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Major Environmental Surveys Carried Out in Relation to the Nagaragawa Estuary Barrage Project

Surveys Carried Out During the Project

After the construction plan for the Nagaragawa Estuary Barrage was confirmed, research on ways of relieving its adverse effects, particularly on fish life, based on the findings of the KTS survey, was commissioned to the Gifu Prefectural Fisheries Research Institute, Gifu University, and others in order to reduce the impact on the environment. Among the researchers' outstanding achievements were the development of innovative fish paths and an artificial "amago" seedling production technology. In order to understand the effects of the barrage on the environment, investigations were conducted on a wide range of general items, both before and after work on the blanket (the building of a river terrace, between 1970 and 1980) and before construction was started on the main barrage structure (between 1980 and 1990). In line with "The Views of the Director-General of the Environment Agency on the Problems of the Nagaragawa Estuary Barrage" published in December 1990, the Ministry of Construction (now the Ministry of Land, Infrastructure and Transport) and the Environment Agency (now the Ministry of the Environment) jointly reviewed the contents of the environmental investigations and conservation measures that had been carried out by the Ministry and the Water Resources Development Public Corporation (now the Incorporated Administrative Agency Japan Water Agency) for some time. As a result, additional surveys on three subjects - the effect on water quality, the effect on migratory fishes such as bullheads, and the effect on valuable animals and plants on the river terrace that was to be rebuilt - were carried out in fiscal 1991. In order to ascertain conditions after construction of the main barrage structure had commenced, extensive environmental investigations were undertaken in the section between the river mouth and about 30 km upstream for the period from December 1990 through January 1992 (the separation levees on the Ibi river side and the Kiso river side were included in the survey areas for the flora and fauna).