This course will cover the agricultural and urban water quality issues in Florida, their bases, land and nutrient management strategies, and the science and policy behind the best management practices (BMPs). Students will learn to evaluate BMP research and analyze its role in determining practices and policies that protect water quality.
Water in Florida
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From the course by University of Florida
Sustainable Agricultural Land Management
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From the lesson
Water for Agriculture
For week 7, we will wrap up nutrient management and then move to water for agriculture. We will dive deeper into the water of Florida and then begin the topic of irrigation management.
Meet the Instructors
George J. Hochmuth, Ph.D.Professor
Urban and Agricultural Environmental Sciences
Hello everyone and welcome back. Today I want to start a short section on
water resources. And water management, specifically
irrigation in agriculture. Everyone realizes the importance of water.
We talked a lot about water, water quality.
And I want to talk some now about quantity, because honestly in places like
Florida, it's very, very hard to separate the two.
We want to start with just a general overview of the water cycle, the
Hydrologic cycle. And I've given you a fairly simplified
diagram here in this slide. There are several parts of it that we want
to focus on. Obviously for agriculture, we're very
interested in precipitation, rainfall, snow that might accumulate and add water
to the system. We've learned about how water infiltrates
through our soils. Rain water can do this, especially if we
get more than we want at any one particular time.
We can have run off, and we've learned how to deal with run off, with some of our
soil conservation practices. We'll talk a little bit later on about
evapotranspiration and water requirements for our crops.
So, all of this cycle goes on and the inputs and the outputs from the cycle are
very much interest to us as far as talking about the water requirements of our crops.
And how we can make up for deficiencies in natural sources of water by irrigation.
Here's a pretty scary thought. Most all of the water on this globe is
salt water. This picture, this diagram brings it home.
Very much for me. About 2.5% of the water on the globe is
freshwater. And you'll notice that of that, two thirds
of it is locked up in ice and snow. So about somewhat less than 1% of the
total water on the face of the earth is available as freshwater for us for
drinking, for consump, human consumption and for growing our food.
Agriculture is the largest user of this fresh water.
This slide shoes water use consumption, by sectors.
Agriculture is the largest, about 75 percent of the fresh water withdrawals are
used for irrigating. For producing our food.
Now agriculture doesn't use water in a vacuum, it's not out there just using
water, it's doing it on our behalf. So, for example, our food if you like to
eat vegetables and fruits, about 90% plus or minus of our fruits and vegetables are
water. And so for example, if we're consuming an
orange, a fresh orange, the orange is about 85 or 90 percent water.
And how did that water get into that orange?
It came through, probably, irrigation practices, that the farmer used, to
produce that orange. So agriculture is extremely important and
yes uses a lot of water but we just need to remember that, that water is being used
by agriculture on our behalf for our food production.
Now there are areas around the globe and it doesn't take very long to do a search
and find many of these examples where water is, is, water supplies are stressed.
And I, I'm going to give you an example of one on a, world basis something here in
the United States we'll talk about and also Florida.
We've already mentioned some areas in Florida that are stressed.
On a global basis there are many areas. An, on the globe that are stressed by
water. And, you can see those up here, on the
orange and the yellow colors. The scale is presented here, so the darker
the blue, the less the stress is, or the less vulnerable that water, supply would
be. And most of the times the stressed is
caused by lack of water, lack of available water and also by high demand or
increasing demand in these areas, sometimes a combination of the two.
For example in central Asia, the drying of the Aral sea is one of the examples that
you find very frequently. Over the years the size of the sea is has
declined because the water has disappeared.
And there are some that argue that the drying of the sea is related to increased
diversion and use of water for agriculture in the area.
Just recently here in this country we've had examples of stress on water.
For example, the Mississippi River, the Great Lakes.
The levels of water in those water bodies, have declined.
We learned about the Mississippi water, shed.
