Study On The Influence Of Shallowgroundwater On Water Quality In Jiaozuo Section Of Main Canal Of South-to-North Water Diversion Project

Jiaozuo section of the middle route of the South-to-North Water Transfer Project is a typical inner drainage section.Groundwater enters the main canal through the check valve,which will inevitably affect the water quality of the main canal to some extent.In this paper,the shallow groundwater around the canal system of the Jiaozuo section of the South-to-North Water Diversion Project is taken as the research object,and Take 30 water samples every six months a total of 30 water samples（2018-2020）are taken for laboratory experiment analysis and data processing.WQI comprehensive evaluation method was used to evaluate the water quality,and the water quality of shallow groundwater around the canal system was obtained.The GM（1,1）model is used to simulate the groundwater,and the ion changes in groundwater in recent years are predicted.The influence of polluted groundwater on canal system water quality was analyzed quantitatively by combining the worst analysis method and inverse deduction method.The main conclusions are as follows:（1）Along the slope direction,the hydrochemical types change from low salinity water in the northwest to high salinity water in the southeast.HCO₃-Ca·Mg water is the main water in the north of the South-to-North Water Diversion Main Canal,and HCO₃·SO₄-Mg·Ca or SO₄·HCO₃-Mg·Ca water is the main water in the south of the South-to-North Water Diversion Main Canal.（2）The water quality of shallow underground in the study area in 2020 was evaluated by single factor WQI comprehensive evaluation method.The results showed that the proportion of water quality belonging toⅡclass,Na class,Nu class and Kind class accounted for 6.45%,51.61%,38.70%and 3.23%,respectively.The proportion ofⅣand AA water reached 90.3%.93.55%were ofⅢclass and above.The water quality of shallow groundwater on both sides of Jiaozuo urban area of the middle route of South-to-North Water Transfer Project is generally poor and the pollution is serious.WQI comprehensive evaluation method was used to evaluate the water quality from 2018 to 2020,and contour map was drawn.The comparative analysis results showed that the water quality had a trend of getting worse.（3）By using GM（1,1）model,the groundwater level and plasma of SO₄^2-,Cl^-,Na⁺,Ca^2+,Mg²⁺and HCO₃^-are simulated and predicted,and the results show that the groundwater level is decreasing year by year;The content of Mg²⁺ions in groundwater has a decreasing trend.The concentration of Ca²⁺ions in groundwater is increasing.The content of Na⁺ions in groundwater decreased.HCO₃^-ion concentration decreased;The concentration of Cl^-ion in groundwater tends to increase slightly.The concentration of SO₄^2-ion in groundwater increases.In most areas,the content of ions in groundwater is increasing,and the water quality of groundwater has a trend of deterioration.（4）The worst-case analysis method was used to analyze the influence of shallow groundwater in Jiaozuo section on the water quality of the main channel of South-to-North Water Diversion Project.The highest concentration of ions in the sampled data in recent years was used to analyze and obtain that the hardness of SO₄^2-,Cl^-,TDS and hardness exceeded 0.0066,0.02284,0.04688 and 0.00072 times respectively.Hardness and p H is excessive,but is very close to the requirements of the main canalⅡclass value of water,which in main canal water potential threat.（5）using inverse analysis method,in the main canal when the check valve in the study area in simulation into groundwater quantity and groundwater pollutant concentrations are maximum,in order to ensure the main canal water quality notⅡwater reduced toⅢ,respectively for the original main canal water SO₄^2-,Cl^-,TDS and hardness of the four kinds of pollutants concentration is not more than 248.42mg/L,234.81 mg/L,951.87 mg/L,249.94 mg/L.There are 17 copies of figures,20tables and 73 references.