Recently, the wave of urbanization has been sweeping over the cities and towns in Japan. As a result, in prefectures such as Hyogo, Osaka, Nara, and Kagawa where a number of irrigation reservoirs are being used to supply irrigation water for agricultural lands, a number of them have fallen into disuse, their water area reclaimed, and the land diverted for other purposes such as housing sites, land for factories, public use, and so on.
In Hyogo Prefecture, usage of 139 irrigation reservoirs ceased during the eight fiscal years of 1963 to 1970. These reservoirs were located around 14 cities (Aioi, Akashi, Amagasaki, Himeji, Itami, Kakogawa, Kasai, Kawanishi, Kobe, Mild, Nlshlnomlya, Nishlwakl, Ono, and Takarazuka) and eight towns (Harima, Ichikawa, Inami, Midori, Nandan, Taishi, Tsuna, and Yashiro). Most of these cities and towns are located along the coast of the Inland Sea and are included in the Harima Industrial District having an area of 800km
2, and the rest are located near the city of Osaka.
200.25 ha of the water area of the irrigation reservoirs has been reclaimed andd has been used for other purposes. 126 reservoirs making up 87 per cent (174. 45 ha) of the reclaimed land have ceased functioning in the 14 cities.
The reclaimed land from former irrigation reservoirs in the 14 cities varied from 0.02 ha (in Kasai) to 3.79 ha (in Kakogawa) per reservoir. 65 reservoirs of the 126 disused reservoirs in the 14 cities have been used to construct housing sites. 44 per cent of the 174.45 ha reclaimed land in the 14 cities has been used for housing, and 18 per cent has been used for factories.
The largest number of abandoned reservoirs was in the cities of Kawanishi (30 reservoirs), Akashi (24 reservoirs), and Kakogawa (22 reservoirs). The number of abandoned reservoirs in these cities amounted to 76. The water area amounted to 77.34 ha in Kakogawa, 43.83 ha in Akashi, and 10.64 ha in Kawanishi. This presented 76 per cent of the total water area disused in the 14 cities.
Kakogawa is located at the center of the Harima Industrial District. Therefore, most of the recalimed land from the larger reservoirs have been used for factories. This area represents 91 per cent of the whole diverted area for factories in the 14 cities.
On the other hand, in Kawanishi, 96 per cent of the disused area has been diverted into housing with no factories. A large number of houses will still have to be built, because the city is located near the large city of Osaka, and the ratio of increase of population in this city continues at the highest level in the Prefecture (46.2 per cent from 1960 to 1965 and 42.2 per cent from 1965 to 1970). This is one of the main reasons why so much of the recalimed land have been used for housing in this city.
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