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Water plan prepared as drought saps Darling flows

Water plan prepared as drought saps Darling flows

08 December 2017

WaterNSW is planning to ensure Broken Hill and Menindee communities receive a continuous flow of water even if there is a repeat of the worst drought on record.

The WaterNSW Lower Darling Operations Plan has been developed to ensure critical human water needs can be met while maintaining environmental objectives in the Lower Darling under the worst-case scenario.

Menindee lakes currently sits at almost 29% of its total storage capacity, (Lake Pamamaroo 89%, Lake Wetherell 37%, Lake Menindee 3.5% and Lake Cawndilla 26%) and persistently low inflow rates into the lakes over 2017 have fallen further in recent months.

Barwon Darling Flows Diagram

In the five months to 30 November flows at Mungindi, Brewarrina, Culgoa, Bourke and Wilcannia have been very low with only 55 gigalitres (GL) flowing down the upper Barwon-Darling, 72% of which water reached the lakes. The total to date for the 11 months of 2017 was approximately 160 GL of inflow into the system, of which 114 GL or 70% reached the lakes.

By comparison during the previous six months of 2016 (1July-31 December 2016) the combined total for those locations was 2,381 GL, 85% of which made its way to the lakes.

To date operations planning focussed on maximising releases from the lower storages in Menindee and Cawndilla, while holding water in the upper lakes of Wetherell and Pamamaroo. This strategy will result in 300 GL remaining in the upper storages when the lakes reached the 480 GL mark later this month, assuming the current pattern of low inflows persists.

WaterNSW is using the lowest inflow sequence and maximum evaporation data in its planning to ensure there is sufficient water in storage to meet demand in the following critical situations:

  • Scenario 1 – Sahara – no inflow occurs at Wilcannia through to resource being exhausted;
  • Scenario 2 – Drought - Statistical worst inflow sequence on record - applied from January 2017 – with resources managed to the next significant inflow; and
  • Scenario 3 – Dry scenario - 80th percentile inflow sequences adjusted until January 2018 to represent the likely no inflow scenario.

Key objectives of the plan are to:

  • Maintain supply to meet water demands in Broken Hill;
  • Maintain a continual flow of water along the Lower Darling through drought; and
  • Maximise use of water in the lower lakes to meet customer demand.

WaterNSW has engaged with customers to understand their needs and developed a release strategy to meet the challenges of prolonged drought.

Ensuring water quality and maintaining acceptable salinity levels are also integral components of the operations plan. Water quality in Lake Wetherell will be the key to alternating supply from Weir 32 to Copi Hollow for supply to Broken Hill during drought conditions.

Read the full copy of the drought operations plan (PDF, 1066.73 KB).

Contact: Tony Webber

Phone: 0428 613 478

83.3
Wednesday 13 December
-0.5
2,149,539 ML
2,581,749 ML
11,583 ML
1,655 ML
-10,920 ML
Wednesday 13 December