Studies on the Groundwater in Alluvium （Ⅱ） On the ... 1欧 χ ｢ AjTAipnpuoo oinoaig...

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Studies on the Groundwater in Alluvium

On the Increasing Salinity of Groundwater in the Yamaii Area

at the Lower Basin of Watari River

Chiaki Agemori, Kunihide Chikamori

and Seisuke Matsuda

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Yamaji area is situated on the right side at the distances of 5.56.5 km from the estuary of Watari

River which is discharged into Tosa Bay. And it is small paddy fieldwith about 13 ha. area.

few years ago, Yamaji River streamed along the south side of thisarea. but now it was digged

and enlarged for increasing the discharge of Nakasuji River and it was drived to Sanezaki of A'atrai

River. Recently, tomato and cucumber in this area have been caltivatedingreen house about same

areas (1. 8 hci).

The aquifer in this area became contaminated with saltwater during January and February of 1970

and saltinjury occured. And so, to examine causes an investigation was done by Nakamura office

of ministry of Construction.

In this paper, authers obtained the{ollov/ing results by analyzing thesdata, (a) salt water intrudes

inland through the confined aquifer from Watari River, and (b) the fluctuationof piezometric head

responds to changes in Nakasuji water level with tides. (c) Salt water intrusion has been accentuated

by overpumping due to irrigation.

(Fig. 1), 5.56. 5 km

13 ha

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Fig. 1. Plain view of lower basinof Watari River

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Fig. 2. Geoogical profiles of Yamaji area

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