- 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 introduce to you Kevin Masarik.
He's with both UW-Extension and UW-Stevens Point.
He was born in Milwaukee, went to Thomas Moore High School.
Got his undergraduate degree in Water Chemistry
at UW-Stevens Point
and got a master's degree here
at UW-Madison in Soil Science.
For the last 12 years, he's been working for both
UW-Stevens Point and UW-Extension
doing ground water research and outreach
for the State of Wisconsin.
Tonight we get to hear about Nitrate in Wisconsin's
Groundwater: What, Why and Where.
Please join me in welcoming Kevin Masarik
to Wednesday Nite @ The Lab .
(applause)
- Thank you everybody.
Today I'm gonna be covering a topic that is probably
one of the more challenging groundwater
quality issues that we're dealing with,
not only in Wisconsin, but other Midwestern states
and countries as well.
It combines a lot of my work over the past 12 years
with UW-Extension testing private wells.
It also highlights some of the research I did
as a graduate student in the Soil Science Department here.
We're going to cover a lot of ground today.
Just to get everybody on the same page,
we'll go over some of the basics of groundwater
and how it works,
clear up some misconceptions,
and then get into the topic of tonight,
with is Nitrate in Wisconsin's Groundwater.
Basically, what is it; why do we care;
how does it get into groundwater;
where in Wisconsin do we find it;
is it getting better or worse;
and then, what are ways to improve
the situation that we might find?
Nitrate, especially in Dane county,
has been in the news as of the past week or so.
Statewide there's been a number of stories as well,
so it makes it a very timely topic.
Basically, groundwater...
when we talk about groundwater,
it's important that we understand that groundwater
is not an underground lake.
It's not an underground river.
Our groundwater here in Wisconsin doesn't come from
Canada or Lake Superior.
Groundwater is just rain or snowmelt that infiltrates
down through the pore spaces in the soil
eventually reaches a point below the land surface
where all the empty spaces in between
the soil particles or all the cracks in between the rocks
are filled with water.
Again, it's not an underground lake.
It's not an underground river.
It's just the water that occupies the empty spaces
in the geologic materials below our feet.
Groundwater is always moving very slowly
through those tiny spaces from what we call recharge areas,
those areas in green on this slide
where water can percolate down to what we call
discharge areas or discharge features.
And those are going to be nearby lakes, rivers, streams,
in some cases wetlands.
And if we look at our,
what we call aquifers,
aquifers are basically groundwater storage units.
We have different layers of geology in Wisconsin,
starting with our basement rock
which is that crystalline bedrock.
Crystalline bedrock doesn't hold a lot of water,
so our groundwater sits in those geologic layers
above that crystalline bedrock.
So we have layers of sandstone,
layers of dolomite,
which some people sometimes refer to as limestone.
It's very similar.
Dolomite or limestone is a highly cracked
or fractured rock.
So think of this diagram up here as being
what dolomite or limestone might look like.
And above that we have layers of
sand and gravel that were left behind
or deposited by the glaciers.
The geologic materials, or aquifers,
really determine things like how quickly
our groundwater moves
or how quickly our groundwater becomes contaminated.
Water moving through cracks or fractures
can obviously move much quicker, much faster,
than water moving through maybe the tiny pore spaces
in between sand or sandstone rock aquifers.
So geology is critical for understanding
some of our groundwater issues here in the state.
When we talk about getting an idea of how groundwater
flows through the landscape,
it's important we all have a understanding of a watershed.
And that's just the land area where water originates
for lakes, rivers or streams.
And we know that gravity carries water
from high elevation to low elevation.
It's pretty obvious when we're looking at water
running off over the land surface.
We can see that during spring or after heavy rain.
But what's happening below the landscape?
And this cartoon kind of illustrates that;
where if we scrape away the unsaturated zone
and just look at the water table which is the top of our
groundwater resource or top of the groundwater aquifer,
we see that the groundwater table has changes in elevation
just like the land surface does.
And if we look at high to low elevation,
that gives us some sense for how the groundwater moves.
So drawing those lines perpendicular to the contours
gives us some indication of the direction
of groundwater movement,
showing that anywhere where we have water table
intersecting the land surface that's typically where
we're going to find a river, a lake or a stream.
And their groundwater is flowing to those features.
We see that groundwater moves laterally,
it also moves somewhat vertically.
So if we're near what we call groundwater divides,
these dash lines right here,
that groundwater is going to move down
before it moves laterally.
And that's just in general how groundwater flows
or how we typically think of groundwater movement.
And if we want to experience groundwater
and that interaction of groundwater to surface water,
there's really no better time to see that
than going out on a cold winter day.
Here's a stream in Central Wisconsin.
Many of the lakes here are froze over completely.
They've lost all their heat.
But if you travel to some of these small creeks or streams
or springs out in the wilderness areas
or out in the woods,
it's a great opportunity to see that interaction of
groundwaters and surface waters.
It was negative 10 degrees on Monday when I went out
and took this picture.
