Study On The Monitoring And Evaluation Of Nasi Lake Water Quality Based On Remote Sensing

South-to-North Water Diversion project is a cruicial infrastructure project to solve the severe water resource shortage in northern China. As an important water transfer path and storing lake on the east route of the South-to-North Water Transfer project, Nansi Lake influences the quality of the transferred water directly with its own water condition.The plan for the waster pollution control conducted is based on water monitoring. The manual water monitoring used widely at present has its born deficiency that cannot be conquered. Although precise analysis and evaluation can be achieved, it is still time-consuming, not cost-effective and labor wasting. Meanwhile the limited number of sampling and the frequency make the monitoring result far from reflecting the real condition of the entire water body exactly. However, Using Remote Sensing methods to monitor the water quality has many advantages such as being prompt, highly-effective, cyclical continuous monitoring etc, it can make up for the disadvantages of the traditional manual monitoring and simulation of water quality by mathematical model. Therefore, it is necessary for the planning of water pollution control at Nansi Lake drainage area to adopt remote sensing technology for water monitoring.Based on analyzing the domestic and foreign theory, technology and method of remote sensing water monitoring, Chlorophyll-a and Suspended solid are used as the monitoring indexes , and also the monitoring and evaluation of the water quality of Nansi Lake using the data of Landsat5 TM from China Remote Sensing Satellite Ground Station is demonstrated.Based on the investigation on current condition of nature, society and pollution at Nansi Lake drainage area, a plan is drafted for monitoring the water quality of the lake, meanwhile, remote sensing synchronization data of monitoring sites are preconditioned. Based on spectral characteristics analysis of water quality parameters and Pearson correlation analysis between the remote sensing data and monitoring data, the inversion model of Chlorophyll-a and suspended solid of Nansi Lake water was constructed and used for inversion and evaluating the Chlorophyll-a and Suspended solid of Nansi Lake. In addition, the eutrophication level and distributing rules of Nansi Lake are evaluated using Tropic State Index. The research results show as follows:1) The Chlorophyll-a concentration is within range of 0-60μg/L and 0-15μg/L in Up Lake and Down Lake, respectively, The Chlorophyll-a concentration in Down Lake is lower than that in Up Lak.2) The Suspended solids concentrations range from 0-60μg/L and 5-30μg/L in Up Lake and in Down Lake, respectively. The suspended solids concentration in Down Lake is lower than that in Up Lake3) Large area of the Nansi Lake is eutrophicated. The Eutrophication degree of Up Lake has been higher than Down Lake's, middle eutrophication phenomena has appeared in Large area of Up Lake. Large area of Down Lake has been in Oligotrophy and Mesotrophy degree, but the middle eutrophication phenomenon has appeared in northern area of the Weishan Lake.In conclusion, the Chlorophyll-a and Suspended solids concentration are high in Nansi Lake and eutrophication has appeared.