How a Warm-Water Irrigation Pond Works
Tatsunoumi Pond is located about 600 meters from the Sawasoko River, part of the Tenryu River system. Water is pumped from the river into the pond, where it is temporarily stored and naturally warmed before being released downstream.
This system helps raise the temperature of the otherwise cold river water before it reaches the agricultural fields. Supplying irrigation water at a more suitable temperature can support crop growth and improve agricultural conditions in the area.
The pond’s importance as an agricultural facility has also received national recognition. In 2010, it was selected by Japan’s Ministry of Agriculture, Forestry and Fisheries as one of the 100 Best Irrigation Ponds in Japan. It is officially known as Kōjin’yama Irrigation Pond (Tatsunoumi Pond).
A Lakeside Recreation Area at the Foot of Mount Kōjin’yama
Tatsunoumi Pond lies at the foot of Mount Kōjin’yama, a 764-meter-high hill near the center of Tatsuno Town. The surrounding area has been developed as Kōjin’yama Sports Park, creating a large recreational area where nature, culture, and sports come together.
The park covers approximately 35 hectares and offers a variety of facilities amid changing seasonal scenery. It is a pleasant place to combine a lakeside walk with outdoor activities, cultural visits, or time spent relaxing in nature.
Cherry Blossoms and Spring Festivities
In spring, Tatsunoumi Pond becomes one of the area’s most attractive places for enjoying flowers. Around 800 cherry trees line the lakeside, including Somei Yoshino, weeping cherry trees, and double-flowered varieties. When they bloom, the waterfront takes on a colorful and lively atmosphere.
The annual Kōjin’yama Cherry Blossom Festival is held during this season. Around 150 carp streamers, known as koinobori, are displayed above the pond, their colorful forms fluttering in the spring breeze.
The combination of cherry blossoms, blue skies, and colorful koinobori creates a memorable spring landscape, attracting visitors from both within and outside Nagano Prefecture.
Winter Illuminations by the Water
Winter brings a completely different atmosphere to Tatsunoumi Pond. During the area’s illumination events, the pond, tree-lined paths, and the preserved D51 steam locomotive in the park are beautifully lit after dark.
The lights reflected on the quiet surface of the pond create a magical winter scene. The crisp seasonal air and peaceful surroundings make an evening visit especially atmospheric.
A Relaxing Walking Route Around the Pond
A walking course follows the shore of Tatsunoumi Pond, making it a popular route for local residents who come for a stroll or a run. A complete circuit is approximately 700 meters, so visitors can easily enjoy a leisurely walk while taking in the changing scenery of the seasons.
Spring flowers, fresh summer greenery, autumn foliage, and the quiet winter landscape each give the lakeside a different character.
Hot Springs Near Tatsunoumi Pond
The area around Tatsunoumi Pond is also home to Tatsuno Kōjin’yama Onsen. Facilities including Tatsuno Park Hotel and Yu ni Iku Center offer opportunities to enjoy natural hot springs on a day-trip basis.
After walking, sightseeing, or enjoying sports in the park, soaking in a warm Japanese onsen provides a relaxing way to end the day.
Sports Facilities for All Ages
Kōjin’yama Sports Park is a spacious multi-purpose recreational complex designed to combine outdoor activities with the surrounding natural environment.
Its facilities include lighted tennis courts, a baseball field, the all-weather Hotaru Dome indoor sports facility, a full-scale athletics stadium, and a mallet golf course. The park is used by sports enthusiasts from Tatsuno and neighboring communities.
There is also a gymnasium and a martial arts hall, which serve as venues for local competitions, training, and community activities. Spacious lawns provide places for picnics and leisurely walks, making the park suitable for families, couples, and travelers looking for a relaxed outdoor experience.
Art, Insects, and Local Culture
The Kōjin’yama area offers more than sports and nature. It is also an important cultural and educational center for Tatsuno Town.
Tatsuno Museum of Art presents works by artists connected with the region as well as exhibitions related to local culture and art. It provides an opportunity to explore the artistic side of the town while visiting the surrounding park.
Another unusual attraction is the World Insect Museum. The museum displays specimens of rare insects from around the world, as well as live rhinoceros beetles and stag beetles.
Hands-on exhibits make the museum enjoyable for both children and adults. It is particularly popular during the summer holidays and can also be an interesting destination for children working on school research projects.
Historic and Educational Attractions
The surroundings also preserve traces of the area’s traditional craft culture, including the remains of the Akabane-yaki Kiln, which recalls the local pottery tradition.
Nearby, Tatsuno Mirai-kan Arapa is a science and educational facility where children can learn through interactive experiences and exhibits centered on the future of the local community.
Together, these attractions make the Tatsunoumi Pond area a distinctive destination where nature, sports, culture, history, and education can all be enjoyed in one place.
Convenient Access to Tatsunoumi Pond
Tatsunoumi Pond is located within Kōjin’yama Sports Park, along Nagano Prefectural Route 203. Parking is available within the park, making the area particularly convenient for visitors traveling by car.
For those using public transportation, the area can be reached from Ina-Shimmachi Station on the JR Iida Line or Tatsuno Station on the JR Chuo Main Line. From either station, a taxi or bus takes approximately 10 minutes.
A Place Where Nature and Everyday Life Come Together
Tatsunoumi Pond is much more than an irrigation pond. It is a place where the agricultural life, natural environment, culture, and recreation of Tatsuno Town come together.
Cherry blossoms brighten the lakeside in spring, fresh greenery surrounds the pond in summer, autumn foliage adds warm colors in fall, and winter illuminations create a magical nighttime landscape. Each season offers a different reason to visit.
Combined with Kōjin’yama Sports Park, nearby hot springs, museums, and cultural facilities, Tatsunoumi Pond offers a well-rounded experience for travelers who want to see, play, learn, and relax while exploring the countryside of Nagano.