Water extraction

• Surface extraction - River Kennet, Southern England


  1. Rates of extraction are greater than rates of recharge

  2. Leads to a fall in the water table

  3. River flows falling 10-14%

  4. During the 2003 drought the river dried up completely
• Surface extraction - River Kennet, Southern England


  • Impacts a diverse range of habitats
  • Several urban areas rely on the River Kennet for their water supply
  • The river also supplies local industries and agriculture
• Sub-Surface Aquifers - Boreholes down to extract water

  1. The water table increases or decreases in response to rainfall/drought/extraction

  2. In normal years the level falls September-March and recharges from late autumn
• Artesian Basin


  When an aquifer is confined in between two impermeable rock layers it becomes under pressure
• Artesian Basin


  1. Rain enters the aquifer at the edges where the chalk reaches the surface

  2. Flows, due to gravity, towards the centre of the basin
• London's aquifer


  • An important source of water during normal conditions
  • The artesian pressure makes it easy to extract
• Overexploitation in the 19th and first half of the 20th centuries


  Led to a drastic fall in the water table
• In the past 50 years


  Demand for water has decreased as industries have relocated
• Rising water levels


  Threatens the London Underground