Inverse analysis for transmissivity and the Red river bed's leakage factor for Pleistocene aquifer in Sen Chieu-Phuc Tho-Hanoi by group-well pumping test under the river water level fluctuation

Duc Huy Trieu1
1 National Center for Water Resources Planning and Investigation - NAWAPI

O 10.3 in Wasser und Umwelt in Südostasien

24.03.2018, 09:30-09:45, 2

Aquifer parameters and river bed hydraulic resistance to aquifer have an important role in qualitative assessment of groundwater sources, especially the aquifer recharge from rivers. The analytical determination of aquifer parameters and river bed hydraulic resistance to aquifer is rather complicated in case the water level in the river fluctuates before and during the pumping test time. This is especially true for Pleistocene aquifer along the Red river in Hanoi city, where the river bed has been changed very much during the recent decades. A trial-error inverse analysis in the parameters' determination by group pumping test data obtained in a test located close to the Red river bank in Sen Chieu area, Phuc Tho district, Hanoi city had been carried out. Before and during the pumping test time the water level in the river changed five times. The results have shown that the Pleistocene aquifer has a relatively high hydraulic conductivity of 55.5 m/day, which provides a good role in the transport of a large volume of water recharged by the river to the abstraction wells located near the river. The aquifer storage coefficient had lightly decreased with the pumping time, which is corresponding to the physical nature of that the aquifer storativity is a function of the aquifer pressure. A special point is worthwhile to note that the Red river bed resistance to the Pleistocene is very low, about 0.537 days, which is corresponding to the increase of the distance from the river bank further from the well in 28.4 m to have the river as a specified water level boundary of the aquifer. In contrast, the 1990's investigations had found the Red river bed resistance to the Pleistocene aquifer of about 130 days (Tran Minh, 1984), which is corresponding to the increase of the distance from the river bank further from the well in 28.4 m to have the river as a specified water level boundary of the aquifer of a thousand meters.



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