A resident of Narrabri accused Australian mining firm Santos of causing the death of trees at the Pilliga State Forest due to the coal seam water that leaked from a dam operated by the company.

As proof, Tony Pickard took photos which showed dead ironbark, cypress and bull oak trees and grass and pools of black water. He insisted that he had complained a year ago to the Department of Primary Industries of holes in the dam's liner, but claimed his complaint was ignored. He took the pictures while driving on Friday through the Bibblewindi State Forest located 40 kilometres southwest of Narrabri.

Mr Pickard said either the dam has let go or some of the pipe work had problems which led to CSG water dumping its contents into the forest.

Greens MP Jeremy Buckingham supported Mr Pickard and sought an investigation by the Environment Protection Authority of Mr Pickard's complaint. The MP also sought an explanation from the New South Wales government over Mr Pickard's allegation.

Santos denied the existence of a leak. A company spokesman explained the water to recent rain which has not dissipated yet. He said the eucalyptus leaves made the water turn black.

The Department of Primary Industries backed Santos's claim that the water is natural water pooling, but ordered the CSG operator to fix the drainage.