土地利用の生態からみた長野県のダムに関する一考察

概要

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Today Japanese dams (the modern and larger reservoirs) can be divided following two types. The one is the specialized single purpose type such as exclusively used for hydro-power generation or for urban water to reserve. The other is the multi-purpose type one in which for irrigation purpose water and urban water are simultaneously reserved. Sometimes such multi-purpose dams are designed to facilitate as the flood control ones. The former type one carne into view and had commenced its facilities approximate at the half of 20th century, 1940s, when urban expansions as well as industrial growths were limited within and surrounding Tokyo, Yokohama, Nagoya and Oosaka metropolitan areas. Dam construction places were strategically selected. "Strategic" meant the capture of the water right in the far remote location point from the metropolitan area. Then, except central or metropolitan government, only power companies had sufficient capital to permit development of remote waters. In Nagano prefecture, Miure dam was good examples. After the completions of defeated war rehabilitation, High Growth Era followed. The latter type dams were appeared in this time, during 1960s. Such type dams obtained and supplied waters locally. Water resource development and water supply were for small independent or united local regions. Success in industrial and urban expansions in local levels as well as national level required rapid development of local water resources. Nagano city, the capital of Nagano prefecture, had demanded urgently water supplies by dam construction. Through the long times from the origins of the Japanese padi-cultivation, in many regions a body of informal water law grew in the rice production areas. The water using rule had been facilitated as a common law. Under the traditional water use rules, the "first in time, first in right" priority system afforded security of supply in times of drought to those with early claims, more earlier padi-open farmers. From the early times claims of the padi water use had been cooperative and systematic, because one user's return flows were another's source of supply. Today the basic tenets of the prior appropriation doctrine has never been eroded or weakened. Following the Meiji Restoration the Riparian Act of 1896 was established and put in force and those common water laws had been arranged to modern appropriated water law and firmly established their position in the modern law system. It meant that the great many farmers had their own water right in their hands, reestablished their justification under modern civil law system instead of pre-modern feudal local clan authority. Concerning the water right staking, in case of California State, U.S.A., a water right could be lost if not put to beneficial use over a specific time. On the contrary, in Japan, "use it or lose it" criteria were not expressly defined. Japanese farmers are still allowed priority over any later claimants, urban or industrial water users. It should be kept in mind that to resolve confriction between various water users including agricultural sector itself, in the law court, previous many law-cases judgements had been frequently referred. Agricultural water rights has been protected firmly by many law judgements. Being prevalence of padi-cultivation with long history, in fact, dam construction has been one clever way out of troubles between agriculture and other water using sections avoiding law-battles that was time and finance lossing. Japan has seasonal short rainfall, especially of summer. By traditional padi-cultivation during summer season when padi-water use reaches peak demands available waters were fully consumed. The famous destructive tyhoon rainfalls recovers water deficits only partly. From the beginning of the Modern era along with the commencement of industrialization those situation became bottleneck. To overcom this water shortage, dam constructions had and has been promoted. Dam constructions and the development of supplemental water supply might new water allocations and new water entitlements make it be possible. By regulating river water flows through dams it should also be possible that dam does protect senior users, new commers, from supply interruptions even in the drought year. Then, local dams many of them were multi-purpose ones had been built under the pretext of flood control. For the central or local government dam construction costed a huge expense. Almost all of them were financed by issuing bonds. A major justification for the dam construction rested on the proposition that without flood protection dam, flood dameges might become more larger and more serious. Today, at the beginning 21h century, turning point has come. People has begun to doubt whether dam construction was the only one method to avoid flooding damages. People has begun to believe that they could find any other way to protect their life and properties from the flooding disasters. People has made decision to seek and research another way. Land use transformation is the near future key word.
信州大学の論文
2003-03-14

著者

吉田隆彦
信州大学人文学部

土地利用の生態からみた長野県のダムに関する一考察

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