Water Questions & Answers

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Water Questions & Answers
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 33 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 a county/city water department or private water company. Even some major cities, such as San Antonio, Texas, rely solely on groundwater for all their needs. About 42 percent of the water used for irrigation comes from groundwater. Withdrawals of groundwater are expected to rise as the population increases and available sites for surface reservoirs become more limited.

About 23 percent of the freshwater used in the United States in 2005 came from groundwater sources. The other 77 percent came from surface water. Groundwater is an especially important natural resource in those parts of the country that don't have ample surface-water sources, such as the arid West. It often takes more work and costs more to access groundwater as opposed to surface water, but where there is little water on the land surface, groundwater can supply the water needs of people.

Pies charts showing the percent of total freshwater withdrawals in year 2005 coming from groundwater.

These pie charts show the percentage of fresh groundwater that was used in 2005 for various categories of water use. For most categories, surface water is used more than groundwater, although this pattern varies geographically across the United States. Domestic (self-supplied) water use is almost exclusively groundwater, whereas the water used to produce electricity comes totally from surface water (most of this water is used to cool equipment and often is a "pass-through" process and is returned to the river or lake from which it came.