- Welcome, everyone, to Wednesday Nite @ the Lab.
I'm Tom Zinnen, I work here
at the UW-Madison Biotechnology Center.
I also work for UW-Extension, Cooperative Extension.
And on behalf of those folks and our other co-organizers,
Wisconsin Public Television,
the Wisconsin Alumni Association,
and the UW-Madison Science Alliance,
thanks again for coming to Wednesday Nite @ the Lab.
We do this every Wednesday night,
50 times a year.
Tonight, it's my pleasure to welcome back
to Wednesday Nite @ the Lab, Ken Bradbury.
He's with the Wisconsin Geological
and Natural History Survey.
He was born in Richmond, Indiana,
and graduated from Richmond Senior High School.
And then he went to Ohio Wesleyan University
and majored in geology.
Got a master's degree at Indiana University in geology.
And he came here to UW-Madison to get his PhD
and he went way, way out there
and got a PhD in hydrogeology.
(audience chuckling)
Then he went directly to the Wisconsin Geological
and Natural History Survey, that was in 1982.
He's been there 36 years.
And since 2015, he has been the director there.
And in that role,
he also serves as Wisconsin State Geologist,
which is a role that Thomas Chamberlin
and Charles Van Hise I believe also held.
And they became presidents of the university.
(audience laughing)
Tonight, Ken gets to talk with us about groundwater,
wetlands, and geology, the invisible links.
And now while he's saying they're invisible,
I think we're starting to see more and more that they're pretty visible.
And the question is what do we get to do about that?
So please join me in welcoming Ken
back to Wednesday Nite @ the Lab.
- Thank you, Ken. - Thank you, Tom.
(audience applauding)
Well, thank you, Tom,
and thanks, everybody, for coming tonight.
So this is a reprise of a talk
that I put together for the Wisconsin Wetlands Association
for their conference about a year ago.
The point I wanna make is
that we all like wetlands
and wetlands are pretty prolific in Wisconsin
and the Upper Midwest.
But groundwater,
which as a hydrogeologist is my specialty,
is pretty important for wetlands,
and many people don't understand all the links.
And the more we think about wetlands,
we really have to understand the groundwater system around them.
So this talks a bit about wetlands
and a bit about groundwater and how they act together.
There's a lot of wetlands in the Upper Midwest,
lot of wetlands in the United States.
On this map,
all the green areas are wetlands.
And you can see that in the Upper Midwest,
we have our share of wetlands,
more than many other places in the country.
This hashed area are the pothole prairies
of Minnesota and North Dakota,
where there are many, many, many small wetlands.
And so we have a lot of wetlands in the Upper Midwest.
And these are all connected to groundwater
in one way or another.
Why? Why do we have all these wetlands?
And I think it's interesting
to think about why we have them.
First of all, where do wetlands occur?
They occur in-- The main areas in the United states
are glaciated terrain where we are now,
also in coastal terrain like the coastal plain here
and in Florida and the Southeast,
and then along rivers like the Mississippi
or the Wisconsin, so those are places wetlands occur.
But it's interesting to me that if you look at
the pattern of wetlands in the Upper Midwest,
kind of draw a line like this,
you realize that they really follow our glaciated areas.
So here's a map of the glaciated region
of the Upper Midwest.
So this is the area
covered by glaciers during the Pleistocene.
And you can see that that fairly well matches
the extent of major wetlands in the Upper Midwest.
Why is that? Well, for one thing
it's a fairly leveled or lower leaf topography.
We don't have a lot of mountain ranges unfortunately.
And it's a fairly young landscape
and it's often kind of hummocky and pitted
so there are a lot of places for water to collect.
And in general, we have a humid climate
and it's not too far to groundwater
in most of these places, so all these things work together
to give us a lot of wetlands here.
I mentioned that wetlands are dependent on groundwater.
So most people look at a wetland
and they see a surface water feature
and they don't often think of the subsurface.
So this is a cross-section
across a stream with the wetlands along the shore
and we've got some arrows here.
The importance of this is just
to think about the impact of groundwater
in feeding the wetland.
The wetlands are not always,
to some extent, they're based on surface water
and runoff and rainfall,
but groundwater is an important component
of the wetland water budget.
So in this talk,
some takeaway messages for you is that the groundwater,
wetlands, and surface water are often connected
and we need to think of them as linked environmental systems.
