Newly discovered lake bottom springs from Lake Kawaguchi, the northern foot of Mount Fuji, Japan

Abstract

In Lake Kawaguchi, the existence of lake bottom springs have been estimated based on the patchy distribution of lake ice during winter. However, our knowledge on the detailed distribution and the source of these springs are still limited. In this study, we conducted hydrological and lake bottom survey using a Conductivity Temperature Depth (CTD) profiler, underwater camera and sonar to explore lake bottom springs in Lake Kawaguchi. We found upwelling of relatively warm water with low electrical conductivity (EC) at the 100 m east of the Unoshima Island, suggesting the existence of springs at this point. In addition, the results of lake bottom survey revealed the lack of muddy sediment on the lake bottom surface, a general feature observed in bottom springs, within a radius of 25 m around the springs. Stable isotope ratios of the lake bottom waters around the springs showed the values that are close to those in groundwater around the lake, suggesting that groundwater from the surrounding mountains likely wells out from the lake bottom at this location.