Water, water, everywhere, but not
much to drink!
The most common element in the
Universe is hydrogen. Hydrogen is one of the 93 natural elements that
make up all matter in the Universe. On Earth, pure
hydrogen is a gas and because hydrogen gas is less dense than all of the gases
that make up our atmosphere, any free hydrogen gas simply floats away into
space. Most of the hydrogen on Earth is locked in compounds. One of the most common compounds containing hydrogen is good
old water, H2O. Most everyone has heard of water referred to
as H2O, but do you know what that means? H 2O is the chemical formula for water it means
that every molecule of water has two atoms of hydrogen and one atom of oxygen. Pretty
cool huh, three pieces of gas turn into the most common liquid on Earth.
Water, without water, there would be
no life on Earth, so water is pretty important to us. Over the next few
weeks, we are going to learn some interesting facts about good old H 2O.
The
water on the Earth’s surface is called the hydrosphere. The
hydrosphere is usually divided into seven forms of water. These seven forms of water are the oceans, saltwater seas and
lakes, rivers, freshwater lakes, the atmosphere, groundwater, and in glaciers
and ice caps. Only a small part of the hydrosphere, or water
is available for human use! The majority of the
Earth’s water is contained in the oceans and seas. Altogether, the oceans cover between 70 and 75 percent of our planet.
Most people recognize five oceans: Pacific, Atlantic, Indian, Arctic,
and the Southern Ocean. These five oceans are all connected
together into one giant ocean, sometimes referred to as
the World Ocean. The Pacific Ocean is the largest and deepest
ocean. The Atlantic Ocean is the second largest, then comes the Indian
Ocean, next comes the Southern Ocean, and the smallest Ocean is the
Arctic. The Southern Ocean is all of the water south of the 60 degree S.
latitude.
Oceanographers are
scientists who study the oceans.
All of the world’s oceans and seas contain saltwater and cannot be consumed by
humans or animals. The oceans contain about 97% of all
the Earth’s water. Drinking saltwater will make you very ill and
can cause you to die. Ocean water has a salinity
of 3.5%. When oceanographers refer to the salinity of the ocean, they are referring to the amount
of salt and minerals dissolved in ocean water . So, salinity refers to how much salt is in ocean water.
Gases, such as oxygen and carbon dioxide are also dissolved in the ocean and
can move back and forth between the water and the air. The greatest
amount of saltwater is found in the world ocean, but saltwater is also found in
seas and salt lakes. Think about that, 97% of all
the water on Earth cannot be easily used by mankind.
Ocean water is about 3.5% salt. That
means that if the oceans dried up completely, enough salt would be left behind
to build a 180-mile-tall, one- mile-thick wall around the equator! And more
than 90 percent of that salt would be sodium chloride,
NaCl, or ordinary table salt. The oceans sure contain a lot of salt.
Only 3% of the Earth’s
water is fresh water. About
2/3 of that 3% or about 69% of the world’s fresh water is frozen in glaciers and ice
caps at the North and South Poles. The Arctic Ocean surrounds the
North Pole and a huge area of it stays frozen all year. Greenland, near
the North Pole and Antarctica are almost completely covered in ice all year
round. Many parts of the world also have glaciers. Glaciers are like huge rivers of ice that are slowly moving
downhill or down the side of a mountain.
About 31% of
the world’s freshwater or 1% of all the water on Earth, is useable by mankind.
That sure doesn’t sound like a lot of water for us to use. So where can
we find this little bit of freshwater that we get to use?
Most of the freshwater
useable by mankind is found underground in groundwater. Most of the world’s
useable freshwater is in groundwater. Less than 1 % of all useable freshwater on Earth is found in the
lakes, rivers, swamps, and in the atmosphere.
This is an important concept, only about one percent of
all the water on Earth is useable by mankind.
That one percent is divided into groundwater, rivers, lakes, and the
atmosphere. As we already said, most of the useable water is found in
groundwater. Groundwater is water stored
underground in huge areas of permeable rock and sand called aquifers.
These aquifers can store water for thousands of years. Permeable rock has spaces or pores in it that can hold water.
Layers of soil above an aquifer filter out pollution.
Rural communities and families usually get their water
from wells drilled down into the aquifers. Larger towns and cities may also use
wells drilled into the aquifer, but cities also get some of their water from
rivers and special lakes called reservoirs.
So, look at the picture above. If the pumping well takes water out of the aquifer faster than the precipitation and infiltration can refill it, what will happen to the water table and the stream? Eventually, what will happen to the pumping ell?
In some parts of the world where
freshwater is very scarce, some countries use a process called
desalination. Desalination is the process of
removing salt from ocean water, making it drinkable. Desalination
can be very expensive. Another problem is what to do with the salts and other
materials removed from the ocean water. Think about it, if ocean water
has a salinity of 3.5%, that means for every 1000 gallons of ocean water,
you have nearly 300 pounds of salt to dispose of.