Determination of groundwater recharge rates in the North China Plain using

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The semi-arid North China Plain (NCP) is heavily populated and suffers from water scarcity, made evident 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. This project aims to provide key information for the sustainable management of the precious groundwater resources in this area by integration of geochemical and geophysical data with a comprehensive model of the subsurface water dynamics. The analysis of environmental tracers (stable isotopes, 14C, tritium, noble gases, etc.) enables determination of groundwater residence times and recharge rates. Numerical groundwater flow and transport models enable the integration of hydraulic and tracer data into a mechanistic view of the system with predictive capabilities.The project builds on previous work of the principal investigators, who have established both a groundwater model and a tracer data set from the Shijiazhuang area, a major recharge area but also one of the most heavily overexploited parts of the NCP. This project will combine the two approaches and expand them to the scale of the entire NCP in order to arrive at a much better constrained and detailed understanding of the recharge rates and mechanisms. The tracer data gathered by the German partner will provide indispensible groundwater recharge and age data to significantly reduce the uncertainty in the model being developed by the Chinese partner. Conversely, the model provides an essential vehicle to integrate and interpret the data sets collected by the German partner. The combined approach will also offer many opportunities for links with other research groups taking part in the Sino-German joint initiative on water resources, ranging from studies of the unsaturated zone at the plot scale that are relevant for the interpretation of the groundwater tracers to climatological and remote sensing data that can be linked to the groundwater model on the basin scale.