Test Video 9/27/24
Print
EmailSeptember 27, 2024
Video Transcript
Introduction
My name is bindu bhakta and i'm a natural resources educator for
Michigan State University Extension. In this short video I'm going to be
giving a demonstration using a groundwater model to reinforce
some of the key points that are presented in the water quantity
and the water quality section of the Michigan Water School.
During this video I'm going to give you a brief orientation
to the key features of the groundwater model
and also along the way to find some key terminology.
We'll then be able to review what groundwater is
how it moves and also demonstrate how groundwater and surface water are
connected and how they interact with each other.
Finally, we'll be able to discuss that even though we have a lot of water in
Michigan only a very small amount of it is usable,
and we'll be able to see that groundwater is a limiting resource
in certain parts of our state based on our geology.
And where groundwater is stored as well as some water quality issues
that may connect to that as well. So, briefly
Orientation
for an orientation of the groundwater model
I will direct you to the front of this model where
we'll be able to see imagine going out into a vegetated or a grassy area
and then cutting right through the soil beneath your feet.
Now you'll be able to notice some different layers of sand gravel and clay.
So, these finer the lighter tan represents finer sand down here
you might start to see larger rock materials so
gravel this layer here is a layer of clay. So you can see
different layers and depths you have clay a clay layer here but then
you don't have any clay over here. So, depending on where you are in
Michigan you'll find different depths and different materials
underneath your feet. What we'll be able to see
though when we get to the demonstration portion
of the video is to use different colors of
food coloring so that we will be able to clearly see
that within these layers of rock and soil particles we have a storage of
what we call groundwater. So, the other couple of things that I
wanted to point out are here are some drinking water wells.
You'll notice that they are constructed through different depths.
So, this one here is a deeper well that's constructed through this
bedrock down here which is a very hard rock material on top of which
is the different layers of sand gravel and clay.
We can call all of this material that was deposited on top of the
bedrock as a glacial drift material and we'll talk more about that
momentarily. So, you have this bedrock down here and
Water Cycle
we also want to just point your attention
to make a connection to the water cycle. So, if you imagine
over here where my hand is a rain cloud so water comes down
some of the water hits the land surface denoted by this green layer here.
The water that is able to make its way into
the layers of sand gravel and clay when those soil particles are completely
saturated by water. What you have now is a storage of
groundwater, and so when it comes filters through
those layers of sand grail and clay completely
saturates those particles and rock and then what we can say is that
groundwater keeps moving and moving. So, it'll move through these
materials depending on the type of material it may
move faster or slower, so it keeps moving over time
until it's able to discharge into a nearby river lake or stream. So,
we want to pay attention to the ground the surface water and groundwater
connection. We also noticed a number of wells
that are located here some vegetated areas
here is another body of surface water a lake
and again we want to notice in the demonstration
portion that there are a lot of places under our feet that
water is being stored you just don't um aren't able to see it without
the help of those food colors.
Groundwater
So, just to make sure that we understand what groundwater is
that is when we have rock and soil particles
that are completely saturated by water and so water is stored in the pores
space around rock and soil particles and also within fractures.
So, if you look at this hard bedrock material down here
you can see some cracks and spaces those are fractures that develop in this
very hard bedrock material and over time those fractures now
are able to store groundwater. So, that water that made its way through these
layers of sand gravel and clay and eventually we're able to
permeate through those fractures and be stored
under this area down here. We also want to make sure to note that
groundwater moves through different materials
or has different permeability depending on what it's moving through.
So, water travels through gravel pretty quickly i'm comparing that to
clay where permeability is slower we also
want to consider that certain materials hold on to water.
So, we can talk about porosity or that um term that defines the
capability of soil or rock to hold onto water.
So, if we look at something like this here which is a clay layer
that will basically is made up of very small particles
and are so tightly bound together that they
tend to hold on to water and prevent the downward movement of groundwater and
so we say that that has a very high porosity
because it just likes to hold on to that water.
Aquifers
We also want to consider where water is stored underground.
We want to make sure to go over the term aquifer
and that's simply a geologic media that can store and transmit
groundwater for whatever purpose it is intended.
So, think about that as an underground sponge.
So, when we think about aquifers there are a couple different types
here in michigan we have drift aquifers. So, I wanted to point your attention to
the laser layers of sand and gravel that are deposited on top of
this clay layer here so this will define
an unconfined aquifer up above here up above this clay layer.
When we have rock and soil particles that are
completely surrounded by water we have groundwater stored in
here and when it's stored within these layers
of sand gravel and clay in this glacial drift material that was
deposited on top of the bedrock that is what we
call a drift aquifer. We also have bedrock
aquifers here in Michigan. So, if you look at this
bedrock aquifer down here this hard rock material
we have these fractures that have developed over time
in the bedrock and as you remember water filters down into the
soil layers it completely saturates the rock and
soil that's in its path and it keeps on
moving and moving and over time groundwater then became
stored in these fractures in the bedrock and that's another type of aquifer down
here. This is fractured bedrock that stores
a sizable amount of groundwater that can be used for
whatever purpose it's intended for. So, drift aquifers where water is stored
groundwater is stored in the layers of sand
gravel and clay and this drift material,
also in the bedrock aquifer where water is stored in the bedrock down here.