This stream is no more than probably six inches
to a foot deep in a lot of places.
Yet the whole stream was wide open and flowing.
And that's cause groundwater is flowing to this feature
24 hours a day, 365 days a year.
The thing that we often forget about groundwater is that
it's a relatively constant temperature year round,
roughly 50 degrees.
So it means it's colder in summer and warmer in winter.
And 50 degrees at this time of year
is much warmer than the atmosphere.
Until that stream loses its heat,
it's going to remain flowing.
One thing that might be a little bit difficult to see
is right in this little pocket or pool,
there's a grouping of about eight brook trout
that have culminated or kind of migrated up
into the headwaters of this stream.
And this is just a picture,
a close-up of one of those trout
in its spawning or breeding colors.
And I always like to show the diagram on the right.
Those are blue areas where the majority of streamflow
for those watersheds and those streams
comes from groundwater.
And if we overlay the trout streams on top of that,
we see that there's a very strong connection
between where we find trout
and where we find groundwater- dominated streams and rivers.
If we want to look at how
groundwater flows through Wisconsin,
we're getting back to that concept of the watershed.
Wisconsin has three major basins that we see here,
Lake Superior, Lake Michigan, Mississippi River.
We have what we call subcontinental divide
running through the state.
That subcontinental divide separates the water that flows
to the Atlantic Ocean and the water that eventually
makes its way down to the Gulf of Mexico.
Next to the continental divide over in the Rocky Mountains,
this is the second most prominent divide
in the United States.
And we can see based on the stream movement,
we can see how those watersheds separate
and how the water in those different watersheds moves.
Those major basins can be divided
into what we call regional watersheds.
There's about 20 of them in the state of Wisconsin.
And when we talk about how groundwater
gets to those major rivers or streams,
we really have to think about an even smaller unit
those sub-watersheds.
If we think of those regional watersheds as bathtubs,
within those bathtubs are sub-watersheds
which we might think of as little egg cartons.
And when we start talking about these little egg cartons
and this blue outline is an example of just the scale
we're talking about when we're talking about groundwater,
and the distance it moves before it reaches one of those
surface water features.
When we concentrate certain land use activities
or concentrate groundwater pumping activities
within these small watersheds
it's much easier to see where we're going
to have issues or where we might have problems.
So, I think this is a good analogy.
It's not mine, but it's one I use very often
to help people understand just how local an issue
groundwater really is.
We call groundwater Wisconsin's buried treasure,
I think with good reason.
We rely more heavily on groundwater in Wisconsin
than almost any other state in the country.
Ninety-five percent of Wisconsin communities;
almost 900,000 private residential wells.
Most of the water for livestock, irrigation,
dairy operations, 1/3 of industrial use,
1/2 of commercial use
and then we can't forget that it supplies most of the water
to our lakes, rivers and streams.
It amounts to about 75% of Wisconsin residents
that actually rely on groundwater
as their primary water supply.
So it's extremely vital to the vitality of our communities
and our quality of life here in the state.
We're going to transition now into the kind of nitrate
or the nitrogen side of the talk
now that we all have an understanding
or a background on the water cycle
and the role of groundwater in that.
It's important when we talk about nitrogen and nitrate
that nitrogen is neither created nor destroyed.
It's just this continual cycle of
one form of nitrate to another.
It's a very complicated cycle.
There's nitrogen that we find as gases in the atmosphere.
There's nitrogen that we find in organic material
and plant material.
Some of that material becomes integrated
into our soil which is labeled in this case,
the Vadose Zone.
And then some of that nitrogen can also make
it's way into groundwater as nitrate.
This might look like a very complicated diagram.
The things to keep in mind:
the dashed orange boxes represent
losses out of the Vadose Zone
or out of the soil system.
These green boxes right here on the right-hand side
labeled Sources of Nitrogen
are going to represent nitrogen inputs...
inputs into the soil.
Within the soil we're going to have
various forms of nitrate.
It can be transformed from organic matter.
It can mineralize into ammonium ions, which is NH4.
It can be further transformed through a process
known as nitrification into nitrate.
Both nitrate and ammonium are forms that
plants can take up.
Some of that nitrogen is removed through harvest time.
Some of the nitrogen that's incorporated into plants,
if that residue is returned to the soil,
will be reintegrated into the soil system.
Really for the groundwater system
and the challenges that we're facing,
we're concerned about that nitrate ion.
Nitrate is a negative ion.
Positive ions tend to have an affinity for
soil surfaces and soil particles.
Negative ions don't have that same affinity.
Because nitrate ions are dissolved in water,
wherever that water moves,
there's a potential for that nitrate to move as well.
And that's the main concern,
how is that nitrate getting into our groundwater?
Why is it there?
And, are there ways that we can reduce
or at least minimize the potential for leaching losses?
What are the concerns?
Why do we care?
Nitrate exported to surface waters has the potential
to end up flowing to the Gulf or the Atlantic Ocean.
Saltwater systems tend to be very nitrogen limited.
