Qualla: Lake Suwa

Lake Suwa: Introduction

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit アルトクール, CC BY-SA 4.0. Every winter since at least 1443, priests at Yatsurugi Shrine on the shore of Lake Suwa have watched the water and waited. When temperatures drop far enough, the shallow lake freezes solid, and then something remarkable happens: daily expansion and contraction crack the ice surface, forcing it upward into jagged pressure ridges that can stretch from shore to shore. The Shinto faithful call this the omiwatari -- the 'divine crossing' -- believing it marks the path of the god Takeminakata walking across the frozen lake to visit his consort Yasakatome at the shrine on the opposite shore. For more than six centuries, the priests recorded the date of each crossing. They created, without knowing it, the oldest continuous human-observed climate record on Earth.

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Image: アルトクール | CC BY-SA 4.0

Lake Suwa: The God's Footprints

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit そらみみ, CC BY-SA 3.0. The legend is specific and romantic. Takeminakata, the warrior deity enshrined at Suwa-taisha's Upper Shrine on the lake's southern shore, crosses the frozen water each winter to reach Yasakatome, the goddess of the Lower Shrine to the northwest. The ice ridges are his footprints...

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Image: そらみみ | CC BY-SA 3.0

Lake Suwa: A Lake with a Hot Spring Beneath It

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit Mti, CC BY-SA 4.0. Lake Suwa sits in the Suwa Basin of central Nagano Prefecture, a shallow body of water ranking 24th in surface area among Japan's lakes. The cities of Suwa and Okaya and the town of Shimosuwa line its shores. The Tenryu River -- one of Japan's major waterways -- begins here, flow...

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Image: Mti | CC BY-SA 4.0

Lake Suwa: Six Hundred Years of Vanishing Ice

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit Irvin, CC BY 4.0. The priestly records at Yatsurugi Shrine constitute a scientific treasure. Researchers have used the omiwatari dates to study the effects of sunspots, industrialization, and rising atmospheric carbon dioxide on lake ice formation. Combined with similar records from the Torne Rive...

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Image: Irvin | CC BY 4.0

Lake Suwa: A Godless Winter

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit Alexrk2, CC BY-SA 3.0. In Japanese, a winter without the omiwatari is called a 'godless year' -- the deity did not walk, and the crossing did not appear. What was once an extraordinary rarity has become the norm. The cultural loss runs deeper than meteorology. The three-day ceremony cannot be held. The...

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Image: Alexrk2 | CC BY-SA 3.0