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 third case study of the MAR feasibility project, the Lower Namoi valley in the Namoi River catchment. This case study experiments with using a desktop analysis to initiate discussion from an operational, site specific perspective based on currently available data that draws on, but distinguishes it from, the previous work on MAR in the catchment. The area of interest (AOI) for our sub-regional analysis is the area of previously mapped high MAR suitability in the east of the Lower Namoi groundwater source (between Narrabri and Wee Waa). This area is part of a highly developed irrigated agriculture industry (where cotton is an important crop) that already makes use of large capacities of farm dams, conjunctive surface and groundwater use, and flood water management.

The broad approach taken was to draw on evidence from a holistic feasibility assessment to scope a set of plausible but widely different opportunities (“scenarios”) for MAR, and to test and refine these scenarios with local stakeholders and state government stakeholders. Given the developed nature of the AOI, any new water management solution (in this case MAR) is an attempt to optimise an existing capability rather than an initial attempt at meeting a need. In this respect, gains from optimising the status quo are unlikely to provide new water, but rather to provide greater control over where and when water is available.