Water Use - How Water Is Supplied

Freshwater that is potable (suitable for human consumption) is the most crucial resource for the maintenance of human societies. Freshwater, however, is limited in total supply, unevenly distributed, and often of unacceptable quality, particularly in areas where the supply is limited.

Most people in the United States obtain water through a utility company. These companies are called public water suppliers because they supply water to the public, although the company may be owned by a city, a town, or a private entity. Water utility companies withdraw water from either surface or groundwater sources to supply their customers. The customers pay the utility companies for the water they use. Water may also be self-supplied, that is, withdrawn directly from wells, lakes, or rivers by those users who have the equipment, technology, and water rights necessary to withdraw and process water for their individual use.

Eventually, of course, all water returns to the hydro-logic cycle in some form, but sometimes it is returned in FIGURE 2.1
Water use cycle
SOURCE: Wayne R. Solley, Robert R. Pierce, and Howard A. Perlman, "Water Use," in Estimated Use of Water in the United States in 1995, U.S. Geological Survey, 1998 a condition different from that in which it was withdrawn. This can greatly affect the ability to reuse it. Agricultural runoff may contain pesticides and fertilizers, making it unfit for other uses, such as drinking water. Water that runs down the drain when a person washes vegetables to eat is in basically the same condition as when it came from the tap, but it will likely enter a sewage line where it mixes with raw sewage.

Figure 2.1 shows a model of the different ways in which off-stream water might be withdrawn, delivered to the user, and returned to its source. The water user, in the middle of the picture, receives water from three sources: a public-supply system, which itself has withdrawn water from a surface source (a river) and a groundwater source (a well); and two self-supplied sources, a well and the river. Water that is not consumed is returned directly to the river or to a wastewater treatment plant where, after treatment, it is discharged into the river.