Rivers and Streams in the National Park
Aquatic Environments
The rivers and streams within Akan-Mashu National Park are clearly essential for the plants and animals that inhabit this region. Running throughout the forests, the waterways connect the various lakes to each other and to the sea. They provide a glimpse into the Akan area’s ancient river ecosystems.
In spring, melting mountain snows cause streams to rush with fresh water, sometimes threatening to break their banks. However, dense vegetation grows along these riverbanks, stretching out into marshland areas that provide an important buffer zone from floods. The forests and rivers thus naturally balance, helping each other to contain seasonal changes in water flow.
Ecosystem
Many varied forms of life can flourish due to the interaction between forest and waterway. Rivers sustain the lives of aquatic insects such as caddisflies, fish such as white-spotted char and cottus nozawae, and piscivores like Blakiston’s fish owls and crested kingfishers. In addition, rivers provide land dwellers with water and a vital source of food. Yezo shika deer, brown bears, dragonflies, and butterflies are frequently seen along the riverbeds.
The Akan River is one of the principal rivers of this area. With a length of 98 km, it exits Lake Akan in the Takiguchi Waterfall area, winds its way south towards Kushiro, and empties into the Pacific Ocean. Even smaller tributaries have their own unique attractions: the Ibeshibetsu River, one of many that feed into Lake Akan, has kokanee salmon that swim upstream to their birthplace, laying their eggs there during each spawning period. The Rawan River flows from Lake Onneto and is home to Rawan-buki, a rare giant plant species that grows up to three meters tall.
