Research On Groundwater Emergency Source Field For Drinkingwater In Urban Jilin City

Urban water supply safety is an important part of city safety,water sources field is the starting point of urban water supply system,the safety of water sources field related to the safety of the whole water supply sysem and the stability of whole city.Emergency groundwater source field is the alternative groundwater source under the condition of emergency and the water source fields are out of working,and they are important means to ensure the urban water supply safety.The site selection,emergency capacity assessment,emergency scheduling scheme of groundwater emergency source field in Jilin City have important significance to enhance the city's ability to deal with emergencies,build a harmonious society.Based on the analysis of urban meteorological,hydrological,geological,hydrogeological,social and economic data,through the works of field pumping tests,dispersion test and samples analysis,the determination and assessment of groundwater source emergency field have been done in Jilin City.The main achievements are as follows:(1)The current state of water supply in Jilin City has been recognized,the necessary for establishing of groundwater source emergency field has been determined.There water source is single in urban water supply system,the daily water supply for Jilin City is about 50.5×104 m3,97.2% of the water supply is from surface water and the other 2.8% is from groundwater.The urban supply safety could be affected under the conditons of pollution accident in Songhua River.The industry,agriculture and the human life have high development levels in both sides of Songhua River in Jilin City section,the contaminations from human activies threat the water quality safety of Songhua River,and it is necessary to establish the emergency water sources fields.(2)The basic characteristics of groundwater in urban Jilin City have been recognized,and the feasibility of estabishing emergency groundwater source field has been determined.The Quaternary loose sedimentary layers are the main aquifers,and they are distributed in the valley terrance area of Songhua River,the area with high groundwater yielding capacity is 68.04 km2,which is about 56.03% of the total area.The area with groundwater quality falling in the drinking water standard is about 39.43 km2,there is higher groundwater development degree in urban Jilin City,especially for the right bank of Mangniu River,Qijiazi area,old urban area,Jiangnan area and Hadawan area,however,there still has a certain amount of residual recoverable groundwater resources.(3)The site selection and water resources of emergency groundwater source fields have been determined in urban Jilin City.Based on the fully understanding of the groundwater characteristics in urban Jilin City,10 emergency groundwater source fields have been determined and the total area is 39.43 km2.The water resources of emergency groundwater source fields including the infiltration of precipitation and the available groundwater storage.According to the golden section of aquifer and the ecological water level,the availble water resouces have been divided into blue storage,yellow storage and red storage.The calculation results show that,the average annual recharge of the emergency groundwater source fields is about 519.562×104 m3,available blue storage is 1069.22×104 m3,available yellow storage is 1209.18×104 m3,available blue storage is 1407.60×104 m3,the total available storage is 3686.00×104 m3,which is 62 % of the total storage.(4)The emergency capacity has been cheked through maxium emergency water supply and maxium emergency supply time.The maxium emergency water supply have been calculated in 30 d,60 d,90 d,180 d and 360 d,the maxium emergency water supply is between 2988.16×104m3 and 3501.76×104m3,mainly including the available storage,the maxium emergency supply time is 420 d for 2 million residents in urban Jilin City.(5)Numercial simulation has been applied in groundwater level prediction under 5 emergency groundwater development schemes.The emergency groundwater development time has been set as 30 d,60 d,90 d,180 d and 360 d,the numerical prediction results based on GMS show that,the groundwater level drawdown increased with the extension of emergency time,and the groundwater drawdown is between 2.0 m and 8.0 m,there are no significant influence on the overall groundwater level in Jilin City.(6)The groundwater quality evolution has been predicited by the numerical simulation under the designed pollution accident along the Songhua River,the results show that,the emergency groundwater development time should not too long in the right bank of Mangniu River,Hadawan water source field,Jiangnan water source field,Dachangtun water source field and longtanshanxia water source field under the pollution accident condition along Songhua River.