Objective Although the vulnerability assessment methods for pore groundwater have become relatively mature, the improvement of assessment methods and accuracy for karst groundwater vulnerability remains a focus of current research due to data limitations and difficulties in indicator selection. Conducting groundwater vulnerability assessment plays a crucial role in the rational development and protection of water resources, as well as the prevention and control of groundwater pollution.

Methods This study selected the shallow karst groundwater in Tianjin (an area with relatively abundant data) as the research object. After collecting geological and hydrogeological data of the study area, the PLEIK model was adopted based on actual conditions. Additionally, the powerful spatial data processing function of ArcGIS was used to assess the vulnerability of shallow karst groundwater in Tianjin, aiming to enrich the research content and application cases of karst groundwater vulnerability assessment.

Results The groundwater vulnerability in this area is mainly moderate, which is primarily distributed in the central carbonate rock karst fissure water development areas (such as Chuanfangyu and Mopan Valley), as well as the clastic rock intercalated with carbonate rock fissure water areas in the northern and southern parts. The area with high vulnerability is the smallest, mainly concentrated in some villages, towns, and industrial and mining land. Finally, combined with the regional water resources quantity, water quality characteristics, and water use scenarios, suggestions for ensuring the safe development and utilization of groundwater were proposed.

Conclusions The PLEIK method is applicable for assessing the vulnerability of Tianjin's shallow karst groundwater by comparing the results with actual conditions. The protective cover layer has the greatest impact on groundwater vulnerability in the study area, followed by the development status of the karst network, while the influence of recharge types on groundwater vulnerability is minimal. These factors collectively form the vulnerability zonation characteristics of karst groundwater areas. Finally, based on regional groundwater quantity, water quality features, and water use scenarios, recommendations for ensuring the safe and sustainable utilization of groundwater resources are proposed.