more than half of all stream and shoreline miles are reported to be polluted. The same three (Ohio, Southeast, Great Lakes) also include 79 of the 113 second-order watersheds in which aggregated duration-intensity factors exceed the national value. Among them, they include 23.9 percent of the nation's stream miles (third-order streams or greater), but 48.9 percent of the polluted stream miles. The smaller the units of the hydrologic system that are considered, the more apparent it becomes that water pollution may be far more concentrated than is generally supposed. Table 3 provides a demonstration of that fact. It arranges the 241 first-order tributaries of the nine broad, synthetic hydrologic groupings in class intervals according to prevalence of pollution and duration-intensity. The table makes it clear that extensive pollution is very nearly limited to the Ohio, Great Lakes, and Southeastern drainage systems. And though the Northeastern watersheds are in a class with the other three with respect to duration and intensity of pollution, they tend to dominate that measure as well.

Thus the median class interval for prevalence of pollution is: 21-30 percent of stream and shoreline miles for the U.S.

81-90 percent for the Ohio River Basin,

21-30 percent for the Southeastern Basins,

41-50 percent for the Great Lakes Basins, and

11-20 percent for the rest of the nation.

Similarly with respect to duration-intensity of pollution, where the median is:

.410-.509 for the nation,

.410-.509 for the Ohio River Basin,

.610-.709 for the Southeastern Basins,

.410-.509 for the Great Lakes Basins, and

.310–.409 for the rest of the nation.

It is not appropriate to compare 1970 and 1971 conditions of water pollution on the basis of the separate national assessments. The quality of the 1971 survey was far superior to its predecessor, due largely to the facts that an informational and experiential base was established by the 1970 survey that resulted in an improved second effort, and that a more rigorous methodology was imposed on the assessors in 1971. Further, the 1971 assessment included provision for the duration and intensity factors that go into the water pollution index.

A comparison of the common factor of prevalence, however, can be made. Such an evaluation is summarized by major drainage area in Table 4. In general, the major drainage areas with the higher prevalence of pollution in 1970 became even worse in 1971.

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TABLE 4.-WATER POLLUTION INDEX SUMMARIZED FOR MAJOR DRAINAGE AREAS, 1970 AND 1971

Unfortunately, of the four apparently significant shifts in reported water pollution that took place in the Ohio, Gulf, Missouri, and Northeastern Basins-three are so obscured by variations in procedure that it is difficult to evaluate the degree of real change. Both the Gulf and the Missouri Basins reported an enormous improvement in compliance with water quality standards. But in each case, the 1970 assessment failed to make allowance for legally sanctioned breaches of water quality criteria that resulted from precipitation; and in either case, that exception is a significant matter. Apparent improvement, then, can only be ascribed with assurance to compliance with a legal standard, not to better water. And in the case of the Ohio River Basin, the 1970 assessment concentrated on the quality of major waterbodies, overlooking smaller tributaries. But in the Ohio, a phenomenon that is almost unknown elsewhere is common, in that many streams are polluted at the source as a result of the acid drainage of mountain coal mines. Of twenty-one river systems in the Ohio River Basin, nine-the Little Miami, the Licking, the Miami, the Kentucky, the Salt, the Green, the Wabash, and the East and West Forks of the White-are in violation of water quality criteria over their total span during at least part of each year. Three others-the Guyandot, the Hocking, and the Cumberland-have only a few miles free of pollution. Failure to account for this total prevalence of pollution in 1970 is at least partially responsible for the increase in reported pollution in 1971.

On the basis of the data available, if data anomalies are overlooked, we may conclude that substantially the same number of river miles was polluted in 1971 as in 1970 and that the western States had less water pollution and less severe water pollution than eastern States. (The evaluation holds for changes in the water quality of discrete river systems as well as for gross hydraulic groupings (cf.

Table 5). In coming years as comparable data is developed, the water pollution index will be able to better identify trends in pollution for the nation.

"Appendix-presents instructions for calculating the pollution indices, and index data summarized for second-order watershed.

TABLE 5.-SHIFTS IN PREVALENCE OF POLLUTION SUMMARIZED FOR MAJOR DRAINAGE
AREAS, 1970 AND 1971

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The chapter traces quantitatively trends in manufacturing use of water between 1959 and 1968, concentrating on growth of discharge volume, rates, and waste treatment, and relating them to changes in the institutional setting.

SUMMATION

Industrial water intake and discharge is increasing at a less pronounced rate than industrial output. The proportion of industrial wastewater discharge that is treated continues to grow, and amounted to 37 percent of discharge in 1968. Waste treatment growth was less between 1964 and 1968 (3.1 percent annual rate of increase), however, than between 1959 and 1964 (10.5 percent annual rate of increase). Most of the increase in industrial waste treatment occurred at the factory. For, although use of public sewers and waste treatment plants is the main method of waste disposal for a number of manufacturing sectors, the portion of industrial effluent discharged to public facilities dropped from almost 9 percent in 1959 to little more than 7 percent in 1968.

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