The research has covered the river from its upper boundary to Ingiriyawatte.
CEA director general K.H. Muthukudarachchi said most houses located by the sides of the river have diverted their sewerage pipe to the river, while industrial waste too, pollutes the river.
The respective local government bodies have the powers to take legal action against these harmful practices, he said.
Results of recent researches have shown that the Kelani is the worst polluted river in the country.