They're linked in terms of water, chemistry,
water quality.
And what we do to one part of the system
affects another part.
Understanding the geologic setting,
where they occur in the landscape,
what kind of rocks are around,
what the history of that landscape is,
what the topography is
helps us identify the wetland
and helps us understand why the wetlands are there.
And then water systems are transient.
It means they change with time.
They change with climate, with weather,
with short- and long-term climate change
or climate cycles.
They can change due to what we do on the landscape
like changing land use or changing groundwater pumping.
And I'll talk a little bit about that too.
If you're interested in reading more about this,
this is a free publication you can get
from the U.S. Geological Survey,
a really, really good publication
about groundwater and surface water.
And the subtitle here is "a single resource,"
and that's what we like to think about in the Midwest,
particularly in the humid Midwest here.
Groundwater and surface water are not separate things.
They're really one.
They're two parts of a single system.
They need to be thought of and managed together.
So that's kind of our mantra as modern hydrogeologists
that groundwater and surface water
really represent a single water resource.
I know some of you probably know a lot about groundwater,
others, maybe not so much.
So I'm gonna spend a little time
bringing everybody up to speed on what is groundwater.
Groundwater is the water that fills the cracks,
pores, interstices,
voids and fractures
in the rocks and soil
beneath our feet here.
So groundwater is water in the ground
that's filling these voids.
And what do the voids look like?
Well, this is a classic view
of the different sorts of porosity
that you see in geologic materials.
Porosity refers to the open space
between the sand grains or rocks
or whatever is making up the subsurface.
So we can see that these can be
what are called primary openings,
which are the spaces between, say, sand grains.
If you thought of beach sand,
there are spaces between those grains.
Those are the pores.
And depending on how well sorted it is,
whether all the grains are the same size like here
or a mixture of size,
you could have either more or less porosity.
So that's called primary porosity
because that exists
from the time the rock was deposited.
Secondary openings are things that occur later
like fractures or dissolution
or solution features
or caverns in a karst environment or a cave environment
where openings come later
than the rock was originally deposited.
We have both sorts of porosity in Wisconsin.
What does that look like in the real world?
Well, on the upper right, you see a
optical microscope picture of some sandstone
right here from under Madison, some Cambrian sandstone.
And you can see the beautiful rounding
and sorting of these sand grains.
That's a wonderful aquifer.
That's where all of you are getting your water.
If you're drinking any water in Madison,
it's coming out of an aquifer like that.
And here is how it looks in the field on the lower left.
Cambrian sandstone, you can see some cross-bedding in there.
Typically, rocks like this have a porosity of about 15%,
10% to 15%, meaning 10% to 15% of that material
is just open space and that's where
the water can be stored and transmitted.
Now if we go to other kinds of rocks
like limestone or dolomite,
which are not really made of grains,
but instead are... more of a...
formed from layers and layers of tiny sea creatures
that have deposited over the years
and then recrystallized,
this rock is not very porous naturally,
but it has lots of cracks and fractures in it
and the water comes from cracks and fractures.
So you can see this would be a
outcrop that you'd see up in Door County, Wisconsin,
or other places where we have a lot of limestone
or dolostone, dolomite.
I'll talk about the water table
and what the water table is
and what the groundwater system looks like.
So this is a cross-section of a
typical cartoonish landscape.
This is the land's surface.
And anywhere here in Wisconsin,
if we dig a hole or we drill a well,
sooner or later, we're gonna hit water.
And that water, where that sits is called the water table.
The water table is a surface.
And below that surface, it's called the saturated zone,
and all the pores and those cracks
are full of water at that point, so they're saturated.
Above that water table, the pores are not full of water.
They're full of air or carbon dioxide
or something besides water,
probably a mixture of air, carbon dioxide,
and maybe some other gases sometimes.
Often right over the water table,
there's a thin zone called the capillary fringe
where water gets pulled up into the pores
by capillary action,
just like you'd have water moving up in a soda straw,
but that's a fairly, fairly thin zone,
only a few inches thick or less, usually.
But it's important to remember
that the water table is the top of the saturated zone
'cause you're gonna see some other diagrams
that have water tables in them.
And then it's always important to think about the water cycle.
And I'm sure most of you,
if not all of you, understand this,
but water falls in a cycle
starting as precipitation, rain and snow on the landscape,
and then moving in
to partitioning itself as it hits the landscape,
and much of it runs off the landscape.
