water cycle Flashcards
systems?
systems- a set of interrelated components working together towards some kind of process
what are systems made up of?
inputs —> matter or energy is added to the system
outputs —> matter or energy leaves the system
stores —> a part of the system where something is held for a period of time
flows —> a link between 1 store and another, along which something moves
boundaries —> the edge of the system (the line between 1 system and another)
open system, closed system and dynamic equilibrium?
open system —> energy and matter enter and leave the system
closed system —> energy can enter and leave but matter cannot enter or leave (matter can be water) —> it can only cycle between stores
dynamic equilibrium —> inputs and outputs are equal —> no overall change to the system
positive and negative feedback?
positive feedback —> when a chain of events amplifies (increases) the impacts of the original event
negative feedback —> when a chain of events nullifies (reduces or stops) the impacts of the original event
positive feedback examples:
- temperatures increase —> ice melts —> less ice cover —> less of the suns energy is reflected —> more of the suns energy is absorbed —> temps increase
- temperatures increase —> ocean temp increases —> warm water less able to dissolve gas —> CO2 released into the atmosphere —> more CO2 to act as a greenhouse gas —> temp increase
negative feedback examples:
- co2 in atmosphere increases —> extra co2 causes plants to grow —> plants remove co2 from the atmosphere —> amount of co2 in the atmosphere decreases
global water stores
global water stores:
- hydrosphere —> all the water on earth —> it may be in liquid, solid and gas form (water vapour stored in the atmosphere)
- cryosphere —> all forms of frozen water
- biosphere —> all living things e.g. plants, animals, fungi, insects and bacteria
- lithosphere —> the outermost part of the earth, including the crust and upper parts of the mantle
- atmosphere —> layer of gas surrounding the planet
(water is moved between the stores)
water stored in the atmosphere and biosphere —> water is stored there for a short period of time
water stored in the cryosphere and lithosphere (groundwater) —> water is stored there for a long period of time
water?
all water on earth:
- 97% of water is found in oceans
- only 3% of water on earth is fresh water
out of the 3% fresh water:
- only 1% of fresh water is easily accessible fresh water
- 79% of fresh water is stored in ice caps and glaciers
- 20% of fresh water is stored in groundwater
out of the 1% of easily accessible fresh water:
- 52% comes from lakes
- 38% comes from soil moisture
- 8% comes from atmospheric water vapour
- 1% comes from rivers
- 1% comes from water within living organisms
condensation , evaporation, precipitation and cyrospheric processes
- global hydrological cycle —> water is continuously cycled between different stores in a closed system
- closed system —> fixed amount of water on the planet —> water is just moved around (water changes state as it moves between stores)
- gas to liquid/ liquid to gas —> condensation/ evaporation
- solid to liquid/ liquid to solid —> melting/ freezing
- solid to gas —> sublimation
- gas to solid —> deposition
condensation:
- gas to liquid
- the magnitude of condensation flow depends on temperature and the amount of water vapour in the atmosphere e.g. large/rapid drop in temperature and lots of water vapour —> condensation levels will be high
evaporation:
- liquid to gas
- the magnitude of evaporation depends on temperature and supply of water e.g. low temperatures and a small supply of water —> evaporation levels will be low// high temperatures and a large supply of water —> evaporation levels will be high
cloud formation and precipitation:
how do clouds form?
- warm air cools and condenses into water droplets which gather as clouds —> when water droplets get big enough, it falls as precipitation
- water droplets are too small to form clouds on their own, there must be tiny particles of other substances (e.g. dust or soot) to act as condensation nuclei
what causes rain?
