Deforestation in Amazonia
- contains 60% of world’s trees (‘green lungs’ of the earth)
- 20% of the forest being destroyed because of cattle ranching, commercial agriculture and logging.
- destruction of trees leads to run-off, floods and aquifer depletion (as no infiltration to recharge them)
Deforestation in Nepal
- grazing animals leads to soil compaction, increasing run off
- rain strikes directly on soil leading to compaction
- little infiltration (groundwater depletion)
Water budgets: importance of polar regions
- 2/3 of freshwater locked up in the crysophere
- as climate warms this ice melts into sea
- drives hydrological cycle by thermohaline circulation
Water budgets: importance of the tropics
- steep angled sun allows intense solar radiation causing evaporation
- trade winds transfer water vapour to the inter tropical convergence zone, conventional currents lift air and it cools and condenses creating heavy rain storms.
- most of worlds rain is in the ITCZ (biggest flux from oceans-land)
Sahel region: human influences and drought
- human factors do not cause drought but act as a positive feedback loop enhancing impacts
- in Sahel, degrading from overgrazing and deforestation for fuel.
- rural poverty and high demand for food production, as population doubling every 20-30 years, lead to famine.
- war between Ethiopia and Eritrea meant food access was blocked for many.
Drought in Australia
- 30% of the country usually effected by drought each year(common)
- usually due to El Niño effects, variable rainfall and climate change
- major event was THE BIG DRY, where 50% farmland in Murray darling (agricultural heartland) was effected, effected food supplies and exports, reservoirs fell to 40% capacity.
Storm Desmond Cumbria 2015: heavy or prolonged rainfall (physical factor of flooding)
-caused by the deep Atlantic low-pressure system(depression)
-341.4mm rainfall in 24 hours at Honister Pass.
-rivers 50x higher than usual
-5200 Homes were flooded
-roads and rail distrupted
-landslide closed west coast mainline from Preston to Carlisle
-6100 Homes lost power
Human exacerbation:
-overgrazing
-mismanagement of rivers
Pakistan 2010: intense storms (physical factor of flooding)
-primary cause was heavy rain fall of more than 200mm recorded between 3 days in July
-7 million left homeless
-agriculture destroyed, food shortages
-500000 tonnes of wheat lost
Human exacerbation:
-deforestation
-taliban threatened to hijack foreign aid
Philippines 2016: monsoon (physical factor of flooding)
-caused by south west monsoon combined with low pressure weather front
-capital (Manila) received 504mm of rain in one day
-260000 people fled their homes
-14 died
-landslides buried homes and businesses
Human exacerbation:
-dense population
-urbanisation
-elevated surroundings
-deforestation
Siberia: snow melt (physical factor of flooding)
-caused by spring snowmelt floods
-quick transition from winter to spring causes rapid melt to enter rivers Ob and Yenisei
-costs of damages = $8.6 million (2001)
-28% damage is agriculture
-19% transport damage
Human exacerbation:
-climate change
-deforestation
Sahel region: physical factors effecting water supply
-high variability of rainfall at all climate scales:
seasonally
annually
decadal
-1970 onwards = period of decline in average rainfall
-2000 = drought inducing conditions broken by ‘good rains’
Climate change in the Bolivian Andes(Nepal)
- resulting in widespread melting diminishing cryosphere storage
- 95% of glaciers shredding more than adding
China: human factors effecting water supply
- 1/3 of rivers and 25% of coasts are classified as highly polluted
- heavy metal toxins are responsible for 80% of deaths
- 190 million suffer from water illnesses annually
- 300 million use contaminated water daily
Aral Sea
- was once the worlds 4th largest inland sea which has been shrinking since 1960s
- used for irrigation
- by 2007 sea decline by 10% of original size
- left behind unfertile land-no use for food production
- fishing community collapsed (once employed 60000)
Colorado: water conflicts
- overabstraction by farmers, lead to a dispute in allocation of water
- much of the water is already contaminated by agriculture
- matters made worse by construction of dam at southern tip of canyon
Nile river basin: trans boundary conflict
- Nile is the longest river basin in the world (6700km long)
- water is shared by 11 countries
- Egypt depends on it for 95% of its water needs
- construction of dams in Sudan and Ethiopia lead to reduced flow downstream to Egypt
- 300 million people love within the basin
River Kennet: example river regime
-flows over chalk, base flow from chalk aquifers as flow in very dry conditions
China’s south-north transfer (water transfer scheme)
-divert 44.8 billion m^3 of water yearly from china’s south to its dry north
-south=humid, north=industrial and dry
-in the north east half of the population rely on 15% if china’s supply
Negatives:
-huge costs for infrastructure
-energy intensive (pumping)
-damage fish stocks and create alien species by pollution
-spread disease
-increase flood risk in the long term
China’s three gorges (mega dams)
-ability to store 15% of annual global run off
-China is the leading builder of dams
-renewable energy (HEP) for development
-flood control and water supply
Negatives:
-not cost effective
-human activity has already increased flood risk before
Israel’s desalination project
-supplies 624 million litres of water daily (drinkable)
-billions go to Riyadh who’s population is growing
Negatives
-prices high so poorer countries unable to afford
-left over water has 2x amount of salt content than sea water so when it’s dumped near shore line there is consequences for reefs and food webs
The great Ruaha River, Tanzania - water conflict
- this river provides water for rice growth and the generation of HEP and maintains Ramsar-status wetland and important for tourism
- ceased flowing in dry season due to water levels in upper course dropped to critical level.
- low flows mean power shortages through HEP scheme
- wetland diminishing = wildlife problems
- supplies turned off causing conflict
- problems generally caused by mismanagement and overuse for rice irrigation
