Research On Regional Water Environment Risk Assessment And Early Warning Based On GIS

From 2012,China has established the first batch national Eco-city pilot in the country(town).However,the highly centralized discharge of domestic sewage and industrial sewage brought great pressure to the water environment in Ecological Industrial Park.And some special water environment pollutants were produced with introduced high technology.Therefore,it is urgent to study the current water environment.First of all,the risk level of water environment was divided into four levels,including no risk,low risk,moderate risk and high risk,considering to scientific,independent and comparable.And water environment risk assessment model was established coupling AHP and fuzzy theory.Secondly,the water environment risk assessment was carried on about the Shenzhen International Low-carbon City(SILC).It includes that(1)the water environment risk assessment was divided into three categories:nutritional status index,ecological status index and characteristic pollutants index.(2)16 points were selected to monitor the water environment by GIS.(3)11 indexes were selected as the comprehensive water environment risk evaluation index.(4)the water environment risk status of SILC was evaluated,combined with GIS and fuzzy comprehensive evaluation method.Finally,the riverbed activity coefficient ?,Degradation coefficient K of pollutants,dispersion coefficient D of pollutants were estimated.Then,a one-dimensional river pollutants diffusion model was established.The spatiotemporal diffsion law of pollutants in the Long-gang River was predicted,by combining model with GIS.The following conclusions were obtained through the study.(1)Ding-shan river was seriously polluted in residential area.In the upper reaches of the Long-gang River,the concentrations of TN,suspended solids and coliform are 11.71mg/L,29mg/L and 8.65 ×104,respectively,which results in serious pollution of water environment.Chun-zhi River was seriously polluted in flowing through the place.(2)By analyzing the water environmental risk assessment of SILC,The results showed that the nutritional situation was at high risk except Chun-zhi River upstream,The ecological situation was at high risk except Ding-shan River upstream and Chun-zhi River upstream,the characteristic situation was only at high risk in the upper reaches of Ding-shan river.The overall environmental risk in SILC was high.(3)In the high water period,the degradation coefficients of NH3-N,TN,TP and COD in Long-gang River were 0.195,0.183,0.181 0.210,respectively,and the diffusion coefficient was 45.9398.In the low water period,the degradation coefficients were 0.151,0.144,0.148,0.155,respectively,and the diffusion coefficient was 7.0243.(4)By predicting the pollutant transport in Long-gang River,the results indicated that the pollutant transport was mainly migration and diffusion during the high water period,the pollutant transport was mainly degradation during the low water period.Besides,the environmental harm caused by equal amount of pollutants in the low water period was far greater than that in the high water period.Meanwhile,persistent source of pollution makes the downstream at a high risk.