Therefore any additional nitrogen is going to
cause excessive nutrient...
or its excessive nutrients will contribute
to excessive algae growth.
That excessive algae growth can negatively affect
the ecological health of those fisheries downstream.
And we can see from that diagram,
Wisconsin, a large portion,
is within that Mississippi River watershed,
where it is contributing to what we called Gulf Hypoxia.
The other concern which is maybe a little bit closer to home
is how nitrate potentially affects human health.
And when we talk about the current nitrate standard
of 10 milligrams per liter, our primary concerns
really are infants and pregnant women
because of a condition called methemoglobinemia.
The condition is commonly referred to as blue-baby syndrome.
There's possible correlations to
central nervous system malformations.
Within adults there's possible correlations to
non-Hodgkin's lymphoma, various cancers, thyroid function,
some studies suggesting diabetes in children.
It's important that we keep in mind that many of these
health related studies are statistical studies that
provide correlation between nitrate and health problems.
But sometimes there are studies that don't always agree.
So the science isn't conclusive.
But there is enough evidence that most health professionals
would urge caution...
certainly for infants and women who are pregnant,
but also urge caution for older populations as well,
to avoid long-term consumption of nitrate
at excessive or high levels.
The other important thing to consider is that nitrate is
often an indicator of other possible contaminants.
Because it moves so easily through the soil,
if we consider the various sources of nitrogen,
we might also be more concerned about finding things like
pesticides in the water.
Or if the nitrate is related to septic system effluent,
viruses, or pharmaceuticals or personal care products
that we might associate with septic system effluent.
So there's enough evidence that we do urge quite a bit
of caution for people when we find nitrate at high levels.
For the rest of the presentation,
just to get some sense of what these numbers mean,
it's important to compare them to standards.
The standard for nitrate, again, is 10 milligrams per liter.
At that level, we do not encourage...
we ask people do not give that water to infants.
Do not give that water to women who are pregnant
or may become pregnant.
And we recommend everyone avoid long-term consumption
of nitrate above 10 milligrams per liter.
Anything less than 10 is considered
suitable for drinking water.
Less than one is considered natural
or background levels.
So anything between about one,
or actually anything above one,
is giving us some indication that the groundwater
or the water in that area is being impacted to some degree
by the local land use.
When we talk about drinking water,
it's important to distinguish between water sources.
Know that public water supplies are regulated.
They're required to be regularly tested.
They're required to meet drinking water standards.
If the water doesn't meet drinking water standards,
they have to treat the water or perform some sort of
corrective measure to make sure that the nitrate
being distributed to customers isn't above that standard.
Those people on private wells
beyond the time the well is constructed,
they're not required to be regularly tested.
If anything is wrong,
it's not required to take corrective action.
The well owner really has to become their own
water utility manager, in a sense.
They have to understand what those results mean
and know what the proper next steps are.
And that's often a task or things that many homeowners
might not be aware of or might not understand
their role as a private well owner all the time.
When we talk about nitrogen
the thing that makes it difficult
is it's a critical resource for agriculture.
We wouldn't have the same agricultural productivity
on the land surface if it wasn't for nitrogen
and its role in increasing production.
If we don't replace the nitrogen in an agricultural soils
we are, in a sense, mining that nutrient
and other nutrients from the soil.
And as we mine it,
we're going to lose productivity over time.
So we've found ways over the centuries
to increase productivity.
Ancient civilizations farmed the flood plains
cause those soils were more nutrient rich.
We've known that adding manures or animal manures
will increase productivity,
rotating legumes or planting legumes
with certain crops.
Legumes are able to fix their own nitrogen
from the atmosphere and supply some of that nitrogen
to the plants for their growth and their needs.
We farmed prairies because the organic rich soils
that we found underneath those landscapes.
It wasn't until the World War 1, World War 2 eras
where the industrial fixation of nitrogen became
much more prominent.
The same process that was used to produce ammunitions,
the Haber Bosch process,
is the same process used to produce fertilizers.
So it wasn't until that time where we had commercially
available nitrogen being widely produced.
As a result of that commercially available nitrogen,
we have this cheap source of nitrogen now.
Manure is no longer quite as valuable as it once was.
So manure management these days
is a little bit more challenging
because often times it's treated more as a waste source
in trying to find ways to dispose of it or utilize it,
is often one of the more challenging things
that we deal with.
Especially in a state like Wisconsin
which is known for its dairies.
So when we look at fertilizer,
if a little bit is good, more must be better, right?
And that's true up to a certain point.
Plants up to a certain point are going to benefit
from that added nitrogen.
But we've found through yield studies,
through colleagues that some of which are here today,
that do research on soil fertility,
that there is a point where more nitrogen
actually doesn't add much benefit to yield or crop growth.
So we've developed yield response curves
that kind of suggest what are optimal rates
of nitrogen to maximize yield.
One thing to point out is that as you increase,
as you go along that x-axis, as you add fertilizer,
you're seeing that increase in yield or biomass.
