Research On Ecological Risk Assessment For The Drainage Basin Of Nanliujiang In Guangxi

Nanliujiang is the largest river independently flowing into the sea in Guangxi. Inthe drainage basin, its social population, economic growth and agriculturalproductions have held a significant status in Guangxi. Nanliujiang is located in thelow latitudes of China’s South-East coastal areas in Guangxi. Under the influence ofmonsoon and tropical cyclones in China’s South-East coastal area, the rainfallcapacity is rich and it is easily to suffer from the flood disasters in summer.Meanwhile, it is frequently to experience drought in spring and autumn beca use thespatial and temporal distribution of rainfall is uneven. While the population andeconomy is growing, a series of environmental problems are arisen such as waterpollution of drainage basin, air pollution, etc. People pay more and more attentions tothe ecological environment problems in the drainage basin of Nanliujiang. Therefore,the author takes this opportunity to make the ecological risk assessment in thedrainage basin of Nanliujiang. On the basis, the masses will have an in-depthunderstanding on the ecological risk of drainage basin while this paper also providesthe evidence for the decision of ecological risk management.In the paper, the literature method is adopted to analyze the relevant theoriesabout the ecological risk assessment such as the theory of natural science, ecologicaltheory, the theory of natural disasters, and the theory of environmental pollution.According to the actual situation of the basin, ecological risk assessment ofNanliujiang basin is based on five elected risk factors including flooding disasters,drought disasters, water pollution, waste gas pollution and solid waste pollution.Through the analysis of a single risk factor, the district or county (city) is counted as astatistical unit. The inverse distance weighted interpolation method (IDW) is appliedto determine the data of the ignorant zone; Min–Max method is applied to achievethe standardized management on the results obtained from the interpolation method.On the basis of a single risk factor, the method of analytic hierarchy process (AHP) isapplied to construct the judgment matrix and calculate the weight of each single riskfactor. The ecological risk assessment model is used to make the comprehensiveevaluation of the ecological risks in the basin. According to the comprehensive ecological risk assessment results, the ecological risk levels of Nanliujiang basin areclassified into low risk area, relatively low risk area, medium risk area, relatively highrisk area and high risk area. Thereby, it is available to analyze the spatial distributionof each risk area. Based on the county scale, the ecological risks in each district orcounty (city) are analyzed. According to the characteristics of five risk areas, thecountermeasures of the ecological risk management are proposed for the different riskareas.