Some of it evaporates
and a bit of recharges
or percolates down and becomes groundwater,
and then it becomes part of the groundwater system.
And so these rocks and soil down here are
what we would call aquifers
because they can transmit groundwater
along these flow lines that might go to a well
if there's a well there or they might go a long way
to discharge to a lake or a river,
a discharge point,
or they might discharge to our wetland here.
So here comes a wetland.
And then we have other process like evapotranspiration
that's gonna take that water back out
and it's gonna become part of the cycle again.
So remember, it's a closed cycle.
So understanding how all these things fit together
is part of our understanding here.
Groundwater moves in three dimensions.
Groundwater is not static.
It's not just sitting in one spot down there. It's moving.
And in a humid climate like Wisconsin,
it's usually moving from higher parts of the landscape
to lower parts of the landscape.
But it's not just moving horizontally,
it's moving vertically as well.
So if we take this cartoon apart,
we can see that groundwater is-- it's moving laterally,
but it's also moving in these curving flow paths
that go moving down under the higher parts of the landscape
and then actually moving upward
under the lower parts of the landscape
to discharge to a surface water feature.
This happens to be a stream,
but it could be a lake or a wetland as well.
And so it's quite common
to see upward groundwater flow
under these low parts of the landscape.
And so, any of you have ever seen a spring
or a flowing well, an artesian well?
You're getting water that's coming up with pressure
from somewhere deep below the surface,
but that pressure is related to the altitude
at which that water first entered
the groundwater flow system.
And then the other interesting feature here
is that groundwater is moving two different directions
from say the top of this hill.
That's called the groundwater divide.
And that divides groundwater into flow systems
so that on one side of a hill, groundwater's going one way,
the other side, it's going the other way
just as you would have topographic divides in the landscape.
The only difference here is that we can move this divide
by doing things like pumping water
or doing a change in land use.
We can actually move that divide sometimes.
Groundwater moves slowly.
Generally, in a place like Wisconsin,
we're only talking about inches
or a few feet per year.
There are exceptions to that.
In limestone or dolomite where those fractures are,
like I showed you, you could get much more rapid movement,
tens to hundreds to even thousands of feet per day sometimes.
But in general, think of tens of feet per year,
which is not very fast.
Groundwater is moving fairly slowly.
And if we get into something like a clay,
we're talking inches or millimeters per year sometimes.
Sometimes very, very slow.
I already mentioned groundwater flow systems,
but to put it in another context,
we need to think about the whole system
as a place that starts with groundwater recharge
or groundwater as entering the landscape
and then it's moving to groundwater discharge
at a surface water feature
or sometimes to a well,
and then those flow paths, again,
don't just go laterally,
they go vertically downward and then back up.
And depending on the local geology,
they could go very deep, and that water could be in the ground
for maybe thousands of years or they can go very shallow
and just be in the ground for a few days.
And of course, the length of the flow path
has an influence on the chemistry of the water
because the water is dissolving things along the way
and then the water may also be picking up
things that are spilled on the surface
or things that are coming down from the soil.
So understanding the flow path is also important.
And again, I'm telling you all these things
because when we get to think about wetlands,
all these things become important
in understanding wetlands.
I mentioned groundwater recharge.
And here we can think about wetlands a little bit.
Are wetlands places that groundwater is discharging
or groundwater is recharging?
And so this might be a typical cross-section
of a place in Wisconsin.
We have clay moraine.
A moraine is a glacial deposit.
And often in Wisconsin, those are gray clayey
and they create a hummocky upland.
And because it's clay, we may say, well, there's
not much recharge going on there because it's clay.
Over here is more of a sandy place
and there's maybe more recharge there.
And sometimes people want to protect recharge areas
and so they may say, "Well,
"we better protect this recharge area."
But we don't often think of what's going on
up here on the clay moraine.
And in fact, there may be some wetlands up there
we want to protect,
and those wetlands are getting recharge
that's locally up here.
These might be kind of high elevation wetlands.
And so to protect those wetlands,
we need to understand
not only the area to protect down here
with the high recharge area,
but we need to protect the upland recharge areas too.
And so wetlands can be either discharge
or recharge areas depending on where they fall
in the landscape.
So let's look again at our wetlands.
We take our wetland here and we blow it up,
where does the water come from?
The groundwater component of this wetland,
where is this wetland getting its water?
