A geochemical investigation of the Niu-gawa River

Abstract

The Niu-gawa River, a tributary of the Mogami River, starts from the Funagata Volcano of the Ou Mountain Range.
Influenced by the mineral springs and the mineral deposits distributed in the drainage basin, the waters of the upper reaches are characterized by the large contents of SO₄^2- and Ca²⁺. Throughout the drainage system, Cl^- is regarded as a minor constituent of the dissolved substances. As for the water quality of the trunk river, the concentrations of SO₄^2- and Ca²⁺ and the evaporation residue tend to decrease with the increase of distance from its origin respectively. According to the monthly observations in the fixed station of the main stream, the negative correlation is found between the water level and each of SO₄^2-, Ca²⁺, Mg²⁺ content and the alkalinity.