- other air masses —> warm air is less dense than cool air —> when they meet, the warm air is forced to rise —> air cools and condenses to form clouds —> frontal precipitation
- topography —> when warm air meets mountains, it is forced to rise —> air cools and condenses to form clouds —> orographic precipitation e.g. the pennines
- convection —> sun heats up the ground —> moist air rises —> air cools and condenses to form clouds —> convective precipitation
- precipitation is generally higher in the tropics than at the poles
- at the poles, cold air can’t hold as much water —> less rainfall
cyrospheric processes:
- inputs (accumulation) —> snow added to a glacier
- outputs (ablation) —> glacier melts
- positive balance —> accumulation > ablation (colder temps)
- negative balance —> accumulation < ablation (warmer temps)
(negative balance over time due to climate change)
why do some parts of the earth receive more solar radiation than others (affects magnitude of evaporation and condensation)
- curvature of the earth —> more solar radiation is received and absorbed near the equator than at the poles —> the suns rays strike the earth most directly near the equator —> while at the poles the rays strike at a steep angle
- radiation travels through a greater depth of atmosphere nearer the poles —> more radiation is lost to scattering and absorption by gases/particles in the atmosphere
drainage basins
- drainage basin (catchment area for water) —> the area surrounding the river where the rain falling on the land flows into that river (once rain caught within the area, it ends up in the river)
- water shed —> edge of drainage basin —> area of high land that separates the drainage basins —> water on 1 side of high land will end up in one drainage basin and water on the other side of the high land will end up in the other drainage basin
- confluence —> the point at which 2 rivers meet
- tributary —> a small river or stream that joins a larger river
inputs:
- precipitation
outputs:
- evapotranspiration
- discharge
stores: (CIGSS)
- channel storage - water held in a river
- interception - water stored by trees
- groundwater - water stored in the ground
- soil storage - water stored in the soil
- surface storage - water in puddles, ponds and lakes
flows:
- stemflow - water running down a plant stem or tree trunk
- surface runoff/overland flow
- infiltration - water moving from the ground into the soil
- throughflow - flow of water through soil (downhill)
- percolation - water moves from soil into rocks
- groundwater flow - flow of water through rocks
- channel flow- movement of water within the river channel
water balance?
water balance equation:
P = Q + E + S
P = precipitation (inputs)
Q = run-off/discharge (outputs)
E = evapotranspiration (outputs)
S = storage
water balance diagram:
- months along x axis and temperature along y axis
- in summer, trees grow leaves —> more evapotranspiration// less rainfall
- in winter, trees lose leaves —> less evapotranspiration// more rainfall
- field capacity —> maximum amount water that can be stored in the soil
- soil moisture recharge —> precipitation > evapotranspiration
- soil moisture utilisation —> evapotranspiration > precipitation
- soil moisture surplus —> precipitation > evapotranspiration
- soil moisture deficit —> evapotranspiration > precipitation
hydrographs
- hydrographs —> shows river discharge over a period of time
- flood hydrographs—> shows river discharge around the time of a storm event
- river regime —> shows the variations in river discharge over a year
- discharge —> volume of water that flows into a river per second (volume of water - m^3) (discharge is measured in m^3/s —> cumecs)
- lag time —> the delay between peak rainfall and peak discharge —> this delay happens because it takes time for rainwater to flow into a river
- peak discharge —> when the river discharge is at its greatest
- rising limb —> where the river discharge increases as rainwater flows into the river
- falling limb —> where the river discharge decreases because less water is flowing into the river
- base flow —> normal flow of river if there weren’t any heavy rainfall events
- storm flow —> extra water added into river because of rain storm
flashy:
• short lag time
• steel rising and falling limb
• higher flood risk
• higher peak discharge
subdued:
• long lag time
• gentle rising and falling limb
• lower flood risk
• lower peak discharge
factors affecting river discharge (flashy and subdued):
- ground steepness: steep —> less time to infiltrate —> surface run-off increases —> river discharge increases// water flows more quickly downhill —> short lag time
- vegetation: more vegetation —> interception increases —> surface run off decreases —> river discharge decreases// vegetation binds the soil together and increases its capacity to store water —> infiltration increases —> surface run off decreases —> river discharge decreases// interception increases —> trees slow the movement of water into river channels —> longer lag time
- soil type: impermeable soils —> infiltration decreases —> surface run off increases —> river discharge increases// infiltration decreases —> results in rapid overland flow —> shorter lag time —> water reaches channel more quickly
