To celebrate 300 years of scientific hydrology, nearly 400 engineers and scientists from 82 countries attended the Tercentenary of Scientific Hydrology and associated international symposia held at Unesco House in Paris, France, from September 9 to 12, 1974. The celebration was sponsored by Unesco, the World Meteorological Organization (WMO), and the International Association of Hydrological Sciences (IAHS) within the framework of the International Hydrological Decade (IHD).
During the period September 2–14 an International Conference on the Results of the IHD and on Future Programs in Hydrology also took place at Unesco, and the Bureau (executive board) of the IAHS held meetings to carry out its annual business. R.E. Oltman (Engineer Consultant, Falls Church, Virginia) and A.I. Johnson (U.S. Geological Survey, Reston, Virginia) were U.S. representatives at the IAHS Bureau meeting; Johnson also served as U.S. coordinator of the tercentenary and its symposia.