Regional Water Supply in Japan: A Study of Lake Biwa

Abstract

C LUSTERING of population on small coastal river plains in Japan has caused many environmental problems. Tokyo and Osaka are notorious for air, water, and noise pollution as well as for crowdedness. Less well known are the problems of water supply. Watersheds previously sufficient for traditional cities like Tokyo, Osaka, and Nagoya are rapidly becoming inadequate as urban populations grow through natural increase and through in-migration. New and greater demands for fresh water are also related to rapid economic development. For example, adoption of fush toilets by the ten million or so residents of Tokyo will require 200,000 ct1bic meters of water a day-the combined total of seven times the present water requirement of Shizuoka city plus half the daily requirement of Nagoya!' Japanese urban areas, like those in other parts of the world, depend mostly on watersheds in predominantly rural areas. In Japan, however, rural watersheds are generally used intensively for agriculture and as townsites because of high population densities and limited amounts of level land. More recently, especially since I958, a national policy of industrial decentralization has promoted location of factories in these rural areas, creating a new rural interest for fresh water. Thus, increasing urban and rural demands are accentuating the limited nature of the original watersheds. The Osaka-Lake Biwa region (Fig. ) is an excellent example of the recent dilemma of watersheds in Japan. The water demands of Osaka, the second largest city and economic center of Japan, have increased steadily since World War II. The rise of daily per capita water use from 69 gallons in 1958 to 127 gallons in 19702 reflects several phenomena: increased iron and steel production, chemical manufacturing, and other high-volume water consumers; modern, air-conditioned buildings constructed in wardamaged areas; increased use of sewers and flush toilets; adoption of such household appliances as the automatic washing machine; and more than a million commuters who use water at their places of employment in the city. Despite the fact that Osaka's population began to decrease in 1965 as a result of a shift to satellite cities and to suburbs, increased industrial demands and a continuing program to provide sewer lines and Hush toilets throughout the city suggests that per capita water use will continue to increase. 'I'he projected daily per capita use of i45 gallons will be similar to daily use in large cities in the United States.3