The Top End of the NT has significant potential for MAR to support medium scale irrigation. MAR can help overcome the seasonal water balance challenges to increase water availability during the dry season with negligible environmental impacts, and even provide environmental benefits. The Daly River catchment is flagged as a key area for agricultural development due to its proximity to Darwin, soil suitability and water availability. The river is also one of a handful of perennial rivers in the NT, where dry season flows are fed by groundwater from the Oolloo Dolostone and Tindall Limestone aquifers. Environmental flow objectives have led to groundwater extraction being capped and agricultural development is currently limited by the availability of water.
The fundamental advantages of MAR based developments over conventional water sources are explained including the cost of transporting water, lack of evaporative losses, scalability of MAR projects and the variability of the magnitude of the wet season. Conversely the impediments to irrigation based MAR schemes in northern Australia are also discussed. The primary issue is not the technical feasibility, rather it is the economic feasibility of the total irrigation development, which includes a MAR component.
The technical and economic feasibility of MAR are assessed at three sites in the Daly River catchment based on a range of artificial recharge methods and a range of crop types. The concept of using wet season flow for MAR and recovery during the dry season was found to be both technically feasible and economically viable in some areas in the catchment and for some crop types. Outside the Daly River catchment, the potential for MAR to support irrigation exists where there is a suitable source water, target aquifer and arable soils. The potential for MAR in other areas in the Top End is also considered.