Trout Fishing, Two Million Years of History
Column for January 7 2005
Anglers who travel across the Southland Plains are traversing two million years of history that have been our rivers in the making. The geological origin of
these great pathways of life has resulted in them now being great habitats for trout but they were not always so.
Point your car westwards from Wallacetown and you first pass over the Oreti. It lies in a wide plain and its clear waters are evidence that its valley was once
home to a much larger river. The Oreti and the Aparima formed this wide arc of flat land, home to some of the longest bits of straight road in the country, when they were giant rivers carrying glacier meltwater from
the mountains in the north. The glaciers covered all of present day lake Wakatipu and some. The Oreti once flowed south from Mossburn into the present Aparima plains and the Aparima/Oreti flowed down the
present day path of the Waimatuku. There is evidence that the Waiau flowed along this path too perhaps to join the Aparima at Bayswater. Look at the stones in the Oraeua at Feldwick and see their Fiordland origins.
At times the Oreti flowed across the Waimea Plains to join the Mataura north of Balfour. Its source was once Lake Wakatipu at Kingston – the deep valleys you
travel up and down on your way south from Kingston are evidence of this. Landslides at the Jollies cut off this path and the Mataura's journey through the Nokomai Gorge began - in relatively recent times. A Wakatipu
glacial advance once discharged into the Oreti via the Von. This huge river built the wide plains from Centre Hill to Lumsden and beyond.
Many people believe that our rivers are building upwards by the movement of gravel from the headwaters but the terraces that hem them all in now suggest that
they are actually degrading overall rather than aggrading. The plains were constructed by giant rivers fed by glaciers – huge conveyor belts of gravel and sand that existed for millennia. The small clear water
rivers we now have are like slender threads of silver by comparison. Their ability to transport gravel is weak. But because they have beds of hard, well washed gravel they make good homes for trout.
Rivers millions of years in the making – surely well worth protecting for just a few more.
Southland, New Zealand E-mail: firstname.lastname@example.org
Article © 2005 Maurice Rodway, All Rights Reserved.