The Water Cycle Flashcards
4 global stores of water
oceans
lakes
aquifers
cryosphere
what type of system is the global water cycle
closed
how much freshwater is held in the cryosphere
70%
how much freshwater is held in lakes
20%
how much water is accesible
1.3%
how much water is stored as aquifers
30%
where are aquifers found
in porous and permeable rocks such as limetsone and sandtsone
cryosphere stores
sea ice
permafrost
ice caps
glaciers
what are the 5 subsytems
cryosphere
biosphere
lithosphere
hydrosphere
atmosphere
largest store in the global water cycle
oceans 97%
features of flashy hydrographs
short lag time
higher flood risk
high peak discharge
features of subdued hydrographs
long lag time
le
what is the water balance
the balance between inputs and outputs
what is required for there to be a river
stores can release water
direct precipitation and
overland flow into river
when does evapotranspiration increase
when it is warmer, and atmosphere can hold more water vapour than the amount of water available
soil water budget - winter uk
precipitation is greater than potential evapotranspiration and soil is in a water surplus
soil water budget- spring uk
potential evapotranspirtion exceeds precipitation
soil water budget- summer uk
there is a deficit of soil water. river levels fall
soil water budget-autumn
soil water is fully recharged and precipitation exceeds evapotranspiration
what is river discharge
the amount of water in a river flowing past a particular point expressed as m3s-1 (cumecs)
bankfull
maximum discharge that a river channel is capable of carrying without flooding
lag time
time between peak rainfall and peal discharge
factors which interect with river discharge
water resources
water related structures
flood alleviation schemes
why are storm hydrographs important
they can predict how a river might respond to a rainstorm
hydrograph of basin with circular shape
flashy,long,thin
hydropgraph of basin with steep sides (e.g river eden in the penines)
flashier
water flows fast
short lag time
overland flow is fast
how does rock type effect flood hydrograph
impermeable- higher overland flow, lower throughflow and infiltration (flashy)
how does vegetation effect the flood hydrograph
thick vegetation holds water in its leaves, and slows movement of water into channel, subdues the hydrograph increasing lag time and reduces peak discharge
effect of heavy rainfall on the hydrograph
higher discharge
harder to infiltrate
how does deforestation effect the hydrograph
reduces interception, less roots means less infiltration
sedimentation of the channel and reduces the bankfull capacity
how does the growth of urban areas impact hydropgraphs
impermeable surfaces
designed to transfer water away quickly
water abstraction reduces the base flow
what is the water balance equation
precipitation = total run off + evapotranspiration + storage
what is the main input to a drainage basin
precipitation
what are the main outputs of a drainage basin
evopration
transpiration
what are the 3 main stores in the drainage basin system
surface storage, soil moisture storage, groundwater storage
what are the 6 main flows in the drainage basin systm
interception
infiltration
through flow
overland flow
surface runoff
three types of rainfall
relief
frontal
convectional
Atmospheric water
Water found in the atmosphere
Mainly water vapour, liquid water and ice crystals
Hydrosphere
A discontinuous layer of water at or near the earths surface
Includes all liquid and frozen surface waters, groundwater’s and water vapour
How much atmospheric water makes up all water
0.4%
How much do oceans cover
72% of the earths surface
Sea level pH
8.4, slightly alkaline
What is the oceans change in pH due to
Increase in atmospheric carbon having an influence on. Marine ecosystems
Sea ice
Forms when sea is is cooled to temps below freezing
Does not increase sea levels
Platforms of ice shelves move out into the ocean
Ice shelves raise sea level when they disconnect from the land
Ice sheet
A mass of glacial land ice extending more than 50,000km2
Cover most of Greenland and Antarctica
Together they store 99% of freshwater
Form here snow that falls in winter does not melt in summer
Ice caps
Layers of ice on land smaller than 50,000km2
Major source of glaciers
Alpine glaciers
Thick masses of ice found in deep valleys or in upland hollows
Permafrost
Ground soil that remains below 0° for two consecutive years
1-1500 metres thick
Formed during glacial periods
Has begun to melt as the climate warms
Release co2 and ch4
4 types of terrestrial water
Surface
Ground
Biological
Soil
What do surface waters include
Lakes
Rivers
Wetlands
Rivers in the water cycle
Act as a store and a transfer
0.0002% of all water
Largest is the Amazon
Lakes in the water cycle
Greater than 2 ha
Mainly freshwater sources
Collections of freshwater in hollows
Wetlands
Areas where water covers the soil, including during the growing season
Water saturation is high
Support species
Creates favoured conditions for plant growth
Groundwater
Water that collects underground in the pore spaces of rock
Complete saturation of rocks and pores is the water table
Reducing due to extraction for use in agriculture
Soil water
Held together with air in unsaturated upper weathered laters of the earth
Effects run off, infiltration, soil erosion
Soil moisture is a key variable in the transfer of heat and energy (evaporation and plant transpiration)
Biological water
All water stored in biomass
High in rainforests
Trees take in through roots and it leaves through transpiration
Atmospheric water
Most commonly exits as water vapour
Absorbs, reflects, scatters solar radiation to maintain life
Cold air cannot hold as much water vapour
Increase in vapour leads to increase in temps
Clouds are visible - form from air being saturated after cooling of air/ increase in vapour
Three main factors driving changes in magnitude of stores
