2018 Volume 127 Issue 4 Pages Cover04_01-Cover04_02
Lake Suwa (area: 12.8 km2, average water depth: 4.7 m) is a small lake located in central Japan, which is known for its mysterious phenomenon called Omiwatari in the winter season. When the lake freezes, shrinkage and expansion of the ice due to diurnal temperature variations causes an ice-cracking phenomenon Omiwatari, which was said to resemble a bridge crossing the lake. The ancient village people might have believed it to be the track of a god visiting a goddess on the opposite shore.
The dates of complete freezing and Omiwatari have been recorded by the Suwa shrine for the last 574 years since 1444. During a cold winter, Omiwatari would already have occurred by mid-December, whereas in a warm winter, it would be delayed until the end of February, or no Omiwatari would have occurred at all. In recent years, the occurrence frequency of Omiwatari phenomenon has been decreasing rapidly, probably due to global warming. In the most recent winter (2017-2018), we had very cold weather, and Omiwatari phenomenon occurred after the lake had almost completely frozen over. An Omiwatari viewing ceremony was held by “Yatsurugi” Shinto shrine priests on 5th February, and good harvests and a prosperous economy in this year were predicted by referring to the past documentary data for Omiwatari crossing routes.
(Photograph taken by Kiyoshi MIYASAKA on January 31, 2018; Explanation: Takehiko MIKAMI)