Study of Some Problems on the Development and Protection of Fracture-karst Water Resources in North China
Liu Jianli Zhu Xueyu Qian Xiaoxing Dept. of Earth Sciences, Nanjing University, Nanjing, 210093; Faculty of Civil Engineering, Hehai University, Nanjing, 210098
Water resources are in shortage in China, especially in northern China. As surface water often dries in spring and summer, fracture-karst water becomes an important source for supply.Karst in China can be divided into three types: karst in northern China, karst in southern China and karst in western China. Karst in northern China is not a typical karst but a fracture karst. The aquifers are networks of solution fractures, fissures and openings. Some wide solution fractures become strong runoff zones. The aquifer has a large coefficient of transmissibility and small storage capacity. It is strongly heterogeneous and anisotropic. Fracture-karst water flows at a high velocity and so the transport of contaminants is a advection-dominated problem. The amount of fracture-karst water depends on the condition of recharge. As the storage capacity is small, the fluctuation of water level in wells is greater than that in porous aquifer.According to the previous data, some authors suggested that the depths of wells in a fracture-karst aquifer should be less than 100-300 m. In the Zibo area we found that some deep wells (at depths 500-700 m) had also great pumping rates and the yields reached 3000-5000 m3/d. It may be related to the palaeokarst in the geologic history.Fracture-karst water is vulnerable to contamination and the environment is fragile. Therefore, factories, plants, dumps and landfills should not be placed on the recharge areas of fracture-karst water. When making land planning, considerations should be given to protect cultivated land as well as groundwater resources. Compared with porous water both the velocity and the distance of plume movement in fracture-karst water are much larger. The curves of contaminant concentrations versus time in fracture-karst wells often fluctuate greatly, which are different from those in porous water wells. Pumping is one of the best methods for remediation. If the area of the groundwater basin is not large, we can renew contaminated water by pumping. If it is large or the pollution sources cannot be moved out, a hydraulic capture zone will be a suitable method for remediation.
【Fund】： 国家自然科学基金(编号49772162);; 博士点基金(编号1999028421)
【CateGory Index】： P641.8
【CateGory Index】： P641.8