The Water Cycle And Water Insecurity Notes With Answers (134 Solved Questions)

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The water cycle and water insecurity revision notes forA Level Edexcel Geographywhat is a drainage basin - -a river's drainage basin is the area surrounding itwhere 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 systemswhat is a large drainage basin - -steep sides (ability to move precipitation into theriver quickly)-large number of streams, high drainage densitywhat is a smaller drainage basin - fewer streams (low drainage density)drainage basin inputs - -precipitation (all the ways the moisture comes out of theatmosphere)-frontal precipitation, orographic precipitation, convectional precipitation-the areas that are affected the most: south of the equator (around it), areas oflow pressure, tropical regions (Amazon rainforest), coastal areaswhat 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 riseswhat is orographic precipitation - when warm air meets mountains, it's forced torise, causing it to cool

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what is convectional precipitation - when the sun heats the ground, moisture onthe ground evaporates and rises up in a column of warm air, as it gets higher itcools downwhat are the drainage basin flows - interception, infiltration, direct runoff,saturated overland flow, throughflow, percolation, groundwater flowwhat is interception (as a flow) - -when vegetation intercepts the rainfall before ithits the ground-rainfall still gets to the ground but is slowed-during heavy rainfall, interception is minimal as leaves cannot hold anymorewater and rainfall just flows offwhat is infiltration (as a flow) - water soaking into the soil verticallywhat 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 occurwhat is saturated overland flow (as a flow) - water flowing over the land becausethe soil no longer has the capacity to allow any more water to infiltratewhat is throughflow (as a flow) - -water moving slowly downhill through the soil-horizontal movement of water through soilwhat is percolation - is water seeping down through the soil into the water table(vertical)

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what is groundwater flow (as a flow) - water slowly flowing through permeablerock below the water tablethe hydrological cycle - -closed system (no external inputs or outputs of water)-made up of stores (where energy builds up), flows (movements of energybetween stores), inputs (energy is added to the system) and outputs (whenenergy 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) andgravitational potential energy (force that causes water to flow downhill, onsurface 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%what percentage of the earth is freshwater - less than 3%, with the rest beingsaline water-52% in lakes, 38% in soil moisture, 8% in atmosphere, 1% in rivers and 1% inliving thingswhat are the annual fluxes of the water cycle - evaporation, condensation,precipitation, cryospheric processeswhat is evaporation - -water vapour-increases the amount of water in the atmosphere-lots of solar radiation means the amount of evaporation will be high

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what is condensation - -occurs when water vapour changes to become a liquid-temperatures fall at night due to heat being lost to space-lots of water vapour and rapid drop in temperature means condensation will behighwhat is precipitation - -the main flow from atmosphere to ground-warm air cools to condense water vapour into water droplets -which gathers asclouds-when the droplets are big enough they fall as precipitation-there's more rainfall in winter in UK and occurs in tropicswhat are cryospheric processes - -accumulation (build up of ice and snow) andablation (melting of ice and snow) change the amount of water stored as ice incryosphere, these vary with temperature.-in global cold, inputs into cryosphere are greater than the outputs (less melting)what is the largest and most important flux - evaporation of ocean water to theatmospherewhat is the smallest and less important flux - evaporation of water held insurfaces and vegetation to the atmospherewhat is the global water budget - -describes how the water moves between stores-the amount of time water spends in a store is called residence time-despite different residence times, water is constantly circulating between storesand is considered a renewable resource-in some cases, fossil water is in very deep aquifers and is considered finite andnon-renewable (humans are starting to extract this water from Sahara desert)

