Water Distribution on Earth

For humans, water is the most important component of the natural sphere on Earth. Its distribution is highly uneven: **most of the total volume of water on Earth is concentrated in the world's oceans, and only a small portion (3.5%) is freshwater **. It is bound mainly in glaciers and underground deposits. A completely negligible part is represented by surface water in lakes, swamps, and rivers.

Water on Earth occurs in all three states (solid, liquid, gaseous) and is in a constant cycle (**hydrological cycle**). Water exchange can only occur above the ocean (or in areas of drainless basins on land) – in this case, we are talking about the so-called **small hydrological cycle**. If water circulates between a world's ocean and land, it is a so-called **large hydrological cycle**.