The Environmental Health Program (Toxic Substances Hydrology and Contaminant Biology) is supporting integrated science to address the full range of questions related to contaminant and pathogen sources, environmental transport, exposure/transmission pathways, uptake, biological effects, and human health implications.
Science Topics
FAQs
What is the Earth's "water cycle?"
The water cycle, also known as the hydrologic cycle, describes where water is stored on Earth and how it moves. Water is stored in the atmosphere, on the land surface, and below the ground. It can be a liquid, a solid, or a gas. Liquid water can be fresh or saline (salty). Water moves between the places it is stored. It moves at large scales (through watersheds, the atmosphere, and below the Earth...
How much of the Earth's water is stored in glaciers?
About 2.1% of all of Earth's water is frozen in glaciers. 97.2% is in the oceans and inland seas 2.1% is in glaciers 0.6% is in groundwater and soil moisture less than 1% is in the atmosphere less than 1% is in lakes and rivers less than 1% is in all living plants and animals. About three-quarters of Earth's freshwater is stored in glaciers. Therefore, glacier ice is the second largest reservoir...
How important is groundwater?
Groundwater, which is in aquifers below the surface of the Earth, is one of the Nation's most important natural resources. Groundwater is the source of about 37 percent of the water that county and city water departments supply to households and businesses (public supply). It provides drinking water for more than 90 percent of the rural population who do not get their water delivered to them from...