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The surface water/groundwater-continuum flow system is investigated through an intensive field survey downstream of the Baiyangdian Lake watershed, North China Plain. Oxygen and hydrogen isotope and chemical analyses are conducted on surface water, shallow groundwater, and deep groundwater and the results are processed by applying principal component and cluster analyses. The surface water of the Fu River, Tang Reservoir, and Baiyangdian Lake is strongly affected by anthropogenic influence, resulting in high nitrate-ion concentration, a distinct sodium-sulfate water-type derived from industrial wastewater, and enriched stable isotopic compositions due to accumulated evaporation, respectively. In some areas, shallow groundwater shows close chemical and isotopic affinity to surface water, indicating that surface water recharges to shallow groundwater. Deep groundwater shows lower chemical and isotopic signals than surface water and shallow groundwater. However, a slightly high nitrate-ion concentration is observed in some samples of deep groundwater, suggesting a partial communication between shallow and deep aquifers.

Abstract:In arid/semi-arid regions, consumption of deep groundwater resources is increasing due to growing water demand in every sector. Intensive groundwater surveys focused on the Baiyangdian Lake Watershed (BLW) in the northwest of the North China Plain, as the BLW suffers from serious water problems due to high economic growth and improper groundwater resource utilization.To clarify the interaction between shallow and deep groundwater, samples of surface water and groundwater in different aquifers were collected from two cities (Baoding City and Dingzhou City). Major trace element solute ion concentrations and stable isotopes of δ 18 O and δ 2 H revealed that, in a specific region of Baoding, anthropogenic activities have induced interaquifer recharge from Aquifer 1 to Aquifer 2 based on the similarity in chemical tracers. However, such an interaction could not be found in other regions in the study area.

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<p>It is essential to clarify the groundwater flow system and its scale for the sustainable use and management of local water resources. One effective method is to estimate the residence time of groundwater. The Shimabara springs exist in Nagasaki Prefecture, Japan, and its water quality has been characterized over time. However, there have been few studies on water quality characteristics and isotope variations with fine resolution in a region such as Japan, where seasonal changes in precipitation are observed. Therefore, we conducted periodic water sampling at five locations in the Shimabara Springs at a frequency of about once a month, and evaluated water quality characteristics and isotope variations. CFC-12, an age dating tracer, was also used for a multifaceted study. During the observation period, we observed precipitation that was more than five times larger than the normal year, and in response to this, we were able to identify springs that showed changes in various hydrologic parameters. In the presentation, we will discuss the relationship between precipitation, residence time, and water quality, and present a schematic diagram of the mechanism of this spring discharge.</p>