Home' Greymouth Star : August 2nd 2014 Contents Greymouth Star
West Coast feature
Saturday, August 2, 2014 - 7
Harnessing the Waitaha
This week, Westpower lodged a concession application for its Waitaha River
hydro scheme south of Ross. The Greymouth Star took a closer look at the
reports by experts who counted fish, interviewed kayakers and studied the eye-
watering rainfall in this Southern Alps catchment.
Westpower employed a raft of experts to
look into its proposed hydro scheme, and some
of their reports are over 100 pages long. The
Greymouth Star summarised them:
Potential effects on birds and
“Predators are a far greater threat to
terrestrial fauna in the Waitaha Valley than
any possible adverse effects from the scheme.”
Mr Buckingham noted the absence of kiwi
and relatively low numbers of threatened bird
species. That indicated high predation levels in
Construction largely avoided the tall
podocarp-hardwood forest that was considered
most important for bats and forest birds
(especially kaka, kea and rifleman). The
powerhouse and associated infrastructure
would be located on the lower river terrace,
thereby mainly avoiding the loss of large forest
No fernbirds or Powelliphanta snails were
found in 2012.
Potential effect on lizard fauna
Whitaker (CRRCT ) Consultants Ltd
The scheme will have no detrimental effect
on lizards. The area involved was minimal.
However, some skink habitat will be lost at
Kiwi Flat. However, clearing may open up new
rocky areas for them.
Any lizards detected during sur veys or
construction should be captured and sent to
DOC for genetic testing, to truly confirm the
impact on lizard fauna.
Natural character, landscape
and visual amenity assessment
After work, the contractors’ area will be
rehabilitated and backfilled with topsoil
and seeded with indigenous species, where
About 95,000m cubed of spoil from
the tunnel excavations will be placed
on nominated farm land outside of the
Conser vation Area.
The whole Upper Waitaha Catchment
contains very high, near pristine levels of
natural character, due to the general lack of
The area is not rated at the highest end of the
spectrum due to a number of modifications,
including pests, evidence of tracks, huts and
a swingbridge and its popularity for hunting
and kayaking. There is a gold mining permit
within the Upper Waitaha Catchment which
incorporates the project area, as well as
gravel-stone extraction permits, amongs other
consents in the Lower Waitaha Catchment.
The area is not within any outstanding
natural landscapes or features listed in the
Westland District Plan nor the Regional
Policy Statement. However, it is considered
that the Upper Waitaha Catchment would be
an outstanding natural landscape if assessed.
However, the these values are not unique as
other valley catchments hold similar values.
The river would essentially continue to
operate as it does naturally, albeit with reduced
river flows during drier periods. Sediment
would continue to be transported by the river.
The scheme would have an industrial
appearance; however it would be in keeping
with a tradition on the West Coast of such
small scales works juxtaposed against a wild
At Morgan Gorge, careful design will avoid
more significant effects.
Recreation and tourism
Rob Greenaway and Associates
The Waitaha receives low use from kayakers,
trampers and hunters.
However, the scheme has the potential to
affect the quality and nature of the recreation
It would also impact on highly-experienced
kayakers seeking to go down the Morgan
Gorge, and on all kayakers who portage the
Gorge but use the river below it to complete
“(The) change from a natural state water way
means that the final effect on kayaking on the
Waitaha River remains ‘high’.”
The challenge in protecting the regional
kayaking resource, would be establishing a
protocol that was flexible for kayakers, and
ensuring that weir design and construction was
carried out in consultation with kayakers.
Effects on most trampers and hunters would
largely be transitory.
The hot springs in the gorge will remain in
place but within, normally, a quieter and less
dramatic river-side setting.
Terrestrial flora description
and assessment of effects
“ Nothing was identified in the field sur vey
that suggests any vegetation community
uniqueness, attributes or species presence that
would distinguish this site from any other
similar sites throughout the central Westland
area and that would preclude any parts of it
from the proposed activity on the basis of its
Assessments of Environmental Effects by
The fish in the catchment are reasonably
species rich, but poor in weight or total
Tributaries are of greateer importance, apart
form the torrentfish.
