| Shuangcheng District is the municipal district of Harbin.Groundwater resources are its main source of water supply.The existing water supply capacity of Shuangcheng District can no longer meet the demand for water supply.New water sources are planned to alleviate the pressure of water supply.In recent years,due to the unreasonable exploitation of groundwater in the water source,many environmental hydrogeological problems have arisen.Therefore,it is very important to predict the environmental impact of the new water source mining in Shuangcheng District and propose countermeasures.By collecting the natural geography,geological and hydrogeological data,the water balance method and the Nemero method are used to evaluate the groundwater environment status in the study area.The numerical method is used to predict the impact after the water source is mined,and the environmental impact is proposed.Control measures are proposed.It mainly includes the following aspects:1.Using the water balance method and the mining coefficient method,the average exploitable resource in the study area from 2007 to 2016 is 8443.38 million m~3/a,and the water resources are abundant.Through monitoring the data of the buried water depth of the well,the average buried depth of the newly built water source before mining is 16.7m,and the depth of the roof of the aquifer in the water source mining center is 48m.It is safer to choose the water supply source.Groundwater quality was evaluated by the Nemero method.The study area was Class IV and below,mostly due to excessive levels of iron and manganese in the primary environment.At the same time,ammonia nitrogen,nitrate nitrogen,TDS and total hardness exceeded the standard in some areas.2.Based on GMS software to establish groundwater flow model and solute transport model,and propose six mining schemes to predict groundwater volume,water level and water quality impact under different mining schemes.It can be seen from the results that there is no water depletion in any one of the schemes.After 11years of mining,the water level does not reach the natural state side pressure head to1/3 of the aquifer roof.The water source inferior water bodies in urban areas during the mining period will not affect the water quality of the water source.It is recommended that the new water source land be mined in the previous four schemes.This will ensure the safety of the water supply while meeting the requirements of the project requiring mining of 5 million m~3/d.The amount of water source can be appropriately increased according to actual needs.3.According to the environmental impact prediction results,the groundwater level-water level control management is carried out for the newly-built water source,the P-III curve is used to calculate the precipitation at different levels,and the mining coefficient method is used to calculate the recoverable resources of the water source to obtain the water source.The groundwater control management blue line water volume is 353.63 million m~3/a~2521.96 million m~3/a.The control management red line water volume is 2388.00 million m~3/a~5485.62 million m~3/a.Using the principle of“quantity control position”,the groundwater flow model is used to calculate the water level of the groundwater control and management blue line of the water source source is-2.39m~-0.02m,and the water level of the control management red line is-3.72m~-0.19m.Control groundwater quality pollution to reduce emissions of ammonia nitrogen,nitrate nitrogen,TDS and total hardness.This paper has certain practical guiding significance for the groundwater exploitation in Shuangcheng District,which guarantees the safety of water and provides a scientific and reliable basis for the decision of the dual city government to make water decisions. |
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