The water cycle and water insecurity revision notes for  A Level Edexcel Geography

The water cycle and water insecurity revision notes for 
A Level Edexcel Geography

what is a drainage basin - -a river's drainage basin is the area surrounding it 
where the rain falling on land flows into that river (river's catchment)
-the boundary of the drainage basin is called the watershed
-open (with inputs and outputs), the total amount of water changes over time
-local hydrological systems
what is a large drainage basin - -steep sides (ability to move precipitation into the 
river quickly)
-large number of streams, high drainage density
what is a smaller drainage basin - fewer streams (low drainage density)
drainage basin inputs - -precipitation (all the ways the moisture comes out of the 
atmosphere)
-frontal precipitation, orographic precipitation, convectional precipitation
-the areas that are affected the most: south of the equator (around it), areas of 
low pressure, tropical regions (Amazon rainforest), coastal areas
what is frontal precipitation - -warm air is less dense than cool air
-when warm air meets cool air, the warm air is forced up above the cool air
-it cools down as it rises
what is orographic precipitation - when warm air meets mountains, it's forced to 
rise, causing it to cool
what is convectional precipitation - when the sun heats the ground, moisture on 
the ground evaporates and rises up in a column of warm air, as it gets higher it 
cools down
what are the drainage basin flows - interception, infiltration, direct runoff, 
saturated overland flow, throughflow, percolation, groundwater flow
what is interception (as a flow) - -when vegetation intercepts the rainfall before it 
hits the ground
-rainfall still gets to the ground but is slowed
-during heavy rainfall, interception is minimal as leaves cannot hold anymore 
water and rainfall just flows off
what is infiltration (as a flow) - water soaking into the soil vertically
what is direct runoff (as a flow) - -water flowing over the land
-can flow over the whole surface or in little channels
-occurs because rain is falling on the ground faster than infiltration can occur
what is saturated overland flow (as a flow) - water flowing over the land because 
the soil no longer has the capacity to allow any more water to infiltrate
what is throughflow (as a flow) - -water moving slowly downhill through the soil 
-horizontal movement of water through soil
what is percolation - is water seeping down through the soil into the water table 
(vertical)
what is groundwater flow (as a flow) - water slowly flowing through permeable 
rock below the water table
the hydrological cycle - -closed system (no external inputs or outputs of water)
-made up of stores (where energy builds up), flows (movements of energy 
between stores), inputs (energy is added to the system) and outputs (when 
energy leaves the system)
-the volume of water is finite and consistent (limited but stays at same level)
-the cycle is driven by solar energy (from surface to atmosphere) and 
gravitational potential energy (force that causes water to flow downhill, on 
surface and through soil, and precipitation from sky)
where is all the water globally? - -oceans have 96.5%
-cryosphere has 1.7% (frozen part of earth system)
-groundwater has 1.7%
-surface water has 0.01%
-atmosphere has 0.001%
-biosphere has 0.0001%