The variation of the quality-of-water of the Tachiya-gawa River during the season of rapid thaws

Abstract

The Tachiya-gawa River is the second order tributary of the Mogami River. The upper reaches of the drainage system consists of two tributaries, i. e. the Momiji-gawa R. and the Risshaku-gawa R. On the two rivers, the variation of the quality-of-water was observed during the season of rapid thaws. Common to both, between the flow rate and each of chloride ion concentration, calcium ion concentration, hardness and B. C. G. alkalinity, there exists a negtaive correlation respectively.
Regarding the relation between sulfate ion concentration and flow rate, the circumstance is different in the case of the Momiji-gawa R. On this river, the positive correlation is found to exist. In other words, the dissolution effect from the catchment area exceeds the dilution effect by the freshet. In this drainage basin, is distributed extensively the copper deposit ever mined. The sulfate ion derived from the deposit plays an important role in the phenomenon mentioned above.
Moreover, the relations between the flow rate and each of silicate and evaporation residue and C. O. D. were studied. In each case, common to the two tributaries the increase of the flow causes the increase of these values.