In this particular case, we've been experiencing several years of, of drought
conditions. And, for example, on the Mississippi
River, it not only. There's not only a decline in the water
for such uses in urban areas or for agriculture, but also it has a negative
impact on commerce. And in this picture you can see ships
moving barges up and down the river. And when the water level is so low the
loads have to be reduced on those barges and they're restricted to less of the
river, so fewer barges can, can move up and down the river at any one time.
Water in the United States is depicted water use in the United States, is
depicted in this, in this figure. The pink line is the increase in
population. And one of the interesting things that
you'll note at least in this country the water consumption, or the water use has
fallen slightly and, and leveled off after the 1980s.
That's one of the interesting things that we'll, we'll touch on a little bit here.
Here's another slide that has an interesting story to tell, particularly
about agriculture. Here are the total water withdrawals by
several use categories. Public, for example irrigation wi-, which
would be mostly agriculture. A large amount of water in this country is
used to cool the electric generating power plants.
And if you look at the water use, again the same kind of story is told.
So for thermal power again the amount of leveling off of the amount of water
that's, that's used there. Here's agriculture, the same thing, the
blue, the bluish lines. A leveling off, maybe even some would
argue a decline since it's peak in the, in the 1980s.
That's a good story to, to tell about agriculture, and the reason is because
over these years many more farmers have adopted water conserving practices some
best management practices for irrigation on those farms.
It's a little bit hard to tell from this particular picture because of the colors
that were chosen, but the far left histogram bar, the purple one if you
follow that, that's the public supply. If you follow that across with time,
that's the only sector that's actually increasing in water use.
So that tells me that we've got some, we've got some ways to go, with, in our
urban areas and our residential areas domestically to become more efficient in
using water. If you look at, a little bit more closely
to Florida, obviously we have a couple major wa-, sources of our water, ground
water about two thirds of our water that we use in, in Florida comes from our aqua
first. And if you look at how that's divided up
here's the surface water pie over here and you can see a large amount of the surface
water pie is, is used by agriculture, public and power.
And then the same the same sectors are large users of ground water.
Here's agriculture and public. So agriculture plays a, a major role in
the utilization of water, in both those pools of water in this state.
In the state of Florida the management of the water resources to a large degree
falls to what we call water management districts.
And I've given you an outline of the state and a geographic range of these five water
management districts. The water management districts manage and
acquire, when needed, lands for water management purposes.
For water conservation for example. They manage the consumptive use the
aquifer re recharge and also well construction and permitting.
They also do technical studies on the water resource.
For example, some of us at the University of Florida use funds provided by the Water
Management Districts to study irrigation. Particularly irrigation efficiency that
will result in reductions in water consumption by our agriculture industry.
And for us in Florida, this is where a lot of the advances have been made.
Through this kind of public and public private with the growers working together
to develop and institute and adopt best management practices for conserving water.
Here's the Suwannee River, I think we have looked at this picture before, the
Suwannee River runs through one of our water management districts, the Suwannee
River water management districts, district.
And the Suwannee River runs through an area that's heavily agriculture, oriented.
And also we've mentioned before, the dominated landscape by the springs that
are a major tourist attraction. So everyone has a major interest in the
Suwannee River and what goes on. Around and on its banks, particularly with
agriculture. And so there's a lot of emphasis in that
area of the state on water efficiency and helping growers adopt best management
practices to conserve water as much as, as possible.
So I guess the question's boiled down to do we have enough water, and are we using
it wisely? And how can we help agriculture become as
efficient as possible in, in water use. As we studied before I like the idea of a
budget approach. We studied budgets when we looked at
nutrients, nitrogen and phosphorous in particular on farms and looked at the
inputs and outputs of nutrients. On a, on a farm.
We can do the same thing with the water budget.
So you can find, you can describe in, the inputs, for example rainfall and snowfall.
Even though I'm in Florida. We don't see snowfall, at least not very
often, but for the folks, north of me, that would be a major input of water into
the system. Flowing rivers that come across a
particular, area that we want to describe a budget for would be another, input.
