Study On GIS-based Scenic Lake Water Quality Management System (SLMGIS)

In the context of the China's strategic decision of vigorously promoting energy-saving and emission-reduction, building a resource-saving and environment- friendly society, urban construction, especially the promotion of green building and green settlement, gets the quick increase of the quantity of scenic lake. Reuse of reclaimed water challenges water quality management. In addition, most of scenic lakes are polluted seriously. In response to the above problem, a GIS-based scenic lake water quality management system (SLMGIS) was developed. First of all, the water quality model was built according to the characteristics of scenic lakes and management demands, coupled with hydrodynamic model EFDC in order to get three-dimensional simulation of hydrodynamic and water quality. Then the coupled model was calibrated and validated with water quality data of Minzhu Lake. Based on the coupled model, SLMGIS was constructed on the temporal GIS, storing, dynamic visualizing and analyzing of four-dimensional space-time data of hydrodynamic and water quality, and watershed-scale of pollution sources and water quality management could be achieved. At last, LJH-SLMGIS was developed. The system can be used to dynamic visualize, watershed analyze, pollution sources manage, water quality forecast, and design and effect predict of water quality guarantee measures.Based on the published model researches of lake and reservoir water quality, a scenic lake water quality model was constructed, which adapt to scenic lake characteristics and management requirements. The model included nine state variables and five subsystems. The operating results of three kinds of artificial water quality protection measures, plant floating bed, fountain and water-falling and affect of sediment were simulated by making them the water quality boundary. Control equations of the model were discretized by finite difference method. The model was linked with hydrodynamic model EFDC by hydraulic file. Then, the quality model software programmed in object-orented language C++ on Microsoft Visual C++ platform to get three-dimensional simulation of hydrodynamic and quality. The water quality model was constructed separating with hydraulic model and combined applied with it. In this way, hydraulic simulation can be done or not according to the situation and the decision-making efficiency can be improved. From the above mentioned, the coupled model provides technical support for scenic lake design and water quality prediction. The model was verified based on water quality monitoring data of Minzhu Lake. Model parameters values were calibrated by water quality monitoring data of high-temperature and rainy season. Model results were verified by the data of low-temperature and dry season, which confirmed the coupled model can successfully simulate and predict water quality of scenic lake. Then, a numerical experiment was experimentized by the model to discuss the implementation effect of three security measures of“source controlling”,“hydraulic cycle”and“source controlling and hydraulic cycle”. The results showed that source controlling reduced the concentration of pollutants, the hydraulic cycle improved the hydraulic conditions of water bodies, and combined of the two measures could effectively control the water quality of lake.A scenic lake water quality management system was established through the coupled model integrated with temporal GIS. The water quality model and GIS fully integrated, sharing one spatial database for two-way data exchange. Both of them tightly integrated with EFDC through spatial data conversion and hydraulic file. The software was developed on vc++ platform and used COM (Component Object Model-based) technologies, which got the function of simulation and meshing of the EFDC and water quality model, the function of display and query of velocity field and concentration field, and spatial analysis of GIS. For the data storage strategy of the system, netCDF file was used to store results of simulation to achieve the storing, dynamic visualizing and analyzing four-dimensional space-time data of hydrodynamic and water quality, and watershed-scale of pollution sources and water quality management. Therefore, technical support to control and management of scenic lake water quality and sources was then provided.LJH-SLMGIS (Longjing Hu SLMGIS) was developed. A three - dimensional digital model of the park was established. Watershed analysis, pollution analysis, division of calculation grid of the lake and dynamic visualization of simulation results were achieved by GIS. Then water quality after the park completed was predicted by the coupled model. Effect of water quality ensurance measure of“source controlling”was predicted and analyzed. At last, the evaluation of eutrophication was made by assessment method of comprehensive nutrition state index. In short, the application of the scenic lake water quality management system was validated and demonstrated.