Simulation And Evaluation Of Waihai Lake Water Quality Improvement Effect In The Water Diversion Project In Central Yunnan

Dianchi Lake is a typical plateau wide and shallow lake and is divided into two parts by the dam in the north part.The North part,which is commonly known as the Caohai Lake,takes an area of 10.8km2.The South part,commonly known as the Waihai Lake,is 298.7km2.Waihai Lake,as the main part of Dianchi Lake,carryies important tasks such as the city water supply,industrial and agricultural water supply,water storage,flood control,tourism and so on.With the development of local economic and the increacment of urbanization,the sea absorbs more waste water induced by city development,as a result,the lake water quality from the level ? degraded to level worse V.In order to solve the water pollution in Dianchi Lake,six major regulations have been carried out,which are "river regulation,Interception of the lake,Agricultural and rural non-point source management,Ecological dredging endogenous governance,Ecological restoration and construction,Outflow watershed and water saving".All these regulation take effects and slowing the deterioration of water quality in the Dianchi Lake.Especially the replenishment project applied in the Niulan River-Dianchi Lake in September 2013,the water environment ecological capacity increased,water quality got improved and transversed from the level worse ? to level ?.As Preliminary project of water diversion project in Central Yunnan,the results showed that the inter-basin water transfer project work out apparently.We can see that inter-basin water transfer project is an accurate restoration project to improve the water environment of Waihai Lake,and is an effective way to improve the water quality.At present,the governance of the outer shore of the Dianchi Lake is in a harsh time,and six projects have been fully implemented.However,it's difficult to achieve the governance objective,due to the limited water replacement effect,as wide surface of the lake and a lack of available water.During the" 13th Five-Year Plan"period,Yunnan Province will focus on water quality improvement and ecological restoration,speed up the project of the water diversion,continue the water recharge project of the Dianchi Lake,combined with the Niuban River-Dianchi Lake water replenishment project.Based on the above research background,this thesis focus on seeking ways of drainage scheme set up in Kunming section(diversion port,outlet),and optimizing the configuration of water diversion in order to achieve the best improvement effect.Besides,numerical models have been applied to predict the ecological restoration effect of ecological replenishment.Main conclusions have been achieved as follows:(1)The single-port drainage scheme(Haikou River)drainage has an advantage over the two-port drainage scheme of Shuangkou(Haikou River + Haigeng control gate),and the single-port drainage scheme can improve the water quality of Waihai Lake water significantly,CODMn,TN and TP can be improved by 48.7%,11.8%and 20%respectively.The two-port drainage scheme can improve the three index by 25%,3.8%and 5.7%respectively.The CODMn has the best effect,followed by that of TP and TN;(2)The location of the outlet and the size of the diversion has a directly affect on the dynamic characteristics of the lake,especially on the area near the outlet and the outlet;(3)Increment of outlet of the north lake can cause flow from the south to the north,leading to Waihai Lake water flow backward,pollutants migration from the north to the south can be stopped.However,the flow spread along the shortest distance "take the shortcut",the water flows out from the nearest export,the time stay in the lake becomes shorter,which is not conducive to water circulation and replacement,and is likely to cause dead water area in the lake;(4)Changing of the drainage routine makes a small influence on the water dynamics of Waihai Lake.Water diversion may has a significant effect on water hydrodynamic samll water areas.It is envisaged that when single-port drainage scheme is applied in water diversion project in Central Yunnan should achieve treatment standards,the two-port drainage scheme can be started to take the environment management of Caohai Lake water into account;(5)Mike21 model is applied to construct the two-dimensional hydrodynamic and water quality coupled model of Waihai Lake.Effect of ecological water replenishment project can be reflected accurately,diffusion pollutants which can reflected accurately.Therefore,it is reasonable to apply the two-dimensional hydrodynamic and water quality coupled model in the Dianchi Lake treatment.