Karst Groundwater Abundance Analysis In Jingxi Region Of Guangxi

Karst water is groundwater existed in fissures of soluble rock layers and karst caves.Although karst coverage area worldwide only accounts for 12%of global land,karst water provide resources for a quarter of the world population,and it has reached 100 million in China alone.In previous researches,traditional field measurements were mainly used to investigate storage conditions and distributions of karst water in carbonate areas.However,due to the high complexity of karst water,its occurrence and movement are still unclear.Especially,there are difficulties lie in the analysis of karst water enrichment for border regions where are hard to research using traditional investigation.With strongly developed karst and rich karst water resources,our research area Guangxi Jingxi is located in China-VietNam border.It is a key area for karst water migration and abundance.Based on deficiencies in previous studies,this paper utilizes RS and GIS technology to extract information about water-bearing formation,geological structure,topography and vegetation coverage.Then,we obtain water storage relationships and use stratification analysis method to carry out water enrichment assessment,in order to understand karst water abundance regularity better and provide scientific basis for rational utilization of groundwater in Jingxi or similar areas.The major conclusions are summarized as follows:1.Based on structural mechanics analysis,karst water storage conditions in Jingxi are analyzed using fold and fault interpreted by remote sensing.Our results show that the main water-conducting structures include Jingxi-Mengma arc reverse fault,Hurun-Heishuihe strike-slip fault,Huize normal fault,Fulong-Yuewei normal fault,Dizhou syncline,Yandong svncline,Hurun-Yuewei anticline,etc.On the contrary,the main water-blocking structures are Longlin reverse fault,Wuping transverse fault,Tunpan arc reverse fault,Huadong anticline,Dizhou anticline,Nanpo-Jingxi arc fold belt.etc.Karst water tends to be abundant in the intersection of folds,faults as well as limbs of anticlines and synclines,especially limbs of anticlines.Because the axis of folds in study area is distributed as non-karst or weak karst rock formations,karst water is not enriched.Whereas,karst water is abundant in the composite part of fold limbs and faults.Among them,Jingxi-Mengma arc thrust fault from NE to EW is cut into 5 segments by a series of northwest faults?According to variation of groundwater volume,it is inferred that the fifth Mengma-Jingxi arc thrust fault segment controls the confluence of underground river and is a water-conducting structure.Furthermore,the connecting test indicates that underground exits,entrances and pipelines are developed within the 300 m buffer zone of Huize normal fault;and there are groundwater pipeline in Fulong-Yuewei normal fault crushed zone,which is a water-conducting structure.2.We established a karst water abundance evaluation model in Jingxi using GIS spatial analysis technology.The evaluation factors include water-bearing formation,geological structure,topography(relief amplitude and slope),vegetation coverage,surface water density.The model is given as follow:S=0.4843*G1 +0.2653*G2+0.0633*G3+0.0628*G4+0.0343*G,5+0.0900*G6Where S is karst water abundance index and G,(i = 1?2?3?4?5?6)is normalized factor of water-bearing formation,geological structure,relief amplitude,slope,vegetation coverage,surface water density.3.Practical application to the model is carried out and water enrichment zones are devided,which provide scientific basis for development and utilization of karst water in Jingxi.Karst water is most abundant in northwest Guole-Kuiwei,central Ludong-Xinwei-Longlin-Rongluo,Huadong as well as southern Yuewei,and total water volume is predicted to be more than 50L/S.While the karst water abundance in eastern Wuping-Tongde,southeastern Dizhou-Hurun-Xialei is gradually decreased.The amount of karst water in Kuiwei,northwest Nanpo,northern Wuping,eastern Tongde,Tunpan and northern Anning is the poorest,and water volume is predicted to be less than 10L/S.Our experiment also shows that karst water storage in Huadong-Yuewei area is better.,which verifies the karst water abundance evaluation model in Jingxi is reliable.