Water Security Flashcards
How much of all water if freshwater?
Freshwater makes up 2.5%
Oceans make the remaining 97.5%
How much of the freshwater is readily available?
0.3% of freshwater is readily available in lakes, rivers, streams etc.
Freshwater makes up 2.5% of the world’s total water. What are the sources of Freshwater?
79% in Ice Caps and Glaciers
20% in Ground Water
1% Surface Freshwater
Of the 1% of accessible Freshwater, where do the proportions of this lie?
Lakes 52% Soil moisture 38% Water vapour 8% Rivers 1% Accessible water in plants 1%
Explain why there is such limited availability of water on Earth?
Out of all the water on Earth, only 2.5% is Freshwater. Of that 2.5% only 1% of it is surface freshwater (as glaciers hold 79% and groundwater containing the remaining 20%).
Therefore only 0.3% of Freshwater is readily available in lakes, streams, rivers etc.
State the 3 main physical factors that control global water supplies.
Climate, Geology, River Systems.
How is the distribution of water globally, linked to climate?
Equatorial regions receive high annual precipitation and have two distinct periods of wet weather per yr (Amazon).
Monsoon areas such as Southeast Asia have 1 very distinct wet season.
High altitude mountains with snowpack hold vast reserves of water - some of which are released in summer.
Some tropical areas suffer from recurring drought - e.g. Sub-Saharan Africa and the Middle East.
Rainfall can vary between seasons.
How is the distribution of water linked to River Systems?
The world’s major rivers store large quantities of water and transfer it across continents.
The Amazon has 20% of all the river water entering the world’s oceans.
River flow generally increases downstream as tributaries feed into the main river.
High temperatures can lead to considerable loss of water through evaporation.
Seasonal changes in climate can create significant variations in discharge and produce distinctive river regimes.
What is a tributarie?
A river or stream flowing into a larger river.
What is a distinctive river regimes?
The average discharge of a river over a period of time.
How does Geology affect the distribution of global water supplies?
Where rocks underlying a river basin are impermeable, water will remain on the surface as run-off, creating a high drainage density.
Surface drainage occurs on rocks which are impermeable such as Granite and Clay.
Permeable rocks such as Chalk and Sandstone can store large quantities of water underground, they’re called aquifers.
What is drainage density?
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What is surface drainage?
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State physical factors affecting water supply in India
Rainfall variations (June-Sept have high amounts of rainfall)
Temperature
Topography (Himalayers/river differences between S and N)
How does rainfall affect water supply in India?
Monsoon period results in a water surplus (flooding),
high amounts of rainfall occur from June - September.
The Himalayers provide some relief rainfall - humid air colliding with cold air, condensing and turning into rainfall.
November to March have lowest rainfall amounts, resulting in droughts.
Rapid rainfall decline from September-October results in a large decrease in discharge from rivers such as Ganges and Bahmaputra, these effects are magnified by an increase in temp (Inc evaporation).
