Oyama: Omoigawa River and Watarase Retarding Basin

The Watarase Retarding Basin spans parts of four prefectures, Tochigi, Gunma, Saitama, and Ibaraki, covering a vast area of about 3,300 hectares. Most of it lies within Tochigi Prefecture, and much of the grounds, said to be more than twice the size of Haneda Airport, are occupied by one of the largest reed fields south of northern Honshu. Registered as a Ramsar Convention wetland in 2012, it is a precious marsh where many creatures live and the scenery changes with the seasons. The great sky and the reed field stretching as far as the eye can see brim with the openness only the Kanto plain can offer.

Highlights

The Watarase Retarding Basin is a vast basin built to control flooding, and most of its grounds are covered by reed field. This rich wetland environment is home to many plants, wild birds, and insects, nurturing a precious ecosystem. As an important wetland where rare flora and fauna live, it was registered under the Ramsar Convention in July 2012. Within the grounds lies an artificial lake called Lake Yanaka, which is heart-shaped because it was built to avoid the center of the former Yanaka village. The sight of the broad reed field swaying in the wind is grand and sets visitors' minds free.

Enjoying the Seasons

The basin offers many faces of nature through the seasons. In spring the creatures grow active and the fresh green reed field spreads out. The reed burning held around March each year is a traditional practice that maintains the wetland vegetation and protects the ecosystem, and the spectacle of the vast reed field ablaze is dramatic. After the burn, new reeds sprout and the rich nature regenerates. Summer brings lush green, autumn sets the golden reed field swaying beautifully, and winter draws many migratory birds, making for fine birdwatching.

Access and Basic Information

Head to the basin from stations on the JR and Tobu railway lines. By car, the Tohoku Expressway and other routes are convenient. The vast grounds have cycling roads and walking paths, and rental cycles are available at several points, so you can stroll or ride while taking in the grand scenery. On Lake Yanaka you can enjoy waterside activities such as boating.

Practical Travel Notes

• Because the grounds are so vast, touring by rental cycle is efficient and recommended.
• Being open with nothing to block the sun or wind, it helps to prepare for the weather with a hat and a jacket.
• At night a sky full of stars spreads overhead, and the basin is known as one of the best stargazing spots in the Kanto region.
• It is a nationally designated wildlife protection area where a precious ecosystem is preserved, so observe plants and animals with good manners. Pairing a walk here with the nearby waterside of the Omoi River is also recommended.

A Word of Advice

The charm of the Watarase Retarding Basin is above all its sense of openness. Cutting through the wind by bicycle beneath the endless reed field and the great sky is exhilarating. Birdwatching, cycling, stargazing, however you like, spend a while enjoying this grand wetland.

📚 Sources

This article is based on guidance published by the agencies related to the Watarase Retarding Basin and surrounding municipalities, and public materials on its Ramsar Convention registration. Notes on the reed fields, the reed burning, the heart-shaped Yanaka Lake, and the national wildlife protection area refer to on-site guidance and public materials. The reed-burning date and use of rental bicycles and water activities may change, so please confirm with the official information before your visit.

Visitor Checklist

• Estimated time: About half a day to walk the paths or cycle, or more if you add birdwatching.
• Route tips: The grounds are vast, so touring by rental bicycle is efficient and recommended.
• What to bring: The open site offers little shade or windbreak, so bring a hat and jacket as the weather requires.
• Etiquette: It is a national wildlife protection area, so observe plants and animals with good manners.
• How to enjoy: The night sky is brilliant here, one of the Kanto region best-known stargazing spots.

Practical Information for Your Visit

Watarase Retarding Basin and Watarase Reservoir (Lake Yanaka)

• Hours of use: 1 March to 31 October, 9:30-17:00 / 1 to 30 November, 9:30-16:30 / 1 December to the end of February, 9:30-16:00
• Days when it cannot be used: Every Monday (the following day when Monday is a public holiday, and the day after that when both Monday and Tuesday are public holidays), and the New Year period (29 December to 3 January). It is also closed when a heavy rain or flood advisory or higher is in effect, and during flood periods
• Parking: There is a car park in the Children's Plaza zone reached through the North Entrance, with 8 spaces for large vehicles. Once the hours of use are over the gates close and you cannot drive through
• Bicycle rental: Lake Yanaka Children's Plaza Rental Cycle Centre = adults 300 yen for up to 2 hours / 400 yen for up to 4 hours / 600 yen for a full day; children 200 yen for up to 4 hours / 300 yen for a full day. Closed on Mondays (Tuesday when Monday is a public holiday) and over the New Year period, plus a winter closure (TEL 090-3147-1926)
• Watarase Hands-on Activity Centre: 9:30-16:00, admission free of charge (charges apply for the training rooms). Closed on Mondays (the following day when Monday is a public holiday) and over the New Year period (TEL 080-8818-9381)
• Water sports: Canoeing, boating, windsurfing and the like are permitted only in the North Block. No equipment is available for hire, and powered craft such as motorboats and jet skis are prohibited
• Fishing: In the Yanaka Block only bait fishing is allowed; in the South Block bait fishing, lures and flies are all permitted; in the North Block fishing is prohibited. A fishing permit is required (day permit 500 yen in advance / 1,000 yen on the day, from the Shimotsuga Fisheries Cooperative)
• Access: About 20 minutes from "Sano-Fujioka IC" or "Tatebayashi IC" on the Tohoku Expressway / alight at "Itakura-Toyodaimae Station", "Yagyu Station", "Fujioka Station" or "Shin-Koga Station" on the Tobu Nikko Line, or at JR "Koga Station" (approximate walking times to the Watarase Hands-on Activity Centre are about 40 minutes from Itakura-Toyodaimae Station, about 50 minutes from Yagyu Station, about 1 hour from Fujioka Station, and about 1 hour 15 minutes from Koga Station)
• Points to note: Driving cars and motorcycles onto the roads within the reservoir, using open flames anywhere other than the designated area (the barbecue ground), and swimming in the reservoir are all prohibited. From January to March the water surface may be unusable because the water level is lowered for drying out

Note: No admission or parking fees are given on the official website. Please check the information on site before setting out. Note: The dates of the reed burning are decided each year. Please check the official information before setting out.

(Sources: Watarase Retarding Basin Acclimation Foundation (public interest incorporated foundation) official website; Ministry of Land, Infrastructure, Transport and Tourism, Kanto Regional Development Bureau, Upper Tone River Office official website)