The Research On Safety Evaluation Of Nanjing Jiajiang Drinking Water Source Based On GF-1 Data

Jiajang River drinking water source is one of the most important drinking water source in Nanjing,and the water safety situation of this area directly affects the safety of urban drinking water.Based on GF-1 images,the safety of drinking water source was evaluated in Nanjing Jiajiang river from the aspects of water quality and environmental safety.In the aspect of safety evaluation of water quality,the estimation model of CODMn,TP and TN concentration was establish based on GF-1 data.The river water security was evaluated based on single indicators.In the aspect of safety evaluation of environment,a evaluation index system and model algorithm of drinking water source environment safety was established based on non-points source,fixed source and flow source risk.Finally,the security status of drinking water source environment was evaluated integrately.Main conclusions are as follows:(1)Water quality parameter estimation model was established.The ratio of remote sensing reflectance of band2 and bandl was used as the independent variable of CODMn concentration estimation model,the logarithmic fitting method was used to modeling,R2 = 0.7964.The difference of remote sensing reflectance of band2 and band3 was used as independent variables of TP concentration estimation model,the index fitting method was used to modeling,R2 = 0.5125.The remote sensing reflectance of bandl was used as independent variables of TN concentration estimation models,the logarithmic fitting method was used to modeling,R2 = 0.7732.Satellite-ground synchronous data was used to validate the model.As for the estimation model of CODMn,the mean absolute percentage error is 9.43%and the root mean square error is 0.28mg/L useing ground synchronal measured spectral data to validate.The mean absolute percentage error is 17.34%and the root mean square error is 0.51mg/L using the synchronal GF-1 data to validate.As for the estimation model of total phosphorus,the mean absolute percentage error is 14.88%and the root mean square error of 0.01mg/L useing ground synchronal measured spectral data to validate.The mean absolute percentage error is 18.19%and the root mean square error is 0.02mg/L using the synchronal GF-1 data to validate.As for the estimation model of total nitrogen,the mean absolute percentage error is 4.5%and the root mean square error issO.10mg/L useing ground synchronal measured spectral data to validate.the mean absolute percentage error 5.56%and the root mean square error is 0.1 1mg/L using the synchronal GF-1 data to validate.Temporal-spatial change of quality of intake water was analysesed by using GF—1 image of January 6,2014,on April 14,2014,June 11,2014,and until October 15,2014.0n the whole,CODMn concentration shows lower after rising trend and most of the area's CODMn concentration is below 4 mg/L in full-year except qinhuai xinhe river.There is no obvious change on total phosphorus concentration from the time,total phosphorus concentration is stable between 0.1?0.2 mg/L in most of the area for the whole year.Total nitrogen showed lower after rising trend from the time,then CODMn concentration is above 1 mg/L in most of the area's in full-year,it get 2 mg/L in the mutagenicity on January 6,2014.Analysis showed that the temporal-spatial change of water quality parameters is related to the factory sewage of qinhuai xinhe area and the change of water quantity of Yangtze river.In the aspect of safety evaluation of Water quality,most of drinking water source area,including three intake,reached the ? class water quality standards according to the evaluation results of CODMn concentration.Most of drinking water source area reached the ? class water quality in full year according to the evaluation results of total phosphorus concentration,the evaluation results shows that it has reached the standard of drinking water.(2)Drinking water environment safety evaluation index system was established by using nonpoint source,fixed source,mobile source types of risk source as the primary index.Then,GF-1 images was used for land use classification and risk source extracting,got the ratio of cultivated land of all levels of protection area,the ratio of urban and rural residents of industrial land,road length,channel length,and other information.The ground survey data was used to collect the wharf,pumping stations and factory at all levels in the protected area.And the risk index score method was made according to the actual situation of the protected area.Finally,the weight of all evaluation index was obtained by using the analytic hierarchy process(AHP),drinking water environment safety evaluation model was set up,drinking water environment security situation was evaluated comprehensively by using environment safety index(ESI).Drinking water environment safety index of Jiajiang river is 11.17 according to the results of January 10,2014,Drinking water environment safety index of Jiajiang river is 10.89 according to the results of December 24,2014.The results show that in 2014,environment security situation of Nanjing Jiajiang river has improved through the clean-up operation of relevant departments.