| Abstract: |
FULL PROJECT NAME: Improving the knowledge base for prioritising environmental watering of wetland and floodplain trees.
DEWNR are responsible for the management of the three major floodplain complexes and a large number of smaller floodplain-wetland complexes in South Australia. Management objectives for these sites incorporate (but are not limited to) achieving sustainable communities of long-lived vegetation, particularly river red gum, black box, river cooba and lignum. Management actions to support achieving those objectives typically need to overcome stressors generated by catchment development and river regulation including (i) occurrence of extended (multi-year-decadal scale) dry phases (ii) permanent inundation of some wetlands and (iii) reduced depth to saline groundwater. Delivery of environmental water occurs at range of scales, with management approaches spanning: a) large scale releases of water from storages; b) operation of large infrastructure to create managed inundations at the sub-floodplain (1,000's of ha) scale; c) operation of small regulators to allow wetting/drying of pool level wetlands; d) weir pool manipulations; and e) pumping of environmental water into individual wetlands, floodplain depressions and sections of ephemeral (temporary) creeks. The core method for assessing floodplain tree condition uses visual observations of crown extent and density as an indicator of tree condition and trajectory for (i) determining prevailing condition of trees, (ii) reporting against Ecological Targets, (iii) determining the need for management actions in any year, and (iv) assessing responses of trees to management actions. Whilst the approach has proven to be very useful, it does not provide an assessment of soil moisture availability, which is the critical driver of tree condition. Consequently, the existing approach has potential to result in decisions to deliver water to trees that already have access to sufficient soil moisture, or not deliver water to trees that are about to exhaust soil moisture reserves. The project will utilise high frequency measurements of tree physiology and soil conditions to address a number of key knowledge gaps in the link between soil water availability, visual tree condition and the decision making process for management actions. Selected sites will be assessed for tree condition, soil properties, and groundwater conditions. The investigations will be undertaken at Chowilla-Calperum Floodplain by a multi-disciplinary, multi-stakeholder team. The outputs will assist managers to more reliably identify the need to deliver water, including those areas that may receive the greatest/least benefit from actions such as the delivery of environmental water. The project will not replace existing assessment approaches, but will identify a cost-effective pathway to enable managers to more confidently determine the need to undertake management actions in years when results from tree visual condition surveys are not conclusive. Increasing the scientific confidence to underpin strategic delivery has potential to (i) increase the efficiency of environmental water use and (ii) reduce the risk profile associated with management actions. In addition to the core project, options are provided which expand the scope to improve understanding of two key floodplain processes: evapotranspiration and salt mobilisation. The additional works would benefit from the monitoring proposed for the core project, and the initial funding could be leveraged to obtain necessary co-funding from the MDBA, universities, and the ARC. |