Rivers and Floodplains
Rivers and floodplains summary
Most of the direct impacts of climate change on freshwater systems in the Glenelg Hopkins region are predicted to come from a decline in rainfall leading to a decrease in runoff. Modelling of the Southeast Coast drainage division (including the area covered by the five coastal CMAs in Victoria) found strong agreement across 15 climate models that runoff would decrease[i]. With 1 °C of global warming, average annual rainfall is expected to decline up to 9 % and average annual runoff is expected to decline by 2 to 22 %. For 2 °C of global warming, the reductions in both rainfall and runoff are approximately double[ii].
Some generic impacts of climate change on freshwater systems include[iii]:
droughts — which may become more frequent and severe
dry soil conditions — which may follow decreased rainfall (especially in autumn) combined with increased evaporation
bushfires, runoff, sediment — increases in temperature, especially during extreme weather and dry catchment conditions, may increase the frequency and intensity of bushfires along with the severity of their impacts on runoff and sediment regimes
risks to freshwater ecosystems — increased frequency and duration of heatwaves may pose severe risks to freshwater ecosystems
increased water demand — higher air temperatures, combined with decreased rainfall, may lead to an increase in water demand and exert pressure on the storage reservoirs.
Healthy riparian ecosystems are more resilient to change and more able to adapt to climate change impacts[iv]. Improving the current condition of rivers and flood plain areas is the best way of increasing their potential to adapt to a changing climate.
Existing approaches to riparian management such as those undertaken in the Glenelg Hopkins region can be adaptive if undertaken within the climate ready context[v]. Management of non-climate threats through fencing, pest management and flow restoration can reduce the vulnerability of systems and build adaptive capacity. Existing restoration activities, such as riparian revegetation protection, the removal of barriers and the creation of fish ladders, have a critical role to play in reducing the sensitivity of river systems to a changing climate. Under climate change scenarios, the adaptive benefit of ongoing restoration and management can be enhanced if goals remain more open-ended, allowing for a range of future trajectories rather than focusing on meeting specific targets tied to antecedent reference conditions[vi]. For example, attempting to restore a river to pre-European settlement states could lead to maladaptation because it does not take into account changing temperature and rainfall patterns.
The region’s public land will become increasingly important as they provide refugia, reduce the overall sensitivity of the system and increase adaptive capacity across the landscape. Some important refuge areas for aquatic species have been identified within the Grampians by Parks Victoria, and along the Glenelg River, Wannon River, Crawford River and Mathers Creek in a 2010 study[vii]. Protecting existing and potential climate refugia and known resilient systems forms the backbone of biodiversity protection. Landscape-level planning across the Glenelg Hopkins region will be crucial in building the adaptive capacity of systems through improved connectivity via corridors and biolinks. Existing landscape scale projects such as the Glenelg River Restoration Project, Habitat 141 and the Grampians to Pyrenees Biolink provide an opportunity to increase the connectivity of rivers and streams with public land to benefit the ecological resilience of the entire region.
[i] FHS Chiew, J Teng, J Vase, DA Post, JM Perraud, DGC Kirono, NR Viney, Estimating climate change impact on runoff across southeast Australia: method, results and implications of the modelling method, Water Resources Research 45, 2009.
[ii] CSIRO, Climate variability and change in south-eastern Australia: a synthesis of findings from phase 2 of the south east Australian climate initiative (SECI), CSIRO, Canberra, 2012.
[iii] F Dyer, S El Sawah, P Lucena-Moya, E Harrison, B Croke, A Tschierschke, R Griffiths, R Brawata, J Kath, T Reynoldson, AJ Jakeman, Predicting water quality and ecological responses, National Climate Change Adaptation Research Facility, Gold Coast, 2013.
[iv] SJ Capon, LE Chambers, R Mac Nally, RJ Naiman, P Davies, N Marshall, J Pittock, M Reid, T Capon, M Douglas, J Catford, DS Baldwin, M Stewardson, J Roberts, M Parsons, SE Williams, Riparian ecosystems in the 21st century: hotspots for climate change adaptation? Ecosystems 16, 359–381, 2013.
[v] SJ Capon, LE Chambers, R Mac Nally, RJ Naiman, P Davies, N Marshall, J Pittock, M Reid, T Capon, M Douglas, J Catford, DS Baldwin, M Stewardson, J Roberts, M Parsons, SE Williams, Riparian ecosystems in the 21st century: hotspots for climate change adaptation? Ecosystems 16, 359–381, 2013.
[vi] SJ Capon, LE Chambers, R Mac Nally, RJ Naiman, P Davies, N Marshall, J Pittock, M Reid, T Capon, M Douglas, J Catford, DS Baldwin, M Stewardson, J Roberts, M Parsons, SE Williams, Riparian ecosystems in the 21st century: hotspots for climate change adaptation? Ecosystems 16, 359–381, 2013.
[vii] Sinclair Knight Mertz, Refuge habitat mapping for drought and fire refuges in the Glenelg River, Crawford River, Wannon River and Mathers Creek, final report, Sinclair Knight Mertz, Melbourne, 2010.