It will take several billion dollars to save the Great Barrier Reef from water quality threats, a conservation group says.

WWF Australia has grave doubts the Australian Government will meet its current funding commitments to the reef, and even if it does the money won't come close to what's needed to save it from agricultural run-off and sediment build up.

WWF scientist and spokesman Sean Hoobin says a reef rescue plan, on the scale of the one forged for the Murray-Darling basin, is needed.

He expects a key scientific taskforce looking at reef health to recommend a multi-billion dollar investment when it reports back to government next month.