THE impact of long-wall mining could explain why Woronora Dam is not overflowing, a new environmental alliance has speculated.
However, the Sydney Catchment Authority rejected the claim, saying Woronora Dam had received only two-thirds of the rainfall which had fallen in the other catchments in the last fortnight.
While the Warragamba, Cordeaux and Cataract dams reached 100 per cent capacity, the Woronora Dam’s most recent reading was 75.4 per cent.
Peter Turner, the spokesman for Save Our Water Catchment Areas, an alliance of community groups opposed to long-wall and coal-seam gas mining in such locations, said Woronora was ‘‘lagging well behind’’ other major dams supplying Sydney and nearby regions.
‘‘This renews community concerns that long-wall coal-mining is having an adverse impact on water supply,’’ he said.
Mr Turner said the Sydney Catchment Authority had previously attributed the lower level to rainfall variations and water releases required for downstream environmental health.
‘‘The SCA has also undertaken studies that show water is being lost from the Waratah Rivulet as a consequence of alarming subsidence damage caused by long-wall coal-mining below,’’ he said.
Mr Turner said, during good rainfall periods, the Waratah Rivulet, where deep cracks had appeared, supplied 29 per cent of the water flowing into the Woronora Dam, and up to 50 per cent in dry periods.
‘‘Long-wall mining breaks up the underground claystone layers that otherwise act as a natural barrier to water loss from the surface to the mine below,’’ he said.
LET THE RAIN FALL
A SPOKESWOMAN for the Sydney Catchment Authority said, since February23, the Woronora catchment had received a total of 103mm of rainfall.
This was about two-thirds of that received by the Warragamba (170mm), Upper Nepean (151mm) and Shoalhaven (152mm) catchments.
‘‘During this period, the available storage of Woronora Dam increased by 5.5per cent, which is consistent with what’s expected following that amount of rainfall,’’ she said.
‘‘Since this time last year the available storage of Woronora Dam has increased by 45.2 per cent, from 30.2 per cent of capacity to 75.4 per cent of capacity.
‘‘This is the largest increase in terms of percentage of capacity to have occurred across the Sydney Catchment Authority’s network of dams.’’
