Study on the relationship between spatial distribution of karst caves and drainage density: An example of Guizhou Province

Guizhou Province is located in the hinterland of southwest China, an important part of the Yunnan-Guizhou Plateau, with high mountains and deep gorges. It has subtropical humid monsoon climate with large rainfall, where carbonate strata and karst are widely distributed, and karst process is generally developed, resulting in rapid conversion of surface water into groundwater. Here strong dissolution and mechanical abrasion have shaped unique and magnificent karst landforms, such as peak clusters, peak forests, depressions, sinkholes, funnels, and underground rivers. This paper analyzes the relationship between the spatial distribution of caves and the density of river networks based on data of 4，789 caves and an 1∶200,000 hydrogeological map of Guizhou Province, and explains the genesis of such relationship from the perspective of lithology, structure, climate and topography. The results show that the karst caves in Guizhou Province are concentrated in the areas with low and medium river network density, exhibiting a patchy spatial pattern. The normal QQ map largely shows a normal distribution, indicating that the concentration of river network density at cave points is the result of mutual restriction of many factors. The cave points and river network density have a negative correlation in pure carbonate rock, carbonate rock interspersed with non-carbonate rock and non-carbonate rock areas. In carbonate rock area, the density of caves increases with the increases of temperature and precipitation, while the density of river network shows a trend of increase first and then decrease due to the varied degrees of karst development. The centers of folds and faults are the dominant area of cave development, where the density of the river network is relatively low, and the number of caves decreases with the increases of distance. In the terrain area below slope 25°, the number of caves is the largest, and the maximum river network density appears in the gentle area. With the increase of slope, the overall trend is decreasing. In the terrain range of slopes 25° to 30°, the number of caves tends to decrease. The conditions of lithology, structure, and climate have promoted the development of mature surface and underground water circulation systems in Guizhou. The surface water promotes the development of karst caves, which in turn restricts the development of surface runoff, making the density of cave river networks present a trend of concentrated distribution in low and medium values.