Bill Back's review of the report, Opportunities in the Hydrologic Sciences (National Research Council, Washington, D.C., 1991) was interesting not only because of the importance of the report itself, as Back wrote, but also because of the compartmentalized thinking that his review seems to illustrate. The report was compiled by the NRC's Committee on Opportunities in the Hydrologic Sciences. Back's first paragraph ends with “…the book is extremely important, and its basic premise—that there is such a thing as a single ‘discipline’ of hydrology—is contrary to the thinking of many hydrogeologists.” The message in the report's preface by Pete Eagleson, chair of the committee, is that there is a need to recognize hydrology as a science. It is interdisciplinary, and geology (or hydrogeology) is only one of its many subdisciplines.