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 conduit and underground watershed is one of the greatest problems, not adequately solved until now. In the karst terrain of Yunnan-Guizhou Plateau of China, depressions are the products of formation and evolution of the groundwater system, and the distribution of depressions is a direct reflection of inheritance of the earth's crust uplift and development of karstic conduit. The outstanding features is that the region of recharge area is mostly marked by circular and random depressions and the bottom elevation of depressions is higher, called as “higher depression”, and the region of outflow and discharge is mostly marked by depressions with form of long strips or irregular lining with the karstic conduit distribution in plane, and the bottom elevation of depressions is relatively lower, called as “lower depression”. Based on the surface information, the methodology was put forward and aims to determine the possible location and principal direction of the karstic conduits and the underground hydrogeological watershed from the topographic features in the region of the Yunnan-Guizhou Plateau, China. The methodology is assumed that the contour map resulting from determining the altitudes of karstic depression bottoms is sufficient to determine the position of the underground hydrogeological divisions and the karstic channels. Taken the two main conduits systems in Guizhou province as an example, the DEMs was derived from 1:10000 scale topographic maps with ArcGIS10.2, and the bottom elevation of depressions were marked. The contour map of bottom elevation of the depressions was delineated. The directions of conduits and underground watershed in research area were identified from the ridges and valleys of the contour lines. The method offers a new method for determination of the location and geometric properties of karstic conduit and extraction of spatial distribution of water systems in the region of the Yunnan-Guizhou Plateau, China. The methodology could be suitable for the karstic research area with continuous uplift of the earth's crust and the depressions distribute regularly from the region of recharge to discharge with the bottom elevation varying significantly.