About 70 percent of the earth is water, but only 2.5 percent of that is freshwater. Of the freshwater, 68.9 percent is in the form of glaciers and snow cover, 30.8 percent is groundwater, and about 0.3 percent is in lakes and rivers.
Groundwater is water that accumulates underground. It can exist in spaces between loose particles of dirt and rock, or in cracks and crevices in rocks. Different types of rocks and dirt can contain different amounts of water. The saturation zone is the portion of the soil and rock that is saturated with water, while the unsaturated zone is the portion of the soil and rock that is not saturated. The top of the saturated zone is called the water table.
Drinking water is best protected by taking an approach that uses multiple barriers to prevent contamination from affecting our drinking water. Known as the 'multibarrier approach', it includes taking actions to prevent contamination of sources of our water, using adequate water treatment and distribution systems, water testing and training of water managers.