Water Resources: Natural Quality
The Earth's water resources consist of the oceans and seas, polar icecaps and glaciers, underground waters, and the waters in streams, lakes and rivers. Of this so-called hydrosphere, which together with atmospheric water and the water held in living things completes the hydrological cycle, about 97% consists of seawater and about 2% is ice located mainly at the poles. The remaining 1% consists of fresh and brackish inland waters.
Very nearly all of these waters were substantially of natural quality until the Industrial Revolution initiated the growth of modern technology, and human actions began to cause serious local pollution of inland waters and estuaries. Now we have reached the stage where the entire hydrological cycle is contaminated, and apparently no water of absolutely natural quality exists. Fortunately, this global contamination of water is very low, and serious pollution exists only in the inland and coastal waters of the developed countries.