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residence times of water sources - -15,000 years in ice caps and glaciers(cryosphere)-10,000 years in groundwater-10 days in atmospheric moisture-1 week in biospherewhat is fossil/ancient water - undisturbed groundwater in an aquifer, under theSahara desert can be extracted for human use but there is little to no recharge, itis a non-renewable resourcewhat is porous rock - -has gaps in it to allow fast movement of water-aquifers will develop when porous rock lieswhat is impermeable rock - no gaps in it, there is slow/no movement of waterwithinwhat are the drainage basin outputs - evaporation, transpiration,evapotranspiration, channel flowwhat is evaporation (as an output) - water turning into water vapourWhat is transpiration (as an output) - -evaporation from within leaves-plants and trees take up water through their roots and transport it to theirleaves where it evaporates into the atmospherewhat is evapotranspiration (as an output) - the process of evaporation andtranspiration together

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what is channel flow (as an output) - (also called river discharge) is the waterleaving the drainage basin through a river or streamwhy does North Africa have low river flows - -30 degrees N, between Hadley andFerrel cell-lots of sinking air - high pressure - no precipitation-high temperature = high evaporation ratesNorth India and Nepal have high river flows, despite being in an area of sinking air(high pressure) - Himalayas are located here, therefore causing lots of reliefrainfallwhy does the UK have high river flows - -lots of rising air (low pressure)-80% of population live in urban areas, impermeable surfaces so the water flowsas surface run off into rivers-north of UK has high relief (relief rainfall)-an island, prevailing winds come over the Atlantic and therefore bring wetweatherwhat are the physical variables within drainage basins influence inputs, flows andoutputs - seasons and climate, soil, vegetation, geology, reliefhow do 'seasons and climate' influence drainage basins - -water may freeze inwinter (decreasing flows)-hotter temps, more evaporation-climate has an impact on vegetation-intense storms generate more precipitation than light rain showers-larger input of water casues flows and stores to increase in size

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how does soil influence drainage basins - -the rates are influenced by soil type,soil structure and how much water is already in the soil-throughflow is faster through openings, such as cracks in the soil or animalburrows-soil type can influence the type of vegetation that's able to grow in a locationhow does vegetation influence drainage basins - -slows its movement (highestwhen there's lots of vegetation)-more veg = more water lost through evapotranspirationhow does geology influence drainage basins - -flows slowly through most rocks(impermeable)-highly permeable rocks or rocks with lots of joints allow water to flow throughthem, faster groundwater flowhow does relief influence drainage basins - -steeper the gradient, fasterprocesses such as direct runoff and throughflow will be-surface stores have a shorter residence time in steeper areas-gradient can also affect the amount of water discharged from a river to theoceanwhat human factors disrupt processes in drainage basins - deforestation, landuse change, urbanisation, cloud seedinghow does deforestation influence drainage basins - -reduces interception-in forested areas, dead plant material on the forest floor helps retain the water,allowing it to infiltrate the soil rather than run off-when forest cover is removed, less infiltration can take place-soil erosion can occur on exposed land, reducing ability to store rainwater

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how does land use change influence drainage basins - -ploughing breaks up thesurface-farming livestock, means the soil in compacted and trampled, decreasinginfiltration and increasing direct runoff-buildings and roads prevent infiltration - floods more likely-urban drainage systems can feed rivers with rainwater more quickly andincrease dischargehow does urbanisation influence drainage basins - -increases chance of flooding-dam construction - regulates river discharge downstream-groundwater extraction - humans remove water from aquifers for industrial oragricultural use, this lowers water table and allows for increased infiltrationhow does cloud seeding influence drainage basins - -adding particles into the airto allow raindrops to form round them and increase rainfall-they did this in Beijing before the Olympics in 2008 to clear the air from pollution-can alter natural balance of precipitationhumans impact on Amazonia - -lots of moist air is blown towards the Amazon fromthe Atlantic ocean-evapotranspiration rate is high in rainforest itself(warm temperatures)-dense canopy, meaning interception is high-lots of deforestation takes place (to harvest timber or for farming), meaningthere's no tree canopy for interception - more water reaching the ground, watermoves to rivers as saturated overland flow-deforestation also reduces the rate of evapotranpiration - less water vapourreaches the atmosphere, fewer clouds and rainfall is reduced - increases risk ofdrought

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