Originally Posted by
Snoopy
The interesting thing about the Clutha River that feeds Roxburgh, Clyde and maybe Onslow is that, unlike some of the northern hydro catchments, most of the water inflow happens in spring and summer. That is because most of the H2O inflow is a result of snowmelt and not rain. Now it is also true that the maximum power loads occur during the colder winter months. So to prepare for the winter, you would have to pump water up into Onslow in the previous summer and autumn to prepare for the upcoming winter. The Clyde dam is upstream of the Roxburgh dam. If water was taken from above the Roxburgh dam for Onslow, then the Clyde dam would have to supply that water. If the government 'ordered' Contact to release water to do this, then that means potentially less generation capability at Clyde for the winter, and more at Onslow. If Onslow becomes a 'Transpower battery', that in effect would transfer generation capability from Contact to Transpower. Not good for Contact shareholders :-(.
Of course not intimately knowing the seasonal river flow pattern, I may have painted out a pessimistic scenario. Maybe a summer or early autumn storm could push enough water flow into the Clutha river to keep both Clyde and Onslow topped up. I think Jantar has suggested in the past that Contact would be the natural operators of a proposed Onslow for all of these interrelated flow reasons, plus the fact they have maintenance staff on the ground locally..