs]
'Cause one of the ways you try to prevent
that kind of stuff getting into your aquifer
is having your soils filtered out, right?
So, this is just a--
Has anybody seen that DNR groundwater and land use poster?
It shows all this different stuff, right,
like farming and, you know, landfills and urban areas.
And, you know, that stuff is all the stuff
we do on the ground surface, right?
And the precipitation is gonna move through that
and come into our aquifer.
So, you know, we kind of rely on soils
to do a lot of stuff for us,
primarily treat and filter that water
that's coming into the aquifer.
So, in terms of what we really want soils to do,
we want it to hold nutrients in the root zone
so that we can grow crops.
We wanna filter out the microbes
so that, you know, they're not in that brown water
coming into your well.
And, you know, we've got septic fields,
septic drain fields.
We apply sewage sludge to fields.
We apply manure to fields.
And we need to, as that water filters through the soil,
hopefully the little, tiny pore spaces will filter out
all the microbes that we don't want to be ingesting.
We also, you know, like other kind of things
we apply on the land surface,
we want the soil to slow down those movements
or maybe break down those compounds.
So think of, like, chemical contaminants,
like petroleum products, right?
You know, people aren't perfect at the gas station.
Some spills off, right?
Pesticides, those kind of things.
We rely on the soil to kind of break down
and treat that stuff for us.
So, you can kind of see that at least in the east,
soil thickness is a major factor in predicting
whether there's gonna be contamination
in that aquifer, okay?
So, this is a map from Sherrill published by the USGS
back in-- When did this come out?
1978, I think.
This shows depths to soils, or depth to rock.
And then, this is the area
because it's less than 20 feet to rock
where they've changed the code
in terms of how people can manage their manure, right?
Like, less manure can be applied in areas of thin soils.
Like, there's a 0-2 zone and 2-3 and 5-20
and that kind of stuff.
Okay, so, another way
to kind of think about aquifer vulnerability
is to look at what do we know
in terms of where there's water quality problems now.
And there's a great resource if you haven't ever used it.
UW-Stevens Point has this well water data viewer.
It's at the Center for Watershed Science.
They've just done an update on it,
so I actually had to go take my old talk
and pull out all my old pictures and put the new ones in
of what the thing looked like, right?
So you go to the page,
and then you click on that little map,
and it pulls up this web mapping application for you.
And then you can pick different parameters, like,
"I wanna look at arsenic.
"I wanna look at nitrate.
I wanna look at bacteria."
And you can see what the problems are, right?
So, this map that I'm showing right here
is percent of wells that have coliform bacteria in 'em.
And you can see that all of these counties
down here in southwest Wisconsin are more than 25%.
Now, coliform bacteria is everywhere.
It's, like, it's probably on your hands right now.
It's in the soil.
It is not a harmful bacteria.
Sometimes it comes in, you know, just from the ground surface.
Sometimes it comes in through plumbing issues.
It's not a fecal coliform, which is a different issue.
But yeah, you can go get these data.
And if you have any curiosity about
if you're on a private well and you're interested,
you can zoom in at different scales.
You can go county scale, township scale,
or down to the individual square-mile section
and look at the data. It's great.
I kind of introduced it to you
'cause I want to use this example
from northeast Wisconsin.
This is showing you that statewide vulnerability map.
And then on top of it,
it's showing you water quality results.
So, the black dots are areas
where there is a bacteria-positive well,
and the gray dots, which are really hard to see,
are areas where there's not bacteria in the well.
And, you know, there's a pretty good correlation
going on there, right?
And then, over here, we have the nitrate.
And the black dots are where it's greater than 10,
which is the drinking water standard.
And notice, we've got thin soils here, vulnerable.
We've got black dots.
There's thin soils down here, very vulnerable.
We got black dots, right?
So, the things that you would expect to be influencing
whether an aquifer is vulnerable to, like, you know,
like, fertilizer and nitrates coming in,
it correlates pretty well with the existing water quality data.
