| Summary: | The appropriate division of underground drinking water source protection zones is a low-cost method of preventing water source pollution and ensuring a supply of safe drinking water. Based on FEFLOW, a groundwater flow model of large water sources was established for Luan River, North China. Trace lines of particle reverse migration for 100 and 1000 days were obtained by random walks. According to the trace morphology, the water sources in the riverside water source area were divided into four categories. The first- and second-grade protection areas were delimited by ArcGIS, with areas of 0.375 and 1.20 km<sup>2</sup>. The local and global sensitivity of the permeability coefficient (<i>K</i>) and effective porosity (<i>n<sub>e</sub></i>) effects on the area of groundwater protection zones were calculated. The area of the protection zones was positively correlated with <i>K</i> and negatively correlated with <i>n<sub>e</sub></i>. The variation in the protected zone caused by the simultaneous changes in <i>K</i> and <i>n<sub>e</sub></i> is the same as that of <i>n<sub>e</sub></i> alone, and the global sensitivity is closer to the local sensitivity of <i>n<sub>e</sub></i>. This indicates that <i>n<sub>e</sub></i> has a greater impact than <i>K</i> on the scope of groundwater protection zones. Moreover, global sensitivity is not simply a superposition of local sensitivity, and the interaction between parameters can reduce the effect of a parameter acting alone on the delineation of protection zones. This also shows that the global sensitivity is closer to the actual situation than the local sensitivity, thus providing a scientific basis for the delimitation and monitoring of water source protection zones.
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