Numerical Simulation For Wind-Driven Current And Water-transfer-period Water Quality In Nansi Lake

The water resource distribution in our country has a characteristic of rich in south and depletion in north, the shortage and the imblanced distribution of water natural resources seriously hampered the healthy development of the economy and society, and to cause a decline in the quality of the ecological environment, while the South-to-North Water Transger Project is an important strategic which can dispose the water shortage situation in north of China and achieve the optimal allocation of water resources.The eastern first phase of the South-to-North Water Transfer Project has been launched on December, 2013, marking the Shandong Province, the strategy of the “govern, use, protect” simultaneously various pollution control measures, such as small watershed comprehensive pollution control strategy to play a benefit, so that within Nansi Lake Water can achieve water quality requirements, but the water quality standards during the water situation is still not stable ignored.By SMS(the surface water modeling system environment simulation software)surface water simulation software, on the basis of the Nansi lake one over ten thousand topographic map(CAD), in consideration of the barrier action of plant,shoaly land and river channel on water transfer, Nansi Lake hydrodynamic and water quality mathematical model was built by Galerkin finite element method and the numerical simulation of the flow field of Nansi Lake before and after water transfer under different wind condition and the main environment water quality indexes of CODCr, TP are done. The research result shows the following conclusion:(1) Based on the basic situation of SMS surface water simulation software system, the establishment of a two-dimensional hydrodynamic Nansi quality mathematical model, the selection of boundary conditions and model parameters can be within a more realistic reflection of Nansi Lake water quality of the distribution,which the results have a certain reference value application.(2)Through simulation of hydrodynamic Nansi under non-diversion of wind action found: Nansi Lake mainly for non-diversion of the flow of wind, wind-driven flow is mainly affected by wind stress, lake topography and other factors; wind speeddetermine the scope of the raw wind circulation flow, wind speed, the greater the scope of its circulation; the decision of wind direction and wind circulation patterns flow.(3)In the normal design of Nansi Lake water hydraulic conditions, the average wind speed conditions, the effects of different wind direction of wind flow field Lakes is obvious. Even in extreme weather conditions(wind speed v=10m/s) conditions,only a small part of the regional circulation occurs in a wide area of ? ? the Lake District, and less influence. Thus, the effect of the wind on the water flow field Nansi small, which can ignore the wind stress.(4)During the first-stage normal project of the south-to-north water diversion,the outflow concentration of CODCr in the Nansi Lake can attain the third standard surface water quality standards, area where the concentration of CODCr reaches the third standard is about 86.74% of the superior Lake, while the subordinate lake all reaches the third standard. After controlling the sewage lake and the Hukou CODCr concentration slightly lower than the status quo of sewage, the water quality has been further improved in the Nansi Lake.(5)Nansi water under normal design of hydraulic conditions, the status quo of sewage conditions, about 82.75% percent of the regional concentration of T-P in superior of the Nansi Lake can attain the third standard surface water quality standards, while the outflow concentration exceeded; after controlling 83.83% percent of the lake area meet the standard, the superior lake concentration decreased 8% on average, under the status quo sewage conditions, the outflow, the lake and the main channel TP concentration can reach the third standard water quality standards, after controlling for the sewage water quality in the lower Lake has been further improved.( 6) Under the status quo and control sewage discharge conditions, the concentration of CODCr and TP concentration trends and the general law across the lake is basically the same, the TP concentration variation compared to the CODCr, the superior Lake appears more obvious than the subordinate.