The Study Of Water Environmental Characters Near Wudongde Hydroelectric Station And The Influence Of Station Construction On Water Environment

Hydroelectric projects are large-scale man-made engineering activities, which may produce larger influences. The paper, taking Wudongde hydroelectric station for example, analyzes groundwater infiltration flow field, possible changes of water quality and potential influences on environment after building the station through the investigation of groundwater and surface water environment character before building the station. Many methods are used such as geology-hydrogeology survey, hydrogeochemical technique, stable isotope analysis and so on. The paper uses these methods to investigate the characters of natural Hydrochemistry, Oxygen -Hydrogen stable isotope composition and water circulating systems. On the basis of these, do three-dimensional groundwater infiltration flow field numerical model analysis before and after building the station by using the software of Visual MODFLOW.Through each method , combining with synthetic analysis, it can include some main achievements as following:(1) The study area is located on the southwest alar of Fangjiashan syncline. The low-angle dip of stratum is 5—20° . The main outcrop stratum (dolomite rock of Zbd1) is crevice and solution crevice strong aquifer. The quartz conglomerate of P1 is relative water separation stratum. The interbed of sandstone and mudstone (T3-K) is structural and weathering crevice aquitard.(2) According to isotope analysis, the recharge source of surface water and groundwater is precipitate water. The multiplayer mutually independent groundwater systems are caused by the difference of water-bearing statum. The upper aquifer recharge is precipitate water. The under aquifer is recharged by high altitude precipitate water. The groundwater flows into Jingshajiang.(3) the mineralizations of study area are generally low than surface water. The highest mineralization is 443.40mg/L. The main Hydrochemical types are HCO3—Ca . Mg,HCO3.SO4 —Ca . Mg. The groundwater mineralizations are range from 283.9 to 845.5 mg/L and the type of hydrochemistry includes HCO3—Ca . Mg , HCO3 . SO4—Ca . Mg, SO4 . HCO3—Ca . Mg. The quantity of mineralization is influenced by the ion content of Ca2+, Mg2+, SO42-.(4) The software of Visual MODFLOW is used to carry through three-dimensional numerical model for groundwater infiltration flow field, which lays out the watershed between two sides of river valley and river valley, increasing zones of hydraulic gradient with high terrain fall and changes of water level field after building the station . The sudden increasing of hydraulic gradient in the location of dam abutment shows the cut-off function of dam, which makes water-free strata contain water caused by the raise of groundwater.(5) Water flow of local sections in the study area cuts the strata with pyrites, which increases SO42- ion content and mineralization and makes the water with strong acid. This kind of water has strongly crystal corrosion effect on building concretes of base foundation. The hydroelectric construction will influence the environment of study area, change river state of original Wudongde canyon, raise the humidity of climate and make originally single and lean biologic chain become polymorphism, which will bring the economic development of hydroelectric area to the extent.