Abstract
Environmental flows are an integral component for the conservation and management of rivers, flood plains and other wetlands in the Murray–Darling Basin. Under the Basin Plan, environmental water is managed by the Commonwealth Environmental Water Office (CEWO) and the states. We assessed CEWO environmental flows (2014–15 to 2018–19), compared our findings with expected outcomes for vegetation in the Basin-wide Environmental Watering Strategy (EWS) and interviewed water managers about the efficacy of environmental watering. Some 21% of CEWO water was delivered as flood events, to 9 of 19 river valleys, inundating 7% of wetland area in those valleys annually and 0.8% of major Basin wetlands. A consistent pattern was the watering of many small wetlands on the South Australian Murray with small volumes (median area 43ha, volume 125ML). Just 12% of the area of river red gum subject to EWS expected outcomes was flooded, and half these events were likely suboptimal to achieve ecological benefits. Wetlands have not received the water they need and vegetation outcomes cannot be met by completion of the Plan in 2024. Rules that constrain flooding of private land must be relaxed if the Plan is to achieve its statutory requirement of wetland conservation.
Highlights
The Murray–Darling Basin covers 1.06 Â 106 km2 of south-eastern Australia and contains,30 000 wetlands of 25 000 km2 in area, including 6363 km2 of some 16 Ramsar wetlands (Murray–Darling Basin Authority 2010a, p. 59)
We assessed the volume attributed to the Commonwealth Environmental Water Holder (CEWH), States (NSW, South Australia and Victoria) and other sources, including the Living Murray program (TLM), environmental water allocations (EWA) under water sharing plans in New South Wales (NSW) and water from the Snowy Scheme (‘River Murray increased flows’)
There was no overall change in the volume of environmental flows released between 2012–13 and 2018–19 based on the line of best fit, averaging 1905 GL yearÀ1
Summary
The Murray–Darling Basin (hereafter, the Basin) covers 1.06 Â 106 km of south-eastern Australia and contains ,30 000 wetlands of 25 000 km in area, including 6363 km of some 16 Ramsar wetlands (Murray–Darling Basin Authority 2010a, p. 59). Over 100 wetlands are of national importance (Environment Australia 2001), but only 10% of the area of the Basin, is designated for conservation; the rest is mostly dryland pasture (69%) and arable land (12%). Subsequent stressors were river regulation and irrigation water diversions, which increased sharply between 1950 and 1990 (Kingsford 2000; Colloff et al 2015). River flows were further reduced by extended drought (van Dijk et al 2013), climate change (Cai and Cowan 2008), flood plain harvesting (i.e. interception and storage on-farm of overland flows; Steinfeld and Kingsford 2013) and recent increases in irrigation water use, including illegal, unlicensed and unregulated diversions (Wheeler et al 2020)
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