Newsletter 5

Newsletter 5

9th October 2022

Written with memories of Julia; disobedient, possum-mad, beloved dog, who would follow me anywhere and everywhere.

With a day to myself for a change I decided it was time to go and find something I'd found before - and something that I might just be the only living person to see.

Back in the 1890s, Dunedin needed new supplies of drinking water.  The Silverstream was sending water through a race to the Southern Reservoir.  Ross Creek near Leith Valley was supplying from the north, and the Council were looking further up the Leith and beyond for its next water source.

The plan was to take water from a number of side streams of the Leith and also from headwaters of the Waitati stream.  The Waitati takes water from the slopes of Swampy Summit, and it's the swampiness that makes it a reliable source, even in dry weather.  The hill has a lot of swampy areas and they act as regulators of the water flow, making it an ongoing and reliable source.

The route for a pipeline taking in the three main tributaries of the Waitati Stream was surveyed, a road cut through it, a trench dug, pipes bought and laid, and weirs built to direct water into the pipeline.  All of this, of course, cost money.  And a large amount of it was completely wasted.

When arriving at the pipeline track from Waitati Valley Rd, I found myself walking a broad, muddy track beside the currently-used metal pipe which takes water under the Northern Motorway and into Sullivans Dam.  The track used to go upwards on reaching Burns creek but now goes downhill a little to cross the creek then back up to follow the pipeline.  The pipes here are earthenware instead of steel.  Water has never flowed through these pipes towards Dunedin.

Following the pipeline I passed the small creeks that the planners decided not to take into the water supply and two cuttings, dug out by hand.  And also the places where the track, nearly flat with a slight descending slope when new, has dropped down the hill by several metres, taking the pipes with it - some broken, some wrenched out in sections.

The walking track eventually turns uphill to become the Rustlers Ridge track on its way to Swampy Summit.  The pipeline continues and can still be followed, though the route - while flat - is thick with fern which covers the fallen branches that can trip you.  At the end of that track and the pipeline is - nothing.  The pipes are 8 inches/20cm wide and they end in a creek which barely trickles in normal conditions.  Any flow coming down there that would fill the pipes would be far too muddy to use.

The pipeline was intended to end there but it was planned to take in water discharged from a section of pipe further up, which would take a shortcut on the inside line of a wide hillside ledge after taking water from a weir on the northernmost creek, Fergusons.

In years past, I have spent a number of hours looking for the upper section of pipe - once wandering around the area for more than five hours, carrying a compass and trying to intercept a pipeline, or the cutting for a pipeline.  Eventually I found myself dropping into Fergusons creek and decided to search up the creek.  Morrisons, in Leith valley, has an old weir, unused for nearly 100 years, but still largely intact despite the floods which have run over it.  Maybe there was something left of an intake weir on Fergusons.  There wasn't.  I couldn't be sure where the weir might be found but, when it was obvious that the bushline had been reached and passed, I had to conclude that a weir was never built.  On that day I continued up the creek, knowing there was a track passing over it along that side of Swampy Summit.  I'd walked that track a year before, finding the creek then pushing through the nearby manuka to find a viewpoint overlooking the ledge where the pipes were to be laid.  My plan that day had been to drop down the creekline.  My decision that day was to retrace my steps and not be caught out by sunset.

I headed up the Rustlers Ridge track.  All the tracks that day showed signs of recent heavy rain - being swept clean of leaf litter by running water - and were quite muddy.  Not far up the track I saw rosy red shapes on the ground and stopped to taste a few miro berries.  They're edible - more or less - with a thin rind of flesh around a hard seed.  Just enough to tempt a kereru to swallow them and deposit later on.  They kind of taste like a mix of mango and pine resin.  

Moss trails from the trees here.  The hillside intercepts damp air flowing past the Northern Motorway summit and it condenses to fall on the water catchment area.  I have walked the track in constant drizzle then returned to Dunedin and bright sunshine it was part of the attraction to the Council back in the late 19th century.

