Spatial associations between urbanization, watershed runoff potential, and groundwater-depth change in a Semi-Arid Alluvial Plain, Multan, Pakistan

Groundwater decline in irrigated semi-arid alluvial plains reflects interacting land-surface, climatic, pumping, and hydrogeological controls. This study evaluates spatial associations among urbanization, Curve Number-based event-runoff potential, regional climate variability, and groundwater-depth change in Multan, Pakistan. Thirty-nine wells with pre- and post-monsoon observations for 2005, 2010, 2015, and 2018 were assigned to four watershed groups delineated using an approximately 30-m DEM and HydroBASINS Level-12 topology. Land-use/land-cover maps for 2010, 2015, and 2020, SoilGrids Hydrologic Soil Group data, and regional NASA POWER climate data for 2003–2018 were summarized using the same watershed boundaries. Mean groundwater-depth increases from pre-monsoon 2005 to post-monsoon 2018 were 19.32, 7.21, 5.76, and 15.69 m in Groups 1–4, respectively. Only Group 1 had a 95% confidence interval excluding zero. Urban fraction increased in all groups, while mean Curve Number values remained high and increased modestly by 0.24–0.64. Scenario calculations indicated only modest changes in event runoff. Climate analysis showed modest spatial rainfall variability, no significant trends in precipitation, temperature, or reference evapotranspiration, and no significant exploratory climate–groundwater relationship. The non-monotonic group patterns indicate that the available land-surface and climate indicators cannot independently explain the observed groundwater changes. The framework identifies priority areas for additional hydrogeological monitoring and management.