Chief Operating Officer Dr Fifaia Matainaho says the current water rationing exercise is part of their strategy to save water.
“We need to understand that we do not have any other source for water and we all rely on Sirinumu dam for our use,” he says.
Eda Ranu estimates that by the first week of January Sirinumu will have only 100 million cubic metres.
As soon as this happens PNG Power will stop using Sirinumu for power generation and turn to its other source of energy.
Matainaho says a team of technical experts have been put together and are now looking into options for water sources.
For emergency purposes Eda Ranu will now prepare its old pump station at Laloki to pump water from Laloki River and other sources to Port Moresby.
Port Moresby uses 175 million cubic metres and now with the rationing only 120 million cubic metres is being used.
Sirinumu has a total capacity of 340 million cubic metres.
City residents are being urged to use water wisely.
Last week the National Weather Service revealed to LOOP PNG its prediction of a major water shortage for Port Moresby between the months April and December.
Director Samuel Maiha says Sirinumu will not be filled to capacity between now and April next year because of the El Nino.
Then from April to November 2016 PNG will in its normal dry season.
Maiha says this means Sirinumu will not have enough water for power generation and general use in the city.