Fresh tomato production for the Sydney market : an evaluation of options to reduce freshwater scarcity from agricultural water use

In response to the growing concerns of freshwater scarcity, two metrics are considered for assessing the impacts of consumptive water use of a kg of fresh tomato supplied to the Sydney market. The first is the water use efficiency (WUE)-commonly used by agronomists which considers the absolute volumes of water consumed, and second, a recently developed method for water footprints based on Life Cycle Assessment (LCA) which describes the impacts in terms of contributing to freshwater scarcity. The results indicated that although a kg of tomato supplied from within Sydney had the highest water use efficiency (38 L for a kg of tomato as compared to 39-78 L from other regions of Australia), it had the biggest LCA-based water footprint (16 L for a kg of tomato as compared to 1.9-2.2 L from other regions of Australia). WUE as an indicator of agriculture water use is inappropriate to indicate the potential to contribute to local freshwater scarcity; potential stress on local and regional water resources, estimated using LCA-based water footprints, provide useful dimension to assess consumptive water use. Having both metrics will enable to achieve short term benefits at the farm level for saving water (through water use efficiency), while also recognising that longer term changes are required for alleviating freshwater scarcity (through LCA-based water footprints). Scenario modelling indicated relocation of production away from Sydney or modernisation of Sydney tomato greenhouse industry as a priority for reducing freshwater scarcity. The latter may be the best long term option to reduce additional emissions from transport and to take advantage of recycled water sources from Sydney's wastewater.