Impacts of waitaki hydro scheme

General environmental impacts of scheme Large dams, like benmore, have; flooded valleys – benmore flooded the upper waitaki river valley raised lake levels – lakes tekapo and pukaki in particular reduced the flow of major rivers – some rivers such as pukaki are dry around 90% of the year Dams alter the natural flow of water, which in turn alters the habitat for mahinga kai species to live, migrate, and breed. Altered water flow can also lead to erosion of river banks and disruption of habitats. Rivers, like the upper waitaki and pukaki were home to wading birds like the black stilt. These are now endangered.

Case study: Lake pukaki was raised twice 9m in 1952 and was raised 37 metres in 1976 = 46 m in total submerged Five Pound Note Island (Te Kohai Island) As well as valuable farmland. Ferintosh station lost a significant Amount of land and their farmhouse And buildings. 

Southern tip of lake pukaki and the Pukaki river 1959

Raising the lake levels disrupted the lakes natural equilibrium of erosion and deposition around its shoreline. The constant raising and lowering of lake levels is also making this a problem The present shoreline around Lake Pukaki was formed following the raising of the lake in the 1970s but is likely to be still developing towards a new equilibrium. Kirk (1988) estimated that this process could take up to 100 years with erosion and slumping being ongoing processes driven by a dynamic wave environment and fluctuating lake levels.

Wave induced erosion Periods of extreme low lake levels can impact on beaches and shorelines by exposing the shallow shelf and offshore face to wave action. Lake Tekapo and Lake pukaki in particular have problems with this. The above pictures are of lake pukaki – erosion is particularly a problem at the southern end.

Raising the lake drowned a large part of the Tasman delta at the head of the lake and increased its length by ~50% (Figure 1). The lake level is artificially controlled and has a consented range of 14.5 m

Pukaki river bed as it is today 90% of the time. The pukaki spillway which controls the flow of the pukaki river is released only a few times a year Pukaki river bed as it is today 90% of the time.

Dust storms are a common natural feature of shores on lakes and river beds in the South Island but the lowering of lake tekapo has majorly enhanced this and has caused ongoing issues for the residents of tekapo township.

It’s not all bad…. The Waitaki scheme provided thousands of jobs during it’s time of construction. Created new towns like twizel. Created new recreational lakes like lake ruataniwha – international rowing course. Ultimately it provides us with a large percentage of our power in new Zealand through a mostly renewable resource.