This has become a common sight in the Richmond River, according to John Larsson, chairman of the local branch of OzFish.
This has become a common sight in the Richmond River, according to John Larsson, chairman of the local branch of OzFish. Jay Cronan

Richmond River fish kill event 'totally predictable'

LIKE a tidal wave of death, millions of litres of de-oxygenated black water have enveloped the lower Richmond River.

But this dark and destructive event is no freak of nature. It's man made, and entirely preventable.

John Larsson, chairman of the local branch of fish conservation group OzFish, said the latest event was easy to see coming.

An extended run of hot, dry weather provided ideal conditions for the black water, by causing an acid sulphate build up in rural drainage systems.

"All we really needed was the trigger, and the trigger was a significant rain event like we got two weeks ago," he said.

Mr Larsson said the rain sent "hundreds of tonnes" of sulphuric acid from reclaimed wetlands straight into the river.

Black water is caused by two factors. The first is flood-intolerant grasses which break down and release oxygen-consuming bacteria in an extended flood.

The second cause is drainage systems which have disturbed acid sulphate soils. They pose no threat if there is a regular tidal flush, but if the acid builds up it spells trouble.

Mr Larsson said unfortunately "very little work" had been done on fixing the problem despite a Coastal Zone Management Plan in place since 2011 which laid out a precise action plan.

"We have not even started anything significant," he said.

As a result the Richmond catchment has hit rock bottom, with a 2015 University of New England report handing it a D minus overall and several sub-catchments an F.

The good news on the horizon is that OzFish has lodged a successful expression of interest application for "significant" funding with the NSW Department of Primary Industries.

It is confident of securing the funding and working with local councils to achieve real progress on the chronic issue.

Mr Larsson said there were "multiple problems" contributing to the water quality in the Richmond, but one above all.

"The river has got excessive sediment loads... probably more than any other coastal river system, and that's attributable to the very large amount of flood plain we have."

But the problem is not insurmountable, and the mid-1990s efforts to restore the Tweed River had proven that.


"There needs to be a greater team effort," he said, adding it was time to put "egos and agendas aside to work on a common plan".

"We need to bring cash and expertise to a team table and start the process".

The alternative to action wasn't pretty.

Mr Larsson said businesses on the Richmond Valley had been "pounded" over the years from loss of tourism, and "unless we do something, it's going to happen again".