The more the merrier: using environmental flows to improve floodplain vegetation condition

Abstract

Environmental flows are increasingly being used to restore degraded floodplain vegetation; however, the type of flow regime required for recovery to healthy condition can vary depending on the extent of degradation before restoration. Regulation of the River Murray has affected floodplain ecosystems at many locations, including Bottle Bend Reserve, in south-western New South Wales, Australia. Within Bottle Bend Reserve, tangled lignum (Duma florulenta) dominates sections of the higher floodplain elevations. Lignum is an important and widely distributed Australian shrub occurring in arid and semiarid river systems within the Murray–Darling and Lake Eyre Basins. In an effort to restore floodplain vegetation, three environmental flows were delivered to Bottle Bend Reserve between 2013 and 2016. Flows varied in magnitude, leading to a mosaic of different regimes across the area. Condition surveys were undertaken over 1 year, namely, before, during and after delivery of the September 2016 environmental flow. This study found that the greatest response occurred in lignum plants with no recent environmental water, although lignum plants with one or two recent environmental flows still responded relative to the control. Lignum was in a better condition at sites that received more environmental flows, demonstrating the value of increased frequency of flows in recovering vegetation health.