- drainage basins —> larger drainage basins: collect more precipitation —> river discharge increases// water has to travel a long distance before it reaches the river channel —> longer lag time// drainage density (amount of rivers and streams over an area) —> lots of rivers and streams in a small space —> rain doesn’t have to travel very far before it reaches the river channel —> short lag time
- urban and rural areas —> urban: covered in impermeable surfaces —> infiltration decreases —> surface run off increases —> river discharge increases// infiltration decreases —> results in rapid overland flow —> shorter lag time —> water reaches channel more quickly
physical factors affecting the water cycle
extreme weather
storms:
- storms generate precipitation —> soil becomes saturated —> infiltration decreases —> surface run-off increases —> river discharge increases// wind can damage vegetation —> interception and evapotranspiration decreases —> surface run off increases
droughts:
- vegetation dies —> less evapotranspiration —> less precipitation —> drought (positive feedback loop) —> decrease in river discharge
seasonal changes
summer:
- higher temperature cause the ground to be harder and more impermeable —> infiltration decreases —> surface runoff increases
- more vegetation —> interception and evapotranspiration increases —> surface run off decreases
winter:
- vegetation dies and leaves are lost —> interception and evapotranspiration decreases —> surface run off increases
- more rainfall —> discharge increases
human factors affecting the water cycle
deforestation:
short term:
- deforestation —> less evapotranspiration and interception —> surface run off increases —> river discharge increases —> risk of flooding increases (local)
long term:
- deforestation —> less evapotranspiration —> less water vapour in the atmosphere —> fewer clouds form —> less precipitation —> changes in global precipitation patterns —> risk of drought increases (global)
positive feedback loop:
- deforestation to create space for crops —> less evapotranspiration —> less rainfall —> ground becomes drier and less fertile —> new areas of land need to be cleared to grow crops
land use (urbanisation)
- construction creates impermeable surfaces —> infiltration decreases —> surface runoff increases —> river discharge increases
agriculture
- ploughing breaks up the surface of the soil —> infiltration increases —> surface run off decreases
- crops —> interception and evapotranspiration increases —> surface run off decreases (short term)// evapotranspiration increases —> more water vapour in the atmosphere —> clouds form and precipitation increases —> soil becomes saturated —> infiltration decreases and surface run off increases (long term)
- compaction —> livestock and machinery compact the soil —> infiltration decreases —> surface run off increases
- water abstraction for irrigation —> soil becomes dry —> infiltration decreases —> surface run off increases —> river discharge increases
river eden case study
facts and location
- the river eden is 145km long and is located in north west of england in cumbria
- the eden drainage basin is in north west england, between the mountains of the lake district and the pennies —> topography —> clouds form —> rain etc
- it’s source is in the pennine hills in south cumbria
- it’s mouth is in the solway firth at the scottish border
physical causes of flooding in the river eden
geology
- upland areas of river eden are mainly covered in igneous rock —> impermeable surface —> infiltration decreases —> surface run off increases// low land areas of the river eden are mainly covered in sandstone and limestone —> permeable rocks —> become saturated so no more water can infiltrate —> surface run off increases —> flashier hydrograph
gradient
- steep gradient —> elevation drops from 690m to 180m —> water doesn’t have time to infiltrate and will run off —> flashier hydrograph
weather
- rainfall is higher than the national average in the eden basin due to topography —> creates orographic precipitation —> around 2800mm annual rainfall in the upland areas —> lead to surfaces exceeding field capacity —> no more water can infiltrate —> runoff increases —> flashier hydrograph
drainage basin shape
- carlisle sits at the confluence of the rivers eden, petteril and caldew—> lots of water coming together at 1 point
- drainage basin is long and thin —> less places for water to go to —> water concentrated towards carlisle —> flashier hydrograph
human causes of flooding in the river eden
deforestation
- deforestation to make space for housing —> 10,000 new homes were built in carlisle —> deforestation —> interception and evapotranspiration decreases—> surface run off increases —> flashier flood hydrograph (short term and long term)
construction
- surfaces tend to be impermeable —> infiltration decreases —> surface run off increases —> flashier hydrograph
farming
- soils become compacted by heavy machinery or trampling by livestock e.g. between 2000 and 2009, there was a 30% increase in the number of cattle in the eden valley —> compaction increases —> infiltration decreases —> surface run off increases —> flashier hydrograph
