Combined cluster and discriminant analysis based on hydrochemical and isotopic evidence: A case study of the Yellow River Delta in China

Groundwater serves as an indispensable resource, fundamental for both sustaining life and underpinning various human endeavors. However, escalating demands, coupled with climate change, have given rise to significant water scarcity in numerous areas, including the Yellow River Delta (YRD) in China. This study aims to characterize the hydrochemical composition and stable isotopes (δ2H and δ18O) of groundwater in YRD and identify spatial clustering patterns using combined Hierarchical Cluster Analysis (HCA) and Discriminant Analysis (DA). Comprehensive analyses were conducted on the major ions (i.e., K+, Na+, Ca2+, Mg2+, Cl-, SO42-, and HCO3-), water quality indicators (i.e., pH, electrical conductivity (EC), and oxidation-reduction potential (ORP)) and isotopic composition of groundwater samples. Applying HCA on a collection of 38 water samples, the study delineated six distinct clusters, each bearing unique hydrochemical characteristics. DA was used to establish a discriminant model, achieving a classification accuracy of 80% for new groundwater samples. The study underscores that there are localized variations in the hydrochemical characteristics of groundwater in YRD, attributed to different geological conditions and anthropogenic influences. Such insights are instrumental in crafting effective strategies for water resource management, environmental conservation, and sustainable development in YRD and other analogous regions confronted with groundwater challenges.