Aoiike Blue Pond (Biei)

LakesHokkaido, Biei,Japan

An accidental pond on Japan's Hokkaido behind a volcanic mudflow dam, its milk-blue water coloured by dissolved aluminium, with drowned larches standing in plantation rows.

September·Edge of season

Aug–Sep

Late-summer downpours and the odd typhoon flush river silt in and cloud the water milky for days, as after the August 2016 storm, before it clears on dry spells. Broadleaf colour builds by late September.

Year-round The bleached larches stand year-round; the water is blue whenever the river runs clear, and vanishes under snow in winter.

Nothing about Aoiike was planned. The pond lies outside Biei in Hokkaido, in northern Japan, and it exists because Mount Tokachi is a volcano the town has to defend itself against. In 1988 engineers laid a dam of concrete blocks across the Biei river to hold back mudflows, and the water that backed up behind it drowned a larch plantation where it stood. The bleached trunks are still standing in it. The colour is a second accident, and it is not made here at all. About two and a half kilometres up the valley, groundwater bursts out of cracks in a cliff face at Shirahige Falls and drops into the river carrying dissolved aluminium, in particles fine enough to scatter blue light. From the bridge above the falls you can watch the river already running that impossible milk-blue, before it ever reaches the dam. The pond is only the place where the water was made to stand still. The blue is not always there. Meltwater and heavy rain wash the aluminium out and leave the water a milky grey, so June and October give you the deepest and most dependable colour. It wants direct sun: glass at dawn, full cobalt by midday, the shade under the trunks swinging toward green as the sun climbs. Late in October the planted larch on the slope behind turns amber, and the season's first snow usually lands on it while the water below is still open and blue. Then winter takes it completely. From December there is nothing to look at; ice and snow have the surface, and the town lights the bare trunks after dark instead, cycling slowly through white and blue. In winter you photograph the pond's skeleton rather than the pond. The short path along the water's edge is where the accident gives itself away. From one angle the trunks are a random thicket; twenty paces on they snap into the straight rows of the forestry plot they actually were. Where the water is shallow you can follow them on down under the surface.

Worth knowing

Good to know

Give the pond two or three dry days after heavy rain — silt washes down the river and the blue goes milky. It clears on its own, but not overnight.
Come at opening rather than after breakfast — the car park opens early from May to October, and the coach tours land mid-morning. The first hour is the quiet one.
In winter, plan for dusk, not noon — the lights are on the trees, not the water, and they run nightly until 21:00 from late October to late April.
Stay on the marked path — leaving the viewing area or entering the water is banned, and the town warns that the ground beyond the rope is genuinely dangerous.

Things to do

1
Wait for the trunks to meet their own reflections
At first light the surface goes to glass and the dead larches stand doubled, hard to tell from their reflections. Stay a few hours and the colour moves under them, swinging from turquoise to grey-green as the sun climbs and the light angle changes.
2
See the buried pond lit after dark
From December there is no water to look at — ice and snow have taken it. The town lights the bare trunks instead, working through a slow cycle of white and blue from points set around the bank. In winter you photograph the pond's skeleton, not the pond.
3
Walk the bank and find the plantation rows
The short path along the water's edge keeps re-stacking the trunks: a random thicket from one angle, then suddenly the straight rows of the forestry plot they once were. Where the water is shallow and clear you can follow the trunks on down under the surface.
4
Follow the blue upstream to Shirahige Falls
About 2.5 km up the valley, groundwater bursts out of the cracks in a cliff face and drops into the Biei River — this is where the aluminium enters the water. From the bridge above, you can see the river running the same impossible blue, and the pond's colour being made.