Assessing the costs of Managed Aquifer Recharge options to support agricultural development

Managed aquifer recharge (MAR) can play an important role in agricultural water management and productivity where suitable aquifers exist. Yet while the benefits and costs of surface water storage have been extensively reported, the benefits and costs of MAR have been under reported and poorly conceptualised to date. In this study of ten potential MAR schemes in wet-dry tropical climates of northern Australia the estimated levelized costs ranged from US$0.04 to $0.36/m3 for MAR schemes of 0.6–5 Mm3/y capacity. The type of MAR scheme had the largest influence on cost, resulting in the following order of increasing cost for 1 Mm3/y schemes: recharge release, infiltration basin, recharge weir, aquifer storage transfer and recovery (ASTR), aquifer storage and recovery (ASR), seawater intrusion barrier. Infiltration type schemes were typically lower cost than well-injection. Scheme scale, end use and experience with similar schemes were also key influences on cost. A five-fold increase in scale reduced the levelized cost of ASR by 60%. Conceptualisation allows comparison across dissimilar schemes and revealed significant costs (20–100% of operating) associated with approvals and monitoring required for risk-based scheme development and operation. MAR can facilitate conjunctive use of surface and groundwater for improved agricultural water management. Dams typically provide considerably larger storages which results in lower levelized costs, with estimates of $0.03 to $0.18/m3 for options (annual yield 55–1248 Mm3) in the same study area. MAR is more favoured in areas of low relief, offers the benefit of reducing evaporative losses and is well suited to mosaic irrigation with incremental development and relatively low capital expenditure which may be attractive for agricultural irrigation.