Meridian Energy has warned it could fall short of financial targets as it cuts generation to conserve water in southern hydro lakes.
The state-owned enterprise, which is in line for partial sale, says that although it has hit targets for the first half of the year, "assuming average hydrology from this point on, we see some risk to achieving our full-year key statement of corporate intent financial targets".
One of the country's biggest industrial plants, Rio Tinto's smelter at Tiwai Pt, had cut production partly because of high spot prices for electricity.
Drought in the lower South Island had resulted in low lake levels at Lake Te Anau and Lake Manapouri, whose hydro scheme directly supplies the smelter. Inflows for Meridian's hydro lakes in December were 36 per cent of the historical average.
Meridian's general manager of markets and production, Neil Barclay, said rain in the hydro catchments during the past fortnight meant the lakes were back within their main operating range. But further north lakes in the country's biggest hydro system, Waitaki, were below historical averages.