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.
If you plan to swim in a natural body of water like a river, lake, pond, or the ocean, it is important to keep in mind the potential health effects of swallowing the water. Awareness of what else might be floating in the water with you is the first step in knowing how to protect your health. Please do not assume that water from lakes, streams, rivers, or springs is safe to drink. Water in a stream, river, or lake may look clean, but it can still be filled with bacteria, viruses, and parasites that can result in recreational water-related illnesses. If you swallow the water while you are swimming, you can get illnesses like giardiasis (caused by the tiny parasite Giardia) or cryptosporidiosis (caused by the microscopic parasite Cryptosporidium).
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.
