Wakuike, located about 20 meter high from the shores of the River Sai, originated from crater of the Zenkoji Earthquake in May of 1847, is supplied by groundwater and rainfall.
The small lake, 670 meter circumference, 9.3 meter the deepest bottom, has two strata of temperature, that is, differnece 10.1°C between 2-3 meter deep and deeper strata almost without oxigen contains sulphuretted hydrogen originated from dead plankton. Therefore, fishes like carp, crucian, shrimp and so on are found in the upper strata, pH of the water surface is 8.8-9.2 and the transparency is 0.64-1.06 meter in summer. Sulphuretted hydrogen in the deep strata changes water color in spring and autumn, but recently the color change is scarcely found.
