Water Quality Assessment And Prediction In The Upper Reaches Of The Zhanghe River

In recent years,with China's economy maintains rapid and steady growth,China has already jumped to become the world's second largest economy in 2010.However,while the economy is growing,the quality of the water environment is getting worse.The current water pollution problem has seriously restricted the sustainable development of China's economy and society.The Zhanghe River,which flows through the three provinces of Shanxi,Hebei and Henan,is a river with multiple drinking water sources,and its upstream water quality is particularly important.In this paper,the grey relational evaluation method based on combined weighting and the seasonal Kendal test method are used to evaluate the water quality and trend analysis of the upper reaches of the Zhanghe River.And the BP neural network model is used to predict the water quality,which provides a scientific basis for policy makers to understand the water quality and development status and to formulate relevant protection policies.The main research of this paper is as follows:(1)This paper collects and collates the water quality monitoring data of the Matian,Hezhang,Three Provincial Bridge and Guantai sections of the upper reaches of the Zhanghe River from 2012 to 2016,reviews relevant literature on water pollution in the upper reaches of the Zhanghe River,and accords to the water quality characteristics of the river,seven indicators including dissolved oxygen,Permanganate index,ammonia nitrogen,total nitrogen,total phosphorus,Five-day biochemical oxygen demand and fluoride were determined as research object.In the grey relational theory,the analytic hierarchy process and the entropy weight method are introduced to combine the weights of each index to comprehensively evaluate the water quality.The evaluation results of the four sections show that the water pollution in the upper reaches of the Zhanghe River is relatively light from 2012 to 2016,and the water quality is generally above Class II water,and the water quality is good.(2)In this paper,the spatial and temporal variation trend of the water quality indicators in the upper reaches of the Zhanghe River was analyzed,and the PWQtrend2010 software developed based on the seasonal Kendall test principle was used to analyze the five-year trend of the seven indicators in the upper reaches of the Zhanghe River.The results of four sections showed that there was no significant change in permanganate,biochemical oxygen demand after five days and total phosphorus;total nitrogen showed a significant downward trend;ammonia nitrogen and fluoride showed a highly significant downward trend;dissolved oxygen showed significant in the Matian and Guantai sections respectively rising and falling trends.(3)This paper uses MATLAB software to establish a BP neural network water qu ality prediction model based on improved algorithm.Forecasting the water quality stat us in 2020 based on 2016 as the base year,the results shows that the water quality of t he Matian,Hezhang,Three Provincial Bridge and Guantai sections is generally within the Class I water standard,but it is worth noting that the single indicator of total nitro gen exceeds the V standard and the pollution is serious.