IMPACTS OF URBANIZATION ON THE GROUNDWATER RESOURCE: THE CASE OF SHENZHEN, CHINA

Shenzhen is a major economic center in south China, which grew from a fishing village of 50,000 people 35 years ago to an international metropolis of nearly 20 million of inhabitants today. Located between Guangzhou and Hong Kong, Shenzhen covers an area of 2050 km² along the coastal and alluvial plains with lush vegetation, amid valleys and hills. The aim of this study is to estimate the impact of urban expansion on groundwater recharge. Indeed, urban areas, with a dense network of buildings and infrastructures, impede the infiltration and strongly favor the runoff. To study the groundwater impacts, a remote sensing analysis of the urban pattern has been performed using satellite images. Urban areas are detected and delineated on satellite images according to the variation of color, tone and pattern. Three different temporal stages have been identified, including: 1) A full development of the Shenzhen urban pattern (via the 2014 Landsat Copernicus satellite image dataset); 2) An initial construction stage (via the 1979 Landsat satellite image); and 3) Stage zero, before the start of the urbanization process.

The different urban/natural area distribution has been matched with the aquifer map of the Shenzhen area. The aquifer has been subdivided, according to the magnitude of hydraulic conductivity (very high, high, medium, low, and very low) and type of aquifer media (porous, fractured and karst), yielding a total of six sub-classes. For every aquifer sib-class, its infiltration rate has been compiled from literature. The reduction to groundwater recharge for every aquifer over different temporal stages has been evaluated. Analysis shows a groundwater recharge reduction of 53%, due to the urban expansion along the coastal areas and fluvial valleys. The estimation of the impact on groundwater balance, in response to urbanization of different types of aquifers, provides a sound basis for groundwater management in the urban planning.