5.6

• Climate change affects inputs and outputs within the hydrological cycle

  The Intergovernmental Panel on Climate Change (IPCC) predicts considerable changes to the global hydrological cycle as a result of increasing GHGs concentrations and to changes in the ENSO. 

  Changes in temperature, precipitation and evaporation will vary around the world, not everywhere will experience the same changes. The amount of water in active circulation is increasing. This means there is more energy in the atmosphere, this in turn promises heavier precipitation and more severe storms in some climatic regions.
• Climate change affects stores and flows

  Climate change affects stores:

  • Decreases the amount of water held in the form of snow + ice
  • Deepens the active layer of permafrost
  • Lowering water levels in lakes and reservoirs
  • Reduces wetland storage and soil moisture

  For flows, more climate extremes are expected. There will be more high flows (flash floods) and more low flows (droughts). More intense rainfall in some locations will increase runoff rates + reduce infiltration. In areas of mountain ice, melting may cause extremes of flow to begin with.
• Climate change is the outcome of short term and long term changes. 

  However what will happen is uncertain and is dependent on so many factors and this is creating concerns about water management and is creating a series of questions:

  • How reliable are our projections about drought and flood risks?
  • Can we accurately factor in the possibility of more extreme weather events?
  • How accurately can we forecast human pressure on water resources?