Chichester Valley residents who are campaigning to prevent a new dam being built in their community have pointed to potentially devastating impacts on protected wetland systems if the project goes ahead.
Hunter Water is presently considering a site upstream of the existing Chichester Dam and another at Limeburners Creek, east of Clarence Town as potential sites for a new 160 gigalitre dam.
But even though it would be a third the size of the ill-fated Tillegra Dam, which was scrapped a decade ago, residents argue it would still have significant adverse downstream environmental effects.
"This is the same catchment that Tillegra Dam would have been built in," Save Chichester Valley Group member Allan Rumbel said.
"One of the main reasons for not proceeding with Tillegra Dam was the effect that it would have had on the surrounding environment."
The group has cited the research into the likely downstream effects of Tillegra Dam undertaken by University of NSW river ecologist and conservation biologist Richard Kingsford.
Professor Kingsford's research showed Tillegra Dam would have caused considerable reductions in flow to the Hunter estuary, in particular the Ramsar wetland site and migratory shorebirds and their habitats
"We identified measureable changes to the volume, timing, duration and frequency of freshwater flows resulting from the building of Tillegra Dam which would increase the salinity of the estuary and probably affect food webs," Professor Kingsford wrote.
"These reductions will affect the Hunter River estuary, its Ramsar site and biodiversity, including migratory shorebirds."
Part of the Hunter Estuary that would have been potentially affected by Tillegra Dam was designated as a wetland of international importance under the Ramsar Convention in 1986.
"The estuary is the most important area in New South Wales for migratory shorebirds. Shorebird populations have already suffered a serious decline since first estimates in 1970-1990, with the Hunter Estuary now only supporting five of the 11 species which used to occur in nationally significant numbers," Professor Kingsford wrote.
Professor Kingsford's research showed Tillegra Dam would reduce flows to the Hunter River by 5.2 per cent.
A Hunter Water spokesman said a range of options were being explored to ensure there is a sustainable, long term supply of water.
"No decisions have been made to build a dam. At this early stage, we have identified two potential locations. We need to carry out further on-site investigations to understand if a dam would even be feasible at these locations," he said.
The review of the Lower Hunter Water Plan includes options to decrease reliance on drinking water such as recycled water, stormwater harvesting, groundwater, desalination, dams and water sharing with other regions.
"We are investigating a number of shortlisted options to understand if the options are technically feasible, the benefits they may provide, as well as the potential social, environmental and cost impacts," the Hunter Water spokesman said. "Aside from water conservation and leakage reduction we haven't made any decisions about what will be included in the revised LHWSP.
"In addition, we're progressing investigations into a potential groundwater source beneath the Tomago Sandbeds, water recycling and stormwater harvesting opportunities, desalination and inter-regional water transfers."