Evaporation
Condensation
Cryospheric processes
When does evaporation occur
When energy from solar radiation hits the surface of water or land and causes liquid to turn to gas
What does the rate of evaporation depend on
Amount of solar energy
Availability of water
Humidity of the air
Temp of the air
What is transpiration
Water is transported from the roots of a plant to its leaves and lost through its leaves with its stomata
What energy is used during evaporation
Latent heat energy and so it cools its surroundings
Condensation
Excess water in the air is converted to liquid
Water molecules condense on tiny particles (condensation nuclei)
Direct cause of all forms of precipitation
When does condensation occur
When the temp of the air is reduces to dew point but volume remains the same
-e.g. warm moist air passes over surface
When the volume of air increases but there is no addition of heat when air rises and expands in the lower pressure of the upper atmosphere (adiabatic cooling)
When does adiabatic cooling occur
Air is forced to rise over hills
Masses of air of diff temps and density meets
Localised warm surfaces heat the air above
Cryopsheric processes
Accumulation and ablation
Interglacial periods = ablation < accumulation sea levels will rise
Cryosphere is major store of water
Interception storage
Precipitation that calls on the vegetation surfaces and is temporarily stored here
It can be evaporated into atmosphere or absorbed and transmitted to ground storage
Percolation
Downward movement of water within the rock under the soil surface
Saturated
Any water store that has reached maximum capacity
Through fall
Portion of precipitation that reaches the ground directly through gaps in the vegetation canopy, drops from leaves twigs and stems
Occurs when the canopy surface rainwater storage exceeds its storage capacity
Drainage basin
Areas that supply rivers with a supply go water
They are separated by one another with a boundary known as the watershed
Process of precipitation on a hill slope pt.1
-precipitation lands on surface and vegetation (providing interception store)
-a lot of the water captures is evaporated back into the atmosphere
-water makes way to ground through throughfall and stem flow
-the water on the ground is infiltrated controlled by gravity
precipitation in the hill slope pt.2
-a soils porosity is controlled by texture, structure, organic content which determines rate of infiltration
-pores and fissure can be made by organisms
-larger pores allow for more downwards water flow
Soil storage
The amount of water held in the soil
Consists of solid particles with spaces between them
When rainfall intensity is greater than the infiltration rate …
The soil has reached infiltration capacity and the soil will be saturated
Water will build up on the surface (surface storage)
Much of this then evaporates back into the atmospher and lost to the drainage basin
When surface storage is full then overland flow will begin
Lateral movement of the soil = through flow
How does the river transfer water
Channel flow
Rivers only occur if
There is direct precipitation
Over land flow into the riber
River regime
The variability in a rivers discharge throughout the course of a year in response to temperature, precipitation, evapotranspiration.
Characteristics of UK rainfall
Fairly evenly distributed with a slight autumn/winter maximum
Seasonal variations in temp = evapotranspiration concentrated in the summer
What is a storm hydrograph
The graph of the discharge of a river leading up to and following a rainfall event
They can predict how a river might respond to a rain storm
This can help in managing the river
What is rising discharge shown by
The rising limb of the storm hydrograph
What type of hydrography’s are at a circular drainage basin
Flashy - high peak discharge, short lag time
Drainage basins with flashy hydrography’s
Steep sided
Impermeable rock
Already saturated
Drainage basins with subdued hydrograph
Snow rather than precipitation
Low intensity precipitation - high rate of infiltration
Small
Human effects on the flood hydrograph - deforestation
Deforestation - reduces infiltration rate
-rapid overland flow
-flashy hydrograph
-exposes soil to great soil erosion - sedimentation of the channel
Reduces bankfull capacity of river
Human impacts on the flood hydrograph - agriculture
Ploughing breaks up top soil and allows great infiltration
Subdueds the hydrograph
Ploughing wet soil can cause impermeable smears in the soil
Grass crops increase infiltration
Animals can compact soils leading to overland flow
Human impacts on the hydrograph - urbanisation
Impermeable surfaces
Flashy hydrograph
Settlements are built on flood plains
Designed to transfer water quickly
Water abstraction reduces the base flow
Deforestation impacts on the water cycle
Less evaporation
More run off
Stream flow increase
Amount of change depends on-amount of rainfall,how much deforestation, land use after
Positive feedback of deforestation on water cycle
Evapotranspiration is low
Water leaves the area in river channel
Less water vapour in atmosphere
Precipitation levels fall
Flow is reudced
Agricultural soil drainage
Subsurface drainage removes excess water from the soil profile
Costly but beneficial for poorly drained soils
Advantages of soil drainage
Improved soil structure, greater root penetration
Improved aeration, microorganisms thrive in necessary supply
Heavy machinery can work on the land without danger of compaction
Large numbers of animals allowed to graze
Disadvantages of agricultural soil drainage
Increases the speed of through flow increasing likelihood of flooding
Dry topsoil vulnerable to wind erosion
Nitrate loss
Water abstraction
Problems occur when amount demanded exceeds amount available
E.g. in Europe groundwater is main source of freshwater
Would result in sinking water tables and higher extraction costs
