Mr Clarke, keynote speaker at the University of Wollongong's annual Allan Sefton Memorial Lecture, will highlight the "unusual situation" that leaves the catchment inaccessible to the public but open to mining.

Mr Clarke told the Illawarra Mercury the introduction of a state environmental planning policy prohibiting approval of new mines or expansions within designated drinking water catchments would be the simplest way to to safeguard the Upper Nepean Catchment against potential contamination.

The Upper Nepean Catchment supplies water to Wollongong and Sydney.

Mr Clarke added that parts of the catchment not already touched by mining activity could be safeguarded with national park or nature reserve status.

"That would have the effect of prohibiting mining operations in the declared area," he said.

"We've got this very unusual situation where if a member of the public walked into a special catchment area, they could be fined; but at the same time, another part of government continues to approve coalmining activities in the catchment.

"We've seen that this is causing significant damage to the streams.

"There's evidence of ... cracking of stream beds, causing loss of water that would otherwise flow in the supply dams.

"There's one rule for the mining industry and another rule for everybody else."

The council is calling for NSW Premier Mike Baird to adopt the position of predecessor Barry O'Farrell on coal seam gas exploration.

"The commitment from Barry O'Farrell was to prohibit mining in drinking water catchments. Now, obviously there are existing mining operations, so I think we should interpret that as a prohibition on the expansion of mining operations in the drinking water catchment."

Now in its 22nd year, the Allan Sefton Memorial Lecture recognises the late naturalist and conservator of local environment.

Mr Clarke's address, titled From little things, big things grow: Coal, climate and nature conservation in the 21st century, is from 5.30-6.30pm in lecture theatre G01, Building 14, on Friday.