The Border Rivers catchment straddles the Queensland–New South Wales border, with about 50% of its area in each state, covering 24,000 square kilometres in total. In New South Wales the Border Rivers catchment includes numerous anabranches, waterholes and wetlands on a semi-arid floodplain in a relatively low rainfall zone.
The region had suffered severe drought since mid-2017 with rain in early 2020 easing these conditions, though the catchment remained dry until early 2021. Conditions continued to improve with moderate flooding occurring in March–April 2021 and wet conditions continuing into winter. Delivery of minimum daily flow requirements continued from Pindari Dam throughout the 2020–21 water year, but these only maintained flow to Ashford.
In 2019–20 translucent flows (environmental water under water sharing plan rules) were not delivered due to valve maintenance and the undelivered volume was set aside in a payback account. This made approximately 10 gigalitres of translucent flow payback water available for use in 2020–21.
The release of a stimulus flow from Pindari Dam was triggered in October 2020 and delivered the first small fresh between Pindari and Frazers Creek since February 2019. This release of 4.3 gigalitres provided a stable flow to help Murray cod and freshwater catfish recruitment.
The 10 gigalitres of translucent flow payback water was used to provide base flows, contribute to refuge pool replenishment and provide a pre-winter small fresh:
- Just over 2.3 gigalitres provided a stable base flow of 50 megalitres per day from November 2020 to April 2021, in addition to translucent releases resulting from inflows.
- In late December 2020 and early January 2021, 2.8 gigalitres was piggybacked on a WaterNSW block release to Mungindi to replenish refuges in the Barwon River. The Commonwealth Environmental Water Holder contributed an additional 900 megalitres from Pindari Dam to this event.
- The remaining approximately 5 gigalitres provided a pre-winter small fresh to increase system productivity and improve pre-winter condition of native fish.