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%