The question remained. Was walking this leg achievable? Was the Derwent River sufficiently friendly to allow humans to walk its length? With my feet and knees complaining every time I walk for more than a couple of hours, I asked friend Andrew to proxy for me and undertake the walk along the Derwent River from near Tarraleah to Wayatinah. Since Andrew is a fit, agile, very experienced and sensible bushwalker, I felt certain if he could not finish this leg of the walk then no-one could. Besides he has been a positive supporter of the project from day one and was happy to undertake the walk on my behalf.
At 6.30 am, the day started with a drive from Hobart to the bridge crossing the Derwent River at Wayatinah. After parking his ute on the Florentine Road near the salmon hatchery at Wayatinah around 8.30 am, a friend drove him westwards along the Lyell Highway to the junction with Butlers Gorge Road. Under overcast skies on a cool day, Andrew began walking next to Tarraleah Canal No 1 around 9.30 am and continued until he reached the first crossover walkway about one kilometre further on. This location promised the shortest distance down to the Derwent river bed.
Andrew crossed, looked downhill and saw nothing but dense scrub ahead. He remembers remarking out loud “don’t dither, just do it. Don’t delay. Here we go; just do it”. At 10.10 am he left the Canal. Before stepping into the unknown, he spent time getting a GPS position fix and a magnetic bearing. Once set, he plunged into the thicket and took a series of sightings from one key tree to the next. This allowed him to stay on his bearing, and meant he would be able to retrace his steps if the going was too tough and the forest impossibly dense. The route down the steep slope passed massive tree ferns, smaller ferns, myrtles, mature eucalypts and the occasional Sassafras tree. Many fallen trees littered the understorey and it was clear this was an old forest in a constant state of regeneration. Scrambling over or under logs and negotiating rocky bluffs was a normal part of the descent.
Half way down the steep incline, it seemed that serious wind was blowing high up in the trees. Before long it was clear the rushing sound was the water of the Derwent River further below. Once the river could be seen, then it was a comparatively simple process to choose the clearest path to the river bed.
Next to the bridge over the Derwent River on Wayatinah Road, an Atlantic Salmon hatchery owned by Salmon Enterprises of Tasmania Pty Ltd trades as Saltas.
According to the Tasmanian Salmon Growers Association the business was established in 1985 ‘after a report to the Tasmanian Fisheries Development Authority concluded that a salmon farming industry could be successfully developed in Tasmania. As a result, in 1984 fertilised Atlantic salmon eggs were purchased from the Gaden Hatchery (Thredbo River, Jindabyne, New South Wales, Australia), which were from stock originally imported in the 1960s from Nova Scotia, Canada. A sea farm was established at Dover in the south of Tasmania and a hatchery was developed at Wayatinah in the central highlands.’
Innotech Controls claims Saltas is ‘Australia’s largest producer of Tasmanian Atlantic Salmon smolt, supplying over 3.5 million smolt each year to the Salmon farm industry.’ Their website provides details about water temperature management using the water of the Derwent River and Wayatinah Lagoon. ‘At Wayatinah, the water used by the SALTAS hatchery is gravity fed from the River Derwent. During the hot summer months, when river flow is greatly reduced, the water temperature can rise by as much as 10 °C in an 8 hour period. Water temperature in excess of 23 °C can be fatal to the fish stock. Located 1km from the hatchery is Wayatinah Lagoon, a man-made lake that forms part of the State’s Hydro Electric scheme. Research showed that at a depth of 6 metres, the water temperature was consistently between 9 and 17 °C. A project was undertaken to utilise water from the lagoon for temperature control at the hatchery and to provide additional water in times of low flow in the River Derwent. The water temperature is monitored at the hatchery where it is maintained at 16 °C +/- 1 by staging the water pumps at the lagoon.’
A thesis by Anna Do offers ‘SALTAS currently operates two hatcheries: Wayatinah hatchery on the Derwent River and the nearby Florentine hatchery‘. When I walked on the north/eastern side of the river upstream from the Wayatinah Power Station last year I could not identify the buildings near the confluence of the Florentine with the Derwent River. Now I understand that I was looking at the second hatchery. In this thesis on page 8, an aerial photo of the Wayatinah hatchery shows the Derwent River with considerably more water flowing that exists today. Refer to my photos of a stony river bed earlier in this post.