Chapter 4: Water World

Chapter 4: Water World

1. hydrological cycle

   • Evaporation - as water heats up, returns to atmosphere as water vapour
   • Condensation - water vapour cools into tiny water droplets, visible as clouds
   • Precipitation - tiny water droplets collide and grow until under gravity they fall as rain or snow
   • Groundwater flow - Rainwater soaks into the rocks below soil. moves slowly through pores or cracks (joints)
   • Throughflow - Rainwater soaks into soil (infiltration), flows slowly to river
   • Run-off (overland flow) - Rainfall flows quickly over the surface of the ground to reach rivers. responsible for flash floods
   • water stores e.g ice caps, oceans lakes , rivers
     • stops flowing for period of time until evaporation/ ice melt
       • 99% earth's water - in ice caps/ oceans
   • Biosphere
     • forests/ leaves intercept rain and stoop flooding
   • Lithosphere - soils and rocks holding water (depending of how permeable)
     • e.g rainwater in pores of chalk but then stoped by impermeable layer developing water store called aquifer

2. Unreliable water supplies

   • Distinct wet and dry season
     • Sahel - short wet season, high run-off - little water stored
   • Weather cycles occur
     • Sahel- serveral drought years recently - serious food shortages
   • Global warming, rising temps.
     • dry places e.g Sahel get drier and UKwill get wetter
   • Australia
     • Unrelaible water supplies naturally occur
       • threaten an range of agricultural land + industrial activities - seems to be getiing worse
         • Farmers either have to adapt to aridity or 'retreat' and change occupation

3. South west USA

   • Very arid area - Colarado river is the main water source - including irrigation of crops
     • climate change (makes even drier) - Las vegas 2002,2004,2007 drought years
       • Restriction on river water - less irrigation water - fewer artificial green areas (that animals have inhabited)
         • Less water for the rapidly increasing population of Arizona (25% increase between 2000-2010)

4. Threats to the hydrological cycle

   • causes of river pollution
     • Sewage - leads to cholera bacteria
       • Chemicals from factories - poison wildlife and affect water quality
         • 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
   • Management
     • Sewage treatment
       • regulated fertilisers
         • Factories remove waste from water before returing to rivers + environment agency gives heavy fines for not doing so
           • Platic bages recycled

5. Deforestation and Urbanisation lead to accelearated run-off

6. CASE STUDY: Coca-cola

   • Location - drought prone indian state Kerala
     • Large groundwater store near village of plachimada attracted attention of the TNC
       • In 2000 dug 6 wells and tapped into the precious store
         • 2004- desperate situation - wells used by villagers dried up
           • company helped them survive by driving in tankers of clean water

7. Large-scale water management

   • expensive to build + maintain
     • cover large areas
       • organised by local/national governments
         • consist of dams and resevoirs
   • colorado river (developed world) - managed because it feeds 7 states + Mexico and needs a reliable flow all year round
     • +ve
       • regulates flow - reduces summer flooding, winter drought
         • dams generate electricity - homes farms factories
           • lakes form behind e.g lake mead - tourism and irrigation
             • stored water feeds Las Vegas
               • year round supply
     • -ve
       • land lost to flooding
         • sediment build up - inhibits HEP generation
           • less sediment - less heat - less fish - sandbanks shrunk (habitat for animal)
             • less water downstream in Mexico
     • Hoover dam - 1935
       • Glen Canyon dam - 1966

8. Lage scale water management : Three gorges dam, China (developing world)

   • across the Yangtze river in Hubei province
     • world's largest dam + HEP project
       • 1.3 billion population. - moving to urban areas - richer - using more appliances
         • 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
   • +ve
     • decreased flood risk along river
       • irrigation water - lake behind dam
         • HEP generation - replacing the use of 50 mill. tonnes of coal
           • river more navigable for ships
   • -ve
     • good farmlands floods becuse of lake
       • 1.3 mill. forced to move
         • cultural + archaeological sites lost
           • landslides
             • very expensive US$22.5bill.
               • sediment built up
                 • downstream flooding - no sediment to maintain banks
                   • wetlands destroyes

9. Small-scale water management

   • wells
     • dug to reach groundwater in rural areas of developing world. Lined and lidded with concrete to prevent sewage contamination
   • Hand pumps
     • more efficient way of reaching groundwater opposed to bucket and rope - less chance of contamination via mud + dirty hands
   • Rain barrels
     • 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)
   • Afridev Handpump
     • location: East Africa, Tanzania - life expectancy 46 - 70% rural + 30% urban have no access to clean water
       • diarrhoea - 20% of infant deaths - sewage contamination
     • International agency WaterAid
       • new well - 24m deep - 'Afridev Handpump'
         • 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
     • local media radio soap show (Pilika Pilika)
       • spread messages on hygiene, sanitation + water management
   • Intermediate technology
     • local community can use easily, repair themselves, low cost