Well, it's getting rainwater and it's getting some runoff,
but it's also getting groundwater
from some sort of zone that's hydraulically upgradient
that we would call the capture zone
or the contributing area for that wetland.
And so that means that this is the area of the landscape
which is usually-- Whoops, let me go back here-
usually in map view kind of an oval-shaped zone
where groundwater is coming from recharge,
rainfall is landing on the soil,
on the ground, becoming groundwater,
and then that groundwater flow system
is discharging to that wetland.
So this is the area
where groundwater is actually feeding that wetland.
And that's one of the things we do as hydrogeologists,
is try to figure out where those areas are.
So, many of you are probably familiar...
with the springs over in Middleton,
Pheasant Branch Springs, so this Pheasant Branch,
one branch of Pheasant Branch Creek.
This is looking sort of south,
and Lake Mendota would be off here.
If you ever go out to the Pheasant Branch Conservancy,
there's a wonderful big spring,
one of the biggest springs in Dane County, by the way,
that's right here, that's the start of this creek.
And it's nice that it's protected in this conservancy.
My colleague, Randy Hunt at the USGS a few years ago
did some computer simulations
looking at the capture area
or the contributing area of groundwater for that spring.
And so if you keep that spring in mind
and look at this map,
he figured out that the groundwater coming out
of that spring and feeding this wetland around it
comes from a mile or so away in this oblong area.
So that's the contributing area for that spring.
And the reason it's important to know that is that
some of this is an agricultural area, there are highways here,
there are potential contamination sources,
there are potential land use changes
that if they occur up here can affect that wetland.
And so this is why we try to understand these things.
But this is also a good example
of a capture area or a contributing area
for a particular wetland.
So when we think about groundwater and wetlands,
what are the questions we wanna answer?
How much groundwater is coming into a wetland,
the water budget of the wetland?
How fast is that groundwater coming in?
And that has to do with hydraulic gradients, hydraulic conductivity,
which is the ability of that rock and soil
to transfer water,
and its porosity, which I talked about.
How far away this had come from?
That has to do with the groundwater flow path.
How dynamic is this system?
How much does it change seasonally
or with time or with climate change
or even daily in some cases?
What are the characteristics,
the chemical characteristics of the water?
Here we can think about water quality,
mixing of different waters from different places,
even contamination sources on the surface.
And finally, what's the conceptual model of the system?
So what is a conceptual model?
Conceptual model
is a pictorial representation
of the groundwater flow system
that's basically a picture.
We do a lot of modeling in science.
And people often think of models
as something we do with computers, and we often do.
But before we start,
the best practice is to make a cartoon or a picture
or a small diagram of really what you're talking about.
And that's what we call a conceptual model.
What are the sources and sinks
and boundary conditions on a model?
Just what's the concept of your wetland here?
And so for wetlands,
there are at least four conceptual models.
And I'm gonna talk about these and show you examples of them.
And these diagrams are a little small to see,
so I'm just gonna move ahead and you'll see these again.
But they all have to do with different landscape settings
in which wetlands occur.
So let's start in Wisconsin and go to some places here.
I don't know how many of you have been to the Mink River,
the Mink River Estuary up at the tip of Door County.
Really lovely, lovely place to go.
But there are springs there.
And the springs there can be characterized
by a conceptual model like this
which is what we would call a complex flow field model.
Now I'll simplify this for you.
You see two kinds of lines on here.
You see light,
your kind of narrow, dark lines.
Those are lines of equal hydraulic head
or hydraulic pressure.
And then you see these thick or blue lines
with little arrows on 'em.
Those are lines of groundwater flow.
And so groundwater is going to move from higher
to lower hydraulic head,
and it's going to move generally
sort of perpendicular to these equal potential lines
or these lines of hydraulic head.
And so when you see a--
This is called a flow net,
and one of the things hydrogeologists try to do
is to delineate what these things look like
and then try to understand how the groundwater flow lines go.
So you see here,
when you see groundwater coming to the surface,
this is an area where we'd expect wetlands to occur.
If you see the flow lines going downward,
you think no, they're not going to occur there
because that's a place where more recharge is happening.
So if we look at the Mink River, why are we interested in it?
Well, it's a really cool place.
It's a natural area,
a very pristine freshwater estuary
going into Lake Michigan.
And it's really a fairly unsullied place.