Outputs, we're going to talk a little bit more about, plants and their water use.
We call it evapotransporation. Well we have evaporation from the surface,
from our soil surface. And we also have transporational water
losses from the plants themselves. That's where the plants take up the water
through their root. And it travels up through the plant and
most of it exits through the leaves and back out into the atmosphere.
Agriculture uses a lot of water for irrigation, for crop production.
But also for other purposes, and I'll show you a list of those in a minute or two.
And all of these enter into agriculture's water use portfolio or profile.
And all of those areas should be areas that farmers would want to take a look at
to see how they can improve their efficiency.
And then also an output obviously would be where we use water in our, in our homes.
Here's a, a quick look at what a budget might look like.
This happens to be one for a portion or a part a region in the state of Kansas.
And you can see it looks very much like the hydrologic water cycle, and in fact it
really is very similar, except that we've, we've quantified those various pools of
water in the, in the hydrologic cycle. So, for example, here's 2.58 inches of
runoff, here's evapotranspiration loss. You can see how big they can be..
And here's the stream inflow. We have water moving through the soil and
back to the aquifer. And so there's difference, different pools
of water in the budget just like we learned for nutrients, and we can quantify
those. Sometimes it takes estimations to get the
best estimate of the of the quantification.
We can do these water budgets just like we talked about nutrient budgets on various
scales. There are if you search you can find water
budgets for the world, the global water budget.
You can find them on a regional basis, as much as this one is for Kansas, for
states. There's a water budget for states like
Delaware even. You can also look at water budgets on a,
on a watershed scale. I found it interesting that it was very
difficult to find water budgets. Where quantifications of water inputs and
outputs on farms, specific farms with specific farm practices.
There needs to be much work obviously down at the farm level on determining water
budgets for farms. So water budget when, when the outputs
exceed the inputs just like with our nutrient budgets we have problems.
And if you recall back to this, the picture or the video of the Suwannee
River. If we do water budgets for that particular
area, we want to maintain the Suwannee River, levels.
And we want to maintain the water in the springs.
Because of their value, for tourists. But at the same time, we want to make
enough water available in our budget for farmers in that area to carry on their
business of. Producing food and, and livestock
production. So as water tables drop from more output,
more utilization, then in that particular case that's not a good thing because the
spring levels drop and the springs start to dry up.
And that's an economic negative e, economic impact.
Remember back to the triple bottom line. That's an important aspect to that part of
this state. So water is extremely important to
everyone in that regard. So I think knowing something about the
water budget helps us make big decisions about water and where it needs to go and,
and how we can, how we can try to determine best management practices to try
to conserve. If you're going to far in the output
direction, what is driving the output and can we do something about it?
And I think that's where best management practices and knowledge about them are
very important. Florida is underlain by important
aquifers. The biggest of which is the Floridan
aquifer system, and this is where we draw most of our ground water for agriculture
and, and also for urban use. Minimum flows and levels are a way to
track water in these, in the natural system, and these are established for
water bodies in order to prevent significant harm as a result of.
Excessive withdrawals. These minimum flows and levels are
determined by the Water Management Districts, and are reviewed by Department
of Environmental Protection. So here's a picture of how a, an example
of how a water a minimum flow level might work.
So here's a natural system might contain agriculture for example and these MFLs are
designed to prevent harm to this overall system the net, the water resources or the
ecology of the system by permitted withdrawals.
So the idea is that you can manage and control the withdrawal by permitting so
that it has no negative effect on the natural ecosystems and these MFLs then
define the how long. High, how long these high, intermediate
and low water flows, should occur or should be allowed to prevent, prevent
harm. The water levels are going to fluctuate
but the MFLs describe how they're going to or how they should be allowed to fluctuate
and still maintain the natural system and so that we can prevent no harm to the, to
the water bodies. Ground water because we use a lot of it in
Florida. It's a major source of our water.
