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Published: 21 October 2020   •   Opinion pieces

The wet spring brought on by La Nina is bolstering water storages, but it's also raising questions from NSW mid-Murray rice and fodder crop irrigators about the trigger for an unregulated flow event which will give them supplementary access to water.

When rain falls downstream of our storages and cannot be captured, it's referred to as an unregulated flow. An unregulated flow in a reach of the River Murray system is water that is, or is forecast to be, in excess of the minimum flow needed to meet demands along the river and cannot be captured in Lake Victoria.

When it comes to river management, our number one priority is capturing and storing as much water as possible, so it can be allocated to entitlement holders and made available for use later. We run the river on the behalf of Basin governments, and we must run the system efficiently.

Because of the significant and continued rain we've received in the southern Basin in recent months (and we could see that Lake Victoria was going to fill), the Murray River has been unregulated from late June to late September. During that time irrigators were advised by their state water manager if and when they could use their supplementary licence to access this extra water. At the end of September, temperatures and demand increased and the system went back to regulated flow. Lake Victoria's levels have dropped since the end of September and are continuing to fall. As of 19 October, Lake Victoria is sitting at 92%, meaning that there is capacity to capture current and forecast tributary inflows.

To mimic natural river flow, from September and through until December, the Commonwealth and state environmental water holders will be using some of their water allocation for their southern spring flow like they did last year. Water for the environment is being released from Hume Dam to support select wetlands and the river channel from the mid-Murray, to the lower Murray all the way to the Lower Lakes and Coorong. These flows will provide benefits all the way down the river, including food and breeding opportunities for native vegetation, fish and wildlife.

After two dry years, and little water allocation for general security irrigators in New South Wales, we can understand the heightened interest in accessing unregulated flow for their summer crops.

The rain that fell on the weekend just gone (17-18 October) was less than what was forecast by the BoM and wasn't enough to trigger an unregulated event – meaning we could capture and store all the water that is not required to meet demands along the length of the river. There is more rain forecast this weekend (26-27 October) though, so we will continue to monitor the situation closely and will advise the state governments of an unregulated event if one eventuates. We encourage irrigators to stay in touch with their water resource manager for any updates.


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