It's also the home of the Hine's emerald dragonfly,
which is an endangered species that were asked to look at.
One reason we got involved up there
is the Hine's emerald dragonfly takes--
It has to reproduce in small carbonate springs...
in this wetland,
and the nature conservancy and others
wanted to know where the water was coming from
for these springs, so we did some studies
up there at these sites in Door County
to try to understand where the water was coming from
for this Hine's emerald dragonfly habitat.
Interesting enough,
the immature Hine's emerald dragonfly
is just this little beetle thing here
that doesn't look very attractive,
but that's what people are worried about saving.
So the conceptual model though
is that we have this carbonate aquifer,
fractured rock,
we have a flow system
or we have the water table
that's indicated by this dashed line,
and it's sloping down toward the wetland
and toward Lake Michigan here.
We have recharge that's occurring
somewhere up to the left here
and then these groundwater flow paths are going down
and they're coming back up
to the wetland where there's general seepage in the wetland
and there are also springs.
And the Hine's emerald dragonfly
needs carbonate groundwater, and so this is a carbonate rock,
and so water that's going through there
is rich in carbonate minerals.
And so that's good habitat for reproduction.
And so when we looked at that,
here's an air photo of the Mink River Estuary.
This is Green Bay up here, Lake Michigan out here.
And this is the Mink River right here.
And the Hine's emerald dragonfly habitat
and the springs are right in here.
If we zoom in, look at a different photo,
you can see the spring channels here, and these are springs.
And this is all a huge wetland complex,
all being really sustained by groundwater.
It's interesting though, there are some little point discharges
that cause these little springs to come out.
The other interesting thing is this photo was taken
a few years ago when Lake Michigan was low.
If we took a picture like this now,
it would look a lot different 'cause the lake is higher
and most of this is underwater right now
because Lake Michigan has come up.
I also just like to show this because it's so cool.
This is lidar imagery of the same place...
really high-tech topography measured with lasers.
And you can really see the glacial topography
and the way the landscape has gotten sculpted
as the glaciers went over here.
But this is the kind of information
we use now in our mapping.
But anyway, the springs and wetlands
we're interested in here are right in here.
What we did, we built a computer model
based on our conceptual model.
And so this is actually an aerial view.
The blue lines here are lines of equal hydraulic head,
or think of it as a map where the water table is.
And then we can do these flow lines
that are perpendicular to those.
And that outlines the capture area for this,
the springs and wetlands here.
So this would be the area
where groundwater comes from
that actually ends up here.
And we call that the
contributing area for these wetlands.
And so the hashed area are the actual habitat
for the Hine's emerald dragonfly,
and the outlined area is the region
where the water is actually coming from,
the groundwater that's sustaining these springs
and this wetland here.
So that's one type of wetland
and that's the kind of thing that we study
when we're trying to understand the groundwater,
where the groundwater's coming from.
And while we do this,
we can figure out the water budget,
how much groundwater is actually coming in,
what percentage of the overall wetland water budget that is
and so forth.
Let's move a little farther down Door County.
We were up here, let's move down to Peninsula State Park
and the Niagara Escarpment
which is this big dolomite cliff here.
We can look at a different setting for springs here,
springs that occur along a break in slope.
And so if you think of that escarpment,
here's that done in a conceptual model.
We have the land surface,
a big escarpment down to the lake.
And we have a water table in there
that intersects the land surface
right at this nick point or this break in slope.
And so we would expect springs
and wetlands to occur at a place like this,
along this break in slope.
And if you go to Door County,
along the Green Bay shoreline,
it's actually what you see.
Here's a conceptual pictorial
diagram of that area
done by my friends, Stan Collins,
Nancy Alton, who are landscape architects,
just to show you some of the features of Door County.
But the important thing for the talk tonight
is that there are springs and seeps and wetlands,
perennial wetlands right along the base
of this escarpment, and that's what we see here.
And so again, the reason that these springs are here is
that the water table is sloping downward, hitting in a lake,
but it's very near the surface of the land,
right at this nick point right here.
And that's why we see these perennial wetlands in this place.
And again, we can look at the contributing area for that.
This is a map view of the same area.
This is called the Bayshore Blufflands Reserve.
It's along the Green Bay side of Door County.
And we again did some computer modeling
to figure out the contributing area
for the springs and wetlands right along the shoreline.
And again, the groundwater is coming from
even a couple of miles away to discharge there.
