The Effect Of Urbanization Construction To The Underground Water System

Urbanization refers to a transformation process of population,land use,economic and cultural pattern from agricultural society to industrialized society. Urbanization has upset the balance between human society and natural environment and strongly interfered with underground water system.Chengdu is located on the middle and forward edge of alluvial-proluvial fan of Min River through Chengdu plain. Since 1990s, human activities, such as expansion of urban construction, enlargement of building coverage area and asphalt waterproof road, dewatering of surface water, anti-seepage treatment of ditch and underground engineering, have dramatically changed the natural occurrence environment of underground water and regional water cycle conditions and regional ground water system.According to monitoring results of groundwater level and water quality in Chengdu from 1990 to 2000 and the process of urbanization construction in Chengdu, this paper will analyze and summarize the effects of urbanization construction to the ground water system in Chengdu.(1) The Effect of Urbanization Construction to the Ground Water LevelIn the process of urbanization construction in Chengdu, The buildings on the ground and road construction have changed the environment on the ground,pavement hardening has reduced the rainfall infiltration of the ground and rainwater draining through unified drainage pipeline has reduced the rainfall recharge to the underground water in city,which caused the decrease in recharge of underground water in Chengdu. The main northwest lateral recharge has gradually decreased the underground water level year by year in the process of urbanization of the city in Chengdu.In the process of urban development, the river treatment in city includes regulating of river management, dredging river channel, rebuilding dike and so on. Rivers have gradually formed as a separate system accepting no underground water or draining to ground water, which caused the decreasing of the underground water level along two banks of river in urban area with the disturbance of river water.In the urban facilities construction, underground facilites construction will plunge into water table, the large area and long time foundation pit dewatering decreased the underground water level in certain extent, and caused the irregular lowering of local underground water in city. Along the metro, there is a series of underground water level groove with unequal lengths after the excavation of foundation pit during the metro construction. After construction, the underground water during operation period will recovere gradually to original level by ways of rainfall infiltration or lateral recharge.(2) The Effect of Urbanization Construction to the Ground Water QualityAs the industrial scale expands, Chengdu has experienced a transitional period from agricultural society to industrialized society, urban zones in Chengdu has dotted with industrial areas. The emission of industrial waste is large, and harmful and toxic substance within the emission is of a large number and complex, which caused the pollution of river and the quality of the underground water in cities. The effect of the pollutants , such as the vehicle oil pollution, to the water environment along traffic route and the misconduct of waste in tourist sites can influence the water environment in city and then lead to the deterioration of the quality of underground water.Chengdu could decelerate the pollution to underground water in Chengdu by many ways, such as water saving, rational utilization of water resources, rational planning and layout of all kinds of industries, and pollutant emission control.