Special Issue on Expectations for Upgrading Dams Under Operation

Abstract

IntroductionThere are approximately 2,700 dams in Japan. Their total reservoir capacity is approximately 25 billion m3(BCM), far less than the 34.4 BCM of Hoover Dam in the US or the 39.3 BCM of the Three Gorges Dam in China. Lake Biwa, with a capacity of 27.5 BCM, which has recently been used for multiple purposes by the Lake Biwa Comprehensive Development Project, is equivalent in scale to such artificial lakes. On the other hand, dams in Japan that were constructed on mountain rivers with considerable sediment deposits are decreasing their capacity more rapidly than those constructed on continental rivers, so they require measures against deposition to maintain their long-term reservoir capacity. In addition, extreme weather phenomena (increased rainfall and drought intensity) under climate changes increase high demand for storage capacity of dams. In order to effectively use these dams as limited resources and to hand them over to the next generation in healthy state, continuous investment and development of maintenance technology are required. Recently, to promote this investment and development, “A vision for upgrading dams (effective use of existing dams to mitigate damage from frequent floods and droughts and to generate renewable energy)” was established by the Ministry of Land, Infrastructure, Transport, and Tourism (MLIT) on June 27, 2017 [1]. This special issue is collecting the significance of the dam upgrading projects and important challenges from various aspects to be implemented.