So we can understand where the groundwater
came from there.
Now let's look at a different sort of spring,
and we'll move down here to Walworth County
and the village of Eagle in the Kettle Moraine area.
So here, we're looking at a different geologic
and hydrogeologic setting.
And I showed you this picture before where we have a
stream or a river environment
with contiguous wetlands along its shore
and groundwater coming in from the sides.
And this is the kind of environment you get
along the Mukwonago River Watershed,
which is a really high quality
wetland-rich watershed there.
I wanted to point out the importance
of riverine environments in groundwater,
is that there's a lot of geochemistry
and geochemical, biogeochemical changes that go on
right under a stream, right under a wetland
in zone called the hyporheic zone
where there's a lot of-- this is only a few,
maybe a few centimeters or a few inches thick sometimes,
but it's zone where there's a lot of biological activity,
geochemical activity,
and you get a lot of chemical transformations
that are occurring that can change water quality
right under the stream or the wetland here.
So here again, you see a stream
and you see groundwater converging
to put water into that stream
and into that wetland.
If we go to the village of Eagle and the Mukwonago River,
here's the little village of Eagle is up here
and the Mukwonago River goes through here
and it goes through some really high-quality places
that you've probably heard of like Lulu Lake,
Eagle Spring Lake,
and there's a couple of state natural areas here.
A really pristine environment.
Reason we got involved with this study was that
the village of Eagle had two new groundwater wells here
that were drilled to serve the village.
And this is about a mile--
They're about a mile south of the village,
and they're about a mile or two miles
north of the Mukwonago River.
And the question was were these wells,
the pumping of these wells,
was this gonna impact the river and the wetlands around it?
So we developed a groundwater model
for this area.
And as part of that model, again,
we were able to figure out the capture area
or the contributing area for the Mukwonago River
and these wetlands here.
And that's what's shown on this diagram.
This shaded area and all these dark lines
are computer-generated flow lines
going to the river and the wetlands around it.
So this is where the groundwater is coming from.
Now you see this funny pattern right here.
This is the contributing area for those two wells.
So even though those two wells are right here,
they are not pulling any water out of the wetland.
They are just pulling water from this local area right here.
And we can conclude that those wells
really had very little impact on the overall system.
Had they been located in a different place,
they might have had more impact.
They were actually located in a fairly good place
to prevent any impact to the river there.
This also shows you the importance of a groundwater divide
because there was a groundwater divide here between this watershed
and the Scuppernong Watershed which is up here.
And you can see that this groundwater
doesn't cross that divide
unless maybe the pumping can change it a little bit.
But groundwater is coming to the Mukwonago
just from this area, but not from up here.
So it's a real boundary there.
Now let's move to yet a different sort of wetland,
and we'll go way up to Northern Wisconsin
to Bayfield County and the upland sand barrens there
to show you a kind of wetland that's precipitation dominated,
which doesn't mean it's not connected to groundwater at all,
but it's a place where there's groundwater--
It's recharging groundwater rather than the other way around.
So here we see that the water table
is actually sloping away from the wetland.
Groundwater is tending to move downward.
And the wetland is not getting any water from groundwater,
but it's getting water from precipitation.
We see this sort of upland wetland
in places like in Chequamegon-Nicolet National Forest.
And a good place is
what are called the sand barrens in Bayfield County,
sometimes called the blueberry barrens
because it's ripe with blueberries
certain times of the year.
These are old sand dunes.
And the water table can be
a couple of 100 feet down sometimes,
but there are small wetlands up here
that are maintained mostly by rainfall
because this is such a sandy environment.
There's very little runoff.
And that water is then,
after it sits in the wetland for a while,
it gradually soaks in and moves down
to recharge the groundwater system below that.
So these are important areas for groundwater recharge
and the wetland function there is pretty important
for maintaining groundwater recharge in this sandy place.
Now sometimes,
I mentioned things can change with time,
and sometimes things, surface water and groundwater
can become connected or disconnected
different times of the year
or different years depending on
what the weather and the climate are doing.
So here's an example of a place where there's maybe a stream
that was flowing with water.
And it may have been a place where
it was somewhat disconnected from the water table here,
but water was still coming out of the stream
and moving into the water table, and that's why you see
a little mound in the water table here.
But if that stream dries up in a very dry summer,
it's gone and the water table becomes completely flat.
