Mt. Chokai rises on the borders of Yamagata and Akita Prefectures and the foot of the mountain reaches westward to the coast of Japan Sea. The coast as well as the margin of the south-western foot is lined with many springs. Yuza Town is built on the alluvial fan of the Gakko River, where several hundreds of artesian wells are drilled and the total discharge of them is estimated at six million tons per year. In this paper, twG types of springs mentioned above, i. e. contact spring and artesian spring, are mainly discussed from the geochemical pOifit of view.
The springs of the former type are generally good in quality. The main constituents of dissolved substances are represented by sodium and chloride ions which originate primarily from atmospheric salt transported by sea wind.
Regarding the quality of the artesian ground water, pH is in the range of 6.3 to 7.1 and the concentrations of dissolved ions are in the following order:
HCO₃^->C1^->SO₄^2-, Na²>Ca2²⁺>Mg²⁺.
Several types of phreatic ground water are found on the alluvial fan and its surrounding area. They are geochemically classified into five groups, but in general the main dissolved mineral is sodium chloride as in the case of the artesian ground water there.
The quality of the artesian ground water is 1compared statistically with that of the water of contact spring. As a result, the concentrations of sodium, potassium and hloride ions of the latter exceed in average those of the former respectively.