Catchment lake levels at Hawea and Wanaka have dropped by almost 4m during the past two months.
There has been no rainfall in the area since June 23.
Lake Wakatipu has dropped by about two metres since it peaked about 311 metres above sea level - above its first flood alert warning - on May 22.
The three lakes are the main catchment suppliers for Contact Energy's Clutha hydro-electricity generation dams at Clyde and Roxburgh.
Contact's Clutha generation manager Graeme Quinn said natural catchment inflows were "quite low" for this time of the year.
The lack of rainfall was not a cause of concern "at this stage".
Contact was able to store water at Lake Hawea to control flows to its downstream generation schemes, he said.
"We're reasonably comfortable with levels at Hawea and ... at present levels we can hold water there until the end of August if we have to," he said.
Lake Hawea's water level (342.2masl) was estimated to be at about 70% of its storage capacity, Mr Quinn said.
Contact was "at the mercy of mother nature" in regard to the dropping levels of Lakes Wakatipu (309.4masl) and Wanaka (276.4masl), he said.
The two lakes provide about "half each" of catchment flows - via the respective Kawarau and Clutha Rivers - for Contact's dams.
Water has been released from the Lake Hawea control structure at a consistent flow of about 200cumecs for the past two months, to assist with generation, Mr Quinn said.
The lack of rain has also meant no natural snowfall for the Southern Lakes mountains, although frigid temperatures have aided snow-making operations.
A low-pressure weather system forecast by Metservice to bring rain and snow down to 1100masl yesterday, failed to materialise.
