Claims that Shenhua's restricted coal mining will avoid affecting the aquifers of the rich farmlands of the Liverpool Plains are "false and ignorant", former state and private agronomists have said in a letter to Premier Gladys Berejiklian.

The government last month paid the Chinese coal miner $262 million for just over half the exploration licence area of the proposed mine at Watermark in northern NSW. Energy Minister Don Harwin said the buyback would ensure there was no mining on the fertile black soils of the plains.

Liverpool Plains are home to some of Australia's - if not the world's - richest soil. Credit:Kate Ausburn

But the agronomists, five of whom worked for the Department of Primary Industries or precursor departments, said limiting the proposed open cut mine to ridges would still likely affect surface and groundwater flows in the plains and downstream regions.

"The claim that mining the ridges above Breeza will not have an impact on farming operations is false and ignorant," the letter's authors said.



"Hydrogeological investigations have shown that there is a high degree of connectivity between the alluvial aquifers throughout the Namoi Valley."