后寨河流域岩溶含水层脆弱性及其对土地利用方式的响应

由于强烈的溶蚀作用，岩溶地区溶蚀裂隙、管道等高度发育，并相互贯通，形成岩溶区特有的地下、地表“双层空间”结构体系，地下空间成为地下水存储和运移的重要场所。岩溶地区由于土层浅薄或缺失，并且溶蚀裂隙、管道、落水洞、竖井等高度发育，使含水层更易受地表状况的影响，土地利用/覆被变化在很大程度上影响着地下水的水质、水量，岩溶水质的变化能集中反映人类活动胁迫下岩溶含水层脆弱性程度的增加。以典型岩溶单元--贵州普定后寨河流域为例，分析了流域水文地质背景下的岩溶含水层本质脆弱性，结合流域地下河水近20年的水化学资料，分析了含水层脆弱性对土地利用变化的响应。结果显示：土地利用/覆被变化、农业活动、城镇建设及居民活动都对地下水质变化有明显影响。因此，调整土地利用结构，恢复岩溶植被，改善生态环境是保护和改善岩溶水资源的重要途径。

VULNERABILITY OF KARST AQUIFERS IN HOUZHAI RIVER BASIN AND ITS RELATIONS WITH LAND USE CHANGE

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.