While taking a drink of that ice-cold glass of water, do you ever wonder where it comes from? Beyond the pipes in your home, past the local municipality or your own personal well, what’s the source beyond the convenience of immediate consumption?

Drinking water, worldwide, is supplied through precipitation collected in streams, rivers, lakes, seas, oceans or the ground. Water collected in the latter is fittingly known as groundwater. Surface water includes that which is collected above ground, in bodies of water. Though oceans impressively make up 98 percent of the Earth’s water, it is unsafe for human consumption, or non-potable, due to high-salt concentrations. The Department of Energy offers a scientist’s explanation of this commonly-known, but not often understood fact:

“Humans can’t drink salt water because the kidneys can only make urine that is less salty than salt water. Therefore, to get rid of all the excess salt taken in by drinking salt water, you have to urinate more water than you drank, so you die of dehydration.”

This heedful rationale is clear, and naturally points us to the safe, though small supply of drinking water. As stated in our previous post about the water cycle and the need for conservation, less than one percent of the world’s water is potable.

Surface water, which accounts for more than 75 percent of freshwater supplies, is used for various purposes including agriculture, thermoelectric, irrigation, industrial uses, and public supply. Ironically enough, the very places and people who rely on this valuable resource contaminate surface water through hazardous substances, chemicals, pesticides, petroleum, sediment, or heated discharges. Non-point sources, meaning pollutants that wash off the land into bodies of water whose origins are not easily pinpointed, are the primary source of contamination. Much of this pollution has been pinned to the prevalent use of pesticides and fertilizers, and also livestock manure runoff, which contains pathogens that pose risks to humans.

Most groundwater, like surface water, comes from precipitation. Once the rain or snow reaches earth, it trickles down through the top layers of soil, sand, gravel and/or rock until it reaches an area that is saturated with water. A saturated area containing a substantial amount of water is called an aquifer. Most commonly, wells pump water from these aquifers and distribute it to rural homes and towns as well as to farms for crop irrigation. Fertilizers and pesticides also pollute groundwater, as well as underground landfill leaks and/or gasoline leaks.

Although the pollutants are unappealing, local municipalities do a great deal to clean up that murky water. Plus, it’s really quite amazing that Earth has been reproducing water through this same cycle for billions of years, as water is without a doubt, essential for life.

Tell us about the source of your drinking water. Is it surface water or ground water? What do you like and/or dislike about it?