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Quality of seepage groundwater flowing through the lake bed in the littoral zone of lake biwa japan measurements of electric conductivity

Kobayashi, M.; Ishida, Y.

Memoirs of Osaka Kyoiku University Series III Natural Science and Applied Science 35(2): 163-176

1986


Accession: 006238250

Seepage groundwater flowing through the lake bed in the littoral zone of Lake Biwa was collected by direct method using seepage meter from June in 1983 to October in 1984, and electric conductivity (E.C.) of sampled water was measured. The main results are as follows: 1) Electric conductivity of lake water, seepage groundwater and groundwater below the lake bottom was measured at two station for a preparatory work, and it was found that E.C. of seepage groundwater collected by seepage meter was almost equal to that of groundwater in the stratum of 0.3-1.5 m deep below the lake bottom at one station. At the other station, however, E.C. of seepage groundwater was 20-60% lower than that of groundwater in the stratum 0.3-1.5 m deep below the lake bottom. 2) At Wani beach, Shigacho, E.C. of seepage groundwater collected at eight stations on transect at right angles to the shore line decreased exponentially with increasing distance from shore. E.C. of seepage groundwater collected at six adjacent stations changed largely near beachline: there was about twice difference in the value of E.C. even though the distance betweenm two stations was only 100 m apart. The pattern of E.C. distribution of seepage groundwater was similar to that of seepage flux. 3) E.C. of seepage groundwater around entire periphery of the lake was measured. It was found that E.C. was high in the southern lake and in the north region of the northern lake, although in the northern lake, there were rather great local change in the valves of E.C. Factors such as bottom sediments, seepage flux and human activities were infered to exert influence on the local change. These results suggest the importance of direct measurement of seepage groundwater in the littoral zone, especially near beach-line, to measure the quality of groundwater flowing into the lake.

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