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Abstract

After World War II, Japan experienced dramatic economic growth. Behind this growth was the massive development and management of water resources and the hydrology that supported them. This paper overviews the history of hydrology in Japan from the postwar period to the 1970s, focusing on the co-evolution of water resources development/management and science.The first systematic discussion of hydrology in Japan was conducted by Prof. Tojiro Ishihara, Kyoto University. In 1946, Ishihara recognized the importance of hydrology for postwar reconstruction, and published a commentary titled "Hydrology, Hydrological Diagram, Hydrological Statistics" (Ishihara and Iwai, 1946). During the postwar decade, Japan experienced many severe flood disasters. Japan's greatest challenge in this period was flood prevention. In order to effectively allocate budgets to each basin to cope with the frequent floods, research on the application of hydrological statistics has progressed. Dr. Shigehisa Iwai applied the methods of Foster (1924) and Hazen (1930) to Japanese rivers and proposed his own method, the Iwai method (Iwai, 1949).In 1950s to 1960s, the Japanese government promoted the development of dams throughout the country. One of the novel achievements of hydrological study in this period was the "tank model" by Dr. Masami Sugawara (Sugawara, 1979). He was involved in the planning of a hydro power plant and dam on the Naka River in 1956, as a researcher of the Institute of Statistical Mathematics. He conducted runoff analysis to develop a reliable plan based on short-term discharge records. This was the opening of his tank model development.