There are a few quick answers to this question:
– The planet Earth is often described as the “blue planet” due to the abundance of water covering the surface.
– Oceans cover about 71% of the Earth’s surface, while freshwater lakes and rivers make up around 1.6%.
– When all forms of water are combined – liquid, frozen, and vapor – water is estimated to comprise between 70-75% of the Earth’s total surface area.
– So while not exactly 75%, water does make up the vast majority of the Earth’s surface.
Where is Earth’s water located?
The majority of Earth’s water, around 96.5%, is located in the planet’s oceans. The oceans contain around 332.5 million cubic miles of water. Here is a breakdown of where all Earth’s water is located:
| Location | Percentage |
|---|---|
| Oceans | 96.5% |
| Polar ice caps/glaciers | 1.74% |
| Groundwater | 1.69% |
| Surface water (lakes, rivers, etc) | 0.007% |
| Atmosphere | 0.001% |
As the table shows, the vast majority of Earth’s water is found in the oceans, followed by polar ice caps and glaciers.
How much of the Earth’s surface is covered by water?
Approximately 71% of the Earth’s surface is covered by water. Here is a breakdown:
- Oceans – around 361 million square kilometers (139.4 million square miles)
- Seas – around 42 million square kilometers (16.2 million square miles)
- Lakes – around 2 million square kilometers (772,000 square miles)
- Rivers – around 1 million square kilometers (386,000 square miles)
Added together, it’s estimated that water covers around 361.3 million square kilometers (139.7 million square miles) of the Earth’s surface. With the Earth’s total surface area approximately 510 million square kilometers (197 million square miles), that means roughly 70.9% is covered by water.
How much water is there on Earth?
The total amount of water on Earth is estimated to be around 1.386 billion cubic kilometers:
| Water Source | Cubic Kilometers |
|---|---|
| Oceans | 1,335,000,000 |
| Ice caps, glaciers, permanent snow | 24,064,000 |
| Groundwater | 23,400,000 |
| Fresh | 10,530,000 |
| Saline | 12,870,000 |
| Soil Moisture | 16,500 |
| Ground Ice | 300,000 |
| Lakes | 176,400 |
| Fresh | 91,000 |
| Saline | 85,400 |
| Atmosphere | 12,900 |
| Swamp Water | 11,470 |
| Rivers | 2,120 |
| Biological Water | 1,120 |
| Total | 1,386,000,000 |
As the table illustrates, the oceans contain by far the largest amount of water on Earth, holding around 96.5% of the total water. Glaciers, polar ice caps, and groundwater are also significant sources.
How much freshwater is available on Earth?
While around 71% of the Earth’s surface is covered in water, only a very small fraction of that water is freshwater available for human use. Here is a breakdown:
- Total water on Earth: 1.386 billion km3
- Freshwater: around 35 million km3 (2.5% of total supply)
- Fresh groundwater: 23.4 million km3
- Glaciers/polar ice: 24 million km3
- Surface freshwater (lakes, swamps, rivers): around 105,000 km3 (less than 1%)
So while there is a tremendous amount of water on Earth, less than 3% of it is freshwater that is available for drinking, sanitation, agriculture, and other human uses. Much of this freshwater is locked up in glaciers and polar ice caps.
Challenges with freshwater supply
The limited amount of freshwater poses several challenges:
- Only 0.007% of the world’s water is readily accessible for human use
- Water demands are increasing worldwide due to population growth, agriculture, and industry
- Pollution and climate change are reducing available freshwater in many regions
- Much of the world lacks access to clean drinking water and sanitation
Over 2 billion people currently live in water-stressed areas, and it’s projected that global freshwater demand will exceed supply by over 40% by 2030. Major improvements in freshwater conservation, sanitation, infrastructure, cooperation, and sustainability will be needed to address these challenges.
How does surface water move through the earth’s water cycle?
Earth’s water is continuously cycling through different storage reservoirs in what is known as the water cycle or the hydrologic cycle. Here is an overview of how surface water moves through the cycle:
- Evaporation: Energy from the sun causes water at the surface to evaporate into water vapor, such as oceans, lakes, and rivers evaporating into the atmosphere.
- Transpiration: Plants release moisture into the air through small pores in their leaves during photosynthesis.
- Condensation: As moist air rises and cools, water condenses around tiny particles in the atmosphere forming clouds.
- Precipitation: Water falls back to the surface in the form of rain, snow, sleet, and hail.
- Infiltration: Some precipitation soaks into the ground to become groundwater
- Runoff: Excess water flows overland to collect in lakes, rivers, and oceans.
