Yosuke MATSUMOTO

Variation of groundwater level and quality induced by direct recharge of rainwater in wells for snow melting facilities

Hirofumi TOYOTA

This study aims for the practical applications of inland flood control using wells for snow melting facilities. The effects that direct recharge of rainwater has on ground water are verified and the effectiveness of this method on inland flood control is quantitatively estimated. In the concrete, 1) Water quality survey of groundwater and rainwater, 2) Measurement of water level and quality in wells during rainwater injection tests, 3) Reduction effect of outflow of rainwater by the method, are examined in Imamachi area, Mitsuke city of Niigata.
The achieved results are shown as follows:
1) Groundwater and rainwater collected in Imamachi area have satisfied the requirement of environmental quality for groundwater.
2) Clogging substances such as iron bacteria and iron oxide flocks were generated in the injection well about two days after the injection with rainwater gathered from the roof. However, it has been described in literatures that the clogging substances would be able to remove by pumping water.
3) Reduction effect of outflow of rainwater using the method was evaluated in a part of Imamachi area where flood damage has commonly occurred. The reduction ratio against outflow exceeding the capacity of rainwater treatment was calculated under the same level as design rainfall strength in Imamachi area. The reduction ratios using three wells were 80 percent in spring and 30 percent in autumn.
From the results, this method hardly causes groundwater pollution when gathering method of rainwater is appropriate. Then, the method is expected to reduce the damage of inland flood.