Koaro was the only species recorded from
Downstream of Morgan Gorge, there were
eight fish, and a single crayfish.
No species unique to the river were found.
The trout-free koaro habitat was less
common in New Zealand and should be
maintained if the scheme proceeded.
Most of the impacts of construction could be
avoided or minimised with good construction
There were a few species which would sur vive
frequent floods, including midges.
However, the nearby Douglas Creek
Reach was very different, and an important
The biggest risk was the release of sediment
during construction, and vegetation clearance.
However, the construction effect was
expected to me ‘minor’.
In addition, all species were found elsewhere
on the river, on in tributaries.
The experts concluded “no water ways within
the scheme could be regarded as significant ”
under the regional policy statement.
The ‘life-supporting’ capacity of the river was
not likely to be affected.
The ‘Stable Trib’ area on the true right side
could be more susceptible to disturbance, but
mitigation could be carried out.
Instream habitat flow
The proposed hydroelectric power scheme
will substantially change the low to median
flow regime through the 3.3km stretch of the
Once the scheme is in place, there will be
Habitat availability for adult brown trout
will be greatly reduced during dry and typical
flow months, but for native fish will generally
Blue duck, which are found in the Waitaha,
are predicted to have more feeding habitat
available as a result of the proposed changes
“ To put the potential effects of the scheme
in perspective with the wider catchment, the
abstraction reach below Morgan Gorge is
relatively short (2.3km), being approximately
13% of the 1km of river between Morgan
Gorge and the sea ... there are substantial
stretches of river with equivalent habitat
upstream, particularly above Waitaha Gorge.”
Hydrologist Martin Doyle
The Waitaha River is located 38km south of
Hokitika and reaches from the West Coast to
the Main Divide, with a total catchment area
of 223 square kilometres.
“The upper catchment receives considerable
rainfall, ranging from about 5.5m annually
at the Kiwi Flat intake area, to around 12 -
14m annually at the divide. Just on the other
side of the divide from the Waitaha is the
Cropp Valley, where extensive hydrological
monitoring has been carried out for 33 years.
This location holds a number of New
Zealand rainfall records, including the greatest
12 month rainfall (18,442mm), the greatest
30 day rainfall (3800mm), the greatest 24
hour rainfall (758mm), and the greatest hourly
The average annual total is among the
highest yearly rainfalls in the World.
There are 19 small glaciers in the upper
reaches of the Waitaha, and at the end of
summer, snow exists only on these glaciers and
as snow patches, typically above 190m. ”
The Waitaha Hydro Scheme, a
run-of-river hydro scheme, would
would be located north of Hari Hari
on the Waitaha River on stewardship
It would make Grey and most of
Construction would take at least
three to four years, employing about
20 during that time.
The scheme would be automated,
so once up and running would
require one full time worker.
By generating power locally,
Westpower says it would enhance
security of supply.
Currently the annual peak demand
in the Westpower distribution area
is 50MW with up to 25MW being
generated on the West Coast by
a number of small power stations
including the recently constructed
Amethyst Hydro Scheme (7.6MW )
at Hari Hari.
Once operational, and in terms
of current annual peak demand,
it would make the Westpower
area almost self-sufficient thereby
reducing the need for, and
reliance on, electricity generated
and imported from outside the
“It would also significantly increase
the percentage of power generated
and owned by the local community.
Westpower also says the scheme
footprint largely avoids significant
faunal and floral habitat.
The scheme would involve the
construction of a low profile weir
immediately upstream of Morgan
Gorge, a tunnel through the schist
rock north of the gorge and a
penstock, small powerhouse and
switchyard immediately downstream
of the gorge.
The proposed powerhouse site
would be located on the Waitaha
River flats below Morgan Gorge.
“A run-of-river scheme has limited
or no storage capacity. Water
is diverted from the river via a
penstock to a powerhouse.
“The water is then returned to
the river below the powerhouse,”
Westpower says on its website.
“For the Waitaha Hydro Scheme,
this means that there will be no
inundation of Kiwi Flat and no
storage of water, which reduces the
effects on the environment and on
recreational users of the river. ”
Hydro scheme scrutinised
Concept pictures give some idea of what the scheme would look like.
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