Chapter 4: Water World

hydrological cycle
1. Evaporation - as water heats up, returns to atmosphere as water vapour
2. Condensation - water vapour cools into tiny water droplets, visible as clouds
3. Precipitation - tiny water droplets collide and grow until under gravity they fall as rain or snow
4. Groundwater flow - Rainwater soaks into the rocks below soil. moves slowly through pores or cracks (joints)
5. Throughflow - Rainwater soaks into soil (infiltration), flows slowly to river
6. Run-off (overland flow) - Rainfall flows quickly over the surface of the ground to reach rivers. responsible for flash floods
7. water stores e.g ice caps, oceans lakes , rivers
  1. stops flowing for period of time until evaporation/ ice melt
    1. 99% earth's water - in ice caps/ oceans
8. Biosphere
  1. forests/ leaves intercept rain and stoop flooding
9. Lithosphere - soils and rocks holding water (depending of how permeable)
  1. e.g rainwater in pores of chalk but then stoped by impermeable layer developing water store called aquifer
Unreliable water supplies
1. Distinct wet and dry season
  1. Sahel - short wet season, high run-off - little water stored
2. Weather cycles occur
  1. Sahel- serveral drought years recently - serious food shortages
3. Global warming, rising temps.
  1. dry places e.g Sahel get drier and UKwill get wetter
4. Australia
  1. Unrelaible water supplies naturally occur
    1. threaten an range of agricultural land + industrial activities - seems to be getiing worse
      1. Farmers either have to adapt to aridity or 'retreat' and change occupation
South west USA
1. Very arid area - Colarado river is the main water source - including irrigation of crops
  1. climate change (makes even drier) - Las vegas 2002,2004,2007 drought years
    1. Restriction on river water - less irrigation water - fewer artificial green areas (that animals have inhabited)
      1. Less water for the rapidly increasing population of Arizona (25% increase between 2000-2010)
Threats to the hydrological cycle
1. causes of river pollution
  1. Sewage - leads to cholera bacteria
    1. Chemicals from factories - poison wildlife and affect water quality
      1. Fertilisers, pesticides and herbicides (from intensive farming) - cause eutrophication exhausting oxygen in the water, death of fish + water quality
        Plastic bags - don't decay, kill wildlife, block pipes + in warmer can also create warm pools of water where malaria bearing mosquitoes can breed
2. Management
  1. Sewage treatment
    1. regulated fertilisers
      1. Factories remove waste from water before returing to rivers + environment agency gives heavy fines for not doing so
        Platic bages recycled
Deforestation and Urbanisation lead to accelearated run-off
CASE STUDY: Coca-cola
1. Location - drought prone indian state Kerala
  1. Large groundwater store near village of plachimada attracted attention of the TNC
    1. In 2000 dug 6 wells and tapped into the precious store
      1. 2004- desperate situation - wells used by villagers dried up
        company helped them survive by driving in tankers of clean water
Large-scale water management
1. expensive to build + maintain
  1. cover large areas
    1. organised by local/national governments
      1. consist of dams and resevoirs
2. colorado river (developed world) - managed because it feeds 7 states + Mexico and needs a reliable flow all year round
  1. +ve
    1. regulates flow - reduces summer flooding, winter drought
      1. dams generate electricity - homes farms factories
        lakes form behind e.g lake mead - tourism and irrigation
        stored water feeds Las Vegas
        year round supply
  2. -ve
    1. land lost to flooding
      1. sediment build up - inhibits HEP generation
        less sediment - less heat - less fish - sandbanks shrunk (habitat for animal)
        less water downstream in Mexico
  3. Hoover dam - 1935
    1. Glen Canyon dam - 1966
Lage scale water management : Three gorges dam, China (developing world)
1. across the Yangtze river in Hubei province
  1. world's largest dam + HEP project
    1. 1.3 billion population. - moving to urban areas - richer - using more appliances
      1. growing cities - industrial needs for water (threatened by projected shortages - seasonal meltwater run-off from himilayan plateau - supplies could dwindle in climate warming)
        want to release less greenhouse gases
2. +ve
  1. decreased flood risk along river
    1. irrigation water - lake behind dam
      1. HEP generation - replacing the use of 50 mill. tonnes of coal
        river more navigable for ships
3. -ve
  1. good farmlands floods becuse of lake
    1. 1.3 mill. forced to move
      1. cultural + archaeological sites lost
        landslides
        very expensive US$22.5bill.
        sediment built up
        downstream flooding - no sediment to maintain banks
        wetlands destroyes
Small-scale water management
1. wells
  1. dug to reach groundwater in rural areas of developing world. Lined and lidded with concrete to prevent sewage contamination
2. Hand pumps
  1. more efficient way of reaching groundwater opposed to bucket and rope - less chance of contamination via mud + dirty hands
3. Rain barrels
  1. water harvesting - collect rainwater from gutters and stored for drought - stays clean in covered barrel - some have purifcation system (layers of sand, gravel, charcoal - remove impurities)
4. Afridev Handpump
  1. location: East Africa, Tanzania - life expectancy 46 - 70% rural + 30% urban have no access to clean water
    1. diarrhoea - 20% of infant deaths - sewage contamination
  2. International agency WaterAid
    1. new well - 24m deep - 'Afridev Handpump'
      1. 15 families can drink safe water
        communties take ownership of technolgy + responsible for upkeep (simple technology) - caretakers can fix however with more sophisticated technology would need specialist engineer - days without water
  3. local media radio soap show (Pilika Pilika)
    1. spread messages on hygiene, sanitation + water management
5. Intermediate technology
  1. local community can use easily, repair themselves, low cost

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