Chapter 5 - Hydrosphere

• Exploitation of new sources of water - Rainwater collection

  • Collecting rainwater is also important in rural areas where there is no pubic water supply. The water is often cleaner than other sources like rivers
  • A rainwater catchment and storage system that uses surplus water for aquifer recharge.
• Exploitation of new sources of water - rivers

  • River water is often the most convenient source of water. Being long, they are accessible over a large land area. Natural contaminants are rarely a problem until waste from communities didn't break down.
• Exploitation of new sources of water - Reservoirs

  • Allows the storage of water from times where there is a surplus of water so that it can be used when there is a shortage
• Factors affecting reservoir site - Topography

  • The ideal topography creates a narrow exit from a large deep basin so that a relatively small dam can hold back a huge volume of water
• Factors affecting reservoir site - Geology

  • The rock beneath the reservoir must be impermeable so that the water can't percolate into the rock and be lost.
• Factors affecting reservoir site - Catchment area

  • Area of land over which rain will flow or through the ground and then into a river. So that the ability of the reservoir to provide water is controlled by the reservoir site itself and the area that collects water for it.
• Factors affecting reservoir site - Water supply

  • The rainfall or river inflow should be regular and have a large volume. The climate shouldn't be too hot or dry to cause excessive evaporation losses.
• Factors affecting reservoir site - Sedimentation

  • Soil erosion in the catchment area can make the inflow water very turbid, resulting in sedimentation in the reservoir. This gradually reduces the volume of water that the reservoir can hold.
• Factors affecting reservoir site - Existing land use/ land use conflicts

  • The use of the land that is to be flooded can't be so important that it cannot be lost.
  • In the UK, large urban areas and important wildlife conservation areas would probably be protected.
• Exploitation of new sources of water - Seawater

  • Desalination of sea water is very energy intensive and expensive so it is only used in countries where seawater is available and there are inadequate supplies of freshwater.
• Water abstraction - Aquifers (Features)

  • Porosity - rocks volume that is space and can therefore hold water. Eg of porous rock (limestone)
  • Permeability - ease with which fluids may flow through a rock because of the interconnections between the spaces.
  • Geological structures - rock below the water-bearing rock must to impermeable to prevent the escape of the water. Some of the rock above must be permeable to allow recharge of the aquifer.
• Aquifer recharge

  Most aquifer recharge takes place as precipitation landing on the ground surface infiltrates and percolates through soil and rock to the aquifer. Water abstraction from aquifers that are recharged by surface water can be sustainable as long as it doesn't exceed the recharge rate.
• Over exploited aquifers - changes in surface hydrology

  If groundwater is overexploited then the water table may be lowered, reducing the outflow of water into the wetland causing it to dry up.