Studies On Characteristics And Carrying Capacity Of The Water Environment Near The Riverside In Three Gorges Reservoir

In the present dissertation, the environmental characteristics and theenvironmental carrying capacity of the water body near riverside in Three GorgesReservoir (TGR) are studied by means of theoretical analysis and numericalsimulation. To simulate the three-dimensional distribution of the side-discharges intoTGR, a numerical model called σ-Coordinate Multi-layer Model is developed, inwhich the σ-coordinate and layer-integrated are used along the vertical dimension fordealing with both the free water surface and the bottom topography. The model alsointegrates several numerical schemes with regard to Finite Element (FE) such asstreamline upwind Petrov-Galerkin FE, Edge-based FE and Object-oriented FE,which makes the model more suitable for complicated topography. On the other hand,hierarchy mesh combined with local time-step scheme is used to simulate the mixingzone, which has the advantage such as shorter storage, less floating point operations,higher numerical precision, etc. The results demonstrate that the present model isrobust and reliable for the water quality simulation in TGR with free surface, variedtopography, complicated bank and side-discharges.The second part of the dissertation investigates the impact of the slope angle ofbank on the wastewater distribution of side-discharges into the natural river, and ananalytical formula is brought forward as a result. The results show that the slopeangle has great influence on the distribution of the concentration which will decreasewith the increase of the slope angle following the hyperbolic law. Another fruit is thatan obvious three-dimension concentration will distribute when the slope angleexceeds 30 degree, and the simulation is subject to the three-dimension modeling.A detailed analysis is also included of the environmental characteristics and theenvironmental carrying capacity (ECC) of the water body near riverside in TGR.With the determination of permitting mixing zones in TGR, the permitting massloadings of pollutant is calculated from the dominating outfalls in Chongqing, Fulingand Wanzhou under conditions of different flow rate, different water evaluation anddifferent background concentration respectively. The minimum distance betweenoutfalls is also determined based on the impacting zone of outfalls located atupstream and downstream. Finally, studies on the temporal and special distribution ofECC and the impact of the dam on the ECC are carried out with results as below.Firstly, under natural condition, the ECC in TGR changes from season to seasonapparently although it nearly keeps constant in different regions. Secondly, the damwill reduce the ECC a great deal. For the spatial distribution, the reduction inWanzhou is the biggest and the reduction in Chongqing is the smallest. For seasonaldistribution, the reduction in dry season and rain season are the biggest and thesmallest respectively. Thirdly, the dam will change the distribution of ECC nearriverside. The changed ECC in Chongqing, Fuling and Wanzhou are sorted from thelargest to the smallest for spatial distribution. For seasonal distribution, the ECC inrain season, general season and dry season are sorted in the descending order. Thework and conclusions in present dissertation will provide a reliable technical supportfor both environment protection and environment management such as the allocationof wastewater outfalls, the evaluation of pollutant mixing zones, the selection of thecomputing model, and it is necessary to strengthened dynamics managementmeasures of water environment in TGR.