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water cycle and water insecurity - Coggle Diagram
water cycle and water insecurity
global hydrological cycle
stores
:
oceans(1335000)
lakes
aquifiers
cryosphere(26000)
vegetation
soil moisture
groundwater storage(15300)
flows:
infiltration
throughflow
percolation
channel flow
surface runoff
processes:
precipitation
transpiration
evaporation
cryosphere exchanges
runoff
drainage basins
(open system where an area of land is drained by a river)
physical factors affecting drainage basins:
climate
: impacts inputs and outputs
it influences precipitation that goes into basins and evaporation of water. it also affects vegetation type.
vegetation cover:
area with high vegetation cover means it has more interception but less surface runoff.
soil
: impermeable soil can stop infiltration and increase surface runoff, permeable soil can increase infiltration and cause groundwater to recharge
relief
: sleeper slopes mean faster surface runoff
r
ock type
: impermeable rocks stop infiltration and increase runoff, permeable rock increases infiltration and reduces runoff.
human factors affecting drainage basins:
river management/resevoirs:
construction holds back river flow, overabstraction for domestic use reduces river flows
deforestation
: clearing trees reduces evapotranspiration, decreases interception so faster infiltration and surface runoff.
- land use changes:
agriculture- cattle compacts soil so cant take in water
urbanisation- increased impermeable surfaces such as tarmac reduces infiltration and increases surface runoff.
eg amazonia:
deforestation has disruted drainage basin cycle by:
lower humidities
less precipitation
more surface runoff and infiltration
more evaporation
more soil erosion
water budgets and river regimes
water budgets:
they show the annual balance between inputs(evapotranspiration, precipitation) and outputs (runoff).
river regimes:
describes the annual variation in discharge of a river affected by:
size of river
seasonality
temps
geology and soil
type of veg cover (wetlands or forest)
human activity
eg Yukon river, Alaska:
is in a tundra climate
variable climates across seasons
highest peak discharge is in may-june (due to meltwater)
storm hydrographs:
1=peak discharge
2=peak rainfall
3=lag time
4=rising limb
5=falling limb
physical factors affecting storm hydrographs:
size, shape and density of river
larger areas increase peak discharge and lag time
the more circular shape the shorter the lag time
denser network increases flow and peak d
relief and veg:
steeper area increases peak d and reduces lag time
higher veg cover results in higher interception and evapotranspiration
rock and soil type
permeable ones (eg limestone) will be able to have high infiltration and longer lag time reducing peak d
impermeable ones (eg clay) prevent infiltration and deacrease lag time and increase surface runoff
human factors:
urbanisation
deforestation
water management
Droughts
(4 types:
meteorological,hydrological
,agricultural,socio-economic)
physical causes of droughts:
ENSO cycles (changes in the pacific ocean):
normal conditions=
winds from east to west
air pushes warm water up
- El Nino:
every 3-5 yrs and lasts 18months
Wind patterns change from the west pacific and reverse to the east
warm water moves to south-A coasts
cooler air in AUSTRALIA so oceans colder and the is little rainfall so have INCREASED DROUGHT RISK
- La Nina:
low air pressure in south east asia and australia leads to increased rainfall RISK OF FLOODING
south A receives high pressure which reduces rainfall INCREASED DROUGHT RISK
Human causes of drought:
deforestaion+overgrazing:
reduces vegetation cover so reduces evapotranspiration rates reducing atmospheric moisture and precipitation levels, increasing surface runoff
population growth
overabstraction
eg drought in the Sahel:
facing 30-40% annual rain decrease
human factors affecting it= overabstraction+overgrazing of cattle+popuklation growth
droughts affecting ecosystems:
WETLANDS:
= areas of land saturated with water permanently
when water supply is reduced, areas of land will shrink and dry up
results in less habitats for animals and vegetation
extinction and migration of animals
FORESTS:
-functions=habitats, food sources, carbon regulation, timber production
droughts prevent tree growth as they need water for photosynthesis
this ruins water transpors and less carbon taken in, less habitats etc
eg: 2000-2003 USA drought
unusually hight temps caused drought so many pinon trees died
dry condition attracted bug which infected and killed trees
90% trees died
loss of habitats and animals migrated
Flooding
meteorological causes of flooding:
flash flooding due to low pressure producing heavy rainfall
prolonged heavy rainfall due to mid latitiude depression (low air p causing lots of rain), cna lead to saturated soil stopping infiltration increasing surface runoff
extreme monsoon rainfall due to changes in winds of ITCZ as they move north eg suth asia and india are at risk in summer
La Nina in autralia due to low air pressure
human causes of flooding:
urbanisation due to increased impermeable surfaces
