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Shimagawa Dam: A Blue Jewel in Gunma's Mountains

Discover the mesmerizing 'Shima Blue' at Shimagawa Dam, a stunning blend of engineering and natural beauty in the heart of Gunma's mountains.

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Nestled in the mountains of Gunma Prefecture, Shimagawa Dam is a concrete gravity dam that creates the stunning Lake Okushima, known for its mesmerizing 'Shima Blue' waters. Completed in 1999, the dam serves as a multi-purpose facility for flood control, power generation, and water utilization, while also offering breathtaking views and recreational opportunities.

A brief summary to Shimagawa Dam

  • Shima, 4400−28, Nakanojo, 4400 Shima, Agatsuma District, Gunma, 377-0601, JP
  • Visit website
  • Monday 12 am-12 am
  • Tuesday 12 am-12 am
  • Wednesday 12 am-12 am
  • Thursday 12 am-12 am
  • Friday 12 am-12 am
  • Saturday 12 am-12 am
  • Sunday 12 am-12 am

Local tips

  • Visit in the morning for the best lighting and clearest views of the 'Shima Blue'.
  • Check the weather forecast before you go, as the lake's color is most vibrant on sunny days.
  • Consider visiting during the autumn months to witness the stunning contrast of the blue waters against the fiery red and gold foliage.
  • If you're interested in a dam tour, book well in advance and be prepared for a Japanese-language experience.
  • Bring a camera to capture the breathtaking scenery and the unique 'Shima Blue'.
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Getting There

  • Public Transport

    From Nakanojo Station, take the Azuma sightseeing bus bound for Shima Onsen. The bus ride takes approximately 45 minutes. From Shima Onsen bus stop, it is about 15 minutes by car to Shimagawa Dam and Lake Okushima. Bus fare from Nakanojo Station to Shima Onsen is around ¥770. A taxi from Shima Onsen bus stop to the dam will cost approximately ¥2,000-¥3,000.

  • Car

    From Nakanojo, follow Route 353 towards Shima Onsen. Continue past Shima Onsen following signs for Lake Okushima and Shimagawa Dam. The drive from Shima Onsen to the dam is approximately 15 minutes. Parking is available around Lake Okushima. There are no tolls on this route. Parking is free.

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Discover more about Shimagawa Dam

Shimagawa Dam, completed in 1999, stands as a testament to engineering and natural beauty in Nakanojo, Gunma Prefecture. This concrete gravity dam was built on the Shimagawa River to control floods, generate power, and provide a stable water supply. However, it is the dam's creation of Lake Okushima that truly captivates visitors. Lake Okushima is famous for its unique 'Shima Blue' color, a mesmerizing turquoise hue caused by the diffused reflection of light and the hot spring minerals flowing into the lake. The color changes with the seasons, sunlight, and time of day, offering a different spectacle with each visit. The lake's circumference is approximately 4km, inviting visitors to stroll along its banks, rent a bicycle, or drive around (though driving is not possible in winter). Around Lake Okushima, you'll find several parks and observation decks offering panoramic views of the dam, lake, and surrounding mountains. Inatsutsumi Seseragi Park features a boardwalk that leads down to the water's edge, while Hinamimi Park offers an overwhelming perspective of the dam's enormity. For those seeking more active pursuits, Green Discovery offers canoeing and SUP (Stand Up Paddleboarding) experiences on the lake. The Shimagawa Dam itself is an impressive structure, standing 89.5 meters high and 330 meters long. While internal tours of the dam are available, they require advance booking (at least two weeks prior) and are conducted in Japanese only, with a minimum group size of six. However, visitors can obtain a free dam card at the Shimagawa Dam Office (weekdays only) as a souvenir. Located at the innermost part of Shima Onsen, the dam and lake are easily accessible by car. From Nakanojo Station, it's about a 45-minute bus ride to Shima Onsen, followed by a 15-minute drive to the dam. The area offers ample parking, making it convenient for those arriving by car.

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