Spatial distribution of supra-permafrost groundwater in the Qinghai-Tibet Engineering Corridor using inversion models

Supra-permafrost groundwater (SPG) is a key factor that causes damage to highways and railways in the Qinghai-Tibet Engineering Corridor (QTEC). It is difficult to monitor SPG in the field due to their complex formation mechanisms and movement characteristics. Traditional single-site field monitoring studies limit the spatial and temporal precision of SPG spatial distribution. To determine the moisture content of shallow soils and the SPG distribution along the QTEC, this work employed the temperature vegetation dryness index and remote sensing models for groundwater table distribution models. The accuracies of the models were validated using measurements obtained from different sites in the corridor. In the permafrost zones of the QTEC, 72%, 22% and 6% of the SPG were located at depths of 0.5-1, <0.5 and >1 m, respectively. Meanwhile, 79.4% of the area along the Qinghai-Tibet Highway (QTH) (Xidatan-Tanggula) section contained SPG. In these sections with SPG, 37.9% have an SPG table at depths of 0.5-0.8 m. This study preliminarily explored the SPG distribution in the QTEC with a 30 m resolution. The findings can help improve the spatial scale of SPG research, provide a basis for the analysis of the hydrothermal mechanisms, and serve as a guide in the assessment of operational risks and road structure designs.