INVESTIGATION ON THE DISCHARGE AND THE CHEMICAL COMPOSITION OF GROUND WATER IN THE KUSHIBAYASHI LANDSLIDE AREA

The variation with time in the concentrations of dissolved chemical species and the dischargeof ground waters in the Kushibayashi area, Shiga Prefecture were investigated from Oct. 1972 toNov. 1973 in order to obtain the basic data for estimate of the amounts of clay minerals produced byweathering processes through the chemical compositions of ground waters in this area.The authors have examined the relationships among the chemical species contents of the waters, and between the chemical species contents and discharge of the waters. And the following have beenattained: (1) A clear negative relationship is observed between sulfate and bicarbonate contents inthe waters drainaged from the layer about 5 m depth under ground surface, (2) a good correlationis observed between discharge and bicarbonate and sodium contents, respectively, and (3) the trans-ported amount of bicarbonate ions increases with an increase in discharge but suddenly the increasingrate of transported amount changes after a definite discharge and the slpoe in the graph trends tobecome steep in the order 1 m, 5 m, and 10 m depths under ground surface.A hypothesis on the mechanism of this phenomenon is also presented.