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Water: Blue, Green, Grey
"Blue water"
  • 38.8% of total precipitation.
  • Equivalent to the natural water resources: collected in rivers, lakes, wetlands and groundwater.
  • Available for withdrawal (1.5% for direct human use) before it evaporates (1.3%) or reaches the ocean (36%).
"Green water"
  • 61.1% of total precipitation.
  • The rain water absorbed by soil and plants.
  • Never available for capture or storage because it evaporates or transpires from non-irrigated agriculture, pastures and forests.
"Grey water"
  • Urban and industrial waste water.
  • The systematic reuse of waste water for nonpotable applications, with or without treatment, increases the overall efficiency of use of water extracted from primary sources.
3% of all water on earth is fresh water, the rest is salty.

Source: FAO - Food and Agriculture Organization, IWMI - International Water Management Institute )