Cold water pollution (CWP) is the artificial cooling of rivers caused by the release of unnaturally cold water from the bottom of large dams. CWP discharges can disrupt downstream temperature regimes for hundreds of kilometres, with dam releases resulting in persistently cold temperatures or causing acute ‘cold water shocks’. CWP has a wide range of well-documented ecological, economic, and social impacts. For native fish, CWP disrupts all life-cycle stages and is a key contributor to the loss of over half of expected fish species below the major dams in the Murray-Darling Basin (MDB).
The NSW Department of Primary Industries and Regional Development (DPIRD Fisheries), the UNSW Water Research Laboratory, and WaterNSW are working collaboratively to mitigate CWP via bubble plume technology. While bubble plume destratification has been used for decades in small dams to limit cyanobacteria blooms and remediate poor water quality conditions caused by reservoir stratification, bubble plumes also offer an opportunity to mitigate CWP in large dams.
Pindari Dam, located in the northern MDB, has a maximum storage capacity and depth of 312 GL and 73 m, respectively. Funding provided by the Australian Government has resulted in the construction and initial operation of the Pindari bubble plume in early 2026. The six-week trial confirmed that the entire reservoir quickly destratified, with bottom water temperatures increasing by nearly 8⁰C (11.9⁰C to19.5⁰C) and hypolimnetic dissolved oxygen increasing from near anoxic conditions (0.6 mg/L) to 2.4 mg/L.
Results will be presented that confirm the efficacy of bubble plumes to mitigate CWP and poor water quality conditions within large reservoirs which strengthens the case to deploy this technology as an effective option at remaining high priority dams in the MDB.