A total of 8 power tunnels were constructed to deliver water to eight 300MW turbines. These tunnels are lined with either concrete or steel, having an internal finished, intake diameter of 8.5 metres, descending diameter of 7.0 metres and output diameter of 4.85 metres leading to the turbines. The tunnels' length varies from 670 to 760 metres. As the water flows from upstream to downstream gravity and the narrowing of the tunnels increases the speed and velocity powering the turbines.