EQ1- the hydrological system Flashcards
stores
-largest=ocean- 97% of water
-2.5% of stores r freshwater: 69% glaciers/ice, 30% groundwater, 1% surface water
hydrology in Polar regions
-85% of solar radiation is reflected
-permafrost creates impermeable surfaces
-lakes + rivers freeze
-rapid runoff in spring
-seasonal release of biogenic gases into atmosphere
-organic + frontal precipitation
hydrology in tropical rainforests
-Dense vegetation consuming 75% of precipitation
- There is limited infiltration
- Deforestation leads to less
evapotranspiration and precipitation
- Very high temperatures
- Very humid
-Convectional rainfall
drainage basin
-an open subsystem within the closed global hydrological cycle
-an area of land drained by a river and its tributaries, with a boundary (known as the watershed), usually composing of hills and mountains.
water cycle- local vs closed
-local = open system (inputs, outputs + throughputs)
-global= closed system (no inputs/outputs only throughputs)
frontal/cyclonic rain
-mid latitudes (uk) where warm tropical air meets cold polar air
-when they meet they don’t mix well, warm less dense air lifted up + over cold dense air = front rain
Orographic/relief rain
-mountains
-warm moist air meets land of high relief
-act as a barrier + force air to rise above them which creates seeder + breeder clouds
-EG Scotland + Lake District
convectional rain
-daily occurrence
-most common in tropical climates- in rainforests it occurs mid-morning before temp rises too high for condensation to occur
-morning heat drives intense evaporation
-bubble of air rises, it cools + creates vapour
-Cumulonimbus clouds- cauliflower looking clouds
factors affecting volume rainfall
-seasonality
-variability: sudden/long term changes to climate can happen. 3 types:
-secular: long term
-periodic: annual, seasonal or monthly
context
-stochastic: random factors (eg
localisation of thunderstorm)
-latitudes: location of drainage basin. higher latitude=colder climate, more snow then rain. at lats where air cells converge (ITCZ) climate will be categorised by rise/fall of air
interception
-intervention of plants leaves in changing direction/stopping precipitation
-any moisture retained by surface of leaf (interception stores) is greatest at start of storms
infiltration
movement of water from surface to soil. the capacity is max rate at which water can be absorbed by soil and is affected by: soil composition, previous precipitation, type/amount of veg, relief of land
surface run off
-water flows overland rather then permeating deeper levels of ground.
overland flow occurs faster where gradient of land is greater
its the primary transfer of water to river channels- heavily influences discharge (moderate/fast)
percolation
-water moves from ground into pours rock or rock fractures (deeper bedrock + aquifers)
-the rate is dependent on fractures that may be present in rock + its permeability- (slow)
groundwater flow
-gradual transfer of water through porous rock, under influence of gravity
-it can sometimes become trapped within deep layers of bedrock, creating aquifers + long water stores for drainage basin (slow)
through flow
-moves through soil + into streams/rivers
-speed of flow dependent on soil type
-clays w high field capacity+ small pore spaces= slower
-sandy drain quick bc they have a lower field capacity, larger pore spaces + natural channels from animals eg worms
-some sport fields have sandy soils to reduce chance of waterlogged pitches- but may increase flood risk else where (moderate/fast)
evaporation
-direct loss of water moisture from surface if a body of water, soil + interception storage to the atmosphere
-rates rise when weather is warm, windy + dry
factors affecting evaporation rates
-volume + surface area of water body- larger sa=faster rate of e
-vegetation cover/built environment surrounding water- anything that reduces direct sunlight to water body will reduce evaporation
-colour of surface beneath water- black tarmac will absorb heat faster than white snow + evaporation will occur faster on tarmac
transpiration
-biological process
-water lost to atmosphere through pores of plants (stomata)
-rates are affected by seasonality, type of veg, moisture content of air + time of day
stores
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-soil water: store in soil which is utilised by plants- MID TERM
-groundwater: store in pore spaces of rock- LONG TERM
-river channel: SHORT TERM
-interception: intercept by plants on branches/leaves - SHORT TERM
-surface storage: store in puddles, ponds, lakes VARIABLE
the water table
- upper level at which pore spaces + fractures in ground become saturated
-used by researchers to assess drought conditions, health of wetland systems, success of forest restoration programmes etc
physical factors influencing the drainage basin
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-climate
-soil composition
-geology
-relief
-vegetation
-size
anthropogenic (human) factors influencing the drainage basin
-cloud seeding: substances dispersed into air to provide something for condensation to occur on in (eg china Beijing games 2008)
-deforestation
-afforestation
-dam construction ( Lake Nasser behind Aswan dam in Egypt – 10-16 billion m3 water loss from Nile)
-change in land use
-groundwater abstraction: (eg china gw irrigates 40% of farmland whilst 70% dw comes from gw)
-irrigation: drop in water table due to high water usage
-urbanisation
