Workshop 2018
Renli Liu - Vertical Displacements Driven by Groundwater Storage Changes in the North China Plain Detected by GPS Observations - October 29, 2018 • 90 Views
As the main source of fresh water in the North China Plain (NCP), groundwater storage (GWS) is essential to urban and agricultural needs in NCP. Influenced by the long-term overexploitation, the GWS has been suffering the most severe groundwater depletion in China, leading to a broad region of vertical motions of the Earth’s surface. Ten continuous Global Positioning System (CGPS) stations of Crustal Movement Observation Network of China (CMONOC) are selected to study the vertical displacements driven by GWS variations. The linear trends of selected bedrock-located IGS CGPS stations reveal the distinct GWS changes in period of 2009–2010 (decrease) and 2011–2013 (rebound), which are consistent with results from in situ GWS observations. This result implies that the rate of groundwater depletion in NCP has slowed in recent years. The impacts of geological condition (bedrock or sediment) of CGPS stations to their results are also investigated in this study. Contrasted with the slight linear rates ( -0.69~1.5 mm/a) of bedrock-located CGPS stations, the linear rates of sediment-located CGPS stations are between -44 mm/a and -17 mm/a. It is due to the opposite vertical displacements induced by the Earth surface’s porous and elastic response to groundwater depletion, as well as that the elastic response is about 30~80 times smaller than the porous response in those sediment- located stations. Besides, the GPS-based vertical displacement time series, to some extent, can reflect the quicker recovery of shallow unconfined groundwater than the deep confined groundwater in NCP; through one month earlier to attain the maximum height for CGPS stations nearby shallow groundwater depression cones than those nearby deep groundwater depression cones.

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