The infiltration approach to the calculation of surface runoff

Abstract

Some future historian of the development of scientific hydrology will probably be tempted to call the present period the “era of infiltration.” At any rate, the preoccupation of contemporary hydrologists with “the infiltration theory of runoff,” and the vast amount of energy they have expended in an effort to turn this concept to practical account, will certainly be put down as a distinctive feature of our timesThere have, of course, been logical reasons for this remarkable interest in the subject. As in all sciences, many have been attracted to it simply because of its newness. Another class—and the one that has participated most eagerly—is composed of those intrepid practicing engineers who are obliged to make the runoff estimates upon which depend the failure or success of costly flood control, water supply, and similar works. Still another group has been intrigued by a purely scientific interest, sharpened by the fact that the calculation of runoff is the central problem of the science of hydrology and involves all phases of the hydrologic cycle. Among these are scientists in the fields of soils, plants, and meteorology. As a result of these various motivations, vast amounts of labor have been expended—much of it misdirected—and many exaggerated claims have been made, to be countered, naturally, by the disparaging murmurs of the “old guard,” and other important lines of investigation have been temporarily slighted. But real progress has been made. Better estimates of runoff are now possible than could be made previously. Problems that would not yield at all to earlier methods are now soluble, albeit the solutions are sometimes only rough approximations. The inescapable conclusion is that a tool of considerable practical value has been added to the equipment of the hydrologist.