Objectives Groundwater vulnerability assessment and main controlling factor identification serve as an essential prerequisite for precise groundwater pollution prevention and refined zonal management. This study aims to clarify the spatial distribution characteristics of shallow porous groundwater vulnerability in Tianjin, reveal its key influencing mechanisms, compensate for the regional application limitations of the traditional DRASTIC model, and provide a scientific basis for local groundwater resource protection and pollution control.

Methods Based on the geological, hydrogeological, and field pollution source verification data of the study area, the DRASTIC model combined with ArcGIS spatial analysis technology was adopted to quantitatively evaluate the vulnerability of shallow porous groundwater. Single−parameter sensitivity analysis was further applied to identify the main controlling factors of groundwater vulnerability.

Results The vulnerability of shallow porous groundwater in Tianjin can be classified into three grades: low−moderate, moderate and high. Areas including Jizhou, Ninghe and the central urban area fall into the moderate−vulnerability category, whereas northern Jizhou (Yuqiao Reservoir), Baodi, western Jinghai and the southeastern Binhai New Area represent high−vulnerability zones. Sensitivity analysis indicates that groundwater depth is the primary controlling factor, while the hydraulic conductivity of aquifers exerts the weakest influence.

Conclusions The shallow groundwater in Tianjin is generally characterized by moderate to high vulnerability, and groundwater table depth is the decisive factor affecting regional groundwater vulnerability. The traditional DRASTIC model has limitations in local regional adaptation, which can be optimized through targeted corrections to fit the regional hydrogeological conditions. The research findings can provide theoretical support for refined zonal management, pollution prevention, and sustainable utilization of shallow groundwater resources in Tianjin.