The Kakita River is designated as a national monument.

About 10,000 years ago, lava erupted from Mt. Fuji flowed through the valley surrounded by Mt. Ashitaka and Mt. Hakone and reached around here. Meltwater and rainwater around Mt. Fuji flow through this porous lava and gush out from the underground.

On the riverbed of the Kakita River, there are many places where springs well up. Looking closely at these springs, you see tiny white pebbles coming up and down. These pebbles were produced at a volcanic event around 3200 years ago and well up together with groundwater.

***

The Kakita River is a spring-fed river that makes up a unique ecosystem.

Spring-fed rivers are characterized by the stable environment. The water temperature of the Kakita River remains around 15 degrees Celsius throughout the year, so it is cool in summer and warm in winter. You can see living creatures at different timings than at other rivers, including the observation of dragonflies in wintertime. Combined with good water quality, fauna and flora that are endangered today inhabit the stable riverbed of the Kakita River.

In addition, sediments from Mt. Fuji are used as the spawning ground of sweetfish. Even after the breeding season, it sometimes survives the winter due to the warm temperature of the Kakita River.