Up to a certain point, we see that slope starts
to decline as you approach that maximum yield.
So the added yield starts to go down as we approach
that maximum point.
And therefore, the economic optimum,
the fertilizer that's going to achieve maximum profit
is never that maximum yield.
Because eventually you reach a point
where the fertilizer to increase yield
costs more than the benefit you're receiving
from that added yield.
So the economic optimum is always a little bit
slightly less than what we consider to be maximum yield.
Curves like this are what we use to recommend
how much nitrogen do different crops need,
or should they get to maximize profitability for the grower.
Historically, this shows the consumption
or the sales of fertilizer use in the United States.
We see that again, starting after the World Wars,
we see this increase as farmers become comfortable,
receive the equipment that allows
them to spread the fertilizer.
And we see it start...
you could debate whether it's leveled off completely,
but certainly that slope or that increase
has declined over time to the point
where we've seen a stabilization of how much
nitrogen fertilizers is being used.
It can fluctuate from year to year based on
the price of commodities and what's being grown,
the price of energy.
All those things will dictate how much fertilizer
is sold in any given year.
But we have reached a point where
we're not seeing the dramatic increase
in nitrogen use like we once did.
People are often curious how much nitrogen
should I use for different crops.
This graph, I think, is a nice illustration of
the various crops that we find in Wisconsin
and how much nitrogen is being applied
to the different fields.
And we see on this graph maybe 20 to 25
or 30 different crops
and this wide range of the different recommendations.
On the lower end is where you're going to have
all those legumes which are able to fix their own nitrogen.
Therefore we don't have to always supplement.
On the far end, we're going to see crops like
corn, potatoes which tend to require a lot more nitrogen
to achieve those economic, optimal yields,
Anywhere between about 160 and 200 pounds per acre are
recommended rates for nitrogen application of those crops.
Again, look at the variety of crops that we have here.
And if we think about the landscapes that we drive through,
we don't typically see this much variety on the landscape.
It's be great if plants were 100% efficient at utilizing
the nutrients that we apply but they're not.
I think these diagrams are a nice illustration
of the rooting system of row crop agriculture.
We have to realize that there's only an actively
growing root in the soil layer for a portion of the year.
The rest of the year, much of that soil layer is completely
bare if we're not doing things like cover crops,
or planting perennial type of cropping systems.
If we're strictly talking about row crops
where we plant in the spring and harvest in fall,
that leaves a tremendous amount of opportunity
or time period when we don't have actively growing roots.
So the diagram on the lower left is just the seed
at emergence, think April.
And the diagram on the right is the maximum rooting
depth which occurs about 60 days or so
after planting period.
Come late September, October is when those roots
start to die off and we don't have any more uptake
by the plant going on at that point.
So there's a scientist that studied
what is the efficiency of fertilizer
that we use in row crop agriculture,
such as corn, in the Midwest.
And he determined that these systems
are about 37% efficient at utilizing the nitrogen
that we apply as fertilizer.
This leaves roughly 60% or so that either gets
incorporated into the organic matter.
Some of it might volatilize and vent off into the atmosphere
and some of that nitrogen is going to be available
to leach into groundwater.
Understanding how much nitrogen goes where is a really
challenging question sometimes
and one that we're still trying to understand and study.
But we do have some idea based on the research
that I'll show next of how much of that
roughly 60% that's not incorporated
into the plant, makes its way into groundwater.
I just think the slide on the right is a good comparison.
It's basically the same scale.
So where you see those gridlines,
each of those gridlines represents a foot of depth.
The rooting depth of these different types of plants
and different types of systems is important to consider
when we talk about how the nitrate
gets into our groundwater system.
And in a native, kind of perennial, not even...
it doesn't even have to be native,
it could just be a perennial agricultural system,
those roots are always there.
They have a head start come spring.
They probably have a higher capability of doing
uptake later into the fall.
So some of the research I'm going to talk about next
is based on the work that I was involved in
in grad school.
On the lower portion are the links to
some of the research that's been published
related to this work.
It was a long term study comparing
corn agroecosystem at Arlington to a restored prairie
within a mile or two of the field site.
So we look, and if we see...
on this diagram you'll see there's kind of a difference
in the shade of green within that agroecosystem.
That lighter color area represents a portion of the
experiment where we looked at an unfertilized situation
and compared leaching loss and plant growth
to what we would consider to be optimal
recommendations for growing corn.
And again, those systems were compared
to that restored prairie.
If we look at the annual nitrate leaching losses
that we measured we'll see that the eight years
that are represented here cover a range of precipitation.
The diagram on the left is showing precipitation,
cumulative precipitation for each year.
So as we look at those dots we're basically adding
whatever precipitation was in that two week period
to the period prior.
So it's giving us some sense of cumulative precip
over the course of a year.
Each year we reset that so we can compare
one year to the other.
The bars represent the annual mean.
We had a nice mix of years with above average precipitation,
below average and the mean or median level.
And for long term study that's really what we want.
