Our planet is often called the “Blue Planet,” and for good reason. But just How Much Of Planet Earth Is Water? The answer might surprise you. While water covers approximately 71% of the Earth’s surface, the distribution of this water across oceans, ice, groundwater, and the atmosphere is quite uneven. Let’s dive into the fascinating details of Earth’s water distribution.
All the world's water in a blue sphere, illustrating its volume relative to the Earth, positioned over the western United States.
The Global Water Budget: A Breakdown
Earth’s water exists in various forms and locations, constantly cycling through the environment. The vast majority resides in the oceans, but significant quantities are also stored as ice, groundwater, and atmospheric water vapor. Understanding this distribution is key to appreciating the importance of water resources.
Oceans, Seas, and Bays:
The oceans are Earth’s largest water reservoir, holding about 96.54% of the total water volume. This saline water dominates the planet’s surface, influencing climate patterns and supporting diverse marine ecosystems.
Ice Caps, Glaciers, and Permanent Snow:
Frozen water accounts for a significant portion of Earth’s freshwater. Ice caps, glaciers, and permanent snow hold approximately 68.7% of the planet’s freshwater, making them a crucial, yet vulnerable, water source. These frozen reservoirs play a vital role in regulating sea levels and feeding rivers.
Groundwater:
Beneath our feet lies a vast reserve of groundwater, constituting about 30.1% of the total freshwater. Groundwater is a critical source of drinking water and irrigation, particularly in arid and semi-arid regions.
Surface Water:
Lakes, rivers, and swamps represent a relatively small fraction of Earth’s total water, but are vitally important.
- Lakes: Freshwater lakes store only 0.26% of the total freshwater, or 0.007% of total water, but provide essential water for human consumption, industry, and agriculture.
- Rivers: Rivers, though seemingly prominent, contain a minuscule 0.006% of the planet’s freshwater, or just 0.0002% of total water. Yet, these flowing waterways are crucial for ecosystems and human societies, serving as sources of drinking water, transportation routes, and habitats for diverse aquatic life.
- Swamp Water: Swamp water accounts for another tiny fraction – 0.03% of freshwater, or 0.0008% of total water.
Atmosphere:
The atmosphere holds water in the form of water vapor, clouds, and precipitation. This is a relatively small amount (0.04% of freshwater, or 0.001% of total water) but it is constantly replenished by evaporation and transpiration. Atmospheric water is essential for the water cycle and for distributing water around the globe.
Numbers to Consider: Visualizing Earth’s Water
To truly grasp the scale of Earth’s water resources, consider these facts:
- The Water Sphere: If all of Earth’s water were collected into a single sphere, it would be approximately 860 miles (1,385 kilometers) in diameter. This sphere would span the distance from Salt Lake City, Utah, to Topeka, Kansas. The volume of this sphere would be about 332.5 million cubic miles (mi3), or 1,386 million cubic kilometers (km3).
- Atmospheric Water: At any given time, approximately 3,100 mi3 (12,900 km3) of water exists in the atmosphere, primarily as water vapor. If this water precipitated all at once, it would cover the Earth’s surface with only about 1 inch of water.
- Water Over the United States: If all the world’s water were poured onto the contiguous United States, it would submerge the land to a depth of approximately 107 miles (145 kilometers).
The Importance of Groundwater
While surface water is readily visible, the amount of freshwater stored underground far exceeds that found in lakes and rivers. Groundwater is a critical resource, especially in regions where surface water is scarce. It replenishes rivers and streams through seepage, ensuring a consistent water supply, even during dry periods.
Global Water Distribution: A Detailed Look
The following table provides a more detailed breakdown of Earth’s water distribution:
One Estimate of Global Water Distribution (Percents are rounded, so will not add to 100)
| Water source | Water volume, in cubic miles | Water volume, in cubic kilometers | Percent of freshwater | Percent of total water |
|---|---|---|---|---|
| Oceans, Seas, & Bays | 321,000,000 | 1,338,000,000 | — | 96.54 |
| Ice caps, Glaciers, & Permanent Snow | 5,773,000 | 24,064,000 | 68.7 | 1.74 |
| Groundwater | 5,614,000 | 23,400,000 | — | 1.69 |
| Fresh | 2,526,000 | 10,530,000 | 30.1 | 0.76 |
| Saline | 3,088,000 | 12,870,000 | — | 0.93 |
| Soil Moisture | 3,959 | 16,500 | 0.05 | 0.001 |
| Ground Ice & Permafrost | 71,970 | 300,000 | 0.86 | 0.022 |
| Lakes | 42,320 | 176,400 | — | 0.013 |
| Fresh | 21,830 | 91,000 | 0.26 | 0.007 |
| Saline | 20,490 | 85,400 | — | 0.006 |
| Atmosphere | 3,095 | 12,900 | 0.04 | 0.001 |
| Swamp Water | 2,752 | 11,470 | 0.03 | 0.0008 |
| Rivers | 509 | 2,120 | 0.006 | 0.0002 |
| Biological Water | 269 | 1,120 | 0.003 | 0.0001 |
Source: Igor Shiklomanov’s chapter “World fresh water resources” in Peter H. Gleick (editor), 1993, Water in Crisis: A Guide to the World’s Fresh Water Resources (Oxford University Press, New York).
Conclusion: A Precious Resource
While Earth appears abundant in water, the reality is that freshwater, readily available for human use, is a limited resource. The vast majority of water is saline and locked away in oceans, ice caps, and groundwater. Therefore, understanding how much of planet Earth is water and how it is distributed is crucial for responsible water management and conservation efforts. We must protect and preserve our freshwater resources to ensure a sustainable future for all.