Okay, so, there's another thing about recharge
that I want to mention is a lot of times, people think,
"Oh, I got, like, 10 feet of clay."
"Like, I'm not gonna have a problem, right?
That's gonna filter everything out."
And that's kind of true,
but there's these things called soil macropores.
Think like earthworm burrows, right? [laughs]
'Cause if you take a clump of clay
and you stick your finger in it, right,
and you take your finger out, that hole stays there.
You take a handful of sand and you stick your finger in it,
and the hole collapses.
So, if you have fine-grained, sort of cohesive soils,
you can develop macropores.
Like, my backyard is really silty,
and when it gets dry,
I get big desiccation cracks in my yard, right?
And that's gonna affect, like, how stuff moves through it.
So, this is, like, a really graphic demonstration
of what macropores are.
So, this is a guy from Ohio.
He's smoking a stogie, and he's got this machine here.
He's gonna throw it in here,
and he's gonna pump smoke down into a tile line.
You're all good for what a tile line is,
agricultural drainage line, where you put 'em in fields
that are kind of silty or clayey
to help move the water out
so you can get in there in spring
and plant and stuff, right?
So, dude throws his stogie in the little smoke machine.
I got these pictures from Fred Madison,
who is a soil scientist at the survey.
And that's what happens, right?
Like, it just comes right out.
[laughs] And that's through, like, tile lines
are usually a couple feet down, right, to help with drainage.
So, something to think about,
macropores exist, and they can create problems.
This is from Dodge County.
This was an event that happened, I think, in '08
where there was like a little melt in February, right,
and all the water ran down
and kind of ponded up in the corner of a farm field.
And here, you've got silty tills on top of Sinnipee dolomite,
and suddenly, it kind of all went away,
and a bunch of people's wells turned brown.
And then, they went and got a backhoe and dug out a hole.
What do you think is in all these little worm burrows here?
[laughs] It was manure, right?
It just transported right through that soil zone,
And it was through 15 feet of silty clay sediment, right?
So, clay is not always gonna protect you.
Okay, so, that's soils and water quality.
We're gonna look at one more topic,
recharge and water quality,
and then we're gonna come into the geology
and hydrogeology of southwest Wisconsin.
So, we've talked about recharge, when it occurs and stuff.
And this example is gonna be from Kewaunee County,
so it's in the east.
Remember, there's these big vertical cracks
in this system, right?
And it's all dolomite.
There's no shale, there's no sandstone.
It's just all dolomite.
We had done a study in Kewaunee
where we sampled a bunch of homeowner wells
to try to figure out
how much nitrate and bacteria contamination there were,
and then we sampled a bunch of wells for pathogens.
But another objective of that study,
one that I really wanted to do, is how quickly does stuff move
from the ground surface into a homeowner's well?
That's what I was trying to answer.
And this was some data from a while ago.
This was from that other study.
What you've got is the water level here in blue,
and you have what's called fluid conductivity in red.
So, when water dissolves stuff--
Think about taking table salt and throwing it in water, right?
The salt goes away, and then you have ions.
You have sodium and chloride ions.
So, the more stuff that's dissolved in the water,
the more able that water is to transmit an electric current.
So, you can take fluid conductivity
as basically a rough measure of total dissolved solids.
And what you see is there's this melt event here
in late December.
The water level goes up,
and what happens with the conductivity
is it pushes up,
and then it dilutes with that fresh snowmelt coming in.
So, I think you're pushing out the soil moisture,
and then you're flushing in the new melted snow.
Okay, so, when you do that,
like, how quickly does that move down to the water table?
And there'd been a bunch of stories kind of like this one
I'm showing you here from Door County
where people go up,
you know, they go up to a friend's cabin,
they go up north, they go on vacation,
or they just live there,
and they drink the water one day.
It seems fine, right?
And then, the next day, they're sick,
and the next day, the water smells bad.
So it's like, you know, do the little microbes,
because they're little particles,
like, push through first
as you're getting this slug of water in?
Like, how does that happen?