So, here's a complete disconnection
of the groundwater and surface water.
Another example of a wetland like that
is something that I had the pleasure of observing
when I spent some time in Zimbabwe
about 10 years ago.
I worked with some people there on wetlands
in one of the conservancies they had in Zimbabwe.
And in Zimbabwe and Africa, they call these wetlands pans.
And these are the sort of watering holes that
you think of the animals coming and getting a drink
in the dry times and so forth.
But in the dry time of year, this is really the same place.
And you can see that this wetland
is completely dried up
in their dry season, which is November.
And then it's full of water and it's got flowers and plants
and it's a pretty nice-looking place in February.
And we were doing some research there
with South Africans
and some of the scientists from Zimbabwe about trying to
understand where the water came from for this wetland.
Was this groundwater that was rising up
or was this entirely surface-water-dominated?
And so we did some coring by hand
because this was out in a place
where we couldn't get any motorized equipment out.
So we did a lot of hand augering out there.
And what we discovered was that this pan,
this is a cross-section,
was several meters above the regional water table
and in fact never intersected the water table.
So this is a wetland that's completely,
always above the water table,
which doesn't mean it doesn't have anything to do with groundwater,
because when the water soaks in,
it gets down and recharges the groundwater table down here.
But there's a lot of unsaturated zone in between the two.
So this was the profile of the landscape that we developed there
based on these core holes that we drilled
that went from this pan over to the Save River here.
And so that was really interesting work,
but just another kind of wetland to see.
Now we have a lot of lakes in Wisconsin.
And lakes are sort of similar to wetland.
Of course, they represent outcrops of the water table.
And we do a lot of conceptual modeling of lakes too.
Lakes can be places where
they're receiving groundwater
from around their perimeter, or they're seepage lakes,
they're losing groundwater everywhere,
or they're flow-through lakes where groundwater is
flowing in one side and out the other.
And they're very analogous to wetlands
because basically a wetland in a way
is just a lake that's very shallow,
but has sort of the same features.
We spend a lot of time trying to understand how lakes fit
into groundwater flow systems for all the same reasons:
understanding the lake water budget.
And related to that, of course, are springs.
And groundwater is sustaining springs
and springs are usually located
in places again where there are wetlands.
Wetlands and springs often go together.
In the last few years, we've done a lot of work
at the Geological and Natural History Survey,
mapping and compiling records of springs in Wisconsin.
There have been over 10,000 springs
identified in Wisconsin.
There's probably more than that.
Those are the ones we have records for.
As far as big springs, which are over one cubic foot per second,
which is a pretty darn big spring,
there are fewer of those, there are a couple of 100
or more of big springs that people really would note,
although they haven't all been mapped.
And we've just finished up a new mapping
of the big springs in Wisconsin.
But these are all related to where wetlands are as well.
To show you how springs are important,
I love this picture because this,
if you know where Donald Park is
out near Mount Vernon,
this is a picture of people from the town,
the village of Mount Vernon
out around a place called Big Spring in Donald Park
100 years ago or so.
And you can see there's a brass band,
there's people in their Sunday best.
Shows you that springs were a pretty important place.
And here's the whole town having their pictures taken.
That spring is still there and you can go there,
and this is what it looks like now without a brass band.
It's a pretty neat place and if you go there,
there's boiling sand meaning the hydraulic gradients
are making that sand churn
and sort of boil down there
from the hydraulic gradients coming up.
So I recommend a visit to that place.
And just to show you what that's like,
here's another spring from our statewide spring inventory,
some underwater photography just showing how
the groundwater coming in is causing the sediment there
to be roiled up.
So springs are pretty neat places,
but they're always often related to wetlands, of course.
Finally, let's finish up
with talking about high capacity wells
and things that might affect wetlands
that people do.
Basically, high capacity wells
are what we use for water supply.
All the water in Madison is coming out of high capacity wells.
Probably heard of high capacity wells
being used for irrigation of crops.
They're a pretty important feature of our
landscape and our society now.
High capacity wells pull water out of the ground
and they do two things that are just inevitable.
They lower groundwater levels around the well
and they reduce groundwater flow
to nearby surface water features like wetlands.
And so understanding how those things are related
is important for understanding how to protect wetlands.
And the way that works, here's again some conceptual models or cartoons.
