Concept of Environmental Science
Water: Resources and Pollution
“The wars of the twenty-first century will be fought over water.”- Ismail Serageldin , Former
World Bank Vice President
Water is a marvelous substance—flowing, swirling, seeping, constantly moving from sea to land and
back again. It shapes the earth’s surface and moderates our climate. Water is essential for life.
Water is a main compound found in living organisms. It is also known as oxidane (IUPAC name). It
contains two atoms of hydrogen and one atom of oxygen (H2O).
Water has many uses because of its physical and chemical properties such as
1. transparent, colorless, odorless and tasteless liquid.
2. boils at 100 0C and freezes at 0 0C.
3. high heat capacity
4. polar
5. density of ice is lower than the density of liquid water
The units for water measurement are 1 cubic kilometer (km3 ) = 1 billion cubic meters (m3) = 1 trillion
liters = 264 billion galloons
The water we use cycles endlessly through the environment. Water evaporates from moist surfaces,
falls as rain or snow, passes through living organisms, and returns to the ocean in the process called
hydrologic cycle or water cycle.
There are nine (9) major physical processes which form a continuum of water movement:
1. Evaporation – process of transformation of water from liquid to gas by means of solar
radiation as it moves from the ground or bodies of water into the atmosphere.
2. Transportation - movement of water through the atmosphere usually between ocean and
landmasses.
3. Condensation - the transformation of water vapor to liquid water droplets in the air, creating
clouds and fog.
4. Sublimation– the state change directly from solid water (snow or ice) to water vapor.
5. Deposition - also known as desublimation, is a thermodynamic process, a phase transition in
which gas (vapor) transforms into solid (ice).
6. Precipitation - condensed water vapor that falls to the Earth's surface. Most precipitation
occurs as rain, but also includes snow, hail, fog drip, graupel, and sleet.
7. Runoff- includes surface and channel runoff. The water flows it may seep into the ground, or
evaporated into the air, then stored in lake or reservoirs.
8. Transpiration -the release of water vapor from plants and soil into the air. Water vapor is a
gas that cannot be seen.
9. Infiltration –water enters the soil surface after falling in the ground from the atmosphere.
10. Percolation – water moves down further through the soil and rocks under the influence of
gravity.
, The distribution of water often is described in terms of interacting compartments in which water
resides. The length of time water typically stays in a compartment is its residence time . On average,
a water molecule stays in the ocean for about 3,000 years.
Compartment Average
Residence Time
Total 2,800 years
Oceans 3,000 to 30,00
years*
Ice and Snow 1 to 100,00 years*
Saline groundwater Days to thousand of
years*
Fresh groundwater Days to thousand of
years*
Fresh lakes 1 to 500 years*
Saline lakes 1 to 1,00 years*
Soil Moisture 2 weeks to 1 year*
Atmosphere 1 week
Marshes, wetlands Months to years
Rivers, streams 1 week to 1 month
Living Organisms 1 week
* Depends on depth and other factors
About 97.6% of water on Earth is from the ocean which is saltwater, while freshwater makes the
remaining 2.4%.
Allocation of Freshwater
Groundwater 12%
Fresh Surface water 0.08%
Ice and Snow 87%
Of the 2.4 percent of all water that is fresh, nearly 90 percent is tied up in glaciers, ice caps, and
snowfields. Originating as precipitation that percolates into layers of soil and rock, groundwater
makes up the largest compartment of liquid, fresh water.
The groundwater has the following components:
1. Zone of Aeration - shallow layers of the soil containing both air and water. This s where
plants get moisture from a relatively shallow layer of soil.
Water: Resources and Pollution
“The wars of the twenty-first century will be fought over water.”- Ismail Serageldin , Former
World Bank Vice President
Water is a marvelous substance—flowing, swirling, seeping, constantly moving from sea to land and
back again. It shapes the earth’s surface and moderates our climate. Water is essential for life.
Water is a main compound found in living organisms. It is also known as oxidane (IUPAC name). It
contains two atoms of hydrogen and one atom of oxygen (H2O).
Water has many uses because of its physical and chemical properties such as
1. transparent, colorless, odorless and tasteless liquid.
2. boils at 100 0C and freezes at 0 0C.
3. high heat capacity
4. polar
5. density of ice is lower than the density of liquid water
The units for water measurement are 1 cubic kilometer (km3 ) = 1 billion cubic meters (m3) = 1 trillion
liters = 264 billion galloons
The water we use cycles endlessly through the environment. Water evaporates from moist surfaces,
falls as rain or snow, passes through living organisms, and returns to the ocean in the process called
hydrologic cycle or water cycle.
There are nine (9) major physical processes which form a continuum of water movement:
1. Evaporation – process of transformation of water from liquid to gas by means of solar
radiation as it moves from the ground or bodies of water into the atmosphere.
2. Transportation - movement of water through the atmosphere usually between ocean and
landmasses.
3. Condensation - the transformation of water vapor to liquid water droplets in the air, creating
clouds and fog.
4. Sublimation– the state change directly from solid water (snow or ice) to water vapor.
5. Deposition - also known as desublimation, is a thermodynamic process, a phase transition in
which gas (vapor) transforms into solid (ice).
6. Precipitation - condensed water vapor that falls to the Earth's surface. Most precipitation
occurs as rain, but also includes snow, hail, fog drip, graupel, and sleet.
7. Runoff- includes surface and channel runoff. The water flows it may seep into the ground, or
evaporated into the air, then stored in lake or reservoirs.
8. Transpiration -the release of water vapor from plants and soil into the air. Water vapor is a
gas that cannot be seen.
9. Infiltration –water enters the soil surface after falling in the ground from the atmosphere.
10. Percolation – water moves down further through the soil and rocks under the influence of
gravity.
, The distribution of water often is described in terms of interacting compartments in which water
resides. The length of time water typically stays in a compartment is its residence time . On average,
a water molecule stays in the ocean for about 3,000 years.
Compartment Average
Residence Time
Total 2,800 years
Oceans 3,000 to 30,00
years*
Ice and Snow 1 to 100,00 years*
Saline groundwater Days to thousand of
years*
Fresh groundwater Days to thousand of
years*
Fresh lakes 1 to 500 years*
Saline lakes 1 to 1,00 years*
Soil Moisture 2 weeks to 1 year*
Atmosphere 1 week
Marshes, wetlands Months to years
Rivers, streams 1 week to 1 month
Living Organisms 1 week
* Depends on depth and other factors
About 97.6% of water on Earth is from the ocean which is saltwater, while freshwater makes the
remaining 2.4%.
Allocation of Freshwater
Groundwater 12%
Fresh Surface water 0.08%
Ice and Snow 87%
Of the 2.4 percent of all water that is fresh, nearly 90 percent is tied up in glaciers, ice caps, and
snowfields. Originating as precipitation that percolates into layers of soil and rock, groundwater
makes up the largest compartment of liquid, fresh water.
The groundwater has the following components:
1. Zone of Aeration - shallow layers of the soil containing both air and water. This s where
plants get moisture from a relatively shallow layer of soil.
