The hydrosphere is the combined mass of water found on, under, and above the surface of a planet, a minor planet, or Hydrospheres that have been part of Earth for as long as life has been here. Although they’ve been around for billions of years, they continue to change in shape. This is caused by seafloor spreading and continental drift, which rearranges the land and ocean.


Hydrosphere Facts for Kids

There are roughly a billion cubic kilometres (about 332 million cubic miles) of water on Earth. That’s enough water for all our needs. Water is so abundant we often take it for granted.

  • Fresh water makes up about  2.5% of our bodies’ total mass. Saltwater accounts for over 3.5%, so drink up!
  • Of this freshwater, 2.9% is in the form of ice and permanent snow cover in the Arctic, the Antarctic and mountain glaciers; 3.8% is in the form of fresh groundwater; and only 4.3% of the fresh water on Earth is in easily accessible lakes, reservoirs and river systems.
  • The total mass of Earth’s hydrosphere is about 2.4 × 1018 tonnes, or about 3.023% of Earth’s total mass.
  • At any given time, about 20 × 1021 tonnes of this is in the form of water vapor in the Earth’s atmosphere (for practical purposes, 1 cubic meter of water weighs one tonne). Nearly three-fourths of the earth’s surface, or approximately 3.1 x 10^14 cubic meters (181,000,000,000,000 cubic feet), is covered by oceans.
  • The average salinity of Earth’s oceans is about 2.5%. That means every kilogram of water contains, on average, 3.5 grams of salt.

Human Impact on the Hydrosphere

Modern humans have dramatic effects on the hydrologic cycle. We’re withdrawing water at an unprecedented rate. If we continue, we’ll end up with only a trickle left by the end of the century. The Ogallala Aquifer is the main source of water for farmers in the U.S., and if the aquifer goes dry, more than $20 billion worth of food and fibre will be lost from the global market. The aquifer is being depleted at such a rate, it is certain the aquifer will be completely drained in the next 30-years or so. Some 3/4 of the world’s rivers are no longer free-flowing as a result of the extensive use of dams, levees, hydroelectric power, and habitat degradation.

Rivers are an important part of our environment and are critical for providing us with water. However, many of the world’s great rivers have become so polluted that only a small fraction of them are actually free-flowing. In fact, more than half the world’s rivers are too polluted to support even a microscopic amount of aquatic life. Rivers also provide valuable habitats for many forms of wildlife. Unfortunately, many of these species are also suffering from the effects of pollution and habitat destruction.


How is the Hydrosphere Changing?

The hydrosphere is one of the most dynamic and critical components of our global environment. The hydrosphere encompasses all water on the planet, both fresh water and saltwater. Some changes to the hydrosphere are natural, such as ice melting during the summer months. Other changes to the hydrosphere are man-made, such as dumping pollutants into rivers or lakes. The human population and its activities are greatly impacting the global environment to an extent that we may have difficulty reversing the change. They also create legal and regulatory challenges for environmental protection and management.

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