The Impact Research Of Water Diversion Tunnel On The Groundwater Environment Of Yanzidong Scenic Area

Water diversion project in Yunnan as a giant water diversion project aims at solving the serious shortage of living and industrial water in Yunnan. The water diversion line from the Jinsha river, passing through Lijiang, Dali, Chuxiong, Kunming, Yuxi,Honghe and other 35 counties(cities, districts). The proposed Dapozi tunnel of the water diversion line is located in Jianshui, Honghe state and near the Yanzidong which is a national scenic area and national AAAA-class tourist area of underground karst. The tunnel will lead to closure and drainage the recharge of the groundwater and the surface of spring, the reduce of the recharge water source and the pollution of tunnel inflow water will have influenced the gorundwater environment(water quantity and water quality) of Yanzidong scenic area.Therefore through study the tunnel site area and sensitive environment landscape to predict,evaluate the impact of groundwater environment caused by the tunnel during construction and operation periods,put forward reasonable protection measures to guide engineering practice and provide a scientific basis for construction of decision-making and protection of groundwater resources,meanwhile,it has great significance for provide reference of the technology and method to evaluate the same and similar groundwater environment impact of sensitive area.On the basis of date collecte of research area and field investigate, explain the hydrogeological conditions in this paper, qualitative analyze the impact on Yanzidong groundwater environment for tunnel project,take on the water balance analysis for the recharge source decrease of Yanzidong under the influence of tunnel construction, and in view of Visual Modflow 3D numerical simulation to predict the impacet of groundwater seepage field,then evaluate the water quality pollution of the scenic area caused by different construction plan by analytical method and 3D numerical simulation. Futhermore, give some reasonable construction suggestions of pollution prevention and some gorundwater protection measures during the tunnel operation period based on the above ananlysis result. The detail and main result of researching as listed below:(1) Dapozi tunnel crosses two karst hydrogeological units, terrain and geological structure complex and the total tunnel in karst stratum proportion of 66%. Yanzidong is located in the Triassic Gejiu Formation(T2g)schistose of limestone area. Lujiang has high cutting depth in karst area and leads to the formation of under stream cave in Datian mountain. It has been found that the under stream resource of Yanzidong apart from the Lujiang, partly supplied by the lateral flow of Karst groundwater in the north of Lujiang,the other supply is from the surface of spring through the ravine collectiong in the south of Lujiang.(2)The Pan mountain-Datian mountain hydrogeological unit of Dapozi tunnel longitudinal crossing is located in the south side of Yanzidong. The groundwate from the north side will be run off continuous and the surface spring through the ravine collectiong to Lujiang also be captured in the construction of tunnel. It wil give rise to the decline of groundwater level,ground water and wells and spring dry, reduce the underground river supply of Yanzidong.Meanwhile, the pollution source such as mechanical oil and waste slage be drived into Yanzidong scenic area with surface water when discharge the tunnel inflow water in process of construction, it will lead to the pollution of water quality.(3)Quantitative analysis is used to explain the impact on Yanzidong of water reduce in tunnel construction by water balance method.Meanwhile, the pollution source will be drived into Yanzidong scenic area with surface water, it will lead to the pollution of water quality, so calculate the water inflow of tunnel sectionⅠby using the analytical method and 3D numerical simulation. On the basis of arragement of the 1# branch tunnel and 2# branch tunnel also and the entrance of tunnel, predict the size of pollution source that discharged into Yanzidong according the 5 kinds of combination of construction which exist possibly. Futhermore, superiority-inferiority of each construction scheme and wastewater treatment measures be disscussed, the last provide scientific basis for construction, instruct the engineering application.(4)Tunnel will put into operating after construction completed, the groundwater seepage field will return to the unconstruction state gradually and the spring also supply for the under stream continuously. In the process of tunnel operation, the karst groundwater quality may be impacted by the pollution water, meanwhile, it is neccessary to monitor and treat the untreated and improper treated waste water for a long time that produced in the process of construction.Therefore,the important groundwater resource also should be protected in operation to ensure the scenic landscape tourism ornamental value and achieve the sustainable development.