That's what I was trying to figure out, right?
And here's the fancy way of saying that.
What is the timing of enteric pathogen contamination
in relation to groundwater recharge?
You have to write it that way to get the research money.
[laughs] Anyway, so...
And I think what happens is
you kind of push the pathogens through the particles
as kind of the front edge of that new water coming in,
and then kind of the center of mass of that water coming in
is where you get the kind of brown water, right?
And that's why people end up drinking it
before they know it's bad, right?
So, how are we gonna do this?
So, we're up in Kewaunee County,
and we have a couple things going here.
We've got an auto sampler, and I'll show you what that is.
We have a shallow well, KW-183.
There's a weather station,
and there's another well at the fish hatchery.
Okay, so, what we're gonna do is at those,
the wells that weren't the homeowner wells,
the non-pumping wells,
we are gonna measure water levels
and we are gonna measure water chemistry, okay?
So, this is wells KW-183 and that fish hatchery well.
These are shallow wells.
This one's only 33 feet deep.
This one's only 46 feet deep.
'Cause we're trying to get, like, what's right happening
at the top of that water table.
So, like I said, we measured water levels and water quality.
And then, this is a homeowner's well where the auto sampler was.
It only had about two feet of soil.
The casing, which is the metal pipe,
it ran all the way down to 200 feet, right?
But the well was 300 feet deep, so we just had 100 feet
of open rock feeding water into that well.
Okay, and then, what we did
is we used these kind of fancy samplers to pull samples
that we could analyze for microbial targets.
So, microbes are little particles, right?
And how you sample them is you use hemodialysis filters,
just like the things they do with kidney filters.
And you run, like, 800 liters,
200 gallons of water, through this filter.
Then you cap the ends, and you send it off
to Mark Borchardt's lab in Marshfield,
'cause he's the microbiologist on this project
and I'm the hydrogeologist on this project.
And then they analyze it using qPCR.
So, remember when you did the COVID tests,
and they would get analyzed by PCR,
polymerase chain reaction, right,
where they can tell if the genetic material
of, like, the COVID virus was present?
Well, they can tell if the genetic material
of, like, coliform or salmonella
or some other nasty pathogen is in the water, okay?
So, that's how we're gonna be doing these samples.
This is some lovely homeowner's basement
who let us do this, right,
where the water pumped into his tank, right?
And then it came over to our fancy thing over here,
where we had a data logger that ran the whole system.
And over here, there's kind of a Bluesen
that had these different water quality sensors in it.
And then, this is where we pulled the samples.
Okay, so what did we see?
Do you remember that brown water picture from Kewaunee County?
That's the day that we started doing this test, right?
That lady's well turned brown.
So, this is, I've got,
I'm showing you precipitation in hour increments.
So, the rain started at 8 o'clock in the morning
on October 26.
The water level in my shallow well,
we're looking at this well,
starts to rise about five hours later, 1 o'clock.
These are the water chemistry signals from that well,
so we've got fluid conductivity here in red,
which is slowly but steadily going up,
and then we have this other thing called CDOM,
which is colorimetric dissolved organic matter.
So, soils have organic matter, right?
And when water pushes through it,
it sort of flushes that organic matter out.
So, notice, like, if we're taking stuff from the soil zone
and we're shoving it into this shallow well,
it's taken the peak of that.
Like, it starts coming through
at about 2 o'clock on the day of the rain,
and it peaks about 2 o'clock the next day,
about 30 hours later, okay?
I know, this is a lot.
This is probably the trickiest slide.
Now, let's go look at the guy's homeowner well, right,
where he doesn't have much soil,
but he's got pipe down to 200 feet.
And let's see what we saw in his samples.
We didn't see a lot of pathogens.
We did see coliform bacteria,
which is bacteria present in the soil everywhere.
And this is actually a log scale,
so this is like factors of 10, 1, 10, 100.
And we get this really nice peak, right?
And it lines up with this really nice peak,
which it's telling us it's taken 30 hours
from water to move the soil zone
and get all the way down into this well.
