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Skimming the Akatarawas

Yesterday, being bright and sunny, I was looking for something to do, and thought I might attempt to find the proposed location of a new water catchment dam on the Whakatikei River in the Akatarawas. Such a dam is one of three options being put forward as part of the Wellington City Council’s Draft Water Conservation & Efficiency Plan [1], which is being consulted on until 15th October. The other two options are to make everyone install water meters to encourage everyone to use water more efficiently, or to live with periodic water shortages in the region.

Unfortunately my plan didn’t work very well. I started with this great map (below) of the proposed dam site from page 28 of the plan’s PDF discussion document, and I think my admittedly slim knowledge of the Akatarawas didn’t help too much.

Maybe they thought nobody would bother to go out and try to look for this proposed dam site.
IMG_8423 [3]
Wainui Stream.

From the map, I thought it looked as if the dam site was somewhere off the end of Bulls Run Road, a few kilometres off Provincial State Highway 58 between Pauatahanui and the Hutt Valley, so that’s where I started. The road’s nice, it ends in a gate followed by a short walk to an almost immediate stream crossing (not the Whakatikei — I think it’s the Wainui Stream). It’s actually a ford for vehicles, but still at least knee deep and today at least it was flowing quite fast, despite there not having been much rain for a day or three.

I stood knee-deep in the Wainui Stream on a couple of occasions, but decided the current was stronger than I felt comfortable with pressing through on my own. I think it’d have be very crossable, but something didn’t feel quite right and there was nobody around to bounce ideas off, so I didn’t attempt it. Then, after some quick surveying up and down the road during which time I saw a cute flock of 10 tiny ducklings all scrunched together, I went back 10 minutes later thinking I might have missed a better crossing point, and I still didn’t cross. I got really soppy socks, though. I wonder if I should have tried to get in from somewhere slightly different.

IMG_8425_c [4]

So that was unfortunate. Comparing the PDF map with a real map, the Whakatikei River is about 200 metres from the gate on this end of Bulls Run Road, and I’m guessing the proposed dam site might be about 1.5km further up-stream. It’s really hard to tell, though.

Plan B, which wasn’t much of a plan at all, was to drive down to Upper Hutt and attempt to find the other end of Bulls Run Road. (Bulls Run Road is one of those roads that runs a complete length, but for which the middle section is inaccessible.) Plan B didn’t work either, as I never found the other end. According to my topo map and my GPS, it should have come off the end of an Upper Hutt street called Grace Nicholls Grove, and I hoped I might be able to get from there somehow up the Whakatikei River. No luck again — Grace Nicholls Grove ends at a reservoir with a big private property sign which implied that any passing (not just vehicles) was disallowed.

What I figured out from all of this is that I think I need a better plan, and maybe to talk to someone who knows the Akatarawas better than I do. That’ll be another day.

IMG_8434 [5]
There’s a nice Tararua profile between the gorse.

Not wanting to go straight home, I spent a couple of hours walking around the Cannon Point Loop [6], a short and easy loop above the Hutt River. It’s a nice walk that follows a ridge along the edge of the Akatarawas above Upper Hutt, and with very nice and clean tracks cut through the 2-3 metre high gorse.

Here’s the map of the day, much of which just shows my driving around confused.
[Download GPX [7]] [LINZ Topographic Map in new window [8]]

2 Comments (Open | Close)

2 Comments To "Skimming the Akatarawas"

#1 Comment By Philip Wilkie On 22 October, 2010 @ 7:35 pm

Great idea to have a look at the site itself Mike. From what I understand the land itself is a fairly degraded regen that’s at least partially pinus radiata plantation forest (owned by GWRC) . My understanding is that it’s not a high value biodiversity or conservation area.

It’s certainly a lot less valuable than one very prominent alternative which was Skull Gully in the Wainui catchment area. Skull Gully would have provided a very cost-effective storage option for the existing Wainuiomata Treatment Plant. By the time a dry spell is more than 4-6 weeks in duration, the Wainui plant has run out of water that it can abstract from it’s several stream sources…. and a big storage dam to keep it going would make a lot of engineering sense. However it’s one of the very few areas of virgin lowland mixed-podocarp remaining in the lower NI. I’ve been in there a few times; it’s stunningly beautiful. Folk would’ve been queuing up to lie in front of bulldozers if they had gone ahead with that option.

Virtually everyone would prefer not to desecrate Skull Gully.

The big advantage of Whakatikei is that it would provide a secure source/storage north of the main Wellington fault line. At present all the city’s supply is south of it, and much of it exceedingly vulnerable to massive damage in the event that fault moves the 4-10m it is quite capable of. The big downside is that it would require a whole new treatment plant at the site …which implies a big extra expense and major construction activity. The biggest impact might be the need to substantially improve and widen the existing Moonshine Rd, which is a charming drive at present. The other problem with Whakatikei is that the extra treatment plant would need to be a decent size to be viable, but at current consumption growth rates (which are rather flat) it could be decades before it’s sensibly utilised.

The other option that’s recently became public, is the possibility of adding a third storage lake above the existing Te Marua plant, right by Highway 2 as it dips into the Kaitoke valley area. It would more or less triple the existing storage on that site and may well prove to be a decent interim solution as it would simply piggy-back onto the existing infrastructure and capacity and give us a 15-30 year buffer before Whakatikei is on the table again. It’s my pick that this will turn out to be the path we go down.

Currently we are not so much short of water, or ability to meet peak demand…just vulnerable to prolonged dry spells. The 1 in 20 year return figure quoted is not a ‘scare tactic’… Wellington has come closer to dramatic water restrictions several times in the last decade than most people realise.

#2 Comment By Mike McGavin On 28 October, 2010 @ 10:27 am

Hi Philip. Thanks for that extensive background to everything, which goes well beyond anything I was aware of. Actually now I want to go and check out Skull Gully for some reason. 🙂

Regarding the 1 in 20 figure, another thing to consider with these numbers is that probabilities expressed this way tend to be constantly changing, partly due to a lack of historic data but also because of changing environmental conditions, not just climate instability. eg. We’ve had enough 1 in 100 year floods in recent times that are mathematically becoming 1 in 20 or 1 in 10 year floods just through circumstantial and landscape changes.

Do you have any idea off-hand what a new water catchment might do for recreation opportunities in the area? …Keeping in mind that water catchment zones tend to be places where people get discouraged from going near and everything.

In the back of my mind, I think I’m hoping that one way or another things lean towards using water meters as a priority. I don’t like the idea of paying for water, but I can at least think of this more as paying for the service of storing and getting the water through pipes rather than paying for the water itself, and hopefully that’d be spelled out clearly. I guess simply putting a price on it also won’t solve all the problems, and the charging structure would need to be right so it’s affordable but relevant for everyone (not just people with little money).