Spatial classification of groundwater chemistry monitoring data in the Red River Delta, Vietnam using self-organizing maps

Abstract

The groundwater in the Pleistocene confined aquifer (PCA) of the Red River Delta (RRD) was examined using self-organizing map (SOM) and Gibbs diagrams to determine, for the first time, its spatial classifications in terms of its hydrogeochemical characteristics. In this study, the groundwater chemistry dataset used in the analysis is composed of 8 major dissolved ions (i.e. Ca2+, Mg2+, Na+, K+, HCO3-, Cl-, SO42- and CO32-) that are consistently found in 52 groundwater monitoring wells within the study area. Based on the results, the groundwater in the PCA monitoