Healthy Waterways has given Queensland’s Lockyer catchment a ‘D’ health rating.

The conservation group says the southern Queensland catchment is in poor health due to a declining ecosystem and lack of efforts to improve it.

The annual Healthy Waterways Report Card did not think too highly of Queensland’ other major supply - The Upper Brisbane catchment in the Somerset Shire – awarding it a ‘C’ rating.

Healthy Waterways' spokesperson Julie McLellan has told the ABC that the loss of riverbank vegetation was a big factor in the poor scores.

“You lose a lot of that habitat and the water gets warmer quicker, so you lose your fish stocks,” she said.

“We're certainly saying that now is the time to look to our freshwater catchments and to either maintain existing riverbank vegetation or start replanting.”

An ongoing drought was partly blamed for the poor report card too.

But Ms McLellan said some healthy estuarine rivers closer to the coast show that improvement is possible.

“We've had the driest year since we started reporting but if you look further down the estuaries and the bay there's actually been an improvement in both of those grades,” she said.