This continuous cycling of evaporation, condensation, precipitation, infiltration, and runoff transports water from the surface and distributes it around the globe. Energy from the sun provides the driving force for this giant hydrologic system that constantly renews the Earth’s liquid freshwater supply.
What percentage of freshwater on Earth is found in ice and snow?
Around 68.7% of the Earth’s freshwater is stored in ice caps, glaciers, and permanent snow:
- Total global freshwater: around 35 million km3
- Freshwater stored as ice/snow: 24 million km3
Nearly 70% of the Earth’s freshwater is locked up in the enormous ice sheets of Antarctica and Greenland. Mountain glaciers are another significant reservoir, holding around 100,000 cubic kilometers of water.
Only a tiny fraction of freshwater on Earth is found in liquid form on the surface. This includes lakes, rivers, swamps, soil moisture, and rainfall. Around 3% of freshwater is groundwater.
The vast majority of freshwater is unavailable for human use since it exists as ice and snow. Climate change poses a threat to this frozen water reservoir since melting glaciers and polar ice could cause rising seas and increase water scarcity in certain regions.
How does the distribution of Earth’s water compare to the total volume?
While water covers around 71% of the Earth’s surface, the distribution of total water volume differs significantly:
| Source | Percentage of Surface Area | Percentage of Total Volume |
|---|---|---|
| Oceans | 70.8% | 96.5% |
| Ice sheets/glaciers | 9.9% | 1.74% |
| Groundwater | — | 1.69% |
| Lakes | 1.3% | 0.013% |
| Soil moisture | — | 0.001% |
| Atmosphere | — | 0.001% |
| Rivers | 0.006% | 0.0002% |
This comparison shows that while the oceans account for around 71% of the Earth’s surface, they contain 96.5% of the planet’s total water volume. Ice sheets and glaciers contain only a small fraction of total water but cover around 10% of the surface. Most freshwater is underground as groundwater, accounting for over 60 times more water than all lakes and rivers combined.
How does the amount of water on Earth now compare to the past?
The total amount of water on Earth is believed to have remained relatively stable over billions of years. However, the distribution between saltwater in the oceans and freshwater on land has fluctuated significantly over geological history:
- Around 3.8 billion years ago the oceans contained much lower levels of salt than today, meaning more freshwater was likely found on land.
- Huge areas of Earth’s surface were covered by ice during periods like the Snowball Earth glaciations over 600 million years ago.
- Water from melting glaciers buried large areas of land during the ice ages, more than doubling the volume of freshwater lakes.
- Only 15,000 years ago North America still contained massive glacial lakes holding an immense volume of freshwater from melting ice sheets.
While the total amount of water has likely changed very little, the proportions between land and ocean and saltwater versus freshwater have shifted as climates cooled and warmed over time. Earth’s water is constantly moving between different storage reservoirs through the hydrologic cycle.
How do reservoirs of water interact in the hydrosphere?
The hydrosphere refers to Earth’s interconnected water systems and reservoirs. The main interactions include:
- Evaporation transfers ocean water into the atmosphere as water vapor.
- Transpiration moves moisture from plants to the air through respiration.
- Condensation forms clouds from atmospheric water vapor.
- Precipitation adds water to lakes, rivers and glaciers which can increase runoff.
- Runoff and groundwater flow transport freshwater back into the oceans.
- Melting glaciers and ice sheets increase ocean volume.
- Sublimation converts snow/ice directly into water vapor.
Solar radiation provides the energy for continuous exchange of water between the atmosphere, surface, and subsurface. Gravity acts to pull water back down after it evaporates and condensates. The hydrosphere components exist in a complex balance of water inputs and outputs.
Importance of water reservoir interactions
Some key results of the hydrosphere’s water interactions include:
- Renewing freshwater supplies through the recycling of precipitation
- Distributing water over Earth’s surface via runoff and rivers
- Regulating global climate and temperature through evaporation
- Allowing transportation via inland waterways
- Redistributing rainwater for crops and vegetation through irrigation
Disruption of the natural water cycle through climate change, groundwater depletion, and pollution threatens this delicate balance and water availability worldwide.
Conclusion
In summary, while around 71% of the Earth’s surface is covered in water, freshwater comprises only a tiny fraction – around 2.5% – of the total water volume. The vast majority is stored as saltwater oceans and polar ice. Only a small percentage is readily accessible freshwater for human use. Global freshwater supplies are threatened by climate change, mismanagement, and increasing demands. Sustainable management of reservoirs and the water cycle as a whole will be crucial for long-term availability.
