Hydrologic bench marks to distinguish the effects of climate vs. man

There is a vital need for hydrologic data representing various environments that are free from the effects of man's activities. Without such data hydrologists will be stymied in distinguishing hydrologic changes caused by man from those caused by climate. To provide this background information, the U. S. Geological Survey is planning a nationwide hydrologic bench‐mark program in which runoff, transport of sediment, precipitation, changes in vegetation, fluctuations in ground water, and other hydrologic events will be studied in locales unaffected by the works of man. The knowledge gained in operating these bench marks will be invaluable in statistical appraisals of hydrologic data wherein a part of the record is affected by man's activities.