Efforts are being made in the Australian Murray-Darling Basin (MDB) to transfer water from the irrigation sector to environmental flows. However, discussions have been on-going for several years regarding the appropriate way to achieve this goal. Dimensions under discussion include the promotion of improving on-farm irrigation efficiencies, water rights and their buybacks, undocumented use of water for irrigation, and “theft” of water.
A knowledge gap exists regarding the actual amount of water that is being consumed across the MDB, which is the main outgoing component of the basin water balance. Spatial quantification of actual evapotranspiration (ETact) would, for example, allow for estimation of irrigation water consumption in relation to water allocation, and thus support identification of locations where theft of water occurs.
Mapping of ETact has been developed by the scientific community for the past 20 years and has now achieved a degree of technological maturity. This has prompted the distribution of several global ETact products in the public and semi-public domains, which offer a revolutionary and cost-effective way for evaluating and monitoring water consumption. Remote sensing data have been used to analyze water extractions and storage, but not yet for quantification of consumptive use.
A global-scale ETact product was applied in this demonstration project to provide preliminary figures and maps on monthly and yearly water consumption in the Border Rivers subcatchment on different spatial scales.