Water is a common chemical substance essential to all known forms of life. Water dissolves more substances than any other liquid and, wherever it travels, it carries chemicals, including minerals, and nutrients. Somewhere between 70 and 75 per cent of the earth’s surface is covered with water, mostly in oceans and other large water bodies. About 96 per cent of the earth’s free water is seawater, and approximately 3 per cent is snow and ice. Liquid fresh water only constitutes about 1 per cent, and is a relatively scarce resource. Considerably more freshwater is stored under the ground in aquifers than on the earth’s surface.