The Mokihinui River on the West Coast is one of New Zealand’s most stunning rivers and home to some of our most threatened wildlife. Yet a proposed hydro-scheme could destroy the Mokihinui River as we know it. Debs Martin visits a river under threat.
The thunderous roar of nearby rapids envelopes me as I watch the early morning sun penetrate the dark green depths of the Mokihinui Gorge, highlighting its smooth granite surface where the mountain appears as if it has been sliced in half and trees stand parallel to the hillside.
I’m at Welcome Creek – site of a proposed 85-metre hydro-electricity dam. This place is indeed welcoming: a curve in the river at the bottom entrance to the gorge, with giant rock outcrops, deep pools, and the constant cascading of water over greywacke boulders. Its future prospects, if the hydro scheme goes ahead, are anything but welcome.
We have come to see the river under the expert guidance of long-time Forest & Bird member, tramper and “Old Blue” recipient Pete Lusk, whose connections with the Mokihinui River date back more than 30 years, to see what Meridian Energy, a New Zealand State-owned enterprise, is planning for this beautiful, free-flowing river.
Nestled under the western shoulder of Kahurangi National Park, the Mokihinui is the West Coast’s third largest river, draining the vast uplands and mountains of the Lyell, Radiant, Glasgow, Allen and Matiri Ranges, falling steeply through granite and limestone gorges, emerging to meander across open flats, before gathering all its waters together and making a determined charge for the coast through a steep earthquake-shattered gorge.
Released from the gorge, it flows briefly through alluvial flats and a small series of limestone outcrops near the small settlements of Seddonville and Mokihinui before finally flowing into the Tasman Sea.
It is a volatile river, reflecting the intense downpours for which the West Coast is notorious. In times of flood, the water frequently turns the Mokihinui Forks confluence into a vast lake as water builds up behind the bottleneck formed by the narrow gorge.
Venturing into the gorge, we see tall podocarps festooned with kiekie, rata making a glorious late summer show, and dense beech forest clothing the hills.
Lower terraces provide a moist, warm haven for rimu, kahikatea, matai and miro. Abundant in the rich alluvial soils of the bottom slopes of the gorge, their rangy heights lifting them above the canopy of beech. Patches of broadleaf forest and a densely packed understorey of small-leaved rata and luxuriant ferns thrive on well-drained river terraces.
Wide-girthed nikau flourish on the frost-free slopes. Poorly drained surfaces provide boggy patches for dense moss mats and regenerating kahikatea and rimu forests. Slips are frequent and mosses, lichens and herbfields quickly take hold in the nooks and crannies among the blocks of granite and greywacke.
The gorge is home to a number of endangered fauna. Eleven bird species, two giant land snail (Powelliphanta) species, and South Island long-tailed bats have all been recorded in this 16km stretch.
Blue duck (whio) is one of the most vulnerable species found here - recent surveys found seven birds on the river. Little is known about this population and how it survives the frequent floods that regularly lift the river flow up to six metres high along the gorge walls - it is suspected the whio may retreat to the many tributaries streaming into the gorge.
Native wildlife also flourishes below the river’s surface: long-finned eel and giant and short-jawed kokopu are abundant here.
Mokihinui means “big raft” – one traditionally made from raupo and used by Maori to cross major waterways, suggesting that this was the mode of transport used by early Maori travelers here.
It is also a gorge steeped in history of early European exploration, with the original pack route to Karamea clings to the steep valley sides before crossing the river and winding its way up a delightfully-named tributary, the Rough and Tumble. Evidence of ancient campsites and the twisted remains of the original bridge can be accessed from today’s Department of Conservation track.
There are sober reminders of the power of the seismic forces at play in this earthquake-prone land as the track passes by two memorial crosses of men who died in massive slips brought down by the 1929 Murchison earthquake.
Forest & Bird already fought to save this magnificent rainforest once – in the 1980s the Society sought to save it from the ravages of logging and have it protected as public conservation land. Now, decades on, it seems the battle to save the Mokihinui is being fought all over again.
The proposed dam would flood more than 330 hectares – drowning the forests, river terraces and the river gorge itself under a 14-kilometre-long lake. The inevitable question has to be asked: what are we doing still damming our wilderness rivers?
Debs Martin is Forest & Bird’s Top of the South Field Officer