In order to evaluate the effects of modeling transverse joints on the static behaviors of deformation and stress in existing arch dams, numerical analysis was carried out. The elastic deformation is observed in the dam which sustains the influence of horizontal arch displacement, then no effect is appeared of modeling transverse joints in an arch dam. Affected of variable conditions of transverse joints in an arch dam, the inelastic deformation is shown in the dam which excels the influence of vertical cantilever displacement. Affected of modeling transverse joints in an arch dam which seems to behave the nonlinear deformation, the concrete stress level and direction on the downstream surface in winter are different from the dam which seems to behave the linear deformation.

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The development of willow (Salix pierotii) community at upstream inlet area of the reservoir, which is located at 30 years old Egawa dam and is a part of Chikugo River system, was studied. By interpretation of aerial photographs and analysis of tree age, it is determined that the colonization of S. pierotii community started since 1986. Although upstream area of the reservoir is submerged, this area often gets drawdown during seedling period of S. pierotii, and the exposed ground is capable of germination and colonization. S. pierotii is submerged at one meter depth for 66 days per year on average and 200 days in a row per year when submergence occur frequently. Sediment deposition formed by flood also occur at this colonization area, resulting in strict condition for plant, but this S. pierotii community keeps on growing with developing adventive root.

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We were investigated the several examples of the old small earth dams that improved the safety and prevented the leakage of the existing embankment by applying the rehabilitation technique for old embankments using the cement-stabilizeed muddy soil. This paper presents a general considerations of the factors to be considered in designing to improve the safety and to prevent the leakage of a old embankment dam. We concluded that it is important for the dedign of zoning pattern to rehabilitate the old small earth dam to minimize the strength gap between the additional embankment constructed by the cement-stabilized muddy soil and the existing embankment.

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This paper presents the experimental study on the compressed air production from open channel flow with cross-flow water turbine. The water turbine combined with air compressor of linear-crank type is developed for utilizing unused small-scale hydropower at the existing water-use facilities to produce the compressed air. The compressed air is available for water aeration in order to restore the water quality in dam lakes. The turbine performance tests were carried out on two forms of the runner setting where the runner is lying or standing on the channel bed. Examinations are made on the effects of the water discharge on water elevation around the water turbine, the amount of compressed air and the efficiency of the system. The experimental results show that the lying turbine produces a larger amount of compressed air than the standing turbine when the hydropower of effective head exceeds 100 W. When the hydropower becomes less than 100 W, the standing turbine works well with high efficiency. The lying turbine has higher efficiency in a high hydropower range and keeps good efficiency in wide range of hydropower.

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