Study On The Change Of Karst Groundwater In Houzhai River Basin And Its Relation To Land Use

The fissure and conduit are well developed and interconnected in karst aquifer due to intensive corrosion. Finally it has formed "double-layer structure" in karst areas. The groundwater moves and stores in subterranean fissure or conduit. There are so many fissures, conduits, swallow holes and shafts in karst areas that the karst aquifer is more sensitive to land use change.This thesis picked up a typical karst area, Houzhai river basin in Guizhou province, for field investigations, surveys and collecting previous data and new samples for experimental analysis in the laboratory. On the basis of previous research results and by means of the systematic analysis, the change of karst groundwater in Houzhai river basin and its relation to land use are approached.The Houzhai river basin locates on the divide of Changjiang river and Zhujiang river. The karst landscape are intensively developed there. It is also because there are so many swallow holes and shafts in this area that most of the heavy rainfall enter the aquifer via them rapidly. And the groundwater resources are plentiful. The karst aquifer is more vulnerable than that of non-karst areas. And the water quality is affected by land use change to a large extent. Most of the mountains are covered by bared rock due to deforestation. Soil erosion is easily triggered, both because limestone soil are typically thin and because the open joint systems facilitate the washing underground of soil material. It caused increased sediment load and contamination such as inorganic fertilizers or organic pollution. The content of Ca2+, Mg2', Cl~, SO42", HCOj" and the total hardness have rised during the last years. The agriculture activities give rise to nitrate content in groundwater. Based on the factual data of land use change and the change of groundwater chemistry from 1981 to 2002, we find that the water quality is more worse than before and will be even worse because of the rock desertification and unreasonable land use.In order to realize the sustainable development, we must re-arrange the unreasonable patterns of land use to protect the karst groundwater resources. Ecological rehabilitation or reafforestation is required to protect the water supply. In peak cluster-depression, we should exploited the stereo-ecological agriculture model. It can bring us more economical benefit and protect the environment. A better planning for village village, town or factory should be made to prevent the groundwater from pollution.