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