If we were to only conduct the study during the wet years,
we would get completely different results
than if we were to conduct that same study
in two or three dry years.
So this understanding of climatic variability
is really important when we start looking
into these issues such as leaching of nitrate.
The two diagrams on the right,
the upper one is for the no tillage system.
The lower one is for a chisel plow corn system.
And what's interesting about both is that the patterns
are somewhat similar between the two treatments
but just the wide range in variability of nitrate leaching
from one year to the next.
The highest year was responsible for
a large portion of the nitrate leaching
over the course of the whole study period.
That highest year occurred...
that was the wettest year
and it actually turned out to be a wet year
that followed a somewhat dry year.
So wet years following dry years are probably one of the
more critical times where we'd think about
nitrate leaching to groundwater.
The other interesting thing to point out
is that those dash lines represent the date that
fertilizer was added to the system.
And in a lot of cases, we saw significant leaching
occurring before we even applied fertilizer
in any given year.
That tells us there's a lot of carry over
from one year to the next.
There's probably some nitrate that leaches
prior to planting or application of fertilizer
that's coming from the breakdown of the previous
year's residue or organic matter.
So it's not just what's occurring in any given year
that we need to worry about.
We have to consider what was taking place that year prior.
What was the precipitation pattern?
What was the plant uptake in that year?
Understanding that gives us some ability
to better tailor our recommendations
for how much nitrogen we should be using.
If we look at the eight year summary,
the important points
to point out on this for the summary
is just comparing those leaching
losses. In the corn system, the total for the chisel plow
was about 303 kilograms per hectare for the total.
That's similar to what came out of the no tillage system,
about 277 kilograms per hectare.
If we look at the prairie,
the prairie was virtually insignificant.
We found virtually no loss of nitrate
below that prairie system that we were studying.
Much more efficient, granted,
we weren't artificially applying.
We weren't adding nitrogen to the system.
It was just what was coming in through the atmosphere.
But, much less nitrate leaching coming out of
the root zone of those systems there.
Of the percent of nitrogen that we applied,
about roughly 20% or so was lost to the groundwater system.
Twenty percent turns out to be roughly 32 pounds per acre.
So 32 pounds is leaching into the groundwater
compared to the 160 to 170 pounds
that we applied as fertilizer.
And this is under optimal management recommendations.
So a lot of times when we talk about nitrate leaching,
I think there's an assumption that people have
when they find nitrate in their water that it's because of
something that a farmer is doing that's illegal.
Or they're not following best management practices.
And what we find here is that even under
optimal management practices
we are going to expect some leaching loss
below these systems.
That's often a point that isn't made enough
is that nitrate leaching to some extent,
is inevitable.
Reducing that is important
but it's also challenging.
If we look at the situation I described previously
which was a continuous corn system,
we can look at other research that's been done
around the Midwest to get a sense for
is this typical of what we might see in other places
in the Midwest for other types of cropping systems?
And it really turns out that it is fairly representative
for what we see in other areas.
Anywhere between, in this case, 17 kilograms per hectare
per year up to 63 kilograms per hectare per year.
It's kind of the range for what we see in other studies
that have looked at continuous corn.
If we integrate a legume into that rotation
and do corn-soybean, corn-soybean,
we do see a slight reduction in what we'd expect.
Some of these studies are directly comparable.
Like Randall, et al., here it shows up
in multiple categories.
So that gives us some confidence in how we compare
these to the different treatments or the different
cropping systems that we might be interested in.
So the corn-soybean is slightly less.
If we looked at adding some alfalfa...
so this situation was a corn-soybean-oat
and alfalfa-alfalfa rotation.
We're adding some perennials into the mix.
We see that there's a reduction in the amount of
nitrate that's leaching into the groundwater.
And if we look at all perennial systems,
we see those concentrations of nitrate
being reduced even further.
So why is that important?
Because we can create this kind of model for what
we'd expect nitrate leaching below
different agricultural systems.
And it's largely dependent on the types of
cropping systems we have in place
which is obvious related to the amount of nitrogen
that we recommend be applied to achieve optimal yield.
So there's this continuum or this gradient
that we have to consider when we're wondering
about why we have certain problems in certain areas.
Added to the complexity of this issue
is that groundwater susceptibility is
not equal across the state.
The areas in red tend to be more susceptible
to land use impacts than the areas in green.
Not that the areas in green can't become contaminated,
it's just it's a little bit more difficult or challenging
for that nitrate to penetrate down into the aquifer.
So added to this leaching potential,
we can add a third axes which is that
groundwater contamination susceptibility.
And this graph really illustrates this baseline level
of nitrate that we'd expect in our groundwater
that's dependent upon the types of cropping systems in place
and the geology and the soils of a
certain region or a certain area.
Even under best case scenario,
we're always gonna have some potential
or some impact from adding nitrogen to these areas.
People always ask me what about septic systems,
and it's important we don't leave septic systems out.
Failing systems, yes, contribute problems
or issues to groundwater,
but even properly constructed septic systems
are going to be an issue for something like nitrate
or chloride getting into the groundwater.