We also want to talk about unconfined aquifers and confined
aquifers and what confining layers are. So, again
if you point your attention to this area here
so it's this topmost aquifer where you find saturated soil and
therefore, groundwater and it's stored in these
different layers up in here. You'll also notice this clay layer again
and then there's an area here that is storing a separate separated
area of groundwater, so it's separated by this clay layer here and the bedrock
below. So, that's what we call it confined
aquifer. And what that means is that this clay
layer is putting pressure on top of and down on this
geologic unit, or this aquifer here. So, what happens potentially is
that the pressure allows for the case where if there's a drinking
water well that's constructed through that clay layer there's pressure
put on this aquifer here and you may get a
resulting artesian well. So, water can
move it's way through here and naturally flow out of this artesian well here.
Another point about this confining layer oftentimes a good example of that is
clay is that this prevents the downward movement of groundwater. So,
again it holds on to water it
may over time eventually allow the groundwater to move through it but it
will definitely slow it down to some degree.
So, that is just to reinforce the idea of a clay layer
and how sometimes if water moves into the layers of sand gravel and
clay and hits that clay layer that may keep that
groundwater from moving any further down below. So, you can now
see that groundwater is stored in different units
of this model. For the remainder of this video
Dyes
we're going to be able to see how groundwater is stored below
where it's stored and how it moves by using
a couple different colors of food dye. So, the first demonstration we're going
to do is where we'll be adding some red food
coloring into this bedrock well.
So, it's a well that's constructed into this bedrock aquifer down here.
So, it will have the ability to pump water from that structure and pull
it up for whatever use that it is intended. So, we're going
to see how you may not have
been able to notice that there was groundwater stored there
before, but now this red color which will insert here into this well.
We'll be able to see how that moves through the model
and now you can clearly see how groundwater
filters into the layers of sand gravel and clay and then it can
be stored in this bedrock aquifer down here,
and move all the way through. So, moving slowly over time
until it has the ability to discharge here
at this river. So, now you can clearly see the connection of something that
happened at the land surface if it goes into this aquifer. So, it
moves into the ground water and then it keeps
moving and moving until it discharges again so that
groundwater surface water interaction. The next demonstration
will be utilizing some green dye.
So, I'm going to point your attention to this
vegetated area here. For example this lawn area
and we'll be able to see how water moves from the land surface.
How it can interact with the geology below and how it can
move into other bodies of surface water. So, this water bottle is going to
simulate a rainstorm, so that you can see two things.
One that some of the water moved directly
and ran off directly into that lake. Another thing that happened was
that some of that food dye made its way into these layers of sand gravel and
clay and saturated those soil
particles and then kept moving and moving
and some of it discharged directly into that
lake there. So, again illustrating the groundwater surface water connection.
Then if you make point your attention to this well here which is across
the lake from where that food coloring was located deposited
you can see how this groundwater under here pulls
this well pulls the groundwater that's being stored
from some distance away from the well. The last thing
that I would like to demonstrate is to see how there is
groundwater that is stored in this confined artesian
aquifer here, So, there's a confining layer of clay
on top and there's a confining layer which we call an
aquiclude which is that top surface of the bedrock.
So, those two layers can find or allow the groundwater that's being
stored in this geologic unit here to be contained within this
area. This aquitar or confining layer is putting pressure
down on this area of groundwater and so it can allow water to flow freely
into an artesian well. So, we're going to demonstrate that by
adding some blue dye here into this well number six,
so that we can put a little color into this confined
artesian aquifer, and then be able to see how the groundwater moves.
You'll notice that that blue dye is contained
within this area here. It does not filter into the bedrock because it's
being prevented from doing that by this aquiclude or this top surface
of the bedrock. You can see how it started over here and
it moved quickly to this area over here and that's also
to show you how groundwater moves over time.
Then you can also see how that blue color
traveled directly into this well and depending on the the amount of
pressure you may have that blue food coloring
flowing freely through that well or not. So, just wanted to show
how this confining layer will keep or separate I should say
the water that's stored in this unit here
and it'll contain it within that area. So,
there is no
mixing of the water that's stored in that
separated aquifer the unconfined aquifer up here
notice how the blue color stayed here and did not
affect other places of the aquifer. Through this short video I hope you were
able to get a better understanding of what groundwater is,
where it's stored, how it moves, and that there is a direct connection
between or interaction between groundwater and
surface water supplies and that you were able to get a better
visual of where groundwater is stored below our
feet. That it's able to be stored around
rock and soil particles it can be stored in bedrock.
So, there are different defined areas underneath our feet
that have a sizable amount of ground water that normally we can't see,
but through the use of some food colors allows us to see groundwater where it's
stored and how it moves.