If we have a groundwater flow system
and this here, it's shown as a river,
but it could be a wetland or a lake or whatever,
we have again this recharge area up here,
we have flow lines that are going down
and then they're discharging here.
If we put a well here,
near the stream in this case,
and we pump that well, the well causes a corner depression.
That's the drawdown of the water table
above the well here, making that cone.
And that water's getting pumped out.
And because that water is getting pumped out,
that water has to come from somewhere.
And so it's produced by,
first of all, dewatering part of the aquifer here,
but also diminishing the amount of water
that's hitting that stream.
Water is still coming into the stream.
You can see the arrows are still going there,
but there's maybe not as many of them
and there's a little less water for the stream
'cause that water's coming out of the well now.
And here we've increased the pumping of that well even more.
And so now we've actually reversed the flow
and we're pulling water out of the stream
to feed the well.
You don't get something for nothing.
If you're gonna take water of the well,
it always comes from somewhere
and something else gets depleted.
So you've probably heard of the Little Plover River.
It's an area of the state we've done a lot of research on in the last few years.
It's in the middle of our potato-growing area in Wisconsin.
It's a very important vegetable industry,
potatoes and corn and so forth.
But it's also very dependent on irrigation.
And so there's been some controversy over irrigation wells.
So we did a project there a couple of years ago
looking at how irrigation wells in that area
were affecting or interacting with the Little Plover River
and the wetlands around it.
Little Plover River was historically a trout stream.
It's now a state fishery area.
But it's right in the middle
of a number of potato fields.
It has a lot of nice looking wetlands
associated with it.
Here's the Little Plover River.
It's just a couple miles south
of the village of Plover
and then Stevens Point.
Here's its watershed, its surface watershed.
And here's the river itself.
And all these little dots are irrigation wells,
high capacity irrigation wells
that are used mostly for potato growing,
some for corn, and some for beans.
And the question we had was
how are these wells affecting the flow
in the Little Plover River, because there was a perception
that over time, the flow had been diminished.
And there were questions about was that
related to, say, climate change?
Was it related to something else
or could it be traced to just these wells themselves?
And frankly, the records weren't always all that clear.
So here again, this is the results from a model.
You have these lines.
These are these groundwater water table contours
going from higher to lower.
And so we expect groundwater to be flowing
perpendicular to those lines.
So if we take all the wells away and we do a model
without any wells in it
and we look at the contributing area
or the capture area for the river
and the wetlands around it, it looks like this.
This is called the no pumping simulation.
And you can see how-- Just take a look at the size of that.
And so that means that any water,
groundwater that gets into this area
eventually ends up somewhere in this river.
And so there's a balance between
how much water is discharged by the river
and the size of this area.
And then we look at it today with the wells.
And you can see it looks a lot different.
It's kind of jaggedy-looking and that's because these wells,
many of them are intercepting water
that previously went to the river.
And you can see overall
the capture zone is smaller.
And so if you overlay the two, you can see that
it is significantly smaller than it used to be.
And we can trace that directly
to the number of wells that are pumping,
are causing this to be smaller.
Because it's smaller, there's less groundwater captured by the stream.
There's less water going into the river
and so we would expect the flow to be less.
And having a model like this,
we can then do experiments and see which of these wells
we would have to take out or move around to different places
to improve or to restore
flow in the river and flow to wetlands around it.
And actually, there are some groups
that are using the model just for that purpose now.
So to finish up today,
some of the take-home messages are that
wetlands and groundwater and surface water
are all part of the same system.
They should be thought of as one single resource, managed together.
You can't manage one without managing the others.
And you can't affect one
really without affecting the others.
All water comes from somewhere.
And sometimes in my career...
I know people understand this at some point,
but they think you can pump water out of the ground
and it has no effect on anything 'cause it's a limitless supply.
It's not a limitless supply. Everything's connected.
So if you take water out of one place,
it always affects something else.
And so understanding the water balance
is critical for management decisions.
Wetlands are connected to local groundwater systems,
and they are largely controlled by geologic
and topographic settings.
And pumping from high capacity wells
near streams and wetlands can reduce stream flow
or reduce water levels in wetlands.
But these impacts,
they depend on things like the amount of pumping,
the distance between the wetland and the well
or the stream and the well,
how long the well was on and a lot of other things.
So all those are parameters that we have to think about,
but these are some of the main takeaways for here.
I'll stop there and answer any questions you might have.
(audience applauding)