There is no scope of endangering rivers with uncontrolled pollution if the country wants to implement the Delta Plan, speakers said at a programme.
Pollution in the bridge area has caused the width of the Karnaphuli River to shrink to 400 metres from 900 metres, they also said.
The discussion programme was organised marking the World Rivers Day on Sunday.
Zoologist Dr Mohammad Anisuzzaman Khan spoke as the chief guest at the discussion arranged by Green Planet at the Bangabandhu Hall of Chattogram Press Club.
Anisuzzaman said most of the rivers in Chattogram and Chattogram Hill Tracts are still naturally rich although many rivers in the country have been polluted. The fishery resources and biodiversity of rivers and diversity of people living on riverbanks are a matter of pride for Bangladesh.
"If we can save the rivers of these regions, including Karnaphuli and Halda, from pollution, the significance of World Rivers Day will be realised," he said.
The country's rivers could be conserved if people at the state, private and individual levels would play their respective roles, he added.
Haji Mohammad Mohsin College's chemistry department Professor Dr Idris Ali said the Karnaphuli is being endangered due to people's carelessness as water used in 17 industrial zones in Chattogram falls into the river during the tidal surge. Despite having the effluent treatment plants, they discharge the wastages directly into the river.
Halda River Research Laboratory Coordinator Dr Md Manjurul Kibria said the decision to declare Halda as "Bangabandhu Fisheries Heritage" was a landmark step by the government.
"Calculating the amount of eggs and spawns collected from the Halda and the fish produced from here, we found the river contributes around Tk800 crore to the national economy annually in four phases," he said.
Protecting the rivers, Bangladesh will move forward to achieve the Sustainable Development Goals, Vision 2041 and Delta Plan 2100 Goals, Dr Kibria added.
Green Planet's convener architect Mohammad Mizanur Rahman presided over the programme.
Awami League's Chattogram District (South) unit General Secretary Mofizur Rahman, Raozan Municipality Mayor Debashish Palit and others also spoke on the occasion.