Morphological characteristics of thermokarst lakes along the Qinghai-Tibet engineering corridor

In order to determine the distribution and morphometric characteristics of thermokarst lakes on the Qinghai-Tibet Plateau, SPOT-5 satellite images were acquired from the Chumaerhe High Plateau to Beiluhe Basin within a 10-km-wide corridor along the Qinghai-Tibet Railway. A total of 2163 water bodies, having a total area of 1.09 x 10(7) m(2), were identified in the study area using unsupervised classification and image interpretation. Several shape metrics (area, perimeter, circularity index, elongation index, orientation of major axis, and curvature of lake shoreline) were determined for lakes from the imagery, and bathymetric profiles of lake bottoms were derived using ground-penetrating radar. The results highlighted significant morphometric differences between lakes larger than 5000 m(2) among three subregions: the Chumaerhe High Plain (CUP), the Hoh Xil Hill region (HXR), and the Beluhe Basin region (BBR). The lakes in CI-IP usually have a more regular outline and smooth lake bottoms, while the lakes in HXR often have the greatest depths and the most complex shorelines. The most elongated and largest lakes were typically in BBR. Other than a minor NE-SE peak in HXR and BBR, the major axis orientation for lakes in the three subregions is mostly ENE-WSW. The differences in lake morphology between the three subregions are associated with differences in ground-ice content, local relief, and topography. The dominant factors controlling the development of orientated thermokarst lakes in the region are the prevailing summer wind direction and solar insolation.