In its manifesto for the 2009 Lower House election, the Democratic Party of Japan called for stopping the construction of the Yanba dam project in Gunma Prefecture as a symbol of wasteful public-works projects.

But a final decision on the project has yet to be made. One of the reasons for the delay is that then land and infrastructure minister Seiji Maehara made a political blunder. On Sept. 17, 2009, the day after the Hatoyama DPJ Cabinet’s inauguration, he declared that the government will halt the Yanba dam project, skipping the groundwork to build a consensus with concerned local governments and residents.

After receiving a strong reaction from local governments and residents, the government set up an experts’ panel to decide on standards and procedures to examine the need of dam projects. The experts’ panel has been examining 83 dam projects, including the Yanba project.

In mid-September, the land and infrastructure ministry’s Kanto Regional Development Bureau submitted the results of its evaluation of the Yanba dam project and alternative plans to a forum of heads of the local governments concerned.

The alternative plans included dredging the river to make it deeper and limiting land utilization. The bureau said that for flood control, the dam project will be the cheapest, costing ¥830 billion, compared with the alternative plans, and will have the best results 10 years later. For water use, the dam project will also be the cheapest, costing ¥60 billion, and it will meet water demands within 10 years. But it must not be forgotten that ¥330 billion has been already spent for the dam project while the alternative plans are future projects.

The governors of Tokyo, Chiba, Saitama, Ibaraki, Gunma and Tochigi are demanding that dam construction start immediately. Some citizens, however, are suspicious of the regional bureau’s method of evaluation.

It is important to publicly scrutinize the method of evaluation. The points include whether the alternative plans used for comparison are realistic enough, whether the bureau correctly calculated the capacity of forest and other types of land to hold water, whether the local governments’ estimates for water demand are correct, and whether the planned site of the dam — which is close to a volcano — is appropriate. Convincing scientific justification must be the bottom line for any decision to construct a dam.

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