Where the world's water is stored at Higher Level: The same ideas as SL with different examples: Greenland, the Nubian Sandstone Aquifer and Glacier National Park. At HL, expect to name a store and a flow missing from a water-cycle figure.
Practise this as you read
- Rank the stores from the oceans down to living things.
- Link each glacier change to what happens downstream.
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One huge store, five small ones: Almost all of Earth's water sits in one store, the oceans. The other stores are tiny by comparison, but they hold the fresh water that life on land depends on.
The main stores, biggest first
- The oceans hold about 96.5% of all water, and it is salty.
- Glaciers and ice caps hold about 1.7%: most of the world's fresh water.
- Groundwater holds about 1.7%, in rocks called aquifers.
- Surface fresh water (lakes, rivers, wetlands) is only about 0.02%.
- The atmosphere holds about 0.001%; living organisms about 0.0001%.
- Learn the order and rough size: oceans by far the biggest, organisms the smallest.
Real example: the Greenland ice sheet holds so much frozen water that, if it all melted, sea level would rise by about 7 metres. It is part of the 1.7% held as ice.
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Earth is called the blue planet, so why do so many places run short of water? Because almost none of it is fresh, liquid and on the surface.
The points to remember
- About 97% of all water is salty: we cannot drink it or water crops with it.
- Most fresh water is frozen in ice caps or held underground.
- The fresh water easiest to use, in lakes and rivers, is a tiny fraction.
- Deep groundwater refills very slowly, so it is hard to use sustainably.
Remember it as: Salty, frozen or underground: very little is easy to use.
Hard to use
- Ocean water: salty
- Ice caps: frozen and far away
- Deep groundwater: slow to refill
Easy to use
- Lakes
- Rivers
- Shallow groundwater
Real example: the Nubian Sandstone Aquifer under Egypt, Libya, Sudan and Chad holds about 150,000 km³ of fresh water, but most of it fell as rain thousands of years ago and is barely refilled today.
A common question shows a water-cycle figure and asks for a store that is not on it. Run through the list of stores and pick one that is missing.
Stores to choose from
- Fresh water stores: lakes, rivers, glaciers, groundwater (aquifers), reservoirs, soil water.
- Animals and other organisms are a store too, not only plants.
- The atmosphere (clouds) and the oceans are stores as well.
- Name a store (a place, a noun), never a flow such as 'rain' or 'evaporation'.
- If the question asks for a store and a flow, give both for the mark.
Real example: if a full water-cycle diagram leaves one box and one arrow blank, a correct answer names both, such as 'groundwater' for the box and 'infiltration' for the arrow.
A store, not a flow: 'Rainfall' or 'run-off' cannot be a store. And trees are already drawn, so 'plants' would not count.
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Glaciers are frozen stores of fresh water that feed rivers as they melt. Most of them are now shrinking, which changes the rivers below them.
What a shrinking glacier does to its river
- A glacier is a store of fresh water that releases meltwater, mostly in summer.
- While it melts fast, the river gets more water for a while, and muddier water.
- As it shrinks and disappears, the river gets less water, especially in late summer.
- So towns and farms downstream face summer shortages and droughts.
- To read a trend, describe a pattern across the bars, never one bar on its own.
Real example: Glacier National Park in Montana had about 150 glaciers in 1850 and only 26 large enough to count in 2015. The streams they fed now run lower in late summer.
Link the change to its cause: 'The river gets bigger' is not enough. Write 'more meltwater as the glacier melts raises the river's flow at first, but as the glacier disappears the summer flow falls'.
How this comes up: Paper 1: outline how glacier retreat will affect a river [1]. Link the change to the glacier.
The Indus River in Pakistan gets about half of its water from melting snow and glaciers in the Karakoram and Himalaya.
Outline how the retreat of these glaciers is likely to affect the flow of the Indus over time.
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