Main Sources of Water

Polar Ice

• According to the United Nations, most of the planet's fresh water is in the ice within the Antarctic and Arctic circles. This is because when water freezes, elements and chemicals such as salt sink, leaving fresh water behind. The United Nations estimates that 70 percent of Earth's drinkable fresh water comes from melted ice that spreads into freshwater supplies in countries near the Antarctic and Arctic circles.

Groundwater

• About 30 percent of the world's freshwater supplies are in the form of groundwater, according to United Nations estimates. Even though groundwater is only about one-third of the world's fresh water, it constitutes 97 percent of the water that humans drink. Groundwater seeps from basins, permafrost and swamps and ends up in freshwater supplies.

Lakes and Rivers

• Freshwater lakes and rivers do not contain a huge portion of the world's fresh water. Only 0.3 percent of the world's drinkable fresh water is in lakes or rivers, the United Nations Environment Programme states on its website. The only other source of fresh water that is lower is in Earth's atmosphere, but its percentage is so low that the United Nations Environment Programme does not list its amount.

Usable Water

• Only 1 percent of the fresh water from Antarctic and Arctic circle ice, groundwater and lakes and rivers is usable by humans because no access to the remainder exists. Ice water is available only when it melts. Groundwater either has to be drilled or processed from its seepage, and lakes and rivers compose only a small percentage of available fresh water. These factors make all available sources of water seem scarce compared to the amount of water on Earth.