Background

The project ‘Feasibility study of managed aquifer recharge [MAR] for improved water productivity for Australian cotton production’ is investigating the potential to implement MAR at a regional scale in established and emerging irrigated cotton growing regions of Australia. The broad aim of the project case studies was to evaluate how MAR might be feasible for irrigated cotton production and associated cropping systems in the focus regions, and make recommendations on further work to evaluate local hydrogeological conditions, plan the necessary site-specific infrastructure, and establish the legal, social and organisational conditions for implementation of MAR.

The focus of this report is the second case study of the MAR feasibility project, the Gilbert River Agricultural Precinct (GRAP) in the Gilbert River catchment. The study has concentrated on identifying how potential interventions that might provide timely and reliable water yields from the alluvial bed sands adjacent to the Gilbert River might work, and what information would be needed to support investment in the sustainable active management of bed sands.

The broad approach taken was to draw on evidence from a holistic feasibility assessment to scope the most promising opportunities (“scenarios”) for MAR, within an active management paradigm, and to test and refine these scenarios with local stakeholders and state government stakeholders. The key questions we have addressed in the context of seven feasibility criteria are:

1. How might potential strategies (e.g., leaky weirs, recharge weirs, infiltration basins) be applied in the Gilbert River to maximise storage, top up and/or slow down drainage from the bed sands to provide water for irrigation when needed?

2. What are the policy and implementation implications of active management of bed sands? What environmental, social and/or hydrological impacts would need to be tracked?

3. How could an active management approach operate? What governance and information sharing arrangements might be needed?

In addressing these questions, we have identified limitations in the current conceptualisations used in the models underpinning Water Resource Plans (WRP) for the Gulf catchments and, from this, opportunities to improve conceptual understanding of the bed sands.