Its core is low permeability clay material, supported by two massive shoulders of river gravel.

Lake Benmore has a volume of 1.25 billion cubic metres, about 1.5 times as much water as Wellington Harbour.

The dam's spillway can cope with over 6,000 cubic metres of water per second, about 20 times the mean river flow.

Otematata is the small town that was created to support workers who constructed the dam, and their families.

The importance is largely due to the location at Benmore of the southern terminal station of the HVDC Inter-Island link.