Analytical Evaluation And Prediction Research Of Water Quality In Sanmenxia Section Of The Yellow River

With a large population and a long history,the Yellow River Basin is also rich in natural resources and is an important water supply area in China.However,the Yellow River Basin is still facing many problems,such as the contradiction between water supply and demand and water environment risk,fragile basin ecology,and uneven basin development,etc.The ecological protection and high-quality development of the Yellow River Basin is still an arduous task.Scientific evaluation of the water environment status of the basin and its spatial and temporal variation characteristics is the basis for the prevention and treatment of the water environment in the basin.Based on this,the following work was carried out in this study:(1)Taking the Zaoxiang River,Yangping River,Hongnongjian River,and the main stream of the Yellow River in the Sanmenxia section of the Yellow River basin as research objects,six water quality evaluation indicators,including dissolved oxygen,permanganate index,five-day biochemical oxygen demand,ammonia nitrogen,chemical oxygen demand,and total phosphorus,were selected to analyze the water quality of the river through two dimensions of time and space,Combined with Mann-Kendall trend test,the changing trend of different water quality indicators for different rivers from 2019 to 2021 was tested,and then the UF_k value and UB_k value were used to determine whether there was a significant change in water quality and the time point of a sudden change in water quality.The changing trend of various water quality indicators for different rivers from 2019 to 2021 was obtained.(2)Through the combination of the CRITIC weighting method and entropy weighting method for the corresponding water quality indicators,using the single factor pollution index method,improved Nemero pollution index method,and improved fuzzy comprehensive evaluation method,respectively,the Zao Xiang River,Yangping River,Honongjian River and the Yellow River main stream Sanmenxia section of water quality conditions in 2019-2021 The comprehensive evaluation of water quality was carried out,and it was concluded that regardless of the single factor index evaluation method,the improved Nemero pollution index method or the improved fuzzy comprehensive evaluation method,the water quality conditions of different river sections in order from good to bad are:Sanmenxia reservoir section of the Yellow River,Lutai bridge section of the Zao Xiang River,Potou bridge section of the Hongnongjian River,and Zhangcun bridge section of the Yangping River.The improved Nemero pollution index method takes into account both the most serious pollution index and the water quality index with the largest combination weight,which is more accurate than the other two methods for scoring the water quality of rivers month by month and deriving the current pollution level of rivers.(3)The daily water quality monitoring data of the Sanmenxia Reservoir section of the Yellow River from May 2021 to July 2021 at the surface water automatic monitoring station in Henan Province was selected as the research object for water quality prediction.The variational mode decomposition(VMD)was used to denoise the river water quality data,and the Sparrow Search Algorithm(SSA)was selected to optimize the model parameters of the short-term and short-term memory artificial neural network(LSTM)and the support vector regression(SVR),respectively,At the same time,the VMD-SSA-LSTM model and the VMD-SSA-SVR model are constructed,and the two prediction models are analyzed.By comparing their different evaluation indicators,the better prediction effect model is determined.The analysis shows that by comparing the average absolute error(MAE),average deviation error(MBE),mean square error(MSE),and root mean square error(RMSE)of the two prediction models,it is concluded that the MAE,MBE,MSE,and RMSE of the VMD-SSA-SVR model are smaller than those of the VMD-SSA-LSTM model,indicating that the VMD-SSA-SVR model can be more accurate in predicting the water quality changes at the Sanmenxia section of the Yellow River.This study,to some extent,enriches the research on river water quality evaluation and water quality prediction models in the Sanmenxia section of the Yellow River Basin,with a view to providing reference suggestions to the departments concerned with the governance of the Yellow River Basin and contributing to the ecological protection and high-quality development of the Yellow River Basin.