Abstract:

The fissure and conduit are well developed and interconnected in karst aquifers due to intensive corrosion, and a “doublelayer structure” has formed in karst areas. The groundwater moves and stores in subterranean fissure, conduit or enlarged underground spaces. There are so many fissures, conduits, swallow holes and shafts in karst areas that the karst aquifer is more sensitive to land use change. It is also the case that the occurrence of complex and deep interconnections between surface and underground in karst areas makes its groundwater particularly liable to contamination. Changes in the hydrology in karst area may thus be a consequence resulted from all other environmental changes in the area. Taking the typical karst subterranean river basin, Houzhai subterranean river basin in Puding County of Guizhou Province, as an example, the intrinsic vulnerability is analyzed in relation to its hydrogeological conditions. Based on more than 20 years′ hydrochemical data, the vulnerability of karst aquifers was analyzed in relation with the land use change, agricultural activity, urbanization and unreasonable human activities. It is shown that the groundwater quality is affected by the land use change, agricultural activity and unreasonable human activity. The content of Ca2+, Mg2+, Cl-, SO2-4, HCO-3 and the total hardness have risen during the last few years, while the content of K+, Na+ fallen. The agricultural activities have caused the rise of nitrate content and mineralization in groundwater and the COD rise is due to unreasonable human activities. It is apparent that the water quality has become worse than before and will be even worse because of the rock desertification and unreasonable land use. Therefore, the unreasonable pattern of land use must be rearranged to protect the karst water resources. It is necessary to carry out ecological rehabilitation or reafforestation, in order to prevent the groundwater from pollution caused by agricultural activities and unreasonable human activities.

Key words: vulnerability of karst aquifer, land use change, Houzhai subterranean river basin