A geochemical investigation of the Aisawa-gawa River

Abstract

The Aisawa-gawa River is one of the most important tributaries in the lower reaches of the Mogami River. This drainage system starts from the Dewa Hills and is joined by the Mogami River at the eastern margin of the Shonai Plain.
Studies are made of the geochemical relationships of the surface water in the Aisawa-gawa basin during the period 1958-59. The discharge-ion relationships that exist in streams through various stages of flow are especially presented in this paper.
Mineralization in the Aisawa-gawa River near Aisawa fluctatues from 200ppm in a low water stage to 63ppm at a flood stage. Regarding the quality of water, calcium ion and bicarbonate ion are the most prominent constituents. The concentrations of the two ions are related linearly to the logarithm of the stream flow as shown by Figs. 5 and 6. Surface water of the Aisawa-gawa River and its tributaries carries chloride ion in rather high concentration which is derived from atmospheric salt distributed over the drainage basin.
Moreover, equations were developed by the statistical treatment to correlate between the logarithm of flow and several mineral constituents in solution.