The release of the 2014 Healthy Waterways report card contains the same major water supply lesson for Southeast Queensland that it did last year.

And the year before.

The lesson is that silt, mud and and eroded soil running from the upper reaches of the Brisbane river run the risk of again blocking the Mt Crosby Water Treatment plant.

That plant provides most of Brisbane's drinking water.

In January 2013, Brisbane came within six hours of running out of drinking water after storms created flooding also in the nearby Bremer River and Lockyer Creek.

This year's report shows the freshwater conditions in the mid-Brisbane river catchment – just to the south of Wivenhoe Dam and the treatment plant - worsened from a D minus grade to an F grade.

An F grade means "most key processes are not functional and most critical habitats are severely impacted," according to the Healthy Waterways report.

Freshwater conditions in the Bremer dropped from a C-minus to an D-plus grade, while the Lockyer catchment stayed at a D grade, which means "many key processes are not functional and many critical habitats are impacted."

Brisbane's Oxley Creek catchment, which runs from the central part of the city to the southwest suburban areas, sank from a D-minus grade to a F grade.

Water quality tests were done at 389 sites – 135 freshwater and 254 estuarine – over the past 12 months.

There are improvements to some of the algal and nutrient components in several estuarine systems because councils have made improvements to sewerage plants and because the past 12 months have been the driest on record.

However Professor Stuart Bunn, chair of Healthy Waterways Scientific Expert Panel and the director of Griffith University's Australian Rivers Institute, said the large amount of mud from development sites, farms and eroded stream banks washing into the rivers was the main cause of Brisbane's freshwater problem.

"The poor report card scores that we see for catchments basically reflect that these systems are in bad condition and they also mean that our catchments are vulnerable to extreme events," Professor Bunn said.

He said there was no doubt Brisbane's drinking water was at threat if there were severe storms.

"Every time it rains soil gets eroded away, nutrients get eroded away and that material makes its way into our reservoirs," he said.

"It impacts on our water security by reducing the amount of storage and it poses a major cost and risk to our drinking water."

Professor Bunn said it was now widely acknowledged that silt from the Lockyer Valley posed a significant threat to Brisbane's drinking water supplies in a major storm event.

"The moment we have water coming down the Lockyer and the Bremer – which flows directly into the Brisbane River above the water treatment plant, those systems are quite vulnerable to erosion," he said.

"It overwhelms the treatment plant – and even if it does not completely overwhelm the treatment plant – it greatly increases the cost of water treatment."

Professor Bunn said those treatment costs were borne by everybody in their water bills.

Is a new plan to tackle the erosion problem emerging?

In March 2014, the Council of Mayors has set up a "Resilient Rivers" taskforce to co-ordinate the wide range of local projects – mostly run by local councils - to try to tackle soil erosion upstream.

It will co-ordinate local council, state government and the federal government funds to a suite of anti-erosion projects.

Environment Minister Andrew Powell was asked by Premier Campbell Newman to be on the Council of Mayors' soil erosion taskforce, which plans to have firm project recommendations chosen by November.

Mr Powell said for the first decade, Healthy Waterways has concentrated on "point source polluters", effectively sewerage plants and businesses on the river.

He said the Council of Mayors taskforce would now concentrate on revegetation projects to control sediment and silt from upstream, mainly from the Lockyer Valley.

"The taskforce is looking at taking a 'whole of catchment approach' to the management of our river systems," Mr Powell said.

"Previously it has really been a council-by-council approach. This will now look at the whole catchment and what we can do collectively to improve the catchment health."

Mr Powell said the taskforce has met to begin defining what erosion problems can be tackled and how they could be funded.

"The science is telling us our work needs to be up here, it is telling us the things we need to do," he said.

"Riverine re-revegetion, working with our farmers; these are the things that SEQ Catchments have told they are interested in doing.

"They have listed some priorities and now we need to sit down with the Council of Mayors and agree on that action plan."

There are now more than 200 individual community groups working on catchment projects with no central co-ordination, Fairfax Media understands.

Mr Powell said the "reef rescue" concept operating in North Queensland – where farmers voluntarily reduce nutrients was now being trialled in Southeast Queensland.

An environmental trust, called a Brisbane River Improvement Trust, will act as an umbrella body to attract funds from water bodies including Queensland Urban Utilities and Unitywater for these projects.

Mr Powell gave an example in Beaudesert shire where a revegetation project on the Logan River had improved water quality at a fraction of the cost of a new sewage plant.

"To upgrade that facility would have cost about $8 million, and that would have been a cost passed onto the ratepayers through Queensland Urban Utilities," he explained.

"For $1 million they have achieved the same nutrient and sediment load outcome by revegetating and stopping erosion on a 500 metre section of the Logan River.

"That is one example of the kind of innovative solutions we are using to get better outcomes for the environment and for South east Queensland."