The water table is about at 20 feet.
So, this is coming into the water table
and then shoving down, like, 180 feet
to get in this well within 30 hours,
which is kind of amazing.
Okay, so, we're gonna finish up this section,
recharge and water quality.
It's really rapid, okay?
Wells respond one to two days of rain or melt events.
Most of our recharge occurs in early spring with snowmelt,
although you get some fall and winter events as well.
Total coliform counts can vary a lot.
And the reason I think about this a lot
is, like, think about when you tell a homeowner,
take a sample for bacteria.
And he does, right?
Well, what's it gonna be the next day or the next day, right?
With this kind of variable water quality,
it's hit or miss, right?
And then, the thing that's different
about northeast than here
is recharge penetrates hundreds of feet into the saturated zone,
like, in a day or two, right?
So, it also means that well construction
doesn't really protect the homeowner that much.
And that's gonna be different down here.
So, up there, not a big deal.
Down here, it is a big deal.
Okay, now we're finally getting to your homestretch here.
Geology and hydrogeology of southwest Wisconsin,
which is where we are.
So, first, we're gonna look at what is the bedrock geology,
what is the surficial geology, how does groundwater move,
and some results
from the Southwest Wisconsin Geology and Groundwater study.
So, this is a very simplified stratigraphy, right?
So, this is that Silurian dolomite
that we've been talking about up until now, right?
Underneath it is a big, thick shale
called the Maquoketa shale.
And then, we come into
what is your uppermost aquifer down here.
And this is the Sinnipee Group dolomites,
the Galena, the Decorah, and the Platteville.
This is the unit that hosted--
You guys know about your lead mining history, right?
That is the host rock for the ore
is the Sinnipee dolomites.
Your Wisconsin state flag has a miner guy on it, right?
I mean, the big lead, zinc-mining district
and, like, 13 ingots of lead, right?
This was a big mining area in the 1800s
and into the early 1900s.
And it is this unit here that is hosting that.
Underneath these dolomites is sandstone, okay?
Well, this is the St. Peter sandstone.
Then you have another dolomite,
and then you have the thick Cambrian sandstone.
But we're gonna focus on this top part right here now.
So, here's a detailed geologic map of the area.
This is pulled from the state map of the whole thing.
But Eric Stewart, who I work with,
just finished Grant County mapping,
and I think he's gonna finish Lafayette this summer.
So, let's just, again,
that stratigraphy, this greenish unit
is that upper Sinnipee dolomite.
Underneath it, this kind of purply-blue,
is the St. Peter.
And then, underneath that is the Prairie du Chien.
And those are the units we're gonna focus on.
And this is the same sort of thing,
just showing you as stacked rock layers.
Like I said, this is the Sinnipee host rock for the ore.
Then you've got this little shale,
then you've got the St. Peter.
This is gonna matter 'cause the geology matters for wells.
Okay, you guys are also
in what's called the Driftless Area, right?
Which you all know.
This is a map,
sort of a publication we have about glaciation in Wisconsin.
You can see where the big ice lobes were,
and they weren't here.
They didn't come down here, right? [laughs]
So you guys were never glaciated.
And it means your geology,
your landscape looks a little different.
You have a lot more ridges and valleys, right?
You don't have big, thick glacial sediments on top
the way we do in other parts of the state.
Instead, your surficial geology,
you have something like weathering.
We call it weathering residuum, right?
So it's weathered from the carbonate bedrock.
We call it the Rountree Formation.
You also have a lot of windblown stuff.
Some of that is windblown sand, and some of that is loess,
which is sort of silt-sized sediments.
This is just a fancy word, colluvial sediments,
for stuff that's slumping down hillsides, right?
Alluvial sediments is what gets laid in river valleys,
and lacustrine is lake sediments.
So, this is Graham, who I work with.
Eric took this picture.
This is looking at that Rountree formation,
that kind of reddish-brown,
sometimes sandy, sometimes silty
Rountree Formation.
