Water Cycle

ablation

solid to liquid

freezing

liquid to solid

evaporation

liquid to gas

condensation

gas to liquid

sublimation

solid to gas

deposition

gas to solid

energy causing change in states

latent heat

what do hydrostatic charges do

use cohesion and adhesion to help water move through soil and rock

how energy influences evapotranspiration

warmer and brighter regions have increased amounts and speed of evaporation

how surface area influences evapotranspiration

larger surface area means more evaporation

how humidity influences evapotranspiration

determines how much more air the water can hold

relative humidity

% of water that air can hold at a given temperature

HE%

relative humidity

100% humidity

level of saturation in air when water droplets from aka dew point

dew point

100% humidity

how temperature influences evapotranspiration

warmer air can hold more water vapour

how density of vegetation influences evapotranspiration

more plant matter means more transpiration

how types of leaves influence evapotranspiration

effect efficiency, how and when water is moved

radiation fog

the loss of heat to space, when the land cools overnight by thermal radiation meaning the air condenses and allows fog to form

advection fog

the transfer of heat energy to cooler ground/water surfaces, air moves over warm land and meets cool water surface, this causes it to cool into clouds and condense

adiabatic fog

reduction in air pressure as air rises, pockets of warm air rise into areas of less pressure where it cools into clouds and condenses

El Nino

wetter, cooler, snowier conditions as warm water is pushed east toward west coast America and pushes Pacific jet stream south of its neutral position

La Nina

drier and warmer temperatures as trade winds are much stronger during this season pushing warm water toward Asia while upwelling on the west coast of America encourages cool water to the surface which push the pacific jet stream north of it’s neutral position

eccentricity

measures the shape of the orbit, whether it is more cyclical or ovular

impacts of eccentricity

* length of season - a smaller/more cyclical orbit = even season lengths

perihelion

when orbit is closest to the sun (January)

aphelion

when orbit is furthest from the sun (July)

difference between perihelion and aphelion

6\.8% more solar radiation in perihelion, 5.1mill km distance difference, perihelion currently occurs in NH in winter and SH in summer - this will flip in 13,000yrs

obliquity

the axis tilt relative to orbital plane

impact of obliquity

* reason for season
* greater tilt = more extreme seasons and deglaciation

precession

wobble of the Earth’s axis due to tidal forces caused by gravitational influences - causes a bulge at the equator

precession impacts

* makes seasonal contrasts more extreme in one hemisphere and less in the other
* affects seasonal timing
* apsidal precession

apsidal precession

irregular wobble of orbital eclipse which changes orientation of orbit relative to elliptical plain

impact of global warming on the water cycle

more energy means faster transfers between stores and creates a powerful/dynamic system

what does water vapour condense on

hydroscopic nuclei, smoke, dust, pollen

experiences most rainfall annually

India - 230,000mm in 1861

experiences least rainfall annually

Central Chile - 0mm for 14 years

types of rainfall

frontal uplift, orographic uplift, convectional uplift

frontal uplift

occurs when less dense, warm air is lifted over cool air creating a front, this warm air cools and condenses to rain, heaviest rainfall at the front

orographic uplift

occurs in mountainous regions where warm, moist air is forced over high ground, cools as it rises and condenses to rain, as it comes down the other side it cools produces a rain shadow and drier conditions

rain shadow

little rain on other side of orographic uplift

convectional uplift

form when two air masses interact, air travels over a warm spot and so a bubble of air is heated and rises before it cools and condenses into clouds, and rains

source

upland area, the start of a river

drainage basin

area of land drained by main rivers and tributaries

watershed

imaginary boundary of drainage basin

tributary

water stream joining large river

confluence

point where two rivers join

estuary

last section of river influenced by tidal flows and saline water

mouth

where river flows into sea or lake

interception loss

precipitation that doesn’t reach the ground surface

vegetation intercepts …. of precipitation

50%

raindrop splash effect

erosive force which causes weak soil to aggregate and break releasing soil particles

influences on raindrop splash effect

ground cover reduces the effect by slowing runoff and reducing potential for sheet erosion eg grass

