KARSTIC CONDUITS AND WATERSHED IDENTIFICATION BASED ON THE MORPHOLOGICAL CHARACTERISTICS OF THE DEPRESSIONS IN YUNNAN-GUIZHOU PLATEAU OF CHINA

In the investigation of karstic form and underground karst water, determination of the location and geometric properties of karstic conduits and underground watersheds is one of the greatest problems not yet adequately resolved. In the karst terrain of the Yunnan–Guizhou Plateau of China, karst depressions are a product of the formation and evolution of the groundwater system, and the distribution of these depressions is a direct result of crustal uplift and the development of karstic conduits. This terrain is characterized by differences in morphological characteristics of depressions between the region of recharge and the region of outflow/discharge: the region of recharge is marked extensively by circular and random depressions, and is characterized by depressions with higher bottom elevations (referred to here as ‘higher depressions’). Conversely, the region of outflow and discharge is marked extensively by depressions that form long strips or irregular alignments that are distributed along with the karstic conduits, and is characterized by depressions with lower bottom elevations (referred to here as ‘lower depressions’). Here, a methodology has been put forward to determine the possible location and principal directions of karstic conduits and underground hydrogeological watersheds based on surface morphological features of depressions in the region of the Yunnan–Guizhou Plateau, China. The methodology assumes that the contour map that results from determining the bottom elevations of karstic depressions is sufficient to determine the positions of underground hydrogeological divisions and karstic channels. Taking the two main conduits systems in Guizhou Province as an example, a digital elevation model (DEM) was derived from 1:10,000 scale topographic maps with ArcGIS 10.2 and the bottom elevations of depressions were marked. Then a contour map of the bottom elevations of the depressions was produced. The directions of conduits and underground watersheds in the research area were identified from the valleys and ridges of the contour lines. The methodology introduced in this paper offers a new means of determining the location and geometric properties of karstic conduits and extracting the spatial distribution of water systems in the region of the Yunnan–Guizhou Plateau, China. This methodology will be appropriate for investigating karstic areas with continuous crustal uplift and significant variation in the bottom elevation of depressions between the region of recharge and region of discharge.