Really doesn't recognize water boundaries. Our boundaries ca, you know for example so
the, the ground water doesn't recognize boundaries, in these so called water
management districts so, it's very hard to manage.
The water in the ground. And, this brings us to the issue of water
utilization and currently there are challenges in, in a state like Florida
where you have such huge demands. On water.
And so for example, if you have an area that is withdrawing water if the
withdrawal is at such a great amount you can lower the water table.
And that water table might be lowered enough to impact a water body, a stream or
a spring. And that's, even from a long distance
away. And so those are the kinds of scenarios
that cause water management district officials, and other interested parties to
come together,and work together, so that the withdrawal.
In one particular area doesn't negatively impact, another area.
And that's a tough process for everyone to come together.
And, and work together to achieve. Over-pumping has another negative impact.
Particularly in, state like Florida. And for coastal states up the east coast,
of this country. As we.
As we withdraw fresh water, if we withdraw it at such a rate that we reduce the
amount of fresh water to a, a level that allows Salty water or sea water to intrude
and we call this salt water intrusion and when this happens it effectively makes
this source of water here where this pump is, ineffective.
Because if we're using it for irrigation, we can't irrigate crops with salty water
and we can't drink salty water. So that's why these, the situations or
these, processes like MFLs are so important.
Because we want to minimize the chances that we degrade, the source of water that
we have available to us, by over, extraction.
There are 44,000 plus or minus farms in, in Florida.
Many of em doing irrigating but not all of em are, are irrigating.
They're growing crops maybe grasses and pastures that do not require irrigation or
at least a large amount of irrigation. And I've given you some figures here on
water use by agriculture. Half of the, the fresh water withdrawal is
due to agriculture. And half of this is due to a couple of our
major horticulture sectors fruits and vegetables.
Recall that these are very, very valuable. In the state there are large, make up a
large portion of the state's agriculture economic value.
And because of our demands that we as, as consumers put on our vegetables we want
high quality and irrigation is a very important place, a very important role in
producing high yields and high, high quality vegetables.
So it's no wonder that we irrigate vegetables.
We get 54 inches of rain in this state, plus or minus.
And you might say, well that's a, that's a lot of water, and it is.
This state is, very blessed with, with ample rainfall.
The problem is, it seems like it never rains when you really need it and so if
you think back to those vegetable farmers trying to produce high yields of high
quality vegetables. And they enter into a drought period, when
they're not getting enough rain. Then that's when they need the irrigation
system to supplement the rainfall. You might want to take that just as an
aside, you might want to take that 54 inches of rainfall and there's enough
information out there, in publications on the Internet, about Florida, in other
words our land area. And how much water is in an inch of rain.
And figure out how many gallons of water, fall on this state, each year.
And then look and compare that to the amount of water that agriculture uses
every day. I think it'll be an interesting
comparison. Here's some other interesting information
about water. These are some values that are very
interesting to me in terms of the amount of water that it takes For example 70
liters of water to make an apple. And obviously there's not 70 liters of
water in that apple. But over time, in terms of growing that
tree and producing the apple out in the field, then perhaps cleaning, washing the
produce as it's being packed and shipped. So there's a lot of processes that go
into, produ, producing, our food. And also 120 liters of water to make a
glass of wine. So for those of us that like a glass of
wine, in the evening, that's a sobering, thought.
Agriculture water use, doesn't stop with what we use to produce our crops.
That's the, evaprotransporation part of it, and we'll learn a little bit more
about that in our next lecture. But we also use water in many other,
functions on the farm. Field preparation, for example.
Sometimes, we need to irrigate a field to provide, put moisture into the soil so
that we can actually, for example, with vegetables, make raised beds and cover
them with plastic mulch, a very important component of vegetable production.
Crop establishment. Sometimes, we need to irrigate the soil to
speed up or enhance or help improve the uniformity of seedling germination or
transplant establishment. Cooling our produce sometime we use water,
for example, to cool sweet corn when it comes in out of the field on a hot day.
