Led by Olympic equestrian Nikki Richardson, about 300 riders took to the streets on Saturday in defence of the multibillion-dollar Upper Hunter thoroughbred trade.

Organiser Peter White said residents were worried about the mine's potential impact on groundwater networks and the nearby Pages River and Kingdon Ponds.

"This isn't an anti-mining rally per se, it's anti this particular mine," Mr White said.

"Bickham proposes to build its mine 150 metres from the Pages River, the historic tributary of the Hunter River which underpins our horse capital. We must protect our living water."

Landowner Peter Haydon called on residents to draft submissions on the proposal to the Planning Department by Friday's cut-off.

Bickham director John Richards quoted a consultant's report that found the impact on local water systems would be "negligible", and said the project would create hundreds of local jobs.

About 80 Murrurundi residents rallied last week to support the mine.