In general, both continuous turbidity measuring and bottle sampling are used for suspendedsediment concentration measurement in rivers or reservoirs. However, turbidimeters by using an optical method have a subject in long-term stability and high turbidity measurement. As for bottle sampling, it takes a great deal of time and is very difficult to collect samples at the flood peak where short runoff catchments. Here, we have developed a new suspended sediment concentration measuring system by differential pressure measurement. This method has advantages in long-term and high turbidity measurement because differential pressure transducer is measuring density of water directly. Both laboratory and field experiments using prototype-measuring system have revealed this measurement method has sufficient accuracy and reliability.

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Fish ways applied to hi-dams has not been utilized generally in Japan due to their facilities. We have developed a new type fish way, called an airlift fish way, and proved its possibility by using modeled experiments. The airlift fish way has a tube, which connects higher pool with a lower pool. Fishes can be carried to a higher pool through the tube. Compressed air produces airlift water flow in the tube, which send out fishes from lower part of the tube to the higher pool. Fundamental theory of the airlift fish way and outline of the experiment are told in this paper.

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We examined about the precast segment method, which is suitable for the rationalizing the construction execution procedure of fill-type dam gallery, comparing it with precast segment method of gallery of the concrete dam. We enforced the real structure experiment-type using a 60% scale model of fill-type dam gallery, assuming 100m hight fill dam. And, we show briefly the result which was obtained from actual application of precast method of fill-type dam gallery. From the result of the examination, the tension stress of the arch part, and the compression stress of the side walls were transmitted through the boundary between the placed concrete and precast segment. Moreover, we found out that the structual unity of the placed concrete and precast segment, the structure performance which could be secured and which didn't change so far with conventional construction method.

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It is known that selective withdrawal densimetric Froude number G (refer to equation (1) in text) varies with intake dimensions, however, the G has been regarded nearly constant in many cases to determine intake dimensions because of difficulty to obtain convergence for the varying G. Authors present a design method of a selective withdrawal intake considering the above-mentioned varying G. The method is based on self-convergence calculation by ordinary desk top computer program.

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