OPUS International prepared a report "Lake generation potential history" which provides a brief history of the fluctuations in the storage of the major lakes used for hydropower generation in New Zealand.

The lakes covered in the report are: Ohau, Tekapo, Pukaki, Te Anau, Manapouri, Hawea, Wanaka, Wakatipu, Taupo and Waikaremoana.

The report is accompanied by a dataset of lake storages in potential generation (GWh) and volumetric terms (millions of cubic metres) over 1 January 1990 - 30 June 2010. These are based on lake level data from the Power Archive, which is maintained by OPUS International under contract to the various power generation companies.