The Study On Water Quality Evaluation And Algae Change Of Main Channel Of South-to-North Water Transfer Project(Hebei Section)

South-to-North Water Diversion Project is a grand project with strategic significance,which is built to solve the problem of uneven distribution of water resources and seriously affect the economic development of the northern part of China.The middle route project has a total length of 1432 km,including 156 km of the Tianjin water route,which spans a wide area from north to south.In order to ensure the safety of drinking water in north China,water quality requirements are relatively high.It is an important guarantee for the stable operation and optimal management of the middle route project in Hebei Province to understand the water quality situation and its changing characteristics.In view of the risk of algae proliferation in the main channel of the middle route of South-to-North Water Diversion Project(Hebei section),relevant studies were carried out on water quality evaluation and water quality simulation.Based on the study of the current water quality changes of the main canals,the basic conditions of the geographical,natural and hydrological conditions of the main canal(Hebei section)of South-to-North Water Diversion Project were monitored on the spot.Sampling and testing the water intake of six main urban water plants flowing through the main channel of South-to-North Water Diversion Project(Hebei section)in 2018.The research indicators include CODMn,CODCr,BOD5,NH3-N,TN and TP;water quality is adopted The comprehensive pollution index evaluation method,fuzzy comprehensive evaluation method and comprehensive water quality label index evaluation method evaluate the water quality status of the main channel(Hebei section)of South-to-North Water Diversion Project.The evaluation results show that the water quality of the main channel(Hebei section)of the Middle Route of South-to-North Water Diversion is ClassⅢ,and the main pollutant exceeding the standard is TN.The comprehensive water quality index evaluation method is more suitable for the assessment of water quality status.Aiming at the problem of algae proliferation risk,based on the actual detection data of the nitrogen and phosphorus nutrients and algae spores in the main channel,combined with the use of the Monod model to simulate the analysis of the changes in the rate of algae growth across the line,and on this basis,a middle line for South-to-North Water Diversion was established The algae proliferation model of main canal water body was fitted to the field detection data,and an estimation result with a relative median error of 11%was obtained.Based on the construction of the algal growth model of the main channel of South-to-North Water Diversion Project(Hebei Section),the changes in the water quality of the main channel of South-to-North Water Diversion Project from 2019 to 2025 and the spatial and temporal distribution of algae in the whole channel are estimated and predicted.Under the premise that the atmospheric nitrogen and phosphorus deposition values and source nutrient inflows remain unchanged,by 2025,the Hebei section of the main line of the middle line will be in a state of eutrophication,and the algae density in some of the main canals of Baoding will reach 33.84 million/L.The water quality of algal blooms.On the basis of this prediction,an early warning scheme and risk management and control strategy for the middle route of South-to-North Water Diversion Project were proposed to provide scientific support for solving the water quality problems of the middle route.