We want to cool that sweet corn, so that, it maintains its, sweetness, during
shipping. So cooling and using water during the
cooling, process is extremely important. We as a consumer, many consumers may not
understand. That use of water on the farm but for some
vegetable producers that's a significant use of water for just cooling the produce
and maintaining that quality that we want to see when we buy that ear of corn in the
food store. Sometimes Mother Nature deals some blows,
at certain times of the year. For example, our fruit production, our
vegetable production, our strawberry production.
Freeze protection is a very important part of maintaining, a crop.
Particularly here in Florida when we have those changes in weather, during the
spring our strawberry industry in central Florida can be subject to freezes.
And so growers use water to help protect that crop from, freezing.
And that, results in a, a large withdrawal of water from the ground water to put on
that crop and keep it from freezing. The, the freezing process or the freezing
of water, you might see those pictures sometimes on television about growers
using waters to protect their crops. And you see large amounts of ice formed on
those crops. As the water freezes and gives up what's
called it's latent heat of fusion and that heat helps keep that fruit or that leaf at
about 32 degrees which is the mixture of water and ice.
And so as long as the growers keep applying water or sprinkling water on the
crop during the freeze they can protect it to some very cold temperatures.
So that is the way that process works, but it requires, continual application of
water. Washing and cleaning our produce and
processing, our produce also requires water, on the farm.
In some areas the, the country where we have dry climates and soluble salts
buildup in the soil, we use fresh water to move those salts deeper and below the
root, system. Leach them away.
These salts are not like nitrogen. They're usually calcium carbonate or
gypsum, calcium sulfate, those kinds of salts.
They're detrimental to the growth, to the germination of seeds and the growth of
young transplants. So water sometimes on those farms is used
to move those salts deeper into the, the soil and to keep the crops from
experiencing soluble salt injury. And also our animal industry you,
obviously uses water for drinking. So there are many, many uses of, of water.
We might think and look at irrigation and see that but behind then scenes
agriculture is using considerable amounts of water.
But again, remember it's on our behalf because we as consumers want readily, high
value, high value and high quality vegetables and for example and that takes
water. So what can we do to make sure that we're
being as efficient as possible on our farms.
Helping farmers to adopt best management practices for irrigation, so that those
growers are using only the water that is really required.
It's good for them too because growers realize that the less they have to pump,
the less money that they're spending to grow the crop.
So there's a return on investment issue just like we saw with fertilizer.
So sustainable irrigation management is very important to farmers.
And fortunately in, in this country and around the world there's been a
considerable amount of research on developing irrigation systems and teaching
farmers how to use these more efficient irrigation systems.
And having irrigation systems change with time and become more and more efficient.
We'll look at some of this information about water use efficiency on farms and
how we can understand water use on farms, and help farmers adopt.
Best management practices in their irrigation management and we'll take a
look at that in our next, in our next lecture.
But just keep in mind as we learned earlier in the course, the population is
still growing in this world and the food demands are still increasing.
So farmers are going to be asked to produce more and more food and irrigation
is a critical, a must component of successful food production.
We need to understand that as consumers and we also need to help farmers adopt
best management practices so that even though they are using water on our behalf
we all can be as efficient as we possibly can.
So if you look at a few take homes at least from this particular part of the,
the work on water. We know that water is vital to life and we
also know that there is a tiny fraction of it that we can use readily on this planet
and so we want to avoid overusing water. We want to conserve it as best as
possible. We want to help farmers because
agriculture is a large water user, we want to help farmers understand to learn and
adopt. Best irrigation practices so that, so that
they can produce out food in an efficient manner.
So human activity is having a big impact on not only the water quality as we've
spent a lot of time looking at but also on water quantity.
And agriculture, again to produce food on our behalf is the largest water user.
So here's where we can possibly continue to make some positive impacts on improving
efficiency and conserving water, is through working with our agriculture
producers.
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