"The strategy now is to conserve Mazar for as long as possible to buy us time so that everything starts arriving," he told Reuters after a press conference, referring to generators and other measures.
On Monday, authorities said power cuts nationwide would run for up to 12 hours a day. Goncalves had said the dry season in Ecuador - which is heavily dependent on hydropower - had started two months early.
The cuts across the country are expected to continue through Sunday.
The situation at Mazar is at a critical juncture, Goncalves said, adding that recent measures have helped water levels in the reservoir recover by 1.40 square meters.
"We were approaching the turning point where we were losing control," Goncalves said.
