Ojiragawa Valley
The Ojiragawa Valley is located in the foothills of the Minami Alps range in the municipality of Hokuto. It is a popular area for hiking and camping in Yamanashi. The valley is part of the Minami Alps UNESCO Eco Park. The Ojiragawa River flows through the valley; the source of the river is Mt. Kai Komagatake.
The Fuji River runs through the valley. It is one of the three most rapid rivers in Japan and one of the country’s most pristine water sources.
Origin of the River’s Name
The literal translation of "Ojiragawa" (尾白川) means "white tail river". The kanji for “O” at the beginning of Ojiragawa is 尾, which means tail. The kanji for “jira” is 白, or white.
There are two possible origins behind the river's name.
The first possible origin comes from Obi Gonzaburo's (1796–1819) name. He was the first person to climb the nearby Mt. Kai Komagatake. Obi is written 小尾, which includes the kanji for "tail" (尾). His name does hold historical significance. It is said that he was deified after climbing the mountain, and statues in his likeness can be seen on the Kuroto Ridge.
The second possible origin is from the legend of Prince Shotoku (574–622 CE), who is believed to have climbed the mountain riding a black horse with a white tail.
From this, a direct translation of the name would be the White Tail River.
The water of the river appears emerald green to the naked eye but is actually crystal clear. The green color is an optical illusion created by the whiteness of the pebble-covered riverbed and the reflection of the surrounding landscape. When viewed from different angles around the mountain, the color of the water appears to change.
Minami Alps and Mt. Kai Komagatake
The Minami Alps are Japan’s largest mountain range and were registered as a UNESCO Eco Park in 2014. Mt. Kai Komagatake, which is 2,967 meters high and supports a wide range of plant life and wildlife, is highly prized for its environmental, economic, and religious legacy.
The plentiful waters flowing through the mountains sustain numerous species of flora and fauna, including wild strawberries, alpine flowers, the Japanese serow (a type of antelope), and grouse. Bears are also spotted on the mountain from time to time, so it is best to climb with a trained guide.
Mountain Worship
There are still religious groups in Japan that practice traditions of worship for certain mountains. Followers of the religious association called Komagatake Ko worship the mountain by reciting a sutra while climbing to the summit. Near the top of the mountain, members of the group, dressed in white robes, perform ritual dances.
Geology and Freshwater
The Ojiragawa River’s purity can be attributed to the granite rock of Mt. Kai Komagatake. Granite serves as a natural filter for the water that passes through the mountain. In fact, some of the streams in the Ojiragawa Valley carry rainwater that has been passing through the natural filters of the mountain for about 20 years.
Economic Value
The water of Ojiragawa Valley has a direct impact on the Yamanashi economy. The water from Mt. Kai Komagatake feeds the Ojiragawa River, which flows into the Hakushu area of Hokuto. Hakushu water is used by large beverage companies to make sake and whisky. Major beverage companies such as Suntory, Coca-Cola, and Shichiken have factories in Yamanashi because of the purity of the water.