Lake Hokuryuko is a beautiful natural lake nestled in the mountains of Iiyama City, Nagano Prefecture. Surrounded by forests and rich natural landscapes, the lake offers changing scenery throughout the year. It is especially famous in spring, when brilliant yellow rapeseed flowers bloom along the lakeshore at the same time as cherry blossoms.
The sight of yellow flowers, pink cherry blossoms, and the tranquil blue-green surface of the lake creates one of northern Nagano’s most picturesque spring landscapes. Once known as Hokuryu-ike and Saotome-ike, the lake is also associated with old legends and stories that have been passed down through generations.
Lake Hokuryuko was formed naturally when water accumulated in a landscape shaped by movements along active faults and ancient volcanic activity. The lake covers approximately 2.4 hectares and is surrounded by the mountainous terrain characteristic of northern Nagano.
The region is one of Japan’s heavy snowfall areas. In spring, melting snow and rainfall provide abundant water, creating a sparkling lake surface as the surrounding landscape awakens from winter.
From around late April to early May, fields of bright yellow rapeseed flowers spread around the lakeshore. This is one of the most popular times to visit Lake Hokuryuko, when the flowers are accompanied by blooming cherry trees.
The combination of the lake, yellow flower fields, and cherry blossoms creates a colorful landscape that attracts photographers and visitors from throughout the region. In particular, the period around the lake-opening event in late April brings a lively atmosphere to the otherwise peaceful lakeside.
For visitors hoping to experience the seasonal beauty of rural Japan, spring at Lake Hokuryuko offers an especially memorable scene. The contrast between the brilliant flowers and the quiet mountain lake makes the area ideal for photography and leisurely walks.
Lake Hokuryuko was once known as Saotome-ike. The name is associated with the saotome, women who traditionally took part in rice planting. According to local tradition, they came to the sacred pond to cleanse themselves before working in the rice fields.
During the Edo period, embankments were constructed to control the lake’s water and expand its capacity. However, the embankments repeatedly failed, sometimes causing flooding that damaged houses and farmland downstream.
A major turning point came in 1783, when the great earthquake associated with the eruption of Mount Asama caused severe damage to the embankment. The disaster prompted efforts to strengthen the lake’s defenses, but it also became connected with a mysterious local legend.
According to the traditional story, water burst out from the western side of the lake during the earthquake, and a giant serpent said to have lived in the lake swept away the lives of 100 local residents. The serpent is then said to have transformed into a dragon and traveled downstream into the Chikuma River.
Whether understood as folklore or as a symbolic story inspired by a devastating natural disaster, the legend reflects the deep relationship between the local community and the powerful forces of water and nature.
During the Meiji period, improvements to the embankments further expanded the lake, and it became known as Hokuryu-ike. At that time, another lake to the south was known as Nanryuko, or “South Dragon Lake.”
Local mythology told of a male and female dragon living in the two lakes. Nanryuko has since disappeared, leaving Hokuryuko as the surviving lake and the only remaining part of this legendary landscape.
In 1961, the Lake Hokuryuko Tourism Association was established, and the lake adopted its present name, Hokuryuko. From this period onward, tourism development gradually increased and the lake became recognized as an important attraction in the Iiyama area.
Lake Hokuryuko is not simply a scenic tourist destination. Its water also plays an important role in the surrounding agricultural landscape. Today, water from the lake is used to irrigate approximately 24.3 hectares of farmland.
As water is drawn from the lake for agricultural use, its level can fall during summer. At certain times, aquatic plants may grow excessively, creating challenges for maintaining a healthy aquatic environment.
The lake therefore has to serve several purposes at once: supporting agriculture, welcoming visitors, and protecting the natural environment. Aquatic vegetation may sometimes need to be removed to maintain boat access and preserve the lakeside scenery, but excessive removal can potentially affect water quality and the local ecosystem.
For this reason, the future of Lake Hokuryuko depends on finding a sustainable balance between tourism, agriculture, and environmental conservation. This relationship between people and nature is an important part of the lake’s modern story.
Kannon Cape is a quiet promontory extending into the lake. It offers a peaceful place to look across the water and appreciate the surrounding mountain scenery.
Hokuryu Kannon is a Kannon statue enshrined beside the lake and cherished by the local community. Kannon is a Buddhist figure traditionally associated with compassion and mercy, adding a spiritual dimension to the lakeside landscape.
The lake’s spillway is part of the water-management system designed to help control flooding. It offers visitors a glimpse into the practical role the lake has played in the surrounding agricultural landscape.
Rental boats provide a relaxing way to experience Lake Hokuryuko from the water. Looking back toward the shoreline from a boat offers a different perspective on the surrounding forests, flowers, and mountains.
Lake Hokuryuko can be reached from JR Iiyama Station by taking the Nagaden Bus Nozawa Line and getting off at the Hokuryuko Iriguchi bus stop, followed by a walk of approximately 15 minutes. The journey itself passes through a peaceful rural landscape where the scenery changes with the seasons.
Spring is particularly attractive, when rapeseed flowers and cherry blossoms transform the lakeside into a colorful natural garden. In other seasons, the lake offers a quieter experience surrounded by the mountains and forests of northern Nagano.
Lake Hokuryuko is a scenic mountain lake shaped by natural forces, but its appeal goes beyond its beautiful landscape. Stories of sacred ponds, dragons, giant serpents, earthquakes, agriculture, and local traditions have become part of its long history.
For travelers, a visit offers an opportunity to enjoy the peaceful beauty of rural Japan while discovering the stories that connect local communities with their natural surroundings. In spring, especially, the combination of rapeseed flowers, cherry blossoms, clear mountain air, and the tranquil lake creates an unforgettable view of northern Nagano.