Planning to manage sustainably — natural resource geophysics as part of resource assessment

The Western Australia (WA) and Northern Territory (NT) Governments proposed an area adjacent to the Ord River Irrigation Area for irrigation development. The Natural Resource Agencies of the two Governments determined that development would only be authorised once the existing water resource conditions were known, and when the proponent had shown that irrigation could be managed to preserve natural streamflows and operate sustainably. To enable the hydrogeological conditions to be determined and modelled, an airborne electromagnetic survey was commissioned. Each of the hydrogeological environments was evaluated to determine the effects of irrigation and land-use changes on groundwater levels, groundwater quality, and on flows in seasonal watercourses. The results of two generations of groundwater modelling were integrated in the environmental management plan for the irrigation project, with requirements for continuous monitoring and interactive groundwater modelling to be specified throughout the life of the irrigation project. This is an innovative application of geophysics, where the full life cycle of irrigation could be planned and water use managed, based on environments identified in an airborne survey.