THE
HYDROSPHERE
EFT 2173
INTRODUCTION
• A hydrosphere (from Greek - hydor, "water" and - sphaira, "sphere") in physical geography
describes the combined mass of water found on, under, and over the surface of a planet.
• The total mass of the Earth's hydrosphere is about 1.4 × 1018 tonnes, which is about
0.023% of the Earth's total mass. About 20 × 1012 tonnes of this is in the Earth's
atmosphere (the volume of one tonne of water is approximately 1 cubic metre).
• Approximately 75% of the Earth's surface, an area of some 361 million square kilometres
(139.5 million square miles), is covered by ocean. The average salinity of the Earth's
oceans is about 35 grams of salt per kilogram of sea water (35 ‰).
THE HYDROSPHERE
All of the water found on Earth
Forms of water
Forms of water
Distribution of Water on Earth (% statistic)
Distribution of Water
on earth (% statistic)
reservoir
oceans
Water masses at Earth's surface
volume (in cubic kilometres)
1,338,000,000
percent of total
96.5
ice caps, glaciers, and permanent snow
24,064,000
1.74
ground ice and permafrost
groundwater (total)
groundwater (fresh)
groundwater (saline)
lakes (total)
lakes (fresh)
lakes (saline)
soil moisture
atmosphere*
swamp water
rivers
biota
total**
300,000
23,400,000
10,530,000
12,870,000
176,400
91,000
85,400
16,500
12,900
11,470
2,120
1,120
1,409,560,910
0.22
1.69
0.76
0.93
0.013
0.007
0.006
0.001
0.001
0.0008
0.0002
0.0001
101.67
*As liquid equivalent of water vapour.
**Total surpasses 100 percent because of upward rounding of individual reservoir volumes.
URL: https://www.britannica.com/science/hydrosphere
Access Date: June 06, 2020
Source: Adapted from Igor Shiklomanov's chapter "World Fresh Water Resources" in Peter H. Gleick (ed.), Water in Crisis: A Guide to the World's
Fresh Water Resources, copyright 1993, Oxford University Press, New York, N.Y. Table made available by the United States Geological Survey.
Freshwater
• Smaller bodies of water (3% on earth )
• Fresh water is water that not salty and
has little or no taste , colour or smell.
• Most of it at polar regions and glaciers
(68%), some groundwater (30%), only
little in water vapours an lakes or rivers
(2%).
• Examples:
• glaciers
• Streams
• Ponds
• Lakes
• rivers
Iceberg
• Iceberg: a large piece of
freshwater ice floating in
open waters
• Icebergs start out as part of
a glasier
• 80% of an iceberg is under
water
Wetland
An area where the water
table is at, near or above the
land surface long enough
during the year to support
adapted plant growth.
• Swamp:
a wetland dominated by trees
• Bogs:
a wetland dominated by peat
moss
• Marshes:
a wetland
grasses
dominated
by
Groundwater
• Water that is held
underground because
it has soaked into the
ground
and
percolated (water that
is filter by porous
rocks.
• Water the seeps
through soil and gets
stored in underground
rock formations called
aquifers.
• Surface of land where
water seeps is called
recharge zone.
Saltwater
• Larger bodies of
water are saltwater
(97% of earth)
• Saltwater is clear and
taste salty.- higher in
hot and closed seas.
• Temperature: higher
in the surface, colder
in the deep.
• Examples:
• Oceans
• Gulfs
• Seas
Water salinity
• Salt comes from erosion from
rocks on land over millions of
years and underwater volcanic
eruptions
• Salinity can vary depending on
depth of ocean & areas of
evaporation
• E.g:
estuary-where
freshwater river meets
ocean.
• Salt water is more dense than
fresh water
• Ocean water is 3.5% salt
water salinity, defining freshwater, brackish
water, saltwater, and brine water
Transformation of water
• Exothermic – having to release heat to
change state of matter
• Exothermic changes
• Freezing –liquid to solid
• Condensation – gas to liquid
• Deposition – gas to solid
Endothermic-having to take in heat
• Endothermic Changes
• Melting – solid to liquid
• Evaporation – liquid to gas
How is the water is moved and
maintained on earth?
• The un-ending circulation of the Earth ‘s
water is called the hydrologic or water
cycle
• The water present on the earth today is the
same water that was formed with the
planet itself
• The amount of water cannot be increased
or decreased.
The amount of water on earth stays the same.
Hydrologic cycle
• This cycle consists of a group of reservoirs containing water, the
processes by which water is transferred from one reservoir to
another (or transformed from one state to another), and the rates of
transfer associated with such processes.
• These transfer paths penetrate the entire hydrosphere, extending
upward to about 15 km in Earth’s atmosphere and downward to
depths on the order of 5 km in its crust.
Components in Hydrologic
(Water) Cycle
• Evaporation
• Heated by sun and turns into water vapor
• Comes from bodies of water, plant and
animals
• Condensation
• Water vapor forms droplets on dust
particles, form clouds when they collide
and stick
• Precipitation
• Large droplets fall from clouds
• Can be rain, snow, sleet or hail
• Runoff
• Water can run off land into nearest body of
water
• Water can percolate through layers of soil
and get stored underground in aquifers.
The summary
1. Sun heats the water on the surface of earth
2. Freshwater evaporates into atmosphere as water
vapor (salt in ocean stays behind)
3. Water vapor cools & condenses on dust particles
to form clouds
4. Water falls back to Earth as precipitation in the
form of rain, sleet, snow or hail
5. Precipitation that hits surface either gets absorbed
into ground, stay trapped as standing water or
moves downhill as run-off back into lakes, ponds,
rivers, streams oceans
The Hydrologic Cycle (Water Cycle)
Importance of earth’s hydrosphere
The hydrosphere plays a very important role in the evolution of life, as
well as in weather, and erosion.
Helping to regulate temperatures on earth so that they stay within a
range that is acceptable for life to exist. Ocean currents also help to
disperse heat.
Regulating climate One of water's unique characteristics is its high specific heat.
This means that water takes a long time to heat up and also a long time to cool
down. This is important in helping to regulate temperatures on earth so that they
stay within a range that is acceptable for life to exist. Ocean currents also help to
disperse heat.
The hydrosphere provides an important place for many animals and
plants to live.
Water provides a habitat The hydrosphere provides an important place for many
animals and plants to live. Many gases (e.g. CO2, O2), nutrients e.g. nitrate
(NO−3), nitrite (NO−2) and ammonium (NH+4) ions, as well as other ions (e.g.
Mg2+ and Ca2+) are dissolved in water. The presence of these substances is
critical for life to exist in water.
Water is a part of living cells Each cell in a living organism is made up
of almost 75% water, and this allows the cell to function normally. In
fact, most of the chemical reactions that occur in life, involve
substances that are dissolved in water. Without water, cells would not
be able to carry out their normal functions and life could not exist.
Humans use water in a number of ways. Drinking water is obviously
very important, but water is also used domestically (e.g. washing and
cleaning) and in industry. Water can also be used to generate
electricity through hydropower.
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