Research On The Karst Growth Characteristics And Karst Water System In Dam Area Of QiZong Hydropowerstation

The station is located at the boundary of Diqing and Lijiang in Yunnan Province at the junction of the Jinsha River, which is one of the most important stations at the middle reaches of the Jinsha River.The Power station's normal water level elevation is 2150m, the dam is about 165km long and the total storage capacity is about 17.737 billion m3, it is an alpine valley type dam.The Dam area is located in Weixi city of YunNan province,whose climate is sub-thermal or the mountain plateau temperate monsoon,the regional water system developed,the exposed strata are mainly limestone,dolomite,schist and phyllite, the aquifer and the Impermeable layers are separated each other. The dissoluted porosity and caves are developed there, It may cause the water leakage in the reservoir after the water accumulation and have an effect on the beneficial result of impoundment. Therefore, it have an good meaning to research the karst characteristics of dam area.According to the Karst developed conditions of QiZong Hydroelectric Power Station in the inspection process,in which the engineering geological mapping, surveys, drilling, tunnel surveys, as well as a large number of hydro-geological investigation and analysis of water chemistry tests were used.In this paper,on the basis of a large number of geological background information and research a number of exploration means to gain the information and data. The karst areas of the site characteristics and control factors and the characteristics of karst groundwater systems, karst development of the impact of the project several aspects of systems were analyzed, research results mainly in the following areas:(1) Study Area's physiognomy is the typical deep mountain canyon. the both sides of the river at dam site is the main Devonian, lithology is limestone,marble with the slate exposed extensive carbonate aquifer with impermeable layer was inter-layered structure.Folds and faults are more developmental.(2) According to field investigation, karst area is developmental,the main form of corrosion is karst holes and underground river and so on. The study area combined with the geological background analysis, the karst rock composition, faults, surface water conditions have a certain relationship together. (3) Based on the above analysis, these three typical karst water system ZongZa,JiRen and XiangGu are demarcated and the main watershed is bounded to the surface,the karst water system of water Chemical and isotopic characteristics of the results of the analysis showed that surface water and groundwater are relatively rich in Ca²⁺ and HCO₃^-, various types of water supplies are derived from the atmospheric precipitation, karst recharge Stephen elevation elevation higher than the supply of surface streams that have water to karst springs Since the higher elevation of the deep recharge of groundwater with mixed. Balanced use of water points karst water system to verify the delineation of borders is reasonable, the district concluded that the development of karst water system is not strictly restricted by the surface watershed.(4) Through the analysis of the possibility of occurrence of karst seepage analysis of the dam, the proposed dam site selected is not the development of karst valley, the foundation will not have a clear leakage; the area of the upper and lower dam site near the dam axis, there are on the right bank of the Jinsha River thin the watershed have the smaller the amount of leakage and the impact of project construction is not big, but it still need to be taken some measures to prevent the leakage.