Scheme-specific MAR site identification using GIS–AHP and MODFLOW screening in the Lower Campaspe Basin (Victoria): Implications for climate adaptation

Managed aquifer recharge (MAR) is increasingly considered to strengthen water security, especially in semi-arid basins, yet site selection often ends at mapping with limited verification. This study integrates GIS-based multicriteria decision analysis (MCDA) using the Analytic Hierarchy Process (AHP) with groundwater modelling to evaluate recharge suitability signals and subsurface response in the Lower Campaspe Basin, Victoria. Ten factors were harmonized to a common grid, reclassified, and weighted using the AHP. The resulting scheme-specific suitability indices (SI) were generated separately for infiltration ponds and injection wells. Weight patterns aligned with process controls: injection wells were governed by subsurface acceptance and water quality, whereas infiltration ponds were governed by near-surface infiltration conditions. Suitability maps showed broader opportunities for infiltration ponds (Medium = 63.5%, High = 14.0%, Very High = 0.41%) and more selective opportunity for injection wells (High = 11.6%, Very High = 3.0%). A calibrated MODFLOW model was used for hydraulic screening validation at 30 sites per scheme with a 2 m head-rise threshold. SI showed a moderate correlation with hydraulic response (infiltration ponds: r = 0.62 and injection wells: r = 0.56). The median head rise at the reference load declined from Low to Very High, and Very High exhibited the greatest inflow rates for both schemes. The mapping results and model responses show that the AHP-based suitability indices capture key factors controlling recharge potential, and when combined with hydraulic screening, offer a practical and transferable way to prioritize integrated MAR approaches that support climate adaptation.