• Oceans: The largest source of water on Earth, containing about 97% of the planet's water. This water is saline.
• Rivers: Natural streams of water flowing in a definite course or channel.
• Lakes: Large bodies of standing water, typically freshwater.
• Groundwater: Water present beneath Earth's surface in soil pore spaces and in the fractures of rock formations.
  • Aquifers: Geological formations capable of storing and yielding significant quantities of groundwater.
• Glaciers and Ice Caps: Frozen freshwater stored in ice masses.
• Rainwater: Precipitation that collects and contributes to surface water and groundwater sources.

• Atmosphere: Water is present in the atmosphere as water vapor, clouds, and precipitation.
• Biological water: Water contained within plant and animal tissues.

These sources are interconnected through the water cycle, which involves evaporation, condensation, precipitation, and runoff.

For more information, you can refer to these resources:

• USGS - Where is Earth's Water?
• United Nations - Decade on Water