I think Eric has-- Eric Carson.
I work with a lot of Erics. [laughs]
Unfortunately, all of our mappers seem to be named Eric.
So, he did a compilation of the surficial geology
of the Driftless Area.
And I think it has been released now,
so that is available from our web page.
Okay, so, but like, groundwater,
groundwater is what I love, so let's talk about groundwater.
How does groundwater work down here?
Well, a lot of times, what you have
is very short flow paths from a ridgetop
to the adjacent stream valleys, right?
You're not getting really long flow paths
the way you might do from, you know,
halfway across Kewaunee County over to Lake Michigan, right?
You're getting a lot of short, little flow paths.
And you have a lot of springs.
All these little blue dots are springs.
Notice there's, like, not nearly as many up here,
but there's a ton over here in the Driftless Area.
And that's because of that different geology, right?
When I started going through the Sinnipee
and then the Glenwood Formation
and then the St. Peter sandstone,
this is a roadcut near Dickeyville.
It's sort of overgrown now.
But, you know, water, it's gonna rain.
It's gonna soak into the unsaturated--
Look what's happening right here.
All that water is hitting that Decorah layer
and it's going sideways
and coming out on the hillside, right?
So different rock layers,
the sandstone, the dolomite, the shale,
are gonna move water differently
and can lead to a lot of lateral movement
if you have something like a clay or shale in there
that the water doesn't want to go through very easily.
So, essentially, you have multiple aquifers
in southwest Wisconsin.
You have this upper aquifer, which is the Sinnipee group,
and then you have this very hard to see Glenwood shale
that sort of impedes the downward movement of water.
Then you have the St. Peter sandstone.
And most people have their well either up here in the Sinnipee
or down here in the St. Peter,
or unfortunately, sometimes connecting the two,
which we're gonna talk about, okay?
So, the upper aquifer is the Sinnipee.
You've got the Glenwood shale, and then your lower aquifers,
the St. Peter, the Prairie du Chien dolomite,
and the underlying Cambrian sandstones.
Let's go look at some more specific groundwater data.
Do you guys know where Pioneer Farm is,
up near Platteville, College Farm Road?
George Kraft, who is a retired hydrogeologist
from UW-Stevens Point,
put in a bunch of monitoring wells in 2006.
And when I started this project in 2019,
they were still sitting there, which was great.
These are basically six-inch holes,
and you see the steel casing here.
And then, they just drill down
and set the casing into the rock,
and then they put smaller-diameter pipes below it.
So they put in a pipe with sand
and then some bentonite clay and then higher up,
so you can measure multiple water levels in a hole.
Okay, that's what we're doing here.
And this is what that looks like.
So, here's the cross-section line
that we're looking at, B to B prime.
There's a ridge right here, right?
And it kind of slopes down like this.
Slopes down, and then there's the upper Fever River over here.
Right, and these are the depths of the various wells.
And almost all of these wells
are completed in this Sinnipee Group dolomite, right?
This well over here is the only one that goes deeper,
and it goes into the St. Peter, okay?
So, we're gonna look at some water levels from this area
and showing you how they change,
so think of, like, the top of a ridge well,
the mid-slope well, the toe of the slope well.
Okay, another thing to think about
before we get to that water level slide
is this is this set of wells.
And now, this is the grody, detailed geology.
This is all Sinnipee, right?
And then, you have this little shale called the Specht's Ferry.
So this is Galena, Decorah, Platteville,
right, all dolomite.
Then you have another shale,
and then you have a well in the sandstone.
And the reason I'm going into all this grody detail
is look at those water levels.
In the upper Sinnipee, the water level is like 110.
In the St. Peter, it's 920.
Groundwater wants to flow
from higher water level elevation to lower.
The fact that you get that much of a head separation
is because it's really hard to get through that shale, okay?
So here's what water levels look like over time.
The details are not hugely important.
This goes from June of 2020 to August, to the end of 2021.
The main thing I wanna show you is that,
again, recharge happens really quickly
when we have, like, a melt event, okay?
