Research On The Early-warning Mechanism Of Water Environment Carrying Capacity Of Baiyangdian Based On BP Neural Network

Xiong ’an New Area was established as a state-level new area in 2017,Baiyangdian is the largest freshwater lake in North China Plain,located in the core area of Xiong ’an New Area.Based on the analysis of the water environment of Baiyangdian Lake,this paper constructed the pre-warning index system of water environmental carrying capacity of Baiyangdian,determined the index threshold and classification standard,and then established the BP neural network pre-warning model of water environmental carrying capacity.Through the BP neural network to evaluate and analyze the water environmental carrying capacity of Baiyangdian.The main research contents and results are as follows:1.Evaluation of Water Environment in Baiyangdian Lake.Based on the historical data from 2012 to 2018,the water quality,water environmental capacity and eutrophication status of Baiyangdian were evaluated.The evaluation results showed that the overall water quality of Baiyangdian Lake was poor;As the standard of water quality control is III,the chemical oxygen demand of the five state-controlled sections of Nanliuzhuang,Shaochedian,Quantou,Caiputai and Guangdianzhangzhuang all exceeded the standard over the years,the proportions of excessive ammonia nitrogen and total phosphorus were 20 % and 83% respectively.The chemical oxygen demand and ammonia nitrogen water environmental capacity of Baiyangdian were positive over the years;The total phosphorus water environmental capacity was negative in 2012 and2013,and the water environmental capacity was positive from 2014 to 2018.The comprehensive nutritional status indexes of Baiyangdian from 2012 to 2018 were 61.38,57.57,58.37,59.00,55.69,57.04 and 57.87 respectively.It was moderately eutrophic in2012 and mild eutrophication in 2013-2018.2.Construction of pre-warning index system for water environmental carrying capacity of Baiyangdian.By using frequency statistics method to screen out 38 common indexes,and select three other characteristic indexes;12 pre-warning indexes of water environmental carrying capacity of Baiyangdian were determined by principal component dimension reduction analysis of common indexes and characteristic indexes.The pre-warning indexes were classified into four sub-systems: population and economy,water resources,water environment and water ecology.Among them,population and economy sub-systems were per capita GDP,tourism as GDP proportion,textile sewing and leather industry as GDP proportion;Water resources sub-systems were water level,water consumption per ten thousand yuan gdp,annual precipitation,groundwater exploitation rate;Water environment sub-systems were ammonia nitrogen concentration,treatment rate of industrial effluents,chemical oxygen demand concentration;Water ecosystem sub-systems were eco-environmental water use rate and forest and grass coverage rate.3.Classification of pre-warning index for water environmental carrying capacity in Baiyangdian.According to the degree of influence on the water environmental carrying capacity of Baiyangdian,each pre-warning index was divided into five grades.Combined with the mathematical statistics control chart method and regional development planning,the threshold value of the index and the corresponding standard value of each grade were determined,which corresponded to five states of water environmental carrying capacity : weak bearing,weaker bearing,medium bearing,stronger bearing and strong bearing.4.Evaluation of water environmental carrying capacity of Baiyangdian.Through the BP neural network pre-warning model of water environmental carrying capacity,the comprehensive water environmental carrying capacity index from 2012 to 2018 was calculated.It was found that the water environmental carrying capacity of Baiyangdian changed from weak load to strong load state with the passage of time.From 2012 to2016,it were the orange overload warning level,and it was the yellow critical overload warning level in 2017 and the blue critical overload warning level in 2018.5.Pre-warning assessment of water environmental carrying capacity in Baiyangdian.Through the BP neural network pre-warning model of water environmental carrying capacity,the comprehensive water environmental carrying capacity index from 2019 to 2025 was calculated.The results showed that the water environmental carrying capacity of Baiyangdian are generally good,and the water environmental carrying capacity shows an increasing trend with the passage of time.It is the yellow critical overload warning level in 2019,and it were blue critical overload warning level from 2020 to 2025.