How water extraction, including surface extraction and sub-surface groundwater extraction (including aquifers and artesian basins) impact the flows and stores in these cycles

  • Created by: EmilyM17
  • Created on: 22-05-19 08:40
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  • How water extraction, including surface extraction and sub-surface groundwater extraction (including aquifers and artesian basins) impact the flows and stores in these cycles
    • Surface Extraction
      • Reduces levels of channel flow
      • Increases sediment deposited
      • Dissolved CO2 levels fall
      • Water temperatures rise threatening organisms
      • Pollutants are less diluted
      • Fewer floods reduce the supply of alluvium to floodplain
    • Groundwater Extraction
      • Reduces water table in aquifers and artesian basins
        • Aquifers
          • Permeable or porous water bearing-rocks such as chalk and new-red sandstone
            • Groundwater is abstracted for public supply from aquifers by wells and boreholes.
              • Emerging in springs and seepages, groundwater feeds rivers and makes a major contribution to their base flow
                • Upper surface of saturation within an aquifer= the water table. Its height fluctuates seasonally and is affected by periods of exceptional rainfall, droughts and abstraction. Recharge resumes in late April.
        • Artesian basins
          • When sedimentary rocks form a basin-like structure, an aquifer confined between impermeable rock layers may contain groundwater which is trapped under artesian pressure
            • If this groundwater is tapped by a well or borehole, water will flow up to the surface under its own pressure.= artesian aquifer
              • The level of water will rise,- the potentiometric surface- is determined by the height of the water table in areas of recharge on the edges of the basin
                • EXAMPLE
                  • London
                    • Groundwater from chalk
      • Springs and streams dry up
      • Ecosystems are threatened
      • Can extract 'fossil' water (water stored underground) for 100s of years faster than it is replenished

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