Detailed notes for the entire Water and Carbon Cycle topic of AQA A-level Geography, organised in order of the syllabus. The theories are applicable to all case studies, however the two I have chosen and explored deeper in these notes are The Amazon Rainforest and River Exe. These case studies allo...
AQA A-level Water & Carbon Cycle Knowledge Booklet
The Water Cycle
1. Aquifers:
There are two types of aquifers:
- Unconfined- where porous rock is open to surface water and is directly recharged by
precipitation
- Confined- where there are thick layers/beds of rockover the aquifer, known as the
confining beds; these contain the aquifer from the Earth's surface or other rocks
2. Residence Time:
- This is the time that water is held in a store (eg. water is held in soil for 1-2 weeks)
Interception recipitation that is caught and stored
P
(temporarily) on its way to the surface by
vegetation
Surface Runoff This is when water flows over the land's surface
Infiltration When the water enters beneath the surface
Throughflow T he (-->) movement of water through the upper
soil
Percolation T he (-->) movement of water through lower soil
and underlying rock
Groundwater flow ater that has infiltrated past the bedrock and
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below the water table
Evapotranspiration Evaporation and transpiration (plants)
2. Global Processes:
- Climate changeis changing the size of the cryosphere and hydrosphere's
stores
, 3. Local Processes:
- Farming practicescan interfere with natural processeseg. vegetation can
prevent infiltration & over-abstraction for farming removes natural stores of
water
- Deforestationreduces interception and infiltration
- without plant interception water will flow too fast to infiltrate and
soil won’t be broken up from roots to allow infiltration
- Urbanisationreduces infiltration by replacing permeablegeology with
impermeable geology (this can lead to high rates of surface runoff)
4. Drainage Basins:
- An area of land drained by a river and its tributaries. A drainage basin can also be
called a ‘catchment’
a . atershed = the ‘imaginary’ boundary that separates two drainage basins
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b. Source = where the river starts
c. Confluence = where 2+ river meet
d. Tributary = where one stream meets the main river
e. Mouth = where the river meets the sea
NOTE: Hillslopes and Drainage Basins operate similarly, however, hillslopes are more localised
- the flows in both will be affected by antecedent conditions eg. saturation of soil
Many factors can affect drainage basin and hillslope runoff:
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