Posted by barbara on March 14, 2014
Lake Te Anau
For the Waiau River, the largest in New Zealand's Southland Region, the 80 kilometre journey south to the Foveaux Strait starts at Lake Te Anau.
In 1976, this mighty river morphed into the ‘Old Waiau’, courtesy of the epic engineering machinations of the Manapouri hydro-electric scheme.
Figure 1. Map of the South Island, New Zealand, showing the locations of the rivers and lagoons mentioned in the report 'Significant coastal lagoon systems in the South Island, New Zealand' by R.M. Kirk and G.A. Lauder
Where exactly is the Waiau River? To locate the river, check out the bottom left hand side of the South Island in the map above. The Waiau River flows south towards the Foveaux Strait in the direction of Stewart Island.
Ten kilometres south of Lake Te Anau, the Waiau flows into Lake Manapouri.
Completed in 1971, the Lake Manapouri power station major diverted waters from the Waiau River to help generate power for the Tiwai Point aluminium smelter near Invercargill. The underground hydroelecricity power station 'utilises the 230-metre (750 ft) drop between the western arm of Lake Manapouri and the Deep Cove branch of Doubtful Sound'. (Wikipedia)
The Rakatu Wetlands
As a result of water diversions, the upper stretches of the Waiau's route dried up downstream of Lake Manapouri dried up, and remained so for more than two decades. In more recent years, dedicated locals have worked hard to create the Rakatu Wetlands in the original bed of the Waiau River, with the assistance of more generous water releases from upstream.
The Rakatu Wetlands
The width of the valley now occupied by the Rakatu Wetlands attests to the strength of the Waiau River before its diversion.
The Clifden Bridge over the Waiau River. Courtesy of Google Earth
Such was the force of the upper Waiau River before its diversion that early Southland settlers pushed for the construction of a bridge over waters that were often dangerous to cross, especially during Fiordland's spring melt. The first known punt across the Waiau dates back to 1852 and it was 1899 before a bridge was built.
The Google Earth image above shows the original high level suspension bridge (on the left), now pedestrian use only, and its replacement road bridge on the right.
Clifden Suspension Bridge
To the relief of locals and settlers pushing north to take up farming lands, the Clifden Suspension Bridge was constructed in 1899 to provide safe passage across the daunting river.
The Clifden Suspension Bridge, viewed from the north
Twenty-seven steel cables attached to stone pillars support the suspension bridge. Unlimited outcrops of local limestone, visible behind the steel and timber structure, were an ideal building material for the bridge's engineers.
Clifden Bridge tower
The local limestone, visible in the background, was quarried to make concrete to plaster the wooden walls of distinctive high towers at each end of the bridge.
Ciifden Suspension Bridge
The Clifden Suspension Bridge, a pedestrian walkway since 1978, measures 111.5 m in length. At the time it was built, it had the 'longest main span' in New Zealand.
Safe passage across the Waiau
Interpretive signs at the site point out the importance of the Clifden punt before the high level bridge was constructed. A victim of progress, the trusty punt service was superceded by the 'Iron Bridge'.
There goes the river
As the sign above attests, the Waiau River shrunk from 440 cumecs to just one cumec as a result of its diversion into the hydro-electric scheme. For the record, a cumec stands for one cubic metre per second
The erosive force of the river has eroded the local limestone into distinctive patterns.
The Waiau flows into Foveaux Strait
Some 80 km south from Lake Te Anau, the Waiau River reaches the sea, as captured by this Google Earth image, owing much of its current flow to the outflow from Lake Monowai.
Waiau River lagoon
Over time, the process of longshore drifting has redistributed the vast motherload of sediments carried by the Waiau River, creating coastal lagoons, including the one above.
Another view of a Waiau River lagoon
According to the IPENZ Engineering Heritage Report on the Clifden Suspension Bridge (page 16), 'Tamatea, the great early Maori chief and explorer, is said to have had difficulty navigating the Waiau River. Indeed, it was when [his] waka [was] wrecked at the mouth of the river during a storm that he and the other survivors named the river Waiau because of “the swirling nature of its waters.”