Robust Climate Change Adaptation for Environmental Flows in the Goulburn River, Australia

Abstract

Climate change presents severe risks for the implementation and success of environmental flows worldwide. Current environmental flow assessments tend to assume climate stationarity, so there is an urgent need for robust environmental flow programs that allow adaptation to changing flow regimes due to climate change. Designing and implementing robust environmental flow programs means ensuring environmental objectives are achieved under a range of uncertain, but plausible climate futures. We apply stress testing concepts previously adopted in water supply management to environmental flows at a catchment scale. We do this by exploring vulnerabilities in different river management metrics for current environmental flow arrangements in the Goulburn River, Australia, under non-stationary climatic conditions. Given the limitations of current environmental flows in supporting ecological outcomes under climate change, we tested three different adaptation options individually and in combination. Stress testing adaptation results showed that increasing environmental entitlements yielded the largest benefits in drier climate futures, whereas relaxing river capacity constraints (allowing more targeted delivery of environmental water) offered more benefits for current and wetter climates. Combining both these options led to greater than additive improvements in allocation reliability and reductions in environmental water shortfalls, and these improvements were achieved across a wider range of climatic conditions than possible with either of the individual options. However, adaptation may present additional risks to some ecological outcomes for wetter climates. Ultimately, there was a degree of plausible climate change beyond which none of the adaptation options considered were effective at improving ecological outcomes. This study demonstrates an important step for environmental flow assessments: evaluating the feasibility of environmental outcomes under climate change, and the intervention options that prove most robust under an uncertain future.

Effects of altered streamflow on macroinvertebrate taxonomic richness and composition in the Goulburn River, Australia

“…The Goulburn Broken Catchment Management Authority oversees managing water entitlements for the environment, environmental deliveries are only a small proportion of flow in the river (11% of total available volume). Nearly 400 GL of high-security environmental water rights in the Goulburn River are used to meet local environmental objectives and downstream environmental flows in the Murray River (John et al, 2021).…”

Assessing Climate Change Impacts on Yield of “Dual‐Priority” Water Rights in Carryover Systems at Catchment Scale

“…Furthermore, studies investigating climate change impacts on water availability (yield) mostly rely on a hydrological model to simulate runoff (or streamflow) under specific global climate model (GCM) scenarios (Arnell & Gosling, 2013; Haddeland et al., 2014; McFarlane et al., 2012; Mengistu et al., 2021; Schewe et al., 2014; Wasko et al., 2021) and reservoir operation models to simulate reservoir behavior. Such models can be demanding in terms of data and computations (John, Fowler, et al., 2021; Ren et al., 2018) and thus may constrain the assessment of climate change uncertainty (John, Horne, et al., 2021). The complexity of these commonly used methods means that they are usually applied in a single river or catchment.…”

The Role of Weather System Changes and Catchment Characteristics in the Rainfall‐Runoff Relationship Shift in Victoria, Australia

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In the Australian state of Victoria, the 1997-2009 "Millennium Drought" significantly reduced riverine streamflow compared to pre-drought conditions. Key features of streamflow regimes have been altered, including the magnitude of low flow events, wetting and drying sequencing and seasonal streamflow patterns (John et al, 2021;Saft et al, 2015;Stewardson et al, 2017). This placed stress on riverine ecosystems and water security in many Victorian catchments (K. Fowler et al, 2022;van Dijk et al, 2013).

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