A STRATEGY OF GROUND-WATER DISTRIBUTION EXPLOITATION TO MITIGATE THE MAGNITUDE OF LAND SUBSIDENCE

Shanghai is one of the centers in China that suffered the consequences of Land subsidence caused by pumping ground water from the Quaternary porous confined aquifers in Shanghai since 1920's. But such measures as decreasing the pumping of ground water, artificial recharging ground water, and adjusting pumping aquifers have been adopted to mitigate the magnitude of land subsidence in Shanghai downtown area since 1963. Ground-water distribution exploitation has been recognized to be a strategy to ameliorate the enormity of land subsidence in Shanghai downtown area. Some larger annual exploitation intensities of 33.12, 45.68, and 33.42 million cubic m/100 square km.a correspondingly caused some larger subsidence rates of 40.3, 98.6, and 59.3mm/a respectively in the downtown area during the fast sinking stage from 1949 to 1956, the severely sinking stage from 1957 to 1961, and the mitigating stage from 1962 to 1965. But some smaller annual exploitation intensities of 4.42, 5.60, and 4.29 million cubic m/100 square km.a correspondingly caused some smaller subsidence rates of ¨C3.0, 3.5, and 15.0mm/a respectively in the downtown area during the rebounding stage from 1966 to 1971, the slightly sinking stage from 1972 to 1989, and the growing sinking stage from 1990 to 2000. And the annual exploitable volume of fresh ground water has been assessed to be 142 million cubic m/a within Shanghai. The results of modeling of ground water flow and compaction of Shanghai aquifers system have also indicated that subsidence rate will be much less if the ground water exploitation is distributed in the suburbs and counties of Shanghai instead of only in the downtown area.