羊蹄山の湧水とその水収支について

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概要

• 論文の詳細を見る

• Mt. Yotei is a typical conide with the area of 104 km<SUP>2</SUP> and the altitude of 1893 m. It is situated in southern Hokkaido and composed of numerous lava flows and pyroclastics, is called “Ezo Fuji” after its shape because of resembling to Mt. Fuji and one of the well known mountains in Hokkaido.<BR>The composed rocks have high permeability so that the rain fall does not stay on the surface to be ground water. Therefore, there are many springs with rich discharge amount, in the piedmont of this conide.<BR>The present authors selected 17 springs of which the discharge amount is more than 20 <I>l</I>/second and carried out 7 surveys on the discharge amount and chemical property of those springs from 1969 to 1971. The results are as follows ;<BR>1) Each spring mentioned above is found from an the altitude of 215 m to 270 m and each of them flow out along the basemental plane of Mt. Yotei. As to those 17 springs, there are two, each of which the discharge amount is over 500 <I>l</I>/second and ten of them over 100 <I>l</I>/second respectively. There is no relation between discharge amount and altitude, but is a regional trend on the connection between distribution density and discharge amount. That is to say, there are several rich springs in the eastern piedmont, while many poor ones, but no rich on in the western part.<BR>2) The water shed drawn in a map by the catchment area calculated by the discharge amount of each spring, reveals no relationship to the surface topography of this conide. There are some rich springs of which the catchment area reaches to the western piedmont through under the summit of Mt. Yotei.<BR>3) The maximum discharge amount is recorded in May and the minimum in February. The ratio of the maximum to the minimum is small and 1.1-1.9 in the eastern piedmont, but increases to be 1.6-5.5 in the western piedmont.<BR>4) Spring in the eastern piedmont, of which the water temperature is below 7°C and its concentration of dissolved ion contents is low and less than 2.5 epm, has the property of the river water type. On the contrary, those of the western piedmont of which the water temperature is above 7°C and its concentration of dissolved ion contents is more than 2.5 epm, have the property of the ground water type.<BR>5) The total runoff of all springs is about 1250 mm, the areal rain fall of Mt. Yotei is estimated to be 1700 mm and the evapotranspiration is 450 mm through an average year. Consequently, the water economy is well in equilibrium and the ratio of the runoff is 74 %.

• 社団法人 東京地学協会の論文

著者

• 山口 久之助

  北海道立地下資源調査所

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• 羊蹄山の湧水とその水収支について

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