The hydrosphere is one of the four spheres of the Earth system; the other three are the geosphere or lithosphere (solid rocky part of Earth), atmosphere (gases surrounding Earth), and biosphere (living things).
The hydrosphere consists of all of the water on, in and surrounding Earth. The water in the hydrosphere is distributed among the ocean, glaciers and ice caps, groundwater, surface water and water in the atmosphere in the form of water vapor and clouds. The water is present in all three phases: solid, liquid and gas. Life on Earth depends on the water of the hydrosphere.
Earth is known as the water planet for good reason. More than 71% of Earth's surface is covered with water. The total amount of water on Earth is approximately 333 million cubic miles (1,386 million cubic kilometers). Only a small fraction of the total amount of water on Earth is available for drinking, washing and irrigating crops because most of it is either salty or frozen.
The global ocean, along with seas and bays, accounts for 97% of all the water on Earth, about 321 million cubic miles. Ocean water is salty and is not suitable for drinking or other everyday uses. Only 3% of the water on Earth is fresh (not salty). Over two-thirds of the freshwater is in the form of ice, in glaciers, polar ice caps or permafrost. Another 30% of the freshwater is groundwater. This leaves less than 1% of the freshwater, or 0.007% of the total water on Earth, on the surface in lakes and rivers that are easily accessible.