Average inflow rates into the Clutha River are at their lowest point since records began more than 85 years ago, forcing hydroenergy to be imported from the North Island.
A Contact Energy spokesman said inflow into the Clutha over the past 10 years were on track with previous long-term trends, until unusually dry conditions in March, April and May.
"Inflows into the Clutha catchment were relatively normal until February this year ... [but] inflows over the last three months have been unusually dry."
The Transpower risk meter has been set to "watch" and power is currently being imported via Cook Strait, but Contact Energy said that it was "not uncommon" for energy to be imported from the north when conditions were dry.
"Typically the flow is from south to north but it’s not uncommon and would be expected to occur when South Island catchments become dry and thermal plants in the North Island run harder to meet demand in both islands."
The news comes as the Otago Regional Council researches flow rates of the Clutha between Lake Wanaka and Dunstan to determine minimum flow recommendations, with consulting due to begin for the Upper Clutha later this year.
The National Institute of Water and Atmospheric Research has forecast equal chances of average or below average rainfall for the district over the coming winter months.