Water

• What is water scarcity?

  Not enough water to supply needs
• What does water insecurity imply?

  Uncertainty whether enough water will be available
• How does the Sahel's climate affect water availability?

  It has short rainy seasons and large dry seasons
• How does topography influence water storage?

  Mountainous areas experience higher rainfall and runoff
• Which mountain range provides water to the Ganges and Indus rivers?

  The Himalayas
• What human activities contribute to water pollution?

  Industrial waste and agricultural runoff
• What is economic water scarcity?

  Lack of infrastructure and governance limits access
• Which countries are mentioned as having economic water scarcity?

  Tanzania and Ghana
• What is saltwater intrusion?

  Saltwater mixes with freshwater aquifers
• What is a consequence of large-scale dams?

  Reduced water availability downstream
• How did the saline content of the Aral Sea change over time?

  It rose as water evaporated
• What percentage of the Aral Sea's volume was lost from 1960 to 1998?

  80%
• What is groundwater?

  Water held within permeable rocks
• What is interception in hydrology?

  Temporary storage of water by plants
• What is fossil water?

  Ancient groundwater from past periods
• What are the effects of population growth in the Sahel region?

  • High birth rates and lower death rates
  • Increased immigration due to conflicts
  • Strain on fragile ecosystems and resources
• How does ENSO affect water availability?

  Normal conditions- Trade winds push warm, moist air and water to Australia, causing precipitation in Australia, Upwelling- cold water replaces hot water. Peru- colder air sinks, causing dry conditions

  El Nino- Weaker trade winds- causing warmer air and water to travel to Peru. Peru- slightly wetter. Australia- slightly dryer

  La Nina- (Extreme of normal conditions) Strong trade winds towards Australia. Hot air leads to high precipitation in Australia. Australia- flooding. Peru- drought.
• What is the impact of drought in wetlands?

  • Less water in wetlands causes soil and water acidification, leads to more decomposition of organic matter, releasing CO2 and methane e.g. Iraq, Australia
  • Less flood control
  • Wetlands filter water- less fresh water supplies
  • Less critical breeding ground for species
• What impact does drought have on forests?

  • Tree mortality- California drought 2010s caused death of 100M
  • Increased wildfire risk, fires spread rapidly through dry vegetation e.g. California
  • More vulnerable to pests and diseases
  • Exposed areas are more vulnerable to soil erosion- less fertile soil
• What is flash flooding?

  Flooding caused by intense, heavy rainfall in a short period of time. Not much infiltration occurs and lag time is short, so surface-run off significantly increases. e.g Spain 2024
• How is climate change affecting the hydrological cycle?

  • Increased precipitation in high latitude regions e.g. Northern Europe and America
  • Decreased precipitation in Mediterranean, Southern Africa and Australia. Leads to decline in groundwater levels
  • Tropical regions- Intense rainfall events in wet seasons and longer dry seasons in Amazon and Central Africa
  • Reduced water storage in cryosphere, Affects countries that rely on glacial meltwater in dry seasons e.g. Central Asia, Andes
• How do shared water supplies create conflict?

  • Diminishing supplies- Climate change, Water pollution
  • Rising demands- population growth, economic development
  • Users compete upstream and downstream
• How can dams cause conflicts?

  • Colorado River- Use of dams has Mexico has reduced water flow downstream
  • Aral Sea- Use of dams has increased water capacity on Kazakhstan but not Uzbekistan
  • River Nile- Construction of dams on Blue Nile, Ethiopia will affect Egypt's water availability
• Define the different flows in a drainage basin

  • Interception: Water is absorbed by vegetation  before reaching soil.
  • Infiltration:  Water is absorbed by the soil.
  • Percolation: Water is absorbed by permeable rocks
  • Throughflow: Water is transferred through the soil.
  • Groundwater flow: the very slow transfer of percolated water through permeable rocks.
  • Surface runoff- the movement of water that across the surface of the ground
  • Channel flow is where water flows in small channels into another larger drainage basin
• What are types of rainfall?

  • Frontal rainfall- warm moist air rises over  a colder air mass, causing rain along warm and cold fronts. Occurs in low pressure areas e.g. UK
  • Orographic rainfall- Warm moist air is forced to rise due to high relief. Air condenses which produces rainfall e.g. Himalayas
  • Convectional rainfall- Solar energy causes moist air to rise due to evaporation and evapotranspiration. The air condenses which produces rainfall. Occurs in warm, tropical areas e.g. Brazil
• What are inputs to the drainage basin?

  Inputs are the addition of water to a drainage basin through precipitation
• How do inputs vary?

   Inputs vary through form  (rain, sleet, snow)  intensities (flood, drought) and  frequency (monsoon, seasons).
• How do humans disrupt the drainage basin?

  • Irrigation- water is transferred to farms with a soil moisture deficit
  • Deforestation- less water is intercepted and absorbed into soil. Soil becomes less permeable over time. Loss of vegetation leaves soil vulnerable to erosion.
  • Groundwater abstraction- use of freshwater stored in groundwater aquifers.
  • Construction of dams- reduces water flow downstream. Soil becomes less permeable over time. When water is let downstream due to risk of overflowing, there is more surface runoff downstream and soil cannot infiltrate.
  • Urbanisation- use of impermeable materials like concrete and tarmac increase surface run-off
• What are the different parts of the storm hydrographs?

  • Peak rainfall- highest amount of rainfall
  • Peak discharge - highest amount of water carried in the river channel
  • Lag time- Time period between peak rainfall and peak discharge
  • Base flow- normal flow of river
  • Storm flow- Flow from increased precipitation, involving surface and thorough flow
  • Rising limb- flow of discharge is rising
  • Falling limb- flow of discharge is falling
• Name water projects learnt:

  • Three Gorges dam and water transfer project
  • Desalinisation
  • Recycling water- Singapore
  • Rain water harvesting jars- Uganda