In Okayama Prefecture, which is one of the districts with the smallest precipitation in Japan, there have been many water reservoirs (ponds or tanks, TAMEIKE in Japanese) and many mountains, so-called Ryuozans, where the people has prayed for rain. At first, we calculated the climatological water balance by using Thiessen Method and Thornthwaite Formular and made its geographical distribution maps in Okayama Prefecture including some boundary areas of Hiroshima, Tottori and Hyogo Prefectures. Any contour lines of water balance are generally running from west to east, but it is locally noted that the contour lines are slightly fluctuating to meridional direction. It seems to have some connection with main three big rivers in Okayama Prefecture, the Yoshii, Asahi and Takahashi Rivers. In order to clarify the features of three drainage basins, we analized the annual variation patterns of water balances, the run-off and its coefficience, and the relationship between peak run-off and flood. As the results of comparing with each other, it is certainly that the Asahi River has the greatest water-hold capacity not only because of the largest run-off coefficience but also because of comparatively poor forest. From the view-point of water balance, each drainage basin can be divided into three regions.

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This paper aims to clarify the characteristics of regional infrastructural disparities and their causes in Japan since 1960 till 1980. The studies of regional disparities have mostly been conducted in our country in order to make clear the regional variation of economic and industrial growth. But regional disparities in the level of living or the quality of life have been neglected in those studies. Infrastructure as the object for this study relates to this ignored part of disparities. The improvement in geographical distribution of infrastructure produces regional growth in the backward region. The diffusion rates of six infrastructural facilities at prefectural (ken) level are used as indices for this analysis. The six facilities are highway, hospital, old-age home, library, water supply and public sewerage. Analysis has been made on the indices in each five years from 1960 to 1980 except for sewerage from 1965 to 1980. The results obtained are as follows : 1) Among the facilities mentioned above, the water supply has already been pervaded to all prefectures of our country by 1980. The coefficients of variances for the diffusion rates of four facilities, i.e. water supply, highway, public sewerage and libraly have decreased with time. The correlation coefficients of each index between 1960 (1965 for public sewerage) and 1980 for the four facilities are high. These facts indicate the tendencies toward abolition of regional disparity of the facilities without the change in ranking order of prefectures. These indices except library are also closely related to the level of urbanization represented by the percentage of DIDs' population in the prefecture (DID stands for Densely Inhabited District). 2) On the other hand, the tendency toward abolition of regional disparities is not recognized by analysis of the coefficients of variances for the diffusion rates of the other two facilities i.e. hospital and old-age home. Besides fractuation of the ranking order in the diffusion rates of the facilities is known from the correlation coefficients during the period. 3) Each index is weighted in proportion to its public demand, so that the six indices can be summed up to an integrated index. According to this analysis the integrated index is related to the level of urbanization for each prefecture; its value in 1980 is relatively higher in the metropolitan areas (Tokyo, Osaka and Nagoya), Hokuriku and Hokkaido, whereas it is lower in nouthern Kanto, Chubu, southern Kinki, Chugoku, Shikoku and Kyushu (Fig.3). 4) Public investments for the improvement of living conditions have mainly developed the equipment of infrastructure. Although this investments were concentrated in some urbanized areas in 1960's, such a spatial pattern has been relaxed and regional disparities of this investment has tended to be abolished. It will take some time until the reluxation leads almost to the solution of the regional problems caused by the regional disparities in infrastructure by prefectural level.

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