The Study Of Groundwater Evolution And Rational Exploitation And Utilizing In Jiangsu Coastal Area

Jiangsu coastal area is located in the southeast coast of China,where is a new industrial base and an important coastal and Land Resources Development Zone of China.Since "Jiangsu Coastal Development Plan" has been carried out,this area ushers in new development opportunities,while also face more serious shortage of water.In the areas with strong human exploitation activities,regional groundwater evolution is obviously affected by human activities.In order to solve the environmental geological problems caused by groundwater exploitation,we must find out the forming conditions of regional groundwater hydrodynamic field,the impact of human activities on groundwater hydrodynamic field evolution and hydrogeochemical evolition.Based on these results,scientific management and reasonable exploitation of the regional groundwater resources can be provided for the best utilization.This paper relies on key cooperation project "Study on groundwater circulation and evolution model in the coastal area of Jiangsu",which is the sub-project of project "Comprehensive geological survey of the coastal areas of Jiangsu".These projects are funded by Jiangsu Provincial People's government and the Ministry of land and resources.Taking coastal area of Jiangsu as the research area,we investigate and analyze of the regional hydrogeological conditions.The numerical simulation model of groundwater flow was established according to the water power,chemical and isotopic methods,the conditions of water flow and the influence of hydrodynamic field on the water chemical field.We predict that the evolution of regional groundwater dynamics under the influence of human activities and climate change.We also evaluate the influence of groundwater dynamic field evolution on the environmental geological problems caused by groundwater exploitation under various conditions.We get the following conclusions:(1)The recharge,runoff,discharge characteristics of every aquifer were found out.The evolution and driving mechanism of recharge,runoff,discharge characteristics were revealed under the influence of human exploitationThe unconfined aquifer in Jiangsu coastal area diving was mainly rechaeged by precipitation and lateral runoff in the north and west mountain.The first confined aquifer receives the west side of lateral runoff.The first confined aquifer was recharged underwent unconfined aquifer vertical seepage and lateral seepage of Yangtze Riverin Nantong urban area.The second and third confined aquifers weremainly recharged by lateral runoff.The main discharge ways were lateral runoff excretion and artificial exploitation.The unconfined aquifer and the first confined aquifer were discharged into the Huanghai Sea from the west to the east.The second and third confined aquifer formed regional drawdown funnels by the effect of artificial exploitation in the urban area of Yancheng City and Nantong City.In the area of groundwater funnel,groundwater gathered from the funnel edge to the center of the funnel.The second and third confined aquifer was recharged by Late Pleistocene Holocene precipitation.The second and third confined hydraulic aquifers have the connection in Yishuhe hydrogeology zone and Huaihe downstream hydrogeology zone.Because the aquitard is thin in the part of the region and the groundwater was affected by mining,the second confined water flowed to third confined water.The first and second confined aquifers have the close hydraulic connection at the hydrogeological zones in Yangtze River Delta.In the past 25 years from 1990 to 2005,with the decrease of exploitation quantity,confined ?water shows the speed of drop of water level and the area increase speed of groundwater cone of depression became slow.(2)The area of salinization increases first and then decreases from top to bottom.The TDS content of each layer increased gradually from the West to the East region,and the water type changes from type HCO3-Na to type Cl-Na from west to east.The main reason of regional groundwater salinization was excessive exploitation of groundwater,which causes the overlying saltwater leakage into the third confined aquifer.According to water level and water quality data of observing wells,the control threshold of fresh water salinization was-10~-51 m.(3)On the basis of the evaluation of planning exploitation,the rational exploitation schemes of sub-wells were proposed by considering the red level of groundwater salinization.Considering the actual water structure in the area,the rational development and utilization scheme of the sub-wells under the emergency condition was proposed.Taking the full advantage of brackish water of confined aquifer?and controlling the groundwater salinization,optimal exploitation quantity of typical areas Nantong for groundwater quality water supply was 42227m3 /d,and37477m3 /d for typical area Yancheng-Sheyang.When the area had an extreme drought or severe pollution accident,groundwater was used as an emergency water source.The optimal groundwater exploitation scheme for emergency water supply was the third scheme.The groundwater level of Nantong urban area was-15~-35.4m,and the water level of Yancheng-Sheyang area was-35.1~-49.2m.