Septic systems are really designed to dispose of
human waste in a manner that prevents bacteria
from getting into our groundwater.
What they don't do as good a job of
is getting rid of the nitrate or the chloride,
those dissolved ions, which have the potential to leach
into our groundwater system.
And the diagram on the right just shows
a plume of contamination.
Eventually that plume tends to get diluted out over time.
But that's assuming that we don't overload
septic systems all in one area.
When we compare land use impacts,
if we want to compare a kind of a corn
to a septic system to a prairie, we can do that.
We can look strictly at the source.
So if we're looking at corn, roughly 32 pounds per acre
is what we'd expect to end up in groundwater.
If we look at a septic system,
each system is probably releasing about
20 pounds per system, per year.
Those might look directly comparable or very similar,
but it's important to consider how that plays out
on the landscape.
Where most fields aren't being farmed
on one acre sized fields;
we're talking 20, 40, 60 acre fields.
Most septic systems in traditional world development
is going to be one system on maybe a 20 acre parcel
or a 40 acre parcel.
So if we want to compare that, this kind of gives us some
indication of the amount of nitrate that we'd expect
below these fields.
Another diagram here.
If we want septic systems
to achieve the same impact
or expect areas to have the same impact
as that agricultural field,
we'd be looking at a much higher density of septic systems,
roughly about .6 acre lot sizes
is what we'd need to have the same impact.
And in some areas we do achieve that.
We do see it in places right near Stevens Point,
where we have roughly half or one acre lot sizes
where we crammed together all these developments.
We put one well and a septic system on each parcel.
And what ends up happening is that
the septic system effluent leaches into groundwater
and can end up migrating into somebody's adjacent well.
So when we talk about development,
it's really important that we consider issues
or systems like this so that we're not putting people
in a position where their septic system
is contaminating somebody else's down gradient well.
It's often much more expensive to talk about
community water systems.
But often times there's a very good reason
to consider doing that.
So what do we know about nitrate and groundwater?
It turns out we know quite a bit.
There's been a number of studies over the past 30-40 years.
One of the better kind of studies that's performed
every so often is one that's done by DATCP.
And that study shows that roughly 9% of all private wells
in the state of Wisconsin exceed that
drinking water standard.
It bumps up to about 21% in agricultural areas.
We also have quite a bit of information from
private well water testing that we've done.
At our center, State Lab of Hygiene,
various county health departments,
that information has been combined into what we call
the Wisconsin Well Water Viewer.
It's an online tool that anybody can access,
and I'll go through a quick demo in a little bit.
We also have good access to public water systems
which, again, are required to regularly test
and report that information to the DNR,
which is stored in what we call the
Groundwater Retrieval Network.
This shows the map of known private well water
concentrations across the state of Wisconsin.
The blue dots represent those background or natural levels.
The green are slightly elevated.
The orange elevated a little bit more.
And the red would represent samples that are above
the drinking water standard.
It looks worse than it is.
The maximum value is always displayed on top.
So just note that even in the areas that are dark red,
there's going to be a lot of blue values below that.
So how to integrate this data in a way that makes
sense to people or can be used for decision making?
And that's where we came up with the Well Water Viewer.
It'll summarize information by county,
which is this map represented here.
The darker areas have a higher average concentration
than the lighter areas.
We summarize it.
It has the capability to summarize it by township level.
You can even take it down to the section level,
if you wanted...
but the detail starts to diminish as we go down in detail...
or kind of zoom in on the level of detail
that we're looking at.
If we have a minimum number of samples
to create that average, we give it a color.
Those areas in white just represent areas
where we don't have a lot of data
or information to be able to say conclusively
what the concentration might be.
But this shows the pattern for what we see statewide.
Certain areas have higher average
concentrations than others.
Central Wisconsin sticks out.
The area around Madison sticks out.
And there's kind of a line going from Door County
down towards Madison that also sticks out.
And those areas where we routinely see wells
above that drinking water standard.
We could think of it and look at the percent of wells
in a given area that exceed the standard.
And that's what this map represents.
So those areas in red are areas where one in four wells
are above the 10 milligram per liter
drinking water standard.
And it's going to be a similar pattern to the previous map,
just a different way of looking at the data.
The Well Water Viewer, which again is available online,
has the capability to generate tables
where it'll summarize information in any
user defined area if you were interested.
So how do we explain the variability
of nitrate across Wisconsin?
I've kind of distilled it down into three main things
that I think largely control where we'd expect
to find nitrate in groundwater.
And it's coarse textured surficial deposits;
those kind of deposits leftover by the glaciers;
areas where we see a lot of sand and gravel, are a concern.
Areas where we have shallow carbonate rock aquifers.
And areas where we don't have a very diverse,
what I would call, watershed land use portfolio.
And if we look at the coarse textured surficial deposits
and where we find those,
Northern Wisconsin there's a lot of 'em,
Central Wisconsin, the river valleys along
the Wisconsin River and Mississippi River.
