Hi. It’s Mr. Andersen and this is environmental
science video 5. It is on water resources. Our body is filled with over 60 percent water.
And this does not seem like a big deal because the earth is covered with over 70 percent
water. The problem with that is that most of that is sea water that we cannot use. And
the freshwater that remains, most of it is going to be frozen in ice caps and glaciers.
And so the percent that is really fresh water on the surface is a small percent of the water
on our planet and it is finite. The amount of water we have on our planet has never changed.
Now as the sun provides energy to the earth the water will move around through the hydrologic
or the water cycle but we have a finite amount of water. And most of it is going to be sea
water. We have a little bit of fresh water. The sea water moves around through ocean currents.
The fresh water could be divided into ground water, water underneath the surface and then
surface water which is on the surface. Now we need that water. We need it domestically
in the home to take a shower or to drink. But we also need it in industry to make our
goods. And most of it actually goes to agriculture to make the food that we eat. The problem
with water on our planet is that it is unevenly distributed. In some areas there is lots of
water. In some areas however there is going to be scarcity. And so humans have had to
learn how to store water, move it around and in the future we may have to desalinate some
of that sea water so that we can use it as fresh water. Now where is that ground water
stored? It is underneath the ground in aquifers that we can deplete. What about the surface
water? Well it can be stored in reservoirs that occur naturally or ones that are created
as we produce dams. And then we can move it around through aqueducts and even to the planet
itself through irrigation. But we have a finite amount and so conservation is incredibly important.
And economics have contributed to water loss and could help us to actually solve this water
conservation problem. And so the hydrologic cycle works like this. Anywhere there is water
on the surface we can have evaporation. That gets cooled and eventually leads to condensation
and precipitation. Once it is on the surface we call that surface water. It is running
over the surface. That could be lakes and swamps and rivers. After we have that water
hit the ground it can however be infiltrated into the soil and the ground itself. To give
you an example of that imagine I have a beaker here. Is it full? Well maybe full of air.
If I put marbles in it, is it full? No you can see there is spaces in it. What if I fill
it up with sand? Is it full? No. There is still spaces in there. If I fill it up with
water now we are starting to fill up that beaker. And that is what infiltration is.
As the water flows down into the soil we call that now ground water. Let’s say it is not
filling that whole beaker. It is right here. That point at which we have saturation in
the ground water is called the water table. Most of our planet is covered with water,
unfortunately it is seawater. It has salt dissolved in it. If you drink it you will
die. If we put it on our fields the crops are going to die. Now it moves around using
currents. We talked about that in the last video on the atmosphere, it is cells in the
atmosphere and coriolis effect. So we have these general trends in circulation. But also
salinity affects it. And so if we look at an area right here it is a high salt concentration
because we have a lot of evaporation. But up here we have a lot of melting of that glacial
ice. And so we are going to have a low salt concentration. And so the salt concentration
and differences in heat create these thermohaline circulations that really make that whole ocean
on our planet one system. Now if we look at fresh water it can be divided into water that
is above the surface, we call that surface water and then ground water. But what is interesting
is if we look to the sides of that stream you can see the water table in the ground
water. And so if you dig a hole right here it is just going to fill in with water because
of all of that ground water around it. Now this is an aquifer. It is storage of that
water in the ground water. We call this unconfined aquifer because the water can move between
the surface and the aquifer itself. If I were to dig down a little bit we could find what
is called a confined aquifer. And that is going to be stuck between this impermeable
rock down here and above it. Now let’s say we want to get to that ground water on the
surface. If we want some of the surface water we simply pump it out of the stream. But if
we want to get water out of that ground water we could dig a well. Now the water, we could
either pump out the water or sometimes we will have what is called an artisan well where
there is either enough gravity above it or enough pressure in the ground water so it
actually comes out. But as we use that well, just like using a stream the water table is
going to drop. And so we are going to start to deplete that aquifer. Now an important
term in filling an aquifer is something called recharge. So as we get water and infiltration
we are going to fill up that aquifer. But if the outputs, in other words if we pull
out more water then we are putting in, we are going to deplete the aquifer. And what
are we using all of this fresh water for? Well if we break it out using a pie chart
most of it is actually for agriculture. The growing of our food. We use some of it for
industry. And then some of it domestically in the house. The problem again is that it
is unevenly distributed on our planet. Brazil is going to have plenty of water. But if we
look in the desert southwest of the US or in the Sahara there is not going to be any
water right there. And so what have humans done? We have started to store water. So reservoirs
are an example of that. A big example would be the Three Gorges Dam that was built in
China. It was finished in 2006. And so this is what that river, the Yangtze River looked
like before they built the dam. And then they built the dam, finished in 2006. You can see
what it looks like then. So we are storing the water behind the dam. What is nice about
that, now we have water that we can use at will. We also can get energy from it, as we
run that water through a generator. We can control flooding downstream. And also we can
use that for irrigation. Or the Three Gorges Dam they are using to increase shipping on
the Yangtze River. So it sounds great. What is the problem? Well there is going to be
destruction wherever that water went. So we are decreasing 20 percent of the forest in
this Yangtze River. We are displacing over 1,000,000 people that used live there. We
also have evaporation of the water off the surface. And then we are going to have nutrients
that start to deposit there that would have normally moved their way down the river. And
that is going to disrupt wildlife. And so fish obviously cannot spawn, move up and down
in the stream. But it is also going to change the temperature of the water. An example.
