Operation of the scheme

Weirs across the natural lake outlets will establish a spill height at the existing mean annual lake level. Natural fluctuations in lake height above this level, which invariably occur during flood events, will remain unaffected.

The maximum drawdown of the lake during generation will not exceed a level 920mm below the mean annual leve which is the lakes lowest natural level. Normal daily operation is expected to maintain the lower lake level well above this minimum.

A minimum flow of 1000 litres per second measured at the existing slack line just upstream of the east branch will be maintained at all times.

In order to improve efficiency the generator will, in normal operation, either run at full power or be shut down to conserve water for periods of high electricity demand. Occasionally the generator may be run at partial power to maintain the minimum lake level if lake inflows are low.