The Origins and Name of Lake Reisenji
From an Agricultural Reservoir to a Tourist Destination
Lake Reisenji was originally developed as a settling reservoir to improve the quality of water used for agriculture. The name “Reisenji” is associated with traditional legends and religious beliefs that have long been connected with the surrounding area.
Although its original purpose was closely tied to farming, the lake has gradually become an important recreational destination thanks to its beautiful natural surroundings and the many activities available around its shores.
Nature in the Iizuna Highlands
A Scenic Lake Surrounded by Highland Forests
Lake Reisenji can be reached by car from central Nagano via the Asakawa Loop Line, Nagano Prefectural Route 506, which climbs toward the Iizuna Highlands. The journey itself offers beautiful views of green forests and mountain landscapes.
The lake is surrounded by a rich highland environment, and large stands of reeds along the shoreline provide resting and feeding areas for waterfowl. Although Lake Reisenji is an artificial lake, its landscape blends naturally into the surrounding countryside, creating a peaceful atmosphere.
From spring through autumn, visitors can enjoy lush greenery and refreshing highland scenery. In winter, the same landscape is transformed into a quiet world of snow and ice.
Outdoor Activities Around the Lake
A Variety of Recreation in One Highland Area
The area around Lake Reisenji has been developed with a variety of leisure facilities, making it possible to enjoy much more than the lake itself. Depending on the season, visitors can find open grassy areas, campsites, tennis courts, golf facilities, ski areas, hot spring facilities, accommodations, and a dog run.
One of the most distinctive features is a 273-meter floating bridge crossing the lake. The bridge is an unusual landmark that blends into the scenery while providing visitors with an enjoyable way to experience the lake from above the water.
Fishing and Boating
Enjoy the Lake from the Water
Lake Reisenji is home to carp, crucian carp, black bass, and other fish, making it a popular destination for anglers. Fishing provides a peaceful way to enjoy the surrounding mountain scenery.
Visitors can also take a ride on the lake in a small rowboat. Seeing the forests, mountains, and open sky reflected on the water offers a different perspective from walking along the shoreline.
Winter Highlight: Smelt Ice Fishing
Fishing on a Frozen Highland Lake
When winter temperatures remain below freezing, Lake Reisenji can freeze over. During this period, visitors may enjoy the traditional winter activity of smelt ice fishing, making holes through the ice and fishing directly from the frozen surface.
Surrounded by snow-covered mountains and quiet winter scenery, ice fishing offers a distinctly different experience from the lake’s summer activities. It is one of the seasonal attractions that gives Lake Reisenji its special character.
Traditional Legends and Cultural Events
The Tengu of Mount Iizuna
Mount Iizuna, overlooking the area, has long been associated with mountain worship and legends of the Iizuna Saburo Tengu, a supernatural mountain figure in Japanese folklore. These traditions continue to influence cultural events around Lake Reisenji.
During summer, the lakeside hosts performances of Takigi Noh, a traditional form of Japanese Noh theater performed by firelight. The combination of the darkened lakeside, flickering flames, and classical theater creates an atmospheric cultural experience.
Other events, including the Tengu Fire Dance Fireworks Festival, are also held in the area, bringing together local traditions, entertainment, and the natural beauty of the highlands.
A Rare Natural Environment
The Discovery of Reisenji Shajikumo
Lake Reisenji is also significant from a nature conservation perspective. In 2001, a previously undescribed species of algae was discovered at the lake and named Reisenji Shajikumo.
The species is now classified by Japan’s Ministry of the Environment as Critically Endangered. Its presence highlights the importance of the lake’s clean water and stable aquatic environment and demonstrates that Lake Reisenji is valuable not only as a recreational destination but also as a habitat for rare organisms.
Mountain Faith and the Tengu Tradition
The Spiritual Landscape of Mount Iizuna
The mountains surrounding Lake Reisenji have been associated with Shugendo, a tradition of mountain asceticism that developed in Japan over many centuries. Mount Iizuna in particular has a long history of religious devotion and is closely linked with legends of the Iizuna Saburo Tengu.
Facilities such as Tengu-no-Yakata and various local events draw on these traditions, giving visitors an opportunity to encounter the folklore and spiritual culture of the Iizuna Highlands alongside its natural scenery.
Things to See and Do Nearby
The Iizuna Highland Area
The area surrounding Lake Reisenji offers a wide range of seasonal activities. In winter, Iizuna Kogen Ski Area and Iizuna Resort Ski Area provide opportunities for skiing and other snow sports. During warmer months, hiking, mountain walks, and forest excursions are popular.
Mount Iizuna itself is also a popular hiking destination, combining mountain scenery with the area’s long history of religious traditions.
How Lake Reisenji Was Created
An Agricultural Challenge in Iizuna Town
The western part of present-day Iizuna Town has long depended on water from the Sobe River, which originates on the slopes of Mount Iizuna, an impressive 1,917-meter mountain. The river’s water was used to irrigate approximately 65 hectares of farmland.
However, the water contained a relatively high concentration of iron. Over time, this iron accumulated in the soil and caused the rice paddies to become extremely hard. Rice roots could no longer penetrate deeply enough into the ground, creating serious problems for agricultural production.
Research into Water Treatment
Local residents began researching ways to solve the problem during the 1950s. Their studies revealed that the iron could be removed by allowing the water to stand and allowing the iron to settle.
Based on these findings, Nagano Prefecture began the Prefectural Mining Pollution Countermeasures Project in 1966. The project focused on creating a settling reservoir where the iron could be removed before the water was delivered to agricultural fields.
Construction of the Reservoir
Lake Reisenji was completed in 1972. The lake was formed using an earth dam constructed from clay-rich soil. Water from the Sobe River is held in the reservoir for approximately 15 days, allowing iron particles to settle naturally. The clarified upper layer of water can then be supplied to farmland for irrigation.
The total construction cost was approximately 215.7 million yen. About 65 percent was covered by national subsidies, while the remaining 35 percent was shared equally by Nagano Prefecture and the former Mure Village, now part of Iizuna Town.
Improving the Farmland
Construction of Lake Reisenji was carried out alongside a prefectural farmland improvement project. Soil that had become so hard that it was difficult to break even with a shovel was crushed and improved, significantly restoring the agricultural environment.
In this way, the lake was not simply constructed as a scenic reservoir. It represented an important engineering and agricultural project designed to protect farmland and secure a reliable supply of usable irrigation water.
A Highland Lake Where Nature and Culture Come Together
Lake Reisenji has grown far beyond its original role as an agricultural reservoir. Today, it is a scenic destination where visitors can enjoy fishing, boating, camping, hiking, winter smelt fishing, and the changing beauty of the Iizuna Highlands.
Its appeal also extends into the cultural world. Legends of the Iizuna Tengu, traditional performances such as Takigi Noh, and local festivals add a distinctive layer of history and folklore to the landscape.
At the same time, the discovery of a rare algae species demonstrates the ecological importance of the lake. A visit to Lake Reisenji therefore offers more than beautiful scenery: it provides an opportunity to experience the relationship between nature, agriculture, recreation, local folklore, and mountain culture that has shaped this part of Nagano.