Tens of thousands of residents filled the streets, many draped in the national flag, while others waved posters and chanted slogans celebrating the dam, which is known locally as Abay.
People honked car horns, whistled, played loud music, and danced in public spaces to mark the occasion. Hashtags #ItsMyDam, #EthiopiaNileRights and #GERD also trended locally on social media.
The co-ordinated celebration, part of a campaign dubbed ‘One voice for our dam,’ followed Ethiopian President Abiy Ahmed’s July 22 announcement that seasonal rainfall had led to the first successful filling of the mega-dam’s reservoir.
“We have successfully completed the first dam filling without bothering and hurting anyone else. Now the dam is overflowing downstream,” Abiy said.
Officials in the East African nation hope that the 4.6-billion-dollar dam, which has been fully financed by the Ethiopian government, will reach full power generating capacity in 2023.
Now 74 per cent complete, the dam has been contentious for years and has caused animosity amid deadlocked talks with Egypt.
Ethiopia wants the hydroelectric dam to expand its power exports, saying it will lift millions out of poverty.
Egypt, which relies almost exclusively on the Nile for farming, industry and domestic water use, fears that the dam will reduce its water supply, worries that Ethiopia has dismissed.