URANIUM miner Energy Resources of Australia has played down estimates that 150,000 litres of contaminated water seeps out of its Ranger mine tailings dam each day.

The company, which operates the mine near Jabiru in Kakadu National Park, had its annual general meeting in Darwin yesterday.

ERA chairman David Klingner acknowledged a CSIRO report recently estimated up to 150,000 litres was seeping daily and "mingled" with local groundwater" beneath the dam.

"It does seep very slowly from the bottom of it, and there is the build-up of a plume of water beneath the tailings dam," he said.

"Theoretically, there could be as much as 150,000 litres of water seeping below the dam ... each day ... (but) our bores are showing a much lower figure, as low as 500 litres."

He faced questions from Environment Centre NT co-ordinator Stuart Blanch, who asked how much the company would have to spend to rehabilitate the site once its licence to mine ends in 2020.

Dr Klingner said more than $200 million is allocated for rehabilitation of the site.

"We will treat the water, polish it, and in the end it will be able to be (returned) into the environment," he said. "There aren't any shock horrors waiting down the trail for shareholders there."

Supervising scientist Alan Hughes, who oversees mine monitoring, said the larger estimates were conceivable.

He said ERA's lower estimate probably referred to "lateral" seepage from the site.

The water has been seeping out for several years, and is caused by the design of the dam, which Dr Klingner said was "state of the art" 30 years ago.