Changes in groundwater dynamics in the transboundary Ravi river basin using MODFLOW modelling framework

The groundwater resources of the Ravi river basin are facing increasing pressure due to agricultural, domestic, industrial and urban water needs.However, groundwater changes in this basin have not been assessed using a spatially distributed modelling approach.This study used MODFLOW-NWT to assess spatial and temporal fluctuations in groundwater levels across 12 districts of Punjab, Pakistan.The model integrated land-use, soil, climatic and groundwater data.The aquifer was divided into three layers of 80 m, 120 m and 300 m, using a grid size of 6 km × 6 km.Data from 739 piezometric wells (2000-2019) were used for model calibration and validation.During calibration, R², Pearson r and NSE ranged from 0.77-0.84,0.77-0.84and 0.91-0.95,respectively.During validation, the corresponding values ranged from 0.89-0.92,0.98 and 0.89-0.92,respectively.The results indicate that groundwater levels declined at an average rate of 0.5-1.0m/year, reaching 2-3 m/year in some areas, particularly around Lahore, Sheikhupura, Faisalabad and Pakpattan.Sensitivity analysis using the Parameter Estimation (PEST) package evaluated the influence of horizontal (Kh) and vertical (Kv) hydraulic conductivity, recharge (RCH), specific yield (Sy) and specific storage (Ss).Groundwater depletion was spatially variable and particularly significant in areas with high agricultural and urban water demand.Although the 6 km × 6 km grid supports regional assessment, it may not capture local groundwater variations.This quantitative assessment can support regional groundwater management by identifying depletion hotspots and informing targeted interventions, including rainwater harvesting and managed aquifer recharge, to improve groundwater storage and recovery.