Hydrochemical evolution and hydrological zoning characteristics of a
shallow groundwater system in Baiyangdian Wetland, North China Plain
Abstract
A comprehensive understanding of the hydrochemical evolution and spatial
patterns of shallow groundwater systems is essential for water resource
management and wetland ecological restoration. The Baiyangdian Wetland
is one of the most concerning areas because of the development of the
Xiong’an New Area. The spatial characteristics of groundwater
hydrochemistry and potential controlling factors associated with
hydrochemical evolution remain unclear. In this study, hydrogeochemistry
together with the hierarchical cluster analysis were used to elucidate
the hydrochemical processes and hydrological zoning patterns of shallow
groundwater systems in the Baiyangdian Wetland, North China Plain. The
results showed that hydrochemical compositions of shallow groundwater
had considerable spatial variations, which was closely related to the
inflow rivers hydrochemistry and the dynamics of groundwater–surface
water interactions. A significant increase in SO 4
2- concentration occurring at the cone of the
depression was related to extensive pumping caused by anthropogenic
activities. Anthropogenic activities were also a major factor
controlling the spatial distribution patterns of shallow groundwater
hydrochemistry. Ca 2+, Mg 2+, and SO
4 2- in the wetland and shallow
groundwater were primarily derived from carbonate and gypsum
dissolution, while Na + and Cl -
originated from halite and silicate dissolution. Rock weathering
predominated the geochemical evolution of shallow groundwater in
conjunction with carbonate precipitation and cation exchange. The
hydrochemistry of the shallow groundwater system presented distinct
spatial zonation patterns that were classified into four clusters
corresponding to seven subzones. In Zones Ⅰ–Ⅳ, water-rock interaction
was the dominant factor controlling shallow groundwater chemistry, which
was driven by the positive groundwater–surface water exchange. The
coupled effects of anthropogenic activities and river infiltration and
mixing caused the high levels of dissolved components in Zones Ⅴ–Ⅶ.
This study provides deeper insight into the water cycle and hydraulic
connections among different bodies, and will benefit the rational
evaluation of hydrochemical evolution and wetland ecological restoration
in the Baiyangdian Wetland.