river management like dams can protect from floods but sometimes does opposite as it can displace large volumes of water to somewhere else
agriculture increase surface runoff
deforestation as it stops interception from plants increasing surface runoff
eg 2015 floods in UK:
faced unusually heavy rain due to prolonged intense rainfall
carlisle and
cumbria
were worst hit
in cumbria:
42000 homes left with no power
5000 homes flooded in 3 days
the home damage were £150million worth
100 bridges damaged
road and rail travel suspended
businesses had to close
shops lost stock
£200 million loss from economy
climate change and water cycle
effect on inputs and outputs:
precipitation+evaporation:
increased temps increase evaporation from ocean so increases rainfall and tropical storms and flood risks
effect on stores and flows:
stores:
-surface runoff: increases as temp increases
groundwater flow: uncertain due to human abrtaction
flows:
lakes and resevoirs
storage deacrases as temp increases
soil moisture
wherever rain increases soil moisture increases
snow and glaciers
increases climate melts cryosphere
sping melt starts earlier and snow cover season decreased
oceans
possibilities of genaration of more cyclones
rising sea levels
causes of water insecurity
(water stress= <1700m3 per person)
(water scarcity= <1000m3 per person - eg egypt)
(absoulute water scarcity= <500m3 per person -eg in syria+saudi arabia)
human causes:
contamination of water by agriculture industrial and domestic pollution
overabstraction from rivers and lakes
physical causes:
climate change
evaporation
discharge into the sea
saltwater enroachment=when groundwater nearby is contamnated with saltwater- local abstraction increases the risks of it happening
eg saltwater enroachment in the pacific islands:
lowlying lands rely on aquaifiers
these are threatened by saltwater enroachment as a result of overabstraction and population growth
rising demands and future water scarcity:
the UN has predicted an increase in global water demand by 55% by 2050
this is due to secondary industries, thermal electricity genaration, and domestic use
consequences of water insecurity
global pattern of water scarcity:
avaliabilty
access
ultilisation
eg in middle east and north africa face water shortages
importance of water supplies:
agriculture
industry and energy
domestic use
conflicts between water users:
competition between users and uses
transboundary conflicts in
Eg RIVER NILE conflicts
river shared by 11 countries incl egypts, ethoipia, eritrea and kenya
its 6700 km long
water gets used for domestic and industrial and agriculture
pressures increase due pop growth and cliate change
mainly supplies egypt (95%) and sudan
in 1929 water agreement made between egypt and UK to provide more water allocations to sudan which led conflicts on the nile
in 2011 ethiopia announced construction of a mega dam which egypt disagreed with
CONFLICTS REMAIN UNRESOLVED
managing water supplies
Hard engineering:
Water transfers = diversion of water from water from one drainage basin to another
desalination=removing excess salt from water by electrolysis (done in UAE and middle east - is very expensive)
mega dams = managing water supplies and demand which can produce HEP (however results in methane being released which can reudce fish stocks)
EG CHINA SOUTH-NORTH TRANSFER:
delivers 25billion m3 of freshwater/yr to north costs $80million resulted in relocation of 30000 ppl by force there are 2 routes already and 3rd one is being planned doesn't actually address the underlying causes of water shortages in the north (due to inefficient industrial and agruicultural use!!)
sustainable water management:
aims to minimise wastage and pollution of resources, ensure access of safte water to everyone at affordabel orices, and guarntee equal distribution within countries
smart irriagtion- provides crops with suitabel amounts of water which has been found to conserve water with minimal crop loss
done in china and australia eg china saved 25% water and australia up to 60%
rainwater harvesting- where ppl collect rain falling on the roofs and store it in barrels for domestic use
(waterAid is an IGO tht helps this in places like Uganda)
recycled water- reusing water for agriculture (not for humans unless cleaned)
eg SINGAPORE:
use few natural resources
have high living standards and water consumption
they use sustainable methods including water harvesting, reuse resevoir, desalination
eg UK:
water conservation in 2020 when there were hosepipe bans and water saving showerheads in hot dry conditions where droughts were a risk
IWRM:
= integrated drainage basin management
was 1st strated in 1990s and ensures:
environmental quality
water is used with maximum efficiency
distributed equally
used in Nile and colorado river and is in water sharing treaties like Berlin rules
COLORADO IWRM:
long river tht flows through a 600,000km2 basin
97% is in mexico and 3% is in USA
has faced challenges like drought risks and urbanisation and irrigation for agriculture
different areas got different allowances
disputes exist where there isnt enough water for areas
in 1990 lower USA used full alowance making issue worse where they try to negotiatie for more water but they have been told to find altrernatives
