Determination of groundwater recharge rates in the North China Plain using
Final Report Abstract
This project aimed at providing key information for the sustainable management of the precious groundwater resources in the semi-arid and densely populated North China Plain (NCP). This region suffers from water scarcity, as made evident e.g. by the drying-up of rivers and by rapidly falling groundwater levels. Especially the groundwater represents a vital water resource of high quality but finite quantity and limited renewal. The project combined the analysis of environmental tracers (stable isotopes, 14C, tritium, noble gases, etc.), enabling the determination of groundwater residence times and recharge rates, with numerical groundwater flow and transport models, enabling the integration of hydraulic and tracer data into a mechanistic view of the system with predictive capabilities. This report focuses on the tracer data and their interpretation, i.e. the part of the joint project conducted by the German partners at Heidelberg University. The project could built on a tracer data set from a transect through the central part of the NCP starting in the Shijiazhuang area, which was obtained in a previous DFG-funded project. The old data were re-evaluated, in particular with a view towards groundwater age distributions in the recharge area and corresponding conclusions about recharge processes and rates. New tracer data were gathered by sampling 43 wells situated along two transects through the NCP, to the north and south of the transect from the previous project. The majority of the new samples originates from the northern part of the NCP, near to and downstream of Beijing, which is one of the most heavily overexploited parts of the NCP. For the new samples, groundwater ages were determined using the 3H-3He-method as well as the 14C-method for dissolved inorganic carbon, and infiltration temperatures were determined based on dissolved noble gas concentrations. A combination of dissolved anthropogenic trace gases – SF6 and CFCs - was used to complement the 3H-3He-method in order to identify mixing components of young groundwater and to differentiate local contamination or SF6 from terrigenic sources. It could be shown that, similar to the Shijiazhuang area, high recharge rates occur which are due to the return flow of irrigation water, except in the urban areas of Beijing where no irrigation takes place. Differences between the three transects were found concerning the occurrence of terrigenic SF6 which is present in the southern and central transects to a similar magnitude, but not in the northern transect starting near Beijing. Additionally, the new data add to the palaeoclimate record obtained in the previous project. From the noble gas data, the temperature difference between the late last glacial period and the Holocene could be determined to lie between 4 and 5 °C both in the northern and southern part of the NCP. This temperature difference confirms the results of the previous project, adding up to a uniquely dense, spatially and temporarily resolved noble gas palaeotemperature record.
Publications
- 2010. Accumulation of natural SF6 in the sedimentary aquifers of the North China Plain as a restriction on groundwater dating. Isotopes Environ. Health Studies 46: 279-290
von Rohden, C., A. Kreuzer, Z. Chen, and W. Aeschbach-Hertig
- 2010. Characterizing the recharge regime of the strongly exploited aquifers of the North China Plain by environmental tracers. Water Resour. Res. 46, W05511
von Rohden, C., A. Kreuzer, Z. Chen, R. Kipfer, and W. Aeschbach-Hertig
(See online at https://dx.doi.org/10.1029/2008WR007660) - 2010. Using environmental tracers to characterize recharge conditions in the strongly exploited aquifer system of the North China Plain. In: Zuber, A., J. Kania, and E. Kmiecik (eds.), Groundwater quality sustainability (38. IAH Congress, Krakow, extended abstracts), Univ. of Silesia Press, abstr. 163, 1569-1571
Aeschbach-Hertig, W., C. von Rohden, A.M. Kreuzer, Z. Chen and R. Kipfer
- 2012. Regional strategies for the accelerating global problem of groundwater depletion. Nature Geoscience 5: 853-861
Aeschbach-Hertig, W., and T. Gleesen
(See online at https://doi.org/10.1038/NGEO1617) - 2013. Insights into palaeo-hydrologic conditions for groundwater age simulation. MODFLOW and MORE conference. Golden, Colorado
Cao, G., C. Zheng, and W. Aeschbach-Hertig
- 2013. Properties of the closed-system equihbration model for dissolved noble gases in groundwater. Chem. Geol. 339: 291-300
Jung, M., M. Wieser, A. von Oehsen, and W. Aeschbach-Hertig
(See online at https://doi.org/10.1016/j.chemgeo.2012.08.006)
