Characterization of Shallow Groundwater Circulation Based on Chemical Kinetics: A Case Study of Xiong’an New Area, China

Abstract

Xiong’an New Area, located in the middle of the North China Plain, will have been built as a “city of the future.” Urban planning and construction need to comprehensively consider the constraints of hydrogeological conditions such as aquifer structure and parameters. As the main aquifer in this area, the paleo-channel is heterogeneous and anisotropic, and the two-dimensional hydraulic conductivity in each horizontal direction cannot be obtained from aquifer tests. Therefore, this study adopts a chemical kinetics method to calculate the ionic activity and mineral saturation indices of shallow groundwater, determine the groundwater chemical potential field, and construct a horizontal two-dimensional groundwater chemical kinetics model. This model is used to calculate the hydraulic conductivity, flow rate and retention time of groundwater in areas of different chemical kinetics, as well as evaluate horizontal heterogeneity of the Quaternary paleo-channel aquifer. The results indicate that the groundwater chemical potential field can reflect the characteristics of the groundwater seepage field in each horizontal direction. The paleo-channel is the main channel of groundwater circulation, which shows the statistical difference of its permeability. Alluvial and lacustrine strata affect groundwater circulation due to their different hydrogeological structures and permeability. The groundwater chemical kinetics results of hydraulic conductivity along the paleo-channel are approximately consistent with traditional hydrogeological calculation results derived from aquifer test data. Hydraulic conductivity is higher in the extension direction of the paleo-channel, and lower if the path crosscuts multiple paleo-channels. This feature can be used to build a hydrogeological structure model combined with drilling data. Furthermore, excessive groundwater exploitation will change the actual flow rate and retention time of groundwater, thereby affecting the groundwater circulation conditions. This study of groundwater circulation in Xiong’an New Area by means of chemical kinetics makes up for the deficiency in the study of the unconsolidated sedimentary aquifer anisotropy within the paleo-channel.

Suitability Assessment of Multilayer Urban Underground Space Based on Entropy and CRITIC Combined Weighting Method: A Case Study in Xiong’an New Area, China

“…The study area exhibited distinct sedimentary facies characteristics, with an alluvialproluvial facies observed in the northwestern region and an alluvial-lacustrine facies observed in the southeastern region. This differentiation in sedimentary facies was roughly delineated by the connection line between Rongcheng urban districts and northern Anxin [48].…”

Geo-Environment Suitability Evaluation for Urban Construction in Rongcheng District of Xiong’an New Area, China

“…The Rongcheng district, with an acreage of 314 km 2 , is located northwest of Xiong'an New Area in North China [34], which is part of the alluvial plain of the Taihang Mountains [35] (Figure 1). The surface ground elevation displays a characteristic of decreasing from the northwest to the southeast, and varies from 5 m to 26 m with a gradient lower than 2‰ [36]. The research district belongs to the warm temperate zone with a semiarid climate, and the average annual precipitation is 482.7 mm.…”