The water cycle describes the continuous movement of water on, above, and below the surface of the Earth. Water exists in three states as it moves between oceans, the atmosphere, solid earth, and the biosphere through various processes. The constant circulation of water replenishes ecosystems, affects climate, and is essential for life.

1. THE ROLE OF WATERCYCLE IN REJUVENATINGBIOSPHERE
DISASTERSCIENCE AND MANAGEMENT
UNIVERSITY OF DHAKA

2. Water (H2O),
i. Most abundant compound
ii. Exists in 3 states
iii.Tasteless and Odorless
iv. The universal solvent
v. 55% to 78% of the human body
vi. Has dynamic equilibrium
WHATIS WATER?

3. Water covers
71% of the Earth's surface
96.5% of the planet's water
1.7% in groundwater
1.7% in glaciers
0.001% in the air as vapor, clouds and precipitation
 2.5% of freshwater
98.8% of that water is in ice and groundwater
0.003% is contained within biological bodies and manufactured
products.
WATER

4. Water on Earth moves continually
through the water cycle of
evaporation and transpiration
(evapotranspiration), condensation,
precipitation, and runoff, usually
reaching the sea. Evaporation and
transpiration contribute to the
precipitation over land.
WATER(CONT.)
Water in three states: liquid, solid
(ice), and water vapor (cloud) in the
air. Clouds are accumulations of water
droplets, condensed from vapor-
saturated air.

5. Water constantly moves among the oceans, the
atmosphere, the solid Earth, and the biosphere. This
unending circulation of Earth’s water supply is the
water cycle.
WHATIS WATERCYCLE?

6. WHATIS WATERCYCLE?(CONT.)
• Describes the continuous movement of water
• Balance of water remains constant
• Water moves from one reservoir to another

8. Precipitation
Snowmelt
Runoff
Infiltration
Subsurface flow
Evaporation
Sublimation
Deposition
Condensation
Transpiration
PROCESSESOF WATERCYCLE

9. WATERCYCLERESERVOIRS: RESIDENCETIMES

10. Effects on Ecosystem:
Exchange of energy, that leads to temperature changes
Taking energy, it cools the environment
Releasing energy, it warms the environment
Purifies water
Replenishes the land with freshwater and transports
minerals
Involved in reshaping the geological features of the Earth
Maintenance of life and ecosystems
THEROLESOF WATERCYCLEIN BIOSPHERE

11. Effects on climate:
86% of the global evaporation occurs from the oceans,
reducing their temperature by evaporative cooling.
Aquifer drawdown or over drafting and the pumping of
fossil water increases the total amount of water in the
hydrosphere, and has been postulated to be a contributor to
sea-level rise.
THEROLESOF WATERCYCLEIN BIOSPHERE(CONT.)

12.  Water helps to make macro molecules, transport of
materials, solubilize the chemicals and involve in
chemical reactions.
 The photosynthesis process
 The underground water is used by humans in the
agriculture.
 The plants are dependent on the water which is present in
the soil.
THEROLESOF WATERCYCLEIN BIOSPHERE(CONT.)

13. The clouds are formed by the higher altitudes, cool and condense
water vapors. The precipitation occurs in many forms. It occurs as
snow, rain and hail.
The snow form is deposited in the polar and alpine areas. In the
summer season the ice melts. The rivers are formed by the melting of
snow.
THEROLESOF WATERCYCLEIN BIOSPHERE(CONT.)

14. The plants on land, absorb water from the roots. They loss
the water through transpiration and makes the climate cool
during summer and makes it warmer during the winter
season. It also leads to rainfall.
The animals on land take water from ponds, rivers and
lakes etc. The water is lost through the urine and sweat. The
rest of water is released when the organism dies.
THEROLESOF WATERCYCLEIN BIOSPHERE(CONT.)

15. oThe water cycle is
important in rejuvenating
BIOSPHERE.
THEROLESOF WATERCYCLEIN BIOSPHERE(CONT.)

16. Any questions ???