Global Water Distribution (Cambridge (CIE) AS Environmental Management)

Global Water Distribution

• Water is one of the most essential resources on Earth, crucial for supporting biodiversity, ecosystems, and human activities

• Understanding the distribution of Earth's water across different reservoirs is essential for managing water resources sustainably and addressing global water challenges

• The Earth's water can be roughly divided up into the following categories:

  • Salt water in oceans:

    • Approximately 97.5% of the Earth's water is found in oceans and seas

    • Oceans cover about 71% of the Earth's surface and contain vast quantities of saltwater

  • Surface freshwater:

    • Ice sheets and glaciers:

      • Ice sheets and glaciers store around 68.7% of the Earth's freshwater

      • Most of this freshwater is contained within ice caps covering Antarctica and Greenland

    • Lakes, rivers, swamps and marshes:

      • Lakes, rivers, swamps and marshes collectively hold around 0.3% of the Earth's freshwater

      • These surface water bodies are crucial habitats for diverse aquatic ecosystems and serve as sources of drinking water and irrigation

  • Sub-surface freshwater:

    • Soil Moisture:

      • Soil moisture accounts for approximately 0.05% of the Earth's freshwater.

      • This water is found within the soil profile and is vital for supporting plant growth and agricultural activities

    • Groundwater:

      • Groundwater constitutes around 30.1% of Earth's freshwater resources

      • It is stored in underground aquifers and is accessed through wells for drinking, industrial and agricultural purposes

    • Permafrost:

      • Permafrost, which contains permanently frozen ground, holds a small fraction of the Earth's freshwater

      • While difficult to quantify, permafrost regions contribute to the planet's water cycle and influence surface water availability

  • Atmospheric water:

    • Atmospheric water comprises a tiny fraction of the Earth's total water supply, estimated to be around 0.001%

    • It includes water vapour, clouds and precipitation, which play crucial roles in the global water cycle by transporting water from one location to another