Retired geoscientist and geologist, formerly with Newcrest and BHP, John Holliday, says it will become a key factor in companies deciding whether to open new mines in the region.

"The Central West is not as wet as it used to be," he said.

Mr Holliday said the Cadia mine took water from the Belubula river system and sewerage treatment water from Orange while the planned McPhillamys mine near Blayney was proposing to pipe water from Lithgow.

"If someone else found a big deposit I don't know where they would get the water from," he said.

Mr Holliday will address the next meeting of the Environmentally Concerned Citizens of Orange on Wednesday night to give an explanation of mining practices and processes.

He said water was a vital topic for environmentalists.

"I think the water thing is the biggest concern around, and keeping what water we've got clean," he said.

Mr Holliday said he would explain how a balanced development of mining was good for the region.

"It helps people understand the issues better," he said.

"It's occurred to me a lot of people don't understand what mining exploration means and why the Orange district is a bit of a hot spot for mining.

"There are several belts of rocks that are very prospective."

He said there was potentially room for expansion with more mines but the costs involved, including with providing water, were substantial, and would have to be weighed up by any companies considering it.

Mr Holliday said it would also depend on the level of copper and gold prices.

ECCO spokesman Neil Jones said the meeting in the function room at the Parkview Hotel from 7pm was open to the public.

"The theme of the meeting is focussed around the topic, "The mineralogy of NSW and in particular the Central West region and the Orange and Blayney areas," he said.

"[It's] in order to better understand why historically there has been, and why there is currently, significant interest in gold and copper mining and exploration in our region and future developments."

He said the potential for more gold and copper mines in the region would be discussed.