Sensitivity of permissible aquifer recharge rate to hydrogeological and well design parameters

• 3D numerical groundwater models better represent real-world scenarios in determining PARR . • The adaptive iteration algorithm yields faster calculation of PARR. • The combined variation of the parameters has a more pronounced effect on the PARR. • The Lower Ain River valleys exhibit a high potential for groundwater storage capacity. The maximum injection rate to an aquifer for a given operational time, hydrogeological and well characteristics, and under the constraints of a permissible head is defined as the Permissible Aquifer Recharge Rate (PARR). A local and global sensitivity analysis (Sobol’s Indices) has been presented to address the important hydrogeological and well parameters in determining PARR for confined and unconfined aquifers. A novel methodology to determine PARR for 3D numerical groundwater models has been discussed, and its implementation in Lower Ain Valley has been presented. PARR’s sensitivity varies with specific parameter interactions, particularly between hydraulic conductivity and vertical anisotropy in unconfined aquifers, whereas confined aquifers show a broader range of influential factors mainly due to interaction between location of the well-screen and the aquifer parameters. The methodology for determining PARR with an adaptive iteration algorithm based on the analytical solution to the well is more efficient and requires fewer iterations. The Lower Ain Valley reveals significant spatial variability in PARR (22–7.48 × 10 5 m 3 /day) with aquifer characteristics, highlighting the basin’s strong aquifer storage potential for addressing severe groundwater deficiencies.