Water is the most abundant element on Earth, is the main constituent of all living things and is a major force It is-constantly <: ambiando .in -the superfide terr ~ stre. It is also a key element in the climate of our planet that favors human existence and have major influence on the progress of the civilization. Changes in the distribution, circulation or temperature $ waters on earth can have far-reaching effects; the glaciations, for example, were a manifestation of such effects. Human activities may cause some changes. The beings human plowing the soil, they irrigate crops, fertilize land, deforested forests, groundwater pumping, they build dams, shed waste into rivers and lakes, and do many other constructive things or destructive affecting circulation and water quality in the planet. Water, despite being one of the most important natural resources, is while the scarcest and variab...