A trickle, not a flood: Environmental watering in the Murray-Darling Basin, Australia

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 43 ha, volume 125 ML). 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.