There's a number of areas with these
coarse textured surficial deposits.
And there's a scattering in parts of Southern Wisconsin.
But especially in the Central Sands area
and along the river valleys,
the Wisconsin River and Mississippi River,
we see those high areas correlating really well
with where we have these coarse textured deposits.
If we look at that line from Door County down,
that correlates very well with areas where we have
what we call a shallow carbonate rock aquifer.
That carbonate rock tends to be highly
cracked or fractured.
In areas where we don't have very thick soil deposits
then to be very susceptible.
And the nitrate data illustrates those areas quite well.
And then what I call the watershed land use portfolio.
Watersheds where we have high concentrations of those
nutrient intensive cropping systems are also
one of the explanatory factors for what we see
regarding the nitrate pattern.
And it doesn't have to...
You know we look at this
and when we talk about the landscape,
it doesn't necessarily have to be a completely
natural system that's good for groundwater.
Just integrating more diverse crops,
more perennial crops, lower nutrient intensive crops
is one way to get from the far right side
to the left side.
We'll probably never get to zero,
but if we're talking about ways to reduce those impacts,
we have to really consider that land use portfolio
and the gradient that occurs along that continuum.
So this is just the agricultural lands of Wisconsin.
I don't know how well this shows up in the back,
but the green areas are those areas where we have
high densities of annual row crops.
The green areas are more forage, pasture, CRP lands.
And the areas where we have those,
the high orange or yellow color
correlate really well,
especially in the Southern Wisconsin region
around Madison, south of Madison.
A lot of that variability in the nitrate concentrations
can be explained just by the types of land cover
that we're seeing.
When we talk about trends in nitrate,
one way we've tried to get at that
is this public water system data,
which are required to test on a regular basis.
We looked at the change over time,
and we tried to figure out is there a trend to it.
Yeah, it might be different but is there enough data
to distinguish if that represents a significant trend.
And when we worked up that data,
we had just over 8500 wells.
And what we saw was in about 7500 of those wells,
there was no significant trend.
In 8% there was an increasing trend
and in 5% there was decreasing trend.
These are just examples of wells with decreases.
It's pretty apparent that in some of these
there has been a significant decrease
or a significant trend over time.
These are wells showing an increase in trend.
And then these are wells with no trend.
It doesn't mean that nitrate concentrations
didn't change over time.
It just means that if there was a change,
there was no pattern to it.
It points out to the value in having this continual record.
In some of these wells if we only had one of the low
values and then ten years later we had a high value,
but we missed everything in between,
we might make kind of erroneous conclusions
about what's going on.
So these are examples.
Again, it doesn't mean that groundwater
doesn't have any nitrate.
It doesn't mean that groundwater doesn't change.
It just means that there hasn't been a trend
that we've been able to detect in many of these wells.
When we look at the location,
this map shows the orange or the red dots
are wells that have increased.
The blue dots, which you probably can't see very well,
are decreasing.
And there's a number of yellow dots that are purposely
kind of transparent so you can kind of see the patterns
that occupy much of the state.
These wells were used to create this map right here.
And it shows the counties which have a higher percentage
of these wells that are increasing.
The blue are the counties that have a
higher percentage of wells decreasing.
The yellow counties, there's virtually no difference
between those that are increasing and decreasing.
But it helps highlight those counties
or those parts of the state where maybe
we need to focus more of our efforts
or look a little bit closer at what's going on
in those areas to explain those increases
or decreases over time.
Other data that gets at trends.
This is DATCP data.
And I think one of the positives
that they've found in their data
that if we look at the wells on the left from 1987,
we see large variability or large scatter.
Over time, those excessively high concentrations of nitrate
have gone down.
But the overall mean or median hasn't changed much.
And this slide kind of illustrates that
maybe a little bit better;
the slide on the lower portion where we see the spread
or the variability start to decrease over time.
But one thing that we notice is that
there's a increase in those,
the concentration of those lower level wells
or lower level nitrate values.
So if there's positive, I think it's that the excessively
high concentrations are coming down.
But the low values seem to be creeping up
a little bit in some cases.
This is a study of nitrate in Dane County that just came out
and I think it kind of comes to a similar conclusion
that the low values are increasing in some areas,
and the high values have come down over time.
But we see them converging.
So what I get out of a lot of the research
that's been conducted is that we'd expect nitrate
concentrations to stabilize over time.
I don't know if we're going to have much success
in those concentrations coming down to zero.
In fact, I don't see that happening.
But we, I think, can expect them to stabilize over time.
Why do we have nitrate trends?
What are the reasons?
In the shallow groundwater
some of the changes that we're seeing,
the annual variation is related to just changes in land use
that might be taking place.
In the deeper groundwater or the rivers and streams
when we notice trends in nitrate concentrations,
it's often because of that lag time between
what happens on the landscape
and our groundwater quality below.
And I've got a quick video that I think
illustrates that nicely.
This is a groundwater model.
It kind of represents a cross-section of the earth's crust.
