The incident has been confirmed by PNG Power Ltd.
"It takes an estimated six hours for water flow from the dam area to the Rouna 2 Hydro Power Station to dry up when the valve is turned off," says PPL in a statement.
"This means there will be disruptions to power supply at around 6pm this evening. This will also affect water supply later this evening."
Reasons behind the incident are yet to be made known.
"Stakeholders who are in talks with the Sirinumu landowners are in meetings at the moment to get the issue sorted out immediately.
"We advise consumers to ensure they have back up lights and water this evening if the issue is not resolved.
"For more information and clarification, please contact the PPL National Call Centre on 7090 8000 or 7500 8000."