To reintroduce natural flows to Mowamba River by decommissioning Mowamba Weir, releases from Jindabyne dam need to be reduced to offset losses incurred by Snowy Hydro. It is an interim arrangement that achieves better outcomes from environmental water while limiting the financial impact of lost hydroelectricity production.
Adjustments were applied to the planned releases from Jindabyne Dam based on Mowamba River flows for the period 2011 to 2021, simulating a live application where the yearly Jindabyne releases are known but the Mowamba flows are not. Initial reductions were applied using seasonal proportions, then secondary corrections applied. These scenarios were created through combinations of yearly, quarterly or monthly corrections, immediate or gradual corrections and full or partial protection of the hydroelectricity generations window. Ultimately, a tool is developed to apply the adjustment mechanism to future planning.
Changing release arrangements from Jindabyne Dam to allow for the decommissioning of the Mowamba Weir whilst having a minimal impact on the environment downstream of Jindabyne dam or energy production is possible. There are limitations to the amendment method that are primarily administrative and legislative. Additionally, financial impacts can be minimized and opportunities exist for increasing revenue for Snowy Hydro.
Reinstating environmental flows through the Mowamba River can be achieved without increasing impacts for the Snowy River or power generation. Not only is it possible to achieve environmental outcomes for modified rivers, but it shouldn’t be assumed that it would come at a financial expense.