Water is found in various reservoirs on Earth and is constantly cycling between them through evaporation and precipitation in the water cycle. The largest reservoir is the oceans, which hold about 97.5% of Earth's total water supply. Freshwater makes up only 2.5% and is stored in glaciers, groundwater, lakes, rivers, the atmosphere and soil. The movement and distribution of water between these reservoirs is crucial to sustaining life.

2. Water is everywhere.
71% of earth is covered in water. Oceans takes up 96.5%
of water percentage.
World’s most expensive commodity.
Earth is the only planet where the liquid form of water
exists.

3.  Known as Water Cycle.
 It explains the movement of water
around the earth’s surface and it’s
subsystems.
 It consist of interconnected pathways
and reservoirs.
 Mass balance maintains the total
amount of water.
 Fluctuations may occur on a local
scale.

4.  Earth’s Water Budget is the total amount of water in the planet. It remains
constant through time.
 Water moves and changes it’s form but can neither be created nor destroyed.
 The largest reservoir is the ocean that contains about 97.5% of earth’s water
budget which is mostly saline.
 Freshwater only takes up 2.5% of earth’s water budget. It is found on
glaciers(68.7%), groundwater(30.1%), permafrost(0.8%), surface water and
atmospheric water.

5. GLACIERS
SURFACE WATERPERMAFROST
GROUNDWATER

6.  Residence Time is the average length of time spent by the water
molecule in a reservoir.
 The volume of water varies in each reservoir and their volumes
affect each other.
Note:
When water is in it’s solid state (ice) it will float on water in it’s liquid
state.
Ice occupies more volume per unit weight making it’s density less
than that of water.

7. Reservoirs are places where water resides for an amount
of time.
TYPES OF WATER RESEVOIR:
• Saltwater Reservoir
• Freshwater Reservoir
• Surface Water Reservoir

8. These reservoirs are vast bodies of saline water such as oceans.
Ocean is one of the most valuable resources of Earth.
It is divided into five distinct regions and into numerous seas, gulfs, bays and
straits.
There are four(4) recognized oceans:
-Atlantic Ocean -Pacific Ocean
-Indian Ocean -Arctic Ocean
SALINITY
- is the saltiness of saltwater. Major chemicals present in seawater are
sodium and chlorine ions.
- seawater salinity varies from 33 to 37 parts per thousand.
- volcanic eruptions are the main source of elements mixed in seawater.

9. Water salinity is maintained through hydrologic cycle.
Evaporation removes water that makes the seawater saltier.
Precipitation adds water that dilutes the seawater
Inflow from rivers and ground water also dilutes the sea.
As sea water freezes the salt is excluded.

10.  Surface Layer (1st layer)
- 2% of the ocean that is affected by currents caused by prevailing winds.
Consist of warm, low density water that extends to a depth of 100m. Home of the
majority of marine plants and animals.
 Thermocline (2nd layer)
- water temperature decreases with depth. This layer extends up to 1500m.
 Deep Zone (3rd layer)
- in this layer the temperature is uniformly low. It covers 80% of ocean water.
Affected by Thermohaline circulation propelled by the sinking of cold, salty and dense
water in polar region and rising of warm, less salty waters of tropics.

11. Humans depend on freshwater in almost everything.
GLACIERS AND ICE SHEETS
A Glacier is a permanent body of ice from recrystallized unmelted snow.
These are again covered by another layer of snow as soon as winter arrives
and as the layers accumulate it becomes compacted tuning into a mass of ice.
An Ice sheet is a mass of glacial land ice extending more than
50,000km².
Glaciation result to large amount of water to become locked up as snow
that lowers the sea level and exposes more of lands and coastal areas.

12. There are approximately 24 million km³ freshwater that is
stored in glaciers and ice sheets.
90% is concentrated in Antarctica while the rest is found
in Greenland and in mountain of glaciers.

13. PERMAFROST
Permafrost is a soil, rock or sediments that is frozen for more
than two consecutive years. These are commonly found in polar
regions.
The thickness can reach from a few meters to 150m. During
summer, 30-100cm melts and refreezes during winter.
FRESHWATER IN PERMAFROST
Permafrost comprises 0.8% of total freshwater. It is estimated
to store 300,000km³ of water.

14. Surface waters includes the streams, lakes and wet lands where water from
rainfall, melting snow and ice, and ground water flows. It contains 0.3% of Earth’s
water.
STREAM
A moving body of surface water that flows down towards the sea level
because of gravity.
Streams are interconnected into a tree-shaped network that joined to a large
main stream or river. It holds 1.6% of total surface and atmospheric water.
 Tributaries- smaller streams.
 Drainage basin or Watershed - land area which water flows in particular stream.
 Drainage divide - line that separates individual basin .
 Interfluve - the narrow elongated landform that separates individual streams.

15.  Overland flow – water moves downhill during a heavy rain.
 Streamflow – when water enters the channels.
OVERLAND FLOW STREAMFLOW

16. LAKES
Lakes are large inland bodies that contains either freshwater or saline
water. It forms in places where water is collected due to land depression and
behind natural and man made dams. Lakes stores 67% of total atmospheric
water.
 Ponds – small shallow lakes
 Dams – barriers constructed along streams to contain the flow of water.
WETLANDS
Wetlands are lands where water cover the surface for a period of time. It
constitute 8.5% of total atmospheric water.
Wetlands are great breeding ground for fishes and invertebrates. The water
seeped by the ground can also replenish groundwater.

17. Marsh
- a shallow wetland around lakes, streams, and ocean where grasses
and reeds are the dominant vegetation.
Swamp
- a wetland with lush trees and vegetation found in low-lying areas
beside slow-moving rivers. Oxygen content of swamps are low.
Estuary
- a partly enclosed coastal body of water where fresh water from stream
meets saltwater from sea.

18. ESTUARY
SWAMPMARSH

19. FLOODS
A natural event in which an area that is usually dry is submerged in
water. It occurs when precipitation is higher or when reservoirs collapse.
Vegetation reduces flood intensity.
 Fluvial or Riverine Flood – occurs when a stream’s discharge is greater than
the capacity of the channel.
 Flashflood – characterized by intense, high-velocity torrent of water.
 Coastal Flooding – occurs when water overwhelms in low-lying areas along
the coast.
 Pluvial or Surface Water Flood – occurs when rainfall creates a flood
independent of an overflowing stream.

20. GROUNDWATER
Groundwater is fresh water found in rocks and soil layers beneath the
surface. This is the largest reservoir that hold 30.1% of total freshwater on the
planet.
 Aquifers – are water bearing rock layers. It is akin to a “sponge”.
 Porosity – is the total amount of empty spaces in the rock that determines the
capacity of an aquifer.
 Permeability – the ability of rocks or sediments to allow water to pass through
it.