| In recent years, rapid industrialization and urbanization accelerate the deterioration of water environment, coupled with the deviation of water management concept and lack of understanding of the water environment function, all kinds of water environment problems intensify, urban river are facing serious problems. This paper selected the typical urban river Bahe River Basin as the research object, grasped the basic information of research area, and extracted the terrain and water features of the basin under the GIS platform based on SRTM_DEM data with a resolution of 90m. This paper used ENVI software to extract basin landuse types from the TM image with a resolution of 30m, accessed to relevant information for basin soil types and rainfall data, established basin CN value statistics and verified the applicability of SCS hydrological model in the basin. At the same time, we used the water quality survey data from 2014 to 2015 in the basin as the foundation, applied WASP model to simulate the change of water quality index NH3-N and DO, and we set different types of scenario simulations based on the present situation simulation of water quality. Finally, we combined the extraction information and water quality simulation results, and knew about the terrain features and water quality pollution distribution characteristics of Bahe River Basin, and planned landuse proposals and water quality improvement suggestions.The area of the slope less than 25 degrees in Bahe River Basin accounted for 87.12%, flat ground accounted for 56.25%, eastern slope was the smallest, only accounted for 8.43%; In terrain statistics, the small undulating mountain accounted for 31.98% of the total area and mainly distributed in the southeast. The range of variation for basin surface roughness was 1～1.9. The extraction threshold of river was determined for 3000, river network were divided in 42 watersheds and 9 sub-basins according to the distribution characteristics of the river, and the sub-basins area error range is between 0.07% and 0.95%, accuracy of extraction results were high.By supervised classification, the types of landuse in Bahe River Basin were divided into woodland(27.86%), grassland(27.41%), cultivated land(24.21%), urban and rural residents land(12.40%) and water(8.12%). Basin soil was mainly in the class B and C, CN values’range was 68.88～88.16 in average level (medium moist condition), combined with rainfall data in a year, SCS hydrological model was applied to simulate the rainfall runoff of the basin, and the qualified rate was as high as 80%.We divided the river in 14 segments for the simulation analysis of NH3-N and DO, and DO values of all segments were higher than 7.4mg/L in a year and meet water quality standard. NH3-N values were different in segments, segments in the upstream can not meet the class Ⅱ and Ⅲ water quality standards in the wet period, NH3-N value of the 10th segment in the midstream was above 0.5mg/L throughout the year, it can not meet water quality standard, NH3-N value of the 12th segment in the downstream was as high as 5.6mg/L in the dry period. The simulation results were as the foundation, we set three scenario simulations for the pollution load reduction, boundary conditions change and optimization of hydrological conditions.Based on the above research results, we analysised different landuse directions and the characteristics of river pollution, put forward corresponding suggestions and opinions, and provided a basis for the Bahe River Basin water resources management, and made the foundation for digitized management research. |
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