Higher up the tall timber thinned - the presence of one fruiting totara leads me to think it's a rare survivor of the original forest which was cut through to build the nearby city - and became manuka, turpentine bush and flax.  Then that thinned and the ridgetop began to clear, revealing views over Mt Cargill, Blueskin Bay and the Silverpeaks.  There's a small height along the ridge for those views, the continuing ridge and the small valley I was heading for.  I could hear a lamb calling for its mother - I'd seen feral sheep in the area before.  And goats, and pig rooting.  An entire section of what looks like old-growth forest on another part of the hillside shows many dead trees.  I wonder if that's possum damage.

The track here descended a little on the ridge then came to an intersection.  There, you can continue up Rustlers Ridge, take the track which crosses Fergusons, or the loop track back to the pipeline.  This last I took, down steep, muddy steps to the thing I had come to see.

Where the steps end is Burns creek, and a sizable grassy area.  This is one of the mossy filters which regulate the water.  Crossing the creek on stepping stones, I dropped my camera bag and spare lenses and pushed through bush beside the creek, carrying a camera and ice axe.  And here it was.

In order to decide to take the water of a creek into the city, the city must know how much water the creek has.  To do this a surveyor would build a gauging weir.  It's basically a small dam with a slot in the top and a pool behind it.  The surveyor would camp beside the weir and, every hour or so, measure the depth of the water running through the slot.  He would also drop something buoyant into the pool and, with a stopwatch, use it to measure the speed of the water flow.  From this could be calculated the amount of water passing over the weir.  By doing this every hour, day or night, the average flow could be found.

I found the Burns Creek gauging weir some years ago.  I had crossed the creek and it might have been flowing a little more than normal.  I heard the sound of rushing water and pushed through towards it, hoping to find a waterfall.  Instead I found the 1890s weir, still more or less intact.

It's not that easy to photograph.  I could drop into the pool below it but the drop was a little high, the depth of the pool unknown and digital cameras sensitive to water.  I dropped a shorter distance onto stones upstream of the weir then climbed around and below it to get my photos.  Climbing back up I hooked the blade of my ice axe under a protruding tree root to lever myself back onto the top of the bank.

I have the digital forms in an email that I can print out to apply for registration of the weir.  It's one of the many things that will happen when I have the time and inclination.

The loop back to the pipeline wanders around the manuka, flax, bush lawyer and tussock then drops into the forest.  As it did so, I looked for something I thought I'd seen the last time I was there.  A 19thC log haul track is easy to find if you know what it looks like - cut wider than a walking track and at a fairly precise angle.  When hauled by bullocks, the track needs to be steep enough not to tire them out too much but if too steep the log can run into the bullocks' back legs.

I think the track uses an old haul road, but it's very difficult to discern.  I think the slumping of the hillside, which makes the track along the earthenware pipe as lumpy as it is, is also going on here.  There is certainly the width of track. Maybe one day I'll find a map of those old trails.

The descending track was muddy.  Drainage work has been done recently to prevent erosion of the track - I've seen patches of the old walking trails eroded out to near shoulder height. I reached the steel pipeline again and followed it back to the Waitati Valley Road.

As I said, the pipeline to Fergusons creek was never completed.  The mystery of why it was built so far and never finished bugged me for years.  Finally, "Papers Past" arrived and I was able to search it for clues.  Fergusons was one of the creeks gauged (I've looked for the weir on it, without success), the lower pipeline was built after some debate over the final route, but the upper one had the track cut but no pipe laid.  A few decades later the use of Fergusons was suggested but decided against due to an unreliable flow.

So the mystery persists - why was Fergusons good enough in the 1890s but not in the 1920s? One day I'll calculate the amount of money wasted. The local newspapers completely missed a minor scoop back in the day. There's much more exploring to do this summer. I'm looking forward to sharing what I find. 

'Til next time,