There is a freshwater dolphin that went extinct in the Yangtze River and the Three Gorges
Dam may have contributed to that. We can also store it underground. That is naturally stored
in what are called aquifers. One of the largest ones on the planet is the Oglala Aquifer.
It is going to be found in the midwest. And so here it is in Nebraska. But it goes all
the way down to Texas and up into South Dakota. It is a huge aquifer. So if we look at the
amount of water stored underground it is over 1000 feet of infiltrated saturated water underneath
the ground that we can use. And you can see right here that there is tons of irrigation
going on. This is in Kansas. They are using center pivot irrigation so they can grow their
crops. It seems great but what happens again is that we can deplete that. So if we look
at, this is during a 15 year period of time, there is an increase in the aquifer in certain
areas but most of the time we are seeing depletion. And sometimes that aquifer has kind of disappeared.
And a lot of scientists think in the next 100 years the Oglala Aquifer is just going
to disappear. Why is that a problem? It could take another 6000 years to fill it up again
through natural recharge. Now we also have to move water around. So looking to California
is a great example of that. So if we look in California they need a lot of water in
the central valley and then in the south, Los Angeles and San Diego. So they built this
huge system where they can move water where it is, in the mountains, and they can move
it through these aqueducts to where it is needed. Now you can see that is controversial.
So people in this area are saying you are depleting our rivers. In this area we are
saying we have more population. We are growing your food so we need more of that water. And
this conversation becomes more heightened when we move into drought. And California
is in an awful drought right now. Drought occurs when you receive way less then the
normal amount of water. And so as we use that for agriculture, irrigation movement is super
important. So how do we move the water actually to the plant. The easiest way to do that is
using furrow irrigation. You can see it is easy. You just dig a trench. What is the problem?
We have efficiency rates of around 60 percent. What is that? That is how much of the water
is actually going to the plant without being evaporated and infiltrated into the soil.
So we could move to flood irrigation. Higher efficiency but it is going to damage the plant
a lot of the time. We could move towards a spray irrigation, high efficiency, but what
are we doing? You can see we are adding equipment. This is the center pivot. So that costs money.
Or we could move to drip irrigation. And you can see that it is going to 95 percent efficient
but it is going to cost the farmer a lot more money to do that kind of irrigation. As we
move into drought situations desalination becomes an option. We can remove the water
from sea water. One way to do this is through distillation. What you do is you heat up the
water and it evaporates. It is kind of like the hydrologic cycle. You then cool it down
usually through pipes and what you do is you remove the water. What is a problem? It costs
a huge amount of money. We could also do that through reverse osmosis. This is a reverse
osmosis plant over on the side. What you do is put a membrane right here and then we squeeze
the water and as you squeeze the water you move the water through but you leave the salts
behind. Now we have fresh water. What is the problem. It costs a lot of money. About 1
percent of the people on our planet are using water that is created through desalination.
But by 2025 we should have 14 percent of the people on our planet in water scarcity and
so desalination may be an issue. Now how did we get to this problem? It seems like we have
an unlimited amount of water? And remember our model the earth provides the life support
for society and the economy on the inside. And so the economy got us to this point. The
decisions that we as governments made got us to this point. Where is the big mistake
we made? Well water does not cost enough. It is low cost water. In other words governments
are subsidizing the cost of water so farmers and industry and you are not really paying
the amount that water costs. And as a result you are not going to conserve it because it
is just pennies on the gallon. It is incredibly cheap. And so how could we solve this problem?
People might not like it but if we increase the price of water people are going to start
to conserve. And we can also use incentives. In other words we can pay people, pay farmers
for example to use irrigation that is going to be more efficient or to conserve water.
That is another way that economics can start to solve this problem of water conservation.
And so did you learn the following? I would pause the video at this point and try to fill
in all the blanks. But let me do that for you. Remember the water resources move through
the hydrologic cycle. We have sea water. We have fresh water. Ocean circulation and desalination
could help us solve this problem. The fresh water can be ground water or surface water.
We use it for domestic, industry and agriculture, would be what is here. We can store the surface
water through reservoirs, aquifers is ground water. And then we are going to use aqueducts
and irrigation to help us move that water around. But again, conservation is incredibly
important. Economics are going to drive that. And I hope that was helpful.