Hydrogeological Conditions Of Jiuzhaigou Area And Chenglan Railway Impact Studies On The Regional Groundwater Environment

The Railway from Chengdu to Lanzhou, starts in Chengdu, traverses the Jiuzhaigou, and extends to the hadapu station of the Railway which is from Chongqing to Lanzhou, and further, the two railways constitute the passenger and freight's main channel, which would form the national railway network in the Northwest and Southwest Regional.That the ChengLan railway is constructed is both conducive to the needs of economic development in developed regions, and improves the efficiency of development and utilization of regional tourism resources. To minimize the impact on vegetation of the surface, and to retain the rare wild animal's ecological corridors in the northern region of Minshan,such as giant pandas, the construction of the Chenglan railway in Jiuzhaigou will most use tunnel through the mountain.The Chenglan railroad traverses the Huanglong scenic area, Jiuzhaigou ditch scenic area, the Minjiang River source water protectorate and the west of ShenXianchi scenic area, and the distance is 80.038km, which have 8 tunnels in the section,moreover,the 8 tunnels'total length is 45.768km, accounts for 57.2% of the planning to construct railroad.Jiuzhaigou area is typical Mountainous Fragile Eco-regions in western China, which have the group of the natural landscape which give priority to Jiuzhaigou Scenic Area which is World Heritage Site. In order to effectively protect and improve the landscape and enhance the landscape value of the ecosystem, and promote social and economic sustainable development, it is formulated strict regulations in scenic area, such as engineering construction is prohibited in the areas within a 7 km distance from Jiuzhaigou scenic area. However,The tunnel construction will produce a certain negative effects to groundwater environment, which may make the river dry up, or make the area of pools zone reduce, or make the wetlands disappear, or make the native landscape be destroyed, or make the birds, fish and other wild animals lose the breeding sites, thereby affecting the development of the regional pillar industrie which is tourism.In this thesis, I take Jiuzhaigou area in the north plateau of the Western Sichuan as the research background, according to the research results of the predecessor and the geology﹠ hydrology geological investigation in the field, I will discusse hydrogeological conditions of the research area, and divide aqueous system of the research area, and analyze the hydraulic connection between the tunnel area and the core of the scenic area,and evaluate the negative effect of groundwater environment from the tunnel engineering.Through the generalized analysis, the main conclusions of this thesis are as follows:(1)Appearing stratum in Jiuzhaigou area is the Qinling stratum area of Kunlun Mountains, is from Silurian system to Triassic system and Tertiary system,Quaternary system,but have the lacuna of Jurassic system and Cretaceous system. According to the Heye rift system, the Minjiang River rift system and the snowy mountain rift system, Jiuzhaigou area is divided into Motianling district of the western Qinling stratum district and Jinchuan district of the Maerkang stratum district. However,the stratum in the area where the Chenglan railway traverses belongs to the Jinchuan area,whose main lithology is sandstone, slate and phyllite, and whose karst is not developed.(2)According to the local lithological characteristics, the groundwater hydrodynamic characteristics and the type of storage space, the groundwater in Jiuzhaigou may be divided into the loose Quaternary rock pore water, the bedrock fissure water and the carbonate rocks karst water. The Chenglan railway lies to the west of the survey region,whose main lithology is sandstone, slate and phyllite,and whose groundwater is bedrock fissure water.(3)The main hydrochemistry type of groundwater in Jiuzhaigou is HCO₃^-Ca, and next is HCO₃^-Ca·Mg and HCO₃^-Mg·Ca. The natural water's isotope analysis in the entire district indicates that the surface water and groundwater originates from the mospheric water. The hydrochemistry type of groundwater in the tunnel area is HCO₃^-Ca.(4)JiuZhaigou area should be divided into two first-level groundwater systems, for instance, Minjiang River water system and Jialing River water system, and 12 second-level groundwater systems, for instance, BanDanggou water system, XiaRike water system, ShenXianchi water system, GaWagou water systema, ReMoke water system, Jiuzhaigou water system, YangDonghe water system, Minjiangyuan water system, Zhanna River water system ,Fujiang River water system ,Minjiang River water system(from Chuanzhushi to Shilixiang) and Huanglong water system. The Chenglan railway passes through the Minjiang River and Jialing River watershed, and refers to Minjiang River water system(from Chuanzhushi to Shilixiang), YangDonghe water system, ReMoke water system, GaWagou water system, BanDanggou water system. Whether or not there is the hydraulic connection between the tunnel area and water system in the core of the scenic area, it don't have no impact on the core of the scenic area from tunnel construction.(5)According to the geological environment and the hydrogeological conditions, I predicte water inflow of the tunnel, and use groundwater environmental assessment indicator system of negative effect to analyze in the tunnel construction. According to the evaluation results,the effect from the tunnel construction which is from Hongqiaoguan to Yalongnari in the Chenglan railway to groundwater environment in the tunnel is between weak and moderate. It can be seen that it has less impact on the groundwater environment of the tunnel area and the local natural ecosystem when the tunnel is constructed.