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22 I OFFSTREAM USE Public supply refers to water withdrawn by public and private water suppliers and delivered to multiple users for domestic, com- mercial, industrial, and thermoelec- tric power uses.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 The difference in the quantity of water withdrawn by public suppli- ers in a water-resources region or State and the quantity of water de- livered to all users represents losses in the collection and distribution systems, public use (water for fire- fighting, street washing, municipal parks. and swimming pools) and, in a few areas, water transferred between adjacent States or water~re- sources regions. These differences are shown in the chart below and in tables 9 and 10, as "Public use and losses". Information on public supply generally was available from State health agencies and through State permitting offices. The U.S. Envi- ronmental Protection Agency's Public Drinking Water Supply file also was used as a reference. Data on population served and withdraw- als usually are accurate because local and State agencies maintain relatively complete information. SOURCE Deliveries from public suppliers to various users are more difficult to obtain and the information general- ly is less accurate. The quantity of water with- drawn for public supply during 1990 was an estimated 38,500 Mgal/d (tables 9, 10), or 5 percent more than during 1985. Total pub- lic-supply withdrawals avera'ged 183 gal/d for each person served. Public-supply withdrawals repre- sent 11 percent of total freshwater withdrawals for all offstream cate- gories. 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 chart below. 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 per- cent. 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-snpply water to adjacent areas; negative values indicate imports of public-supply water from adjacent areas to the ex- tent that public-supply deliveries in a region or in a State exceed public- snpply 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-resourc- es regions, three of the most popu- lated regions, accounted for about 43 percent of total public-supply withdrawals (figure 8; table 9). Surface water was the source for 81 percent of public-supply withdraw- als in the New England, Mid Atlan- tic, and Great Lakes regions. Ground water was tlie 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 withdraw- als in Hawaii. Public, supply with- drawals in California, New York, and Texas, the three most populous States (26 percent of the Nation's population), accounted for 31 per- cent of nationwide public-supply withdrawals (figure 9; table 10). DELIVERY _____ Public use ___ and losses 14 38,500 MILLION GALLONS PER DAY ./ Thermoelectric ,/ power less than 1 PUBLIC-SUPPLY SOURCE AND DELIVERY. 1990, IN PERCENT ~..""'~