沖積地の地下水に関する研究（皿）渡川下流山路地区地下水の塩水化について上森千秋・近森邦英・松田誠祐 (農学部利水工学研究室) Studies on the Groundwater in Alluvium （Ⅱ） On the Increasing Salinity of Groundwater in the Yamaii Area at the Lower Basin of Watari River Chiaki Agemori, Kunihide Chikamori and Seisuke Matsuda （Ｌａｂｏｒａtｏりof Ｗａtｅｒ-ＵtiliｚａtｉｏｎＥｎｇｉｉｉｅｅｒｉｎｇ, ＦａｃｕllｙｏｆＡｇｒicｕltｕｒｅ） Yamaji area is situated on the right side at the distances of 5.5～6.5 km from the estuary of Watari River which is discharged into Tosa Bay. And it is small paddy fieldwith about 13 ha. area. Ａ 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 ぺA'atrai River. Recently, tomato and cucumber in this area have been caltivated ingreen 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 thesやdata, (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. まえがき山路地区(Fig. 1)は，土佐湾の南西部に流入する渡川の河口から, 5.5～6. 5 km」二流の右｡岸側に位置し，面積約13 ha の小地区である。かつてこの地区の南側には山路川が流下していたが，中筋川流域の排水向上のため，甲峯を開削し，山路川の拡幅と掘削を行ない，中筋川を下流実崎まぷ゜゜ J Fig. 1. Plain view of 山ｅ lower basin of Watari River

Studies on the Groundwater in Alluvium （Ⅱ） On the ... 1欧 χ ｢ AjTAipnpuoo oinoaig 沖積地の地下水に関する研究べn）（上森・近森・松田） Distances from

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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

toft-tilit ,ll iclt

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

J

Fig. 1. Plain view of lower basinof Watari River
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13.512.5 2.3

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Bor. No.20.195 m

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Bot. No 33.80 m.

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Fig. 2. Geoogical profiles of Yamaji area
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