Protect Our Water Alliance shed light on the "escalating damage" to Sydney's water catchment from coal mining at a water forum on Wednesday.
More than 150 people heard from guest speakers who explained how coal mining can contaminate catchment rivers and creeks, even years after mining activity is stopped.
Speakers included Western Sydney University's Dr Ian Wright, who is an expert on the affect mining has on rivers, National Parks Association of NSW's Julie Sheppard and Lock the Gate Alliance representative Nic Clyde.
Illawarra Residents for Responsible Mining spokesman Gavin Workman said one of the main takeaways was that mining under watch catchments needed to stop.
"It is clear that loss of water from the catchment and contamination of the water by heavy metals can worsen over time," he said.
"These issues continue and become problematic even after the mines close down.
“Who is responsible for the clean-up and ongoing maintenance after these mines close down?
"The responsibility for the damage to the water catchment and the polluted fall out will fall on tax payers and future generations."
Mr Workman said attendees saw images of the "horrific damage occurring in the water catchment from coal mining".
The Alliance is calling on the government to prioritise the environment and water catchment areas over mining.
“The responsible government authorities still don’t know how much of our water is being diverted from the water supply of Greater Sydney and yet these same authorities continue to approve mining expansions," Mr Workman said.
"Government departments are still discussing the ‘level of acceptable damage’ to the catchment rather than insisting on no damage at all.”
Mr Workman said he was pleased state MPs and state election candidates were in attendance.
"Ryan Park, member for Keira on behalf of Labor and Kaye Osborn, Keira candidate for the Greens spoke at the forum," he said.
"They agreed on the need for action to protect the water catchment, for transition away from coal and for government planning and support for Illawarra workers affected by these changes.”
Mr Workman said the forum was also timely because of the drop in levels of drinking water reservoirs and the activation of the desalination plant.
The forum was supported by Lock the Gate Alliance, Illawarra Knitting Nannas Against Greed, Illawarra Residents for Responsible Mining Inc., National Parks Association NSW and Wollongong Climate Action Network. Wollongong Lord Mayor Gordon Bradbery also attended.