Journal of Japan Society of Dam Engineers

A Study on Water Level Operation (Air-Drying) for the Maintenance of Aerobic Condition and Control of Phosphorus Elution in the Reservoir

—Local Experiment in Watarase Reservoir and Application to Another Dam—

Hiroaki SATOU, Masaaki AMANO

2009 Volume 19 Issue 1 Pages 5-16
Published: March 15, 2009
Released on J-STAGE: July 02, 2009

DOIhttps://doi.org/10.11315/jsde.19.5

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Watarase Reservoir, located in Kanto plain in the central part of Japan, has been suffering from the problem of moldy smell in drinking water supplied from the reservoir since its commencement in 1990. The cause of the moldy smell is 2-MIB(2-methylisoborneol) produced by Phormidium sp. In order to reduce Phormidium taxa, we have conducted field experiments to test the effectiveness of water level drawdown and bed desiccation of the reservoir during early spring. The 9-years trial indicated that the reservoir bed exposure to the air and the sunlight reduced the annual maximum concentration of 2-MIB. In addition, the maintenance of aerobic condition and control of phosphorus elution in the reservoir is expected as for the effect of air-drying in the reservoir. We executed the field experiment and local experiment, and considered the effect of the water level operation and air-drying in the reservoir.

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Hydraulic Design of Floating Log Prevention Screen for Stream Type Flood Control Dams

Toshiyuki SAKURAI, Noriaki HAKOISHI, Josuke KASHIWAI

2009 Volume 19 Issue 1 Pages 17-28
Published: March 15, 2009
Released on J-STAGE: July 02, 2009

DOIhttps://doi.org/10.11315/jsde.19.17

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Recently, stream type flood control dams come to be spotlighted, because they have advantages in the viewpoints of sedimentation problem or environmental preservation. However, the usual type log boom is considerably difficult to install in stream type flood control dams. Then, floating log prevention measures at inlets for the dam is required. In this study, we carried out the hydraulic model test of floating log blockage of the floating log prevention screen that was proposed by authors in 2006. We also do the experiment of water head energy loss of floating log blockage using the real floating logs. As a result, the hydraulic design methods of floating log prevention screen were proposed.

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Investigation on the Characteristic of Sediment Outflow During a Flood at the Dry Dam

Shinichi SAKKA, Hiroki TAKEUCHI, Daigo AOSHIMA, Akira SAITO

2009 Volume 19 Issue 1 Pages 29-40
Published: March 15, 2009
Released on J-STAGE: July 02, 2009

DOIhttps://doi.org/10.11315/jsde.19.29

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A dry dam accumulates water only during a flood. Therefore, water usually flows through the river channel. In current examination reports, the characteristic of sediment outflow during a flood at the dry dam was examined by using one-dimensional calculation of river-bed variation. But there was not the example that measured an effect in the field. In this report, we monitored suspended solid, turbidity, and a particle size distribution, of inflow and outflow water during flood at the farmland disaster prevention dam which has similar structure of the dry dam. And we analyzed a characteristic of sediment outflow and sediment movement in reservoir during a flood by comparison of examination of results of this investigation and the previous examination.

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