Over 70% of our Earth's surface is covered by water ( we should really
call our planet "Ocean" instead of "Earth"). Although water is seemingly
abundant, the real issue is the amount of fresh water available.
97.5% of all water on Earth is salt water, leaving only 2.5% as fresh water
Nearly 70% of that fresh water is frozen in the icecaps of Antarctica
and Greenland; most of the remainder is present as soil moisture, or lies in
deep underground aquifers as groundwater not accessible to human use.
< 1% of the world's fresh water (~0.007% of all water on earth) is accessible
for direct human uses. This is the water found in lakes, rivers, reservoirs
and those underground sources that are shallow enough to be tapped at an
affordable cost. Only this amount is regularly renewed by rain and snowfall,
and is therefore available on a sustainable basis.
●12,000 yrs. ago: hunter-gatherers continually return to fertile river valleys
● 7,000 yrs. ago: water shortages spur humans to invent irrigation
● 1,100 yrs ago: collapse of Mayan civilization due to drought
● Mid 1800's: fecal contamination of surface water causes severe health
problems (typhoid, cholera) in some major North American cities,
● 1858: "Year of the Great Stink" in London, due to sewage and wastes in
● Late 1800s-early 1900: Dams became popular as a water management
● 1900s: The green revolution strengthens human dependency on irrigation
● World War II: water quality impacted by industrial and agricultural
● 1972: Clean Water Act passed; humans recognize need to protect water
ice sheets ice
caps glaciers icebergs bogs ponds lakes rivers
According to WIKIPEDIA
A unit of rock or an unconsolidated deposit is
called an aquifer when it can yield a usable
quantity of water.
An aquifer is an underground layer
of water-bearing permeable rock or
unconsolidated materials (gravel, sand,
or silt) from which groundwater can be
extracted using a water well. The study
of water flow in aquifers and the
characterization of aquifers is
The freshwater biome is made up of any of body of
water that is made of freshwater such as lakes, ponds,
streams, and rivers. They cover roughly 20% of the Earth
and are in various locations spread out all over the world.
Most freshwater biomes consist of moving water and contain
many types of fish.
Seawater is water from a sea or ocean.
On average, seawater in the world's oceans has a salinity of about
3.5% (35 g/L, or 599 mM).
Seawater is denser than both fresh water and pure water because
the dissolved salts add mass without contributing significantly to
the volume. The freezing point of seawater decreases as salt
concentration increases. The coldest seawater ever recorded (in a
liquid state) was in 2010, in a stream under an Antarctic glacier,
and measured−2.6 °C (27.3 °F).