surface storage

* occurs when infiltration rate is exceeded and local area is saturated


* temporary and varies in size

how human activity has influenced surface storage

* soil compaction
* deforestation
* soil ploughing
* impermeable surfaces (tarmac)
* reservoirs

soil moisture

influenced by soil depth, structure, texture, bedrock geology, temp, humidity, precipitation, wind, vegetation type, growing season, human activity

how soil moisture is removed

by evapotranspiration, percolation, and plant uptake

field capacity

when water balance is at equilibrium

deficit

output exceeds inputs

drought - needs recharging

surplus

inputs exceed outputs

saturation leading to water logging and flooding

types of overland flow

* rills
* gullies
* sheet flow

rills and gullies

temporary channels cut by overland flows - gullies are bigger

causes and impacts of overland flow

when precipitation exceeds infiltration, causes soil erosion

sheet flow

thin layer of surface water covering a large area

through flow

* underground lateral flow in soil when it is fully saturated, flows until it reaches a body of water


* faster along soil pipes (eg worm holes or dead plant root holes)

water table

upper limit of saturated bedrock, rises and falls relative to rainfall

what through flows cause at surfaces

* springs
* bogs
* marshes

groundwater flows

slow moving water through permeable rocks

* fastest along limestone potholes and cave systems

artesian wells

when water pressure is great enough to push water to surface

water balance equation

p=q+et+/-s

p

precipitation

q

discharge

et

evapotranspiration

s

store

impacts of soil moisture deficits

* dry and cracked land
* vulnerable to wind erosion
* drought
* crop failure

infiltration rate influences

* soil structure - permeable (sand) /impermeable (clay)
* soil depth - influencing field capacity

human impacts on infiltration

* deforestation removes surface cover exposing soil to raindrop splash effect
* machinery compacts soil reducing infiltration rates and increasing surface runoff
* urbanisation increases areas of impermeable surfaces increasing runoff and decreasing infiltration

maximum sustainable yield

most water that can be retracted from a drainage basin before soil and aquifers need to recharge

why the water balance equation is used

to help hydrologists manage drainage basins, warn governments of water shortages, and monitor the effects of pollution

how precipitation causes variation in water balance

* intensity
* duration
* type

how discharge causes variation in water balance

* speed of water transfer to river
* size and shape of basin
* relief
* human activities and management

how evapotranspiration causes variation in water balance

* temperature
* windspeed
* amount of surface storage
* vegetation type and cover

how stores causes variation in water balance

* soil type and depth
* geology
* vegetation type and cover
* temperature (cryosphere)

how the water balance is measured

* rain gauge (mm) placed around basin to maintain average reading

volume of water input into a system

rainfall x basin area

how discharge is measured

* river gauging stations on major tributaries and principle river of drainage basin to monitor flow changes and outputs
* m3/s

discharge equation

x - sectional area x velocity

measuring discharge allows

short term reaction to storm events, awareness of time it takes river to return to base flow, monitoring of seasonal/annual flow variation

ground water station

* detects level fo water table
* uses pressure and infrared sensors

ground water station indicates

* infiltration capacity
* saturation level
* flood risk
* soil moisture level
* need for recharge
* aquifer supply
* spatial and temporal variations

how relief influences discharge

steeper = quicker runoff

how climate zones influences discharge

wetter along equator meaning there is more discharge here

how weather conditions influences discharge

* drier = less discharge
* extreme rainfall = hugely increased discharge

how rainfall influences discharge

* high rainfall = greater discharge (eg in winter and when there is less plants meaning quicker overland flows)
* less rainfall and more plants = lower discharge (eg summer)

how land use influences discharge

less vegetation = greater discharge

how rock and soil type influences discharge

permeability and porosity

river discharge

volume of water passing measuring unit at a given time

higher discharge, higher rainfall, less evapotranspiration

winter

causes river discharge to fall

* in spring and summer when plants take up more water and leaves grow, increasing evapotranspiration
* late summer when temps are at their highest and plants in full leaf

steep hydrograph

* steep relief
* impermeable ground surface
* bare earth