That little depression area on the right hand side
of this model represents a river or stream.
And the both sides might represent what we would consider
to be groundwater divides.
So the sandy area is what we would consider
to be our watershed.
And then this example, it simulates what might happen if we
cut across the landscape, cut down all the vegetation
and applied nitrogen or some sort of compound
or chemical to the entire landscape.
How long would it take for that nitrate
to penetrate the entire aquifer?
So it goes pretty quick.
But when we see that green dye
which represents maybe nitrate,
it takes a while for that nitrate to fully penetrate
those deep portions of the aquifer.
And it takes a long time for that stream to completely
equilibrate with what's going on in the landscape.
So we'll watch it one more time.
It goes pretty quick.
But that kind of shows one of the challenges
in detecting trends, it's just that lag time
between what happens on the landscape
and the groundwater quality below.
So what can be done to reduce nitrate levels over time?
It's a challenging issue.
We saw from the previous clip that it might take years
or decades for what we do on the landscape
to have impacts to the wells or rivers and streams below.
We often have to have short term solutions
to many of our nitrate problems.
For municipal wells, that might be treatment.
It might be drilling a new well.
It might be blending water.
As of 2012, 47 systems have had to take remedial action.
And that's cost greater than $32 million as of 2012.
When we look at private wells, what options are available
for private well owners?
A new well has been estimated, on average,
to be about $7200 per year.
It's not guaranteed.
The deeper you drill is going to add expense to that cost.
Bottled water is about $190 per person per year.
Water treatment or reverse osmosis,
distillation and an exchange,
you're talking about $800 for that initial purchase price
and about a hundred dollars per year
in just routine filter replacement.
So short term, it's important we have short term strategies.
A lot of people are interested in what long term solutions
are available for improving groundwater quality.
And there's research investigating
improving fertilizer use efficiency.
So can we improve the timing or the delivery of fertilizer?
Are there compounds we can add to inhibit
the rate at which it transforms into
the leachable form of nitrogen?
What we see when we talk about the timing
and the inhibitors are that their effectiveness...
they're effective, but the effectiveness is marginal
and probably not likely to have dramatic impacts overall
in the areas where we're experiencing the greatest
issues or greatest problems.
Cover crops?...
28 - 31%;
these are studies that were done in Iowa.
I think we need to be cautiously optimistic
about the potential for cover crops to reduce
nitrate leaching to groundwater.
Cover crops are difficult to establish because
of the growing season limitations in Wisconsin.
So they might be slightly more effective in some of the
southern states or areas south of Wisconsin.
But again, cautiously optimistic
that there's potential there.
If we look at planting perennial systems
or using extended rotations,
that's an area where I think the research
conclusively shows benefits to groundwater quality.
But those are often...
the most difficult solutions to try
and implement because of the types of systems
in place are the types of things that there's crops
that there's a market for.
There are crops that farmers
have the tools to grow, to harvest.
We have the processing in place to process those crops.
A lot of those other crops that we saw on that diagram,
we don't always have the market for.
Farmers might not have the equipment for;
even if they could get it off the field,
they don't necessarily have some place to take it.
So policy comes into play here in terms of one of the
main challenges to implementing a lot of these solutions.
It's just the challenges of getting those crops
to market and getting farmers to the point
where they want to grow those is difficult.
So my conclusions.
What do we expect for nitrate?
What does it mean?
Where do we expect to go from here?
I think the positives are that there's been
some success in bringing down excessively high
concentrations in the groundwater over time.
I think one of the...
I wouldn't say it's a negative,
but one of the ongoing challenges is
that nitrate loss to groundwater is inevitable,
even under current best management practices.
And that's something that I think a lot of us
have to come to terms with,
is given our economy and given the current state
of land use some nitrate loss is inevitable.
And are we going to be accepting of that?
If not, how are we going to move forward from here?
Another positive is that in areas
where land use is consistent,
we can expect groundwater nitrate concentrations
to stabilize over time.
It's important we realize this increase in nitrate
we see in some of these wells is not an indefinite
increase forever into the future.
Eventually, the will stabilize.
Unfortunately, in some areas, they might stabilize
at levels above what's considered acceptable for drinking.
And a positive and a negative:
in areas where land use changes,
we can expect concentrations to either increase or decrease.
If we have an area that's forested,
we chop down the forest and we put it into production,
we would expect nitrate concentrations below that field
to increase over time.
If we have an area which is intensive
row crop agriculture now and we integrate some more
diversity, some longer, extended rotations,
mix in some perennial systems into that rotation,
we would expect the situation to improve,
not get to zero, but we would expect it to improve.
So I see some positives from the information
that's out there but I also see some ongoing challenges
to how we move forward from here.
And in summary,
if you've forgotten everything I've talked about,
this is the cheat sheet or the Cliff Notes.
Land use plus soils and geology really is what explains that
a lot of the nitrate groundwater quality issues
that we find in Wisconsin.
And with that, thank you.
And I'll take any questions if people have them.
(applause)