The hydrosphere is often called the "water sphere" as it includes all the earth's water found in streams, lakes, the soil, groundwater, and in the air. The hydrosphere interacts with, and is influenced by, all the other earth spheres. The water of the hydrosphere is distributed among several different stores found in the other spheres. Water is held in oceans, lakes and streams at the surface of the earth. Water is found in vapor, liquid and solid states in the atmosphere. The biosphere serves as an interface between the spheres enabling water to move between the hydrosphere, lithosphere and atmosphere as is accomplished by plant transpiration. The hydrologic cycle traces the movement of water and energy between these various stores and spheres.
Distribution of water
The world's oceans contain 97% of the water in the hydrosphere, most of which is salt water. Ice caps, like that found covering Antarctica, and glaciers that occupy high alpine locations, compose a little less than 2% of all water found on earth. Seemingly a small amount, the water stored as ice in glaciers would have a great impact on the environment if it were to melt into a liquid. One fear is that global warming will cause the melting and collapse of large ice sheets resulting in sea level rise. Rising sea levels could devastate coastal cities, displace millions of people, and wreak havoc on freshwater systems and habitats.
Water beneath the surface comprises the next largest store of water. Groundwater and soil water together make up about .5% of all water (by volume). There is a difference between ground water and soil water. Soil water is the water held in pore spaces between soil particles. Soil pore spaces usually are partially void of water most of the time but fill with water after a rain storm. Groundwater, on the other hand, is found where earth materials are saturated throughout the year. That is, the pore spaces are always occupied with water. Both soil and...