Water cycle on a global scale Flashcards
What is the global water cycle?
The global water cycle encompasses all of the water on earth and the process and flows it goes through.
On a global scale, the water cycle is a closed system as there are no inputs and no outputs.
The global water cycle has different sub-sections which can be open systems.
What are the four major stores of water?
- Hydrosphere, is all water stored within the oceans and is the largest store. (96% of the earths water)
- Lithosphere, is any land based storage such as rivers.
- Cryosphere, is frozen water such as snow and ice.
- Atmosphere, is any water in the air and in the clouds. Receives water through evaporation (90%) and transpiration (10%). Smallest store as water continually returned to earth.
What is the definition of the water cycle?
The water cycle is the movement of water across the land.
How much water is stored within the oceans and which ocean is the largest store?
95% of the earth’s water is stored within the oceans and around 97% of water is saline.
The largest ocean store is within the Pacific ocean.
What are the issues with the worlds lakes?
The worlds lake stores have a random distribution and form in areas of impermeable rock.
Lakes such as Lake Chad, are drastically decreasing in size, as they are being over-exploited by surrounding countries.
Lake chad supports 30 million people and has virtually disappeared over the past 40 years, this is due to people using the groundwater stores which supply the river. It has also shrunk due to the creation of dams on its tributaries.
What are the world aquifers?
This is water stored within permeable rock such as Chalk and Sandstone.
These are an important source of fresh water for most countries, and the water is extracted through a borehole which is drilled down into the rock.
Fossil aquifers are ancient stores of groundwater stored in impermeable rock in now arid countries.
What can happen to an aquifer when it is near the coast or saline water?
When the water within the aquifer falls below sea level the aquifer may fill up with sea water and become contaminated.
If this happens it is extremely difficult to remove the salt water and even more expensive to drill further down.
Time scale of changes in the global water cycle?
Time scale of processes and flows can take several months to years.
What is the global atmospheric distribution of clouds?
Warm air rises at the equator and travels to around 30º North where it cools and sinks to the surface. This movement is known as the Hadley cell. At around 30º North the sinking air creates an area of high pressure.
The Ferrel cell is found between the Hadley and Polar cells and lies between 60º North and 30º North. This cell occurs in between the polar cell and the Hadley cell, in this way it is ‘powered’ by the other cells.
The Polar cell occurs when cold air sinks at the North Pole, before flowing south at the surface. Here it is warmed by contact with land/ocean around 60º North, where it rises.
This cell system occurs in both the northern and southern hemisphere.
What type of rain is the three cell model likely to create on a global scale?
This model creates convectional rainfall as it involves warm air full of water vapour rising, it then cools and condenses this is when particles collide until they become too heavy and fall as rain.
