Spatial tool to assist with water management decisions in the Murray-Darling Basin
The Challenge
A new tool, based on ground observations of riparian woody vegetation evapotranspiration has been developed using remote sensing to aid water accounting and management in the Murray-Darling Basin.
Water is highly contested in the Murray-Darling Basin with use of water by irrigators and the environment in conflict. Tools are required to help water managers understand the evaporative losses that are associated with riparian vegetation models to ensure that vegetation remain in a healthy state and that water losses from floodplain trees are not over inflated in water balance models used to make water allocation decisions. Healthy woody vegetation translates into high biodiversity in river basins across the world.
A balance water sharing plan – the Murray-Darling Basin plan, aims to equitably allocate water to support the environment and the economy through irrigated agriculture. Downstream water availability often results in conflict across the Basin states, so accurate water accounting, allocation and evidence of environmental water needs are required.
Young swans leaving their nest. the breeding event was in response to a flood which is critical to support biodiversity. PHOTO: Tanya Doody
Our Response
Our capability
CSIRO maintains expertise in vegetation water use research employing sapflow sensors to understand tree water requirements across the landscape. The Organisation has the ability to access large numbers of sapflow sensors to ensure results are rigorous and suitable to upscale using remote sensing. The reputation of the science produced ensures that external organisations such as Universities are willing to collaborate to add-value across multi-disciplinary fields. This project also extends the use of a remote sensing evapotranspiration algorithm developed in CSIRO to aid water management with the provision of a remote sensing tool.
Science and Innovation
Long-term field data collected by CSIRO, demonstrating daily total water losses from River Red Gum floodplain vegetation (actual evapotranspiration (ETa)) have been used to calibrate a CSIRO MODIS evapotranspiration algorithm to allow broad scale estimation of vegetation evaporative losses across the southern Murray-Darling Basin every 8 days from 2001 to current. CSIRO is the only research Organisation who collects the long term field data required to underpin the remote sensing evapotranspiration tool. The tool provide innovative solutions to water accounting and floodplain vegetation management by providing accurate water loss information and informing when environmental flow allocations are required to specific floodplain areas to ensure ecological function is maintained.
A conceptual model of the spatial evapotranspiration tool that has been developed. IMAGE: Martin Nolan
Results
Evaporative water loss from Red Gum areas is currently overestimated, sometimes by greater than 50%, using current modelling tools. This means that water accounting in a water constrained Basin is inaccurate. This tool called CSIRO-Floodplain actual Evapotranspiration (CSIRO-FETa) provides a method to accurately understand water loss related to River Red Gum to allow for more accurate water accounting and water allocation between the environment and irrigators. The evapotranspiration data also provides a method to monitor tree health and aid environmental water decisions. Floodplain trees have specific water requirements which are supplemented by overbank floods, however during drought periods environmental flows are required to meet those water requirements. In the past, decisions about where to allocate flows have been difficult to make across large scales, however with this tool, water losses can be monitored over time. Once a vegetation area reduces its water losses past a defined threshold over several years, plans can be made to allocate environmental flows to those areas in coming years to preserve ecological integrity. CSIRO-FETa ensures that tree decline in evaporative losses can be monitored allowing more accurate decisions in relation to environmental flow allocations.