Water cycle EQ1 Flashcards
describe the hydrological cycle
a closed system
driven by solar energy & gravitational potential energy
is a fixed amount, not external inputs or outputs
3 states within the system - solid, liquid & gas
stocks = where water is held
fluxes = the rate of flow between stores
processes = physical mechanisms which drive fluxes
what is the crysophere ?
frozen water stores on earth
what is blue water ?
water stored in rivers, lakes etc and groundwater in liquid form ( visible )
what is green water ?
water stored in soil and vegetation ( invisible )
what is fossil water ?
not renewable or for human consumption
what is a drainage basin ?
any area of land where precipitation collects or drains off of into a common outlet
how does climate affect the drainage basin ?
influences the type and amount of precipitation overall as well as the amount of evaporation
also impacts vegetation which influences the amount of green water
how does soil affect the drainage basin ?
determines the amount of infiltration and through-flow
also affects type of vegetation
how does geology affect the drainage basin ?
impacts percolation and groundwater flow
how does relief affect the drainage basin ?
altitude impacts precipitation totals as well as the amount of run off
how does vegetation affect the drainage basin ?
the amount of interception, infiltration and overland flow will be impacted by more or less vegetation
what is a water budget ?
the annual balance between inputs and outputs
can be global or local scale
can have a surplus or deficit balance
how does over abstraction affect drainage ?
how does deforestation affect drainage ?
because tropical forests thrive on thin soil, removing the canopy affects this top soil and then impacts the natural water cycle
how does changing land use ( urbanisation ) affect drainage ?
more impermeable surfaces = reduced infiltration & increased run off
urban drains = water enters river systems quicker and can flood quicker
how do reservoirs affect drainage ?
delay the natural flow of water & removes it from the drainage basin
what is afforestation ?
the planting of trees in an area that hasn’t been forested in recent times
describe orographical rainfall
prevailing winds blow air from sea
relief pushes air up until it cools and condenses
then precipitates
describe cyclonic rainfall
warm moist air rises when it meets a colder air mass
the warm air condenses and forms clouds
a warm front causes mild to moderate prolonged rainfall
cold front = warm air rises and causes unstable weather
describe convectional rainfall
the sun heats the ground and the ground absorbs and reflects this heat
causes the air above the ground to warm too
air rises and condenses at higher altitudes
common in tropical areas and can happen with little warning
what is a rain shadow ?
a dry area of the leeward side of a mountain that gets little rain due to the mountain sheltering it
e.g the Owens valley in California
what are the 6 flows of the drainage basin ?
- interception = retention of water by vegetation and soil
- infiltration = water absorbed or soaked into soil
- percolation = deep transfer of water into permeable rock
- throughflow = transfer of water down slope through soil
- groundwater flow = flow transfer or percolated water through permeable or porous rocks
- surface run off = movement of water that is unconfined by a channel across the grounds surface
what are the 3 outputs of the drainage basin ?
- evaporation = moisture lost directly into the atmosphere from water surfaces, soil & rock
- transpiration = water lost through the stomata of plants through respiration
- channel flow = flow of water now confined to a channel
what is a river regime ?
the annual variation in discharge of a river at a particular point
what is a storm hydrograph ?
the variation in a rivers discharge at a specific point over a short period of time
usually in a storm event
what are the 3 main aspects of a storm hydrograph ?
- lag time = the time interval between peak rainfall & peak discharge
- recession limb = when the discharge starts to decrease
- base flow = the normal day to day discharge of the river
what is a flashy storm hydrograph ?
one with a short lag time, steep rising and recession limb
what is a subdued storm hydrograph ?
one with a long lag time, more sloped rising and recession limb
what 3 factors affect the shape of a storm hydrograph ?
- rock type = impermeable = increased run off = flashy
permeable = more percolation = subdued - vegetation = low density = lower interception = rapid movement = flashy
high density = opposite so subdued - human activity = impermeable surfaces = flashy
permeable = subdued
what is a flood
an event that occurs when the discharge of a body of water is of sufficient quantity to overflow it’s channel and submerge the surrounding land
what areas are most at risk from flooding
- low lying regions / river estuaries
- low lying urban regions
- areas with small basins
