Public supply refers to water withdrawn by public and private water suppliers and delivered to multiple users for domestic, commercial, industrial, and thermoelectric power uses. In this report, public supply includes public and private water systems that furnish water to at least 25 people, or that have a minimum of 15 hookups. The difference in the quantity of water withdrawn by public suppliers in a water-resources region or State and the quantity of water delivered to all users represents losses in the collection and distribution systems, public use (water for firefighting, street washing, municipal parks, and swimming pools) and, in a few areas, water transferred between adjacent States or water-resources regions. These differences are shown in the pie charts below (or as a GIF file), or PostScript file (95Kb)), and in table 9: water-resources regions and table 10: State, as "Public use and losses".
Information on public supply generally was available from State health agencies and through State permitting offices. The U.S. Environmental Protection Agency's Public Drinking Water Supply file also was used as a reference. Data on population served and withdrawals usually are accurate because local and State agencies maintain relatively complete information. Deliveries from public suppliers to various users are more difficult to obtain and the information generally is less accurate.
The quantity of water withdrawn for public supply during 1990 was an estimated 38,500 Mgal/d table 9: water-resources regions and table 10: State, or 5 percent more than during 1985. Total public-supply withdrawals averaged 183 gal/d for each person served. Public-supply withdrawals represent 11 percent of total freshwater withdrawals for all offstream categories. Public suppliers served about 210 million people during 1990, (a 5-percent increase from 1985), or about 83 percent of the total population.
The source and delivery of water for public supply are shown in the pie charts below (or as a GIF file, or PostScript file (95Kb)). Surface water was the source for about 61 percent of public-supply withdrawals. Ground water was the source for 39 percent of withdrawals, about the same as in 1985. Public-supply withdrawals were distributed to users as follows: domestic, 57 percent; commercial, 15 percent; industrial, 13 percent; and thermoelectric power, 0.2 percent. The remaining 14 percent of withdrawals represented public use and losses in the distribution system. Large positive values listed under "Public use and losses" in tables 9 and 10 may indicate, in addition to public use and losses, large exports of public-supply water to adjacent areas; negative values indicate imports of public-supply water from adjacent areas to the extent that public-supply deliveries in a region or in a State exceed public-supply withdrawals. This was the case in Washington, D.C., which imports public-supply water from Maryland.
Public-supply withdrawals in the Mid Atlantic, South Atlantic-Gulf, and
California water-resources regions, three of the most populated regions,
accounted for about 43 percent of total public-supply withdrawals (
figure 8: water-resources region
(or as a PostScript file (620Kb);
table 9: water-resources region).
Surface water was the source for 81 percent of
public-supply withdrawals in the New England, Mid Atlantic, and Great Lakes
regions. Ground water was the primary source in the South Atlantic-Gulf,
Lower and Upper Mississippi, Rio Grande, and California regions. Ground water
was the source for 93 percent of public-supply withdrawals in Hawaii.
Public-supply withdrawals in California, New York, and Texas, the three most
populous States (26 percent of the Nation's population), accounted for 31 percent
of nationwide public-supply withdrawals :
Table 10--Total withdrawals by State:
Figure 9a--Total withdrawals by State: Externally viewable GIF file, or PostScript file (509Kb)
Figure 9b--Surface-water withdrawals by State: GIF file, or PostScript file (968Kb)
Figure 9c--Ground-water withdrawals by State: GIF file, or PostScript file (968Kb)