Photo: Alex Anlicker
Only 3% of the earth’s water is fresh, non-saline water. Of that non-saline water, 31% is accessible as fresh water. For every gallon of fresh surface water, there are 30 gallons that lie underground. The primary source of water for municipalities is ground water.
Water is held in underground reservoirs known as aquifers. To collect in the aquifers, water passes through the atmosphere where it dissolves and collects atmospheric gases such as nitrogen, carbon dioxide and sulfur dioxide. When it falls to the surface as rain, it’s mildly acidic with a pH just below 7.
It then passes through layers of surface soil, clay, sand, gravel and other porous materials. As it passes through those layers, it is filtered, preventing it from dragging most surface impurities with it underground. However, it does carry minute quantities of bacterial spores.
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