So, your aquifer is behaving in that way
very similar to the aquifer in eastern Wisconsin.
Has anybody heard of
the Southwest Wisconsin Geology and Groundwater Study?
Okay, so, this was initiated by your three counties,
Iowa, Grant, and Lafayette.
The counties provided the funding,
plus the Lafayette Ag Stewardship Alliance.
When this project was started,
Ken Bradbury and Mark Borchardt were not yet retired.
Ken is another groundwater scientist like me.
Mark is a microbiologist.
And then there's me and Joel.
And we actually sort of finished this up
'cause these guys retired.
Anyway, [laughs] the reason the study was initiated
is, you know, if you look countywide,
it looks like, oh, that's a really bad bacteria problem.
But in reality, there just weren't that many samples
from Grant or from Lafayette counties.
And so, one of the primary goals
of the project was just, what is the extent
of groundwater contamination in these three counties?
And this is modeled exactly on what we did
in the Kewaunee report.
So, there's about 16,000 wells
in the three counties all together, right?
Private wells.
And then, we randomly selected for the first round of sampling
about 300 wells, and for the second round of sampling,
a little over 500 wells, okay?
So, that's just to see, like, what is the extent
of nitrate and bacteriological contamination?
If the wells had high bacteria or nitrate
and there was like, 126, 147,
then from those wells where we knew there were problems,
we selected wells to look for
whether there was fecal contamination of the aquifer
and what was the source of that fecal contamination.
Okay, so, step one, extent of contamination.
We sampled in November of '18, 2018, and April of 2019.
A number of wells sampled.
We had pretty high total coliforms
in that first sampling round.
Thankfully, not very many fecal coliforms.
About 16% had high nitrate.
And by high nitrate, that means
above the drinking water standard
of 10 milligrams per liter of nitrate as nitrogen.
But when you put the two together,
either high coliform or high nitrate,
about 40% of the wells were not--
You're not supposed to have any coliform in your well.
It wasn't, when we sampled again in spring,
we got some lower rates.
For comparison, these are statewide rates
from a number of sources listed down below.
So, total coliform is typically in the 20-23 range.
Nitrate is in the 7-10% range.
So you're running, like, kind of high on nitrate
and just a little high on bacteria.
Okay, so now, let's figure out,
like, do we have fecal material present, right?
So, I showed you one of those hemodialysis filters before.
This work was really done by Joel Stokdyk and Aaron
from the lab up there.
From the wells where we had problems,
we sampled every quarter, so every four months.
And each time, it was 34 to 35 wells, right?
So, we're gonna test these 138 wells
to see, well, is there poop?
That's really what it comes down to.
Fecal indicators.
So, not to be rude,
but, like, you know, you eat and you excrete, right?
And you excrete things like Bacteroides.
It's not a pathogenic bacteria.
It's just, like, you just poop it, right? [laughs]
Cryptosporidium, other things.
These are all things that could be coming out of you.
Cattles have a different set.
Pigs have a different set, right?
So, these were all the targets
that we tested those samples for.
And what we found is that there was human wastewater present.
There was indications of cattle manure
and a little bit of pig manure.
A lot, 26 wells were positive for multiple fecal sources.
We got a different signal in the northeast.
There's a lot of CAFOs up there,
and we had a lot more manure hits and much less human hits.
And, you know, I kind of thought about this a lot
'cause I was, you know, plotting up wells
and trying to match wells with samples.
There's a lot of sort of exuburbia development
around here, where, like, outside Platteville,
where it's not real big lots,
and each lot has its own well and its own septic.
So, you're putting a source very near your own well.
And I asked somebody, I think it was Linda Zwicker
when she was still with Grant County,
and she's like, "You know,
"'cause there's so much topography,
"to have, like, a centralized sewage system,
"you'd have to have all these lift pumps and stuff,
and it would just be really expensive."
