Part of Stage 1A VCMP feasibility study and the linked NSW RRCP investigated the potential environmental benefits and risks from increasing the limit for environmental water delivery to above the minor flood level. The program aims to assist the Basin Plan objectives, improved condition of the Southern Connected Basin and connectivity into SA, and increase environmental benefits from environmental water delivery. Initial range finding of flow rates conducted for the Goulburn River determined potential scenarios, while Murray River scenarios were taken from RRCP. Ecological modelling was undertaken for vegetation, native fish, waterbirds, and geomorphology response, plus vegetation inundation, water quality, macroinvertebrates/production and connectivity. Additionally, investigations were done on the risks to achieving outcomes, and risks to the environment from the scenarios.
The lower relaxation scenarios indicated some disbenefits, particularly to floodplain vegetation, indicating a high likelihood that areas are currently relying on uncontrolled releases to maintain health – with some relaxation scenarios reducing uncontrolled release without providing comparable benefits. Higer relaxation scenarios showed a likelihood of improved health for vegetation communities, and positive outcomes for all other environmental values investigated.
The outcomes were able to support the feasibility of the VCMP by showing the high potential for environmental benefits resulting directly from the relaxation of constraints. The results recognized the current decline in health for ecosystems that rely (or relied) on riverine flooding and showed not only a value in proceeding to business case stage for both rivers, but that it is imperative to help protect and sustain those environments.