An environmental group says an error in information about untreated sewage being released into Ontario waterways highlights the need for better reporting of such incidents.

Ecojustice says its latest sewage report shows a significant error in the information supplied by Niagara Falls to the provincial government.

The group says that underscores the need for immediate public reporting of all sewage dumping incidents.

It says the error was made when Niagara Falls incorrectly reported the volume of sewage released during a so-called "bypass" event in September 2007 to Ontario's Ministry of the Environment.

The ministry has said sewage sometimes needs to be diverted into lakes and rivers to prevent an overload at treatment plants.

The figure reported for Niagara Falls in 2007 was 6,925,452,000 litres. But that figure has now been corrected to 326,278,590 litres.

Ecojustice says it got the data from the ministry and was never informed of the error or provided with corrected data.

"Seven billion litres of sewage is a number that should have gained the immediate attention of officials," said Elaine MacDonald, a scientist with Ecojustice.

"The fact that this figure wasn't corrected by government officials earlier shows the extent to which Ontario's sewage dumping problem is not being taken seriously."

The group says its report will be revised and an update will be posted online.