So, I think partly that karst landscape
and the hilliness of it
is why the development is happening the way it is,
but I think it also may be a factor
in terms of human wastewater, because the biggest predictor
of whether you'd have a human wastewater hit
was density of septic systems.
Okay, last point, and then we are done, okay?
This is your aquifers again, right?
Upper aquifer, shale layer, lower aquifer.
If you case a well so that it's open in this upper aquifer,
that's all it's gonna see.
Like, this is the steel pipe,
and then, where it's dashed, that's, like, open rock wall.
This kind of construction is great, right,
'cause it's cased through the aquitard,
and it's only open to the deep system.
And the reason I'm gonna go into this
is 'cause now, we're gonna look at nitrate data
in relation to aquifers.
When you look at the map of all the results,
nothing really leaps out at you with patterns, right?
But if you look at it by aquifer, right,
then you start to see some patterns.
So, here are the Sinnipee wells,
wells that the screen was in the open part of the hole,
was in the Sinnipee.
And if you look at that, like...
31% exceeded the nitrate standard, okay?
If you look at the deep aquifer,
5% exceeded the nitrate standard.
In the connected wells,
where the driller just drilled 40 foot down,
cased it in the Sinnipee, and then left the open hole
that connected the Sinnipee to the deep system,
then you get 16% exceedances.
The sand and gravel aquifers coming in at 31%,
but that's pretty much the Lower Wisconsin River Valley.
And then, for wells where we couldn't match
the well construction report to the sample,
you know, it's got a kind of a middle-of-the-range thing.
So, geology really matters, [laughs] right?
How you construct your well really matters.
Elevated nitrate is a lot more common
for the shallow wells in the Sinnipee
and the sand and gravel wells.
Here's some data, also from Pioneer Farm,
'cause as part of a different project,
we were sampling the wells that George put in there.
If we look at the top of the hillside here--
my eyesight's not great--
the two wells here have nitrate at 40 parts per million.
That's four times the drinking water standard, right?
As you come down the hill and it deletes a little bit,
this is in the 20s.
This is in the teens.
If you go to that St. Peter well, right, that's deep,
it had one part per million nitrogen.
Okay, so, that upper Fever River,
which is getting its water from the Sinnipee,
he thought that the base flow to that river
accounted for 80% of the annual nitrate loss
from croplands in the region that fed that river.
We put in a nitrate sensor
that records nitrate continuously over time.
And that sensor was in a spring,
just, like, about a mile upstream from the farm.
And what we saw,
this is the 10 parts per million drinking water standard.
And it kind of diluted out that winter,
but that stream is almost always really high nitrate.
I mean, in the Central Sand Plains,
we think nitrate is high if we have a three.
This stream is a 10.
Okay. [laughs]
So, that upper aquifer--
And you've seen this aquifer if you ever drive 151,
where it's kind of all beaten up and looks Swiss cheesy,
that's what the Sinnipee dolomite looks like, right?
That's what the Galena looks like.
Stuff gets into it really easily, and it moves down.
But when it hits the Glenwood shale,
it goes out and discharges to that stream.
If we connect those two aquifers
through our well construction techniques,
we are taking the water quality problem that's in the Sinnipee,
and we're exporting it to the deep aquifer.
It's not a good idea, [laughs] okay?
In Minnesota, you can't do that.
You cannot cross-connect aquifers.
But our well code doesn't prohibit it.
Okay, takeaway messages.
What is karst?
It forms by dissolving carbonate rocks,
and water can move quickly in those interconnected pores.
Soils help protect it, right?
Thicker soil covers better, but macropores in cohesive soils
can provide pathways for contaminants.
Recharge is how we get the water into the system,
but it varies seasonally.
And so, during the recharge periods, like spring and fall,
that's when the aquifer is most vulnerable to contamination.
Northeast and southwest karst systems are different.
They are not the same animal,
and they shouldn't sort of be treated the same way
in terms of how we try to manage them.
In northeast, thin soils are really the issue.
And in southwest, it's really,
well construction is significant.
And I think that is everything I have for you.
[audience applauds]