OCR Text |
Show completely self-liquidating through payments by the communities benefited. A major function of waterworks is to provide adequate quantities of water at adequate rates of flow for fire protection. While the capital cost of providing for fire protection may represent 25 to 40 percent of the cost of the waterworks, the quantity of water used annually for fire pur- poses is relatively small. In larger systems, it is an insignificant part of total annual requirements. Increasing Requirements The per capita use of water distributed by waterworks is slowly increasing. By 1945, the Public Health Service reported an average in the United States of 127 gallons per capita a day, varying from 60 gallons in communities of 500 population to 140 or 150 gallons in cities of 10,000 and over. Growing commercial and in- dustrial activity, lawn sprinkling and semi-agri- cultural uses, air conditioning, and generally higher standards of living and cleanliness explain, in large part, the increase in use. Higher than average per capita use, taken alone, is not always proof of wasteful use or ex- cessive leakage. Some cities use as much as 300 to 500 gallons per capita a day without waste, due to special conditions such as large estates or greater manufacturing activity. Use in un- metered cities may be much greater, due to waste and inadequate controls. In general, waterworks which account for more than 90 percent of pro- duction through metered sales to consumers re- flect good construction and efficient operation. According to estimates by the Geological Sur- vey the following water uses account for 14 per- cent of the Nation's yearly runoff to the oceans: From From ground streams water and lakes Total Irrigation------------------------ 15 80 95 Industrial------------------------ 5 65 70 Municipal----------------------- 3 9 12 Rural (other than irrigation)- 2 13 Total--------------------- 25 155 180 These figures represent gross withdrawals at sources; net consumptive use is very much less. Domestic use accounts for only about 1 percent of runoff of our rivers. FIGURE 11. The estimate of 70 billion gallons per day by the United States Geological Survey for industrial uses includes water used for cooling purposes. It is 7 times as high as the 10 billion gallons indus- try itself estimates it uses. These high and low figures can be reconciled only on the basis that the Geological Survey- figures include great quantities of cooling water which is returned to the river at higher tempera- ture but essentially unchanged in quantity. By- far the greatest consumptive use of water is for irrigation, 95 billion gpd, followed by municipal and industrial uses which are about 10 billion, gpd each, and nonconsumptive water for cooling and condenser purposes. This latter require- ment sometimes is as great as 700 million gpd at a. single steam electric generating plant and in the aggregate is several times the water requirement for municipal and industrial consumptive uses- Cities and industries located at sea level use large quantities of sea water regularly for cooling and condensing purposes, and in some cases for wash, water. Such uses of sea water may well be further extended. 177 |