“The credit rule is essentially allocating clouds – water that hasn’t even fallen in the catchment yet,” said Celine Steinfeld, lead author of the paper published in the Journal of Hydrology, and also a member of the Wentworth Group of Concerned Scientists. “It was clear that water in the Macquarie had been overallocated.”
By contrast, the Gwydir – fed in part by the Copeton Dam – was managed much more conservatively. Managers waited until flows had reached Copeton before granting water to irrigators and the environment, alike.
The study has implications for other rivers, such as the Murrumbidgee and Lachlan, which also operate with allocations made by a “credit” approach. The Namoi and Border rivers follow the approach used for the Gwydir.
Management of the $13 billion Murray-Darling Basin Plan has come under scrutiny during the recent multi-year drought. One response has been a rush to approve new dam projects rather than to address the rules.
Applying the Gwyder’s rules to the Macquarie could free up as many as 72 billion litres for general security licence holders on the Macquarie, while supporting flows to the internationally significant Macquarie Marshes. Both businesses and the environment would also be better able to endure dry times, the paper argues.
“We found some pretty remarkable effects in both the volumes of water that these rules influence and the availability of water during dry times,” Dr Steinfeld said, adding existing arrangements were “extremely ad hoc”.
Richard Kingsford, director of UNSW’s Centre for Ecosystem Science and another of the report’s authors, said the rules setting allocations were effectively a “black box” that was both opaque and very difficult to change.
For rivers such as the Macquarie, “if you start to get into a dry period that’s not expected, you’re in trouble”.
“This is the most pernicious part of it because we’re getting more dry periods,” with climate change, he said.
Policymakers then rush to “drought-proof” the rivers. The NSW government is examining a plan for a new weir near Narromine that would likely degrade the Macquarie Marshes further, and looking at raising the Wyangala Dam wall on the Lachlan.
“Taxpayers pay for building these dams and upkeep and maintenance,” Professor Kingsford said. “[And] once again, the environment and the people downstream have to pay the price of risky water management.”
Emma Carmody, a special counsel with the Environmental Defenders Office, said the paper demonstrated “the obscurity that still surrounds certain decision-making processes, including the allocation of water under different licences, the suspension of water sharing plans during drought and releases of water from dams”.
“There is a need to codify in law the processes underpinning these decisions,” she said. “Codification would improve transparency, ensure there is a justified method underpinning each decision, and help to build confidence in the system.”
Peta Derham, acting executive director of water resource planning and accounting for the Murray-Darling Basin Authority, said water resource plans were “tailored to the needs of each catchment and must meet Basin Plan requirements”.
“We look forward to receiving NSW’s plans by the end of the month, when they will be assessed on their merits by the MDBA,” Dr Derham said.
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Peter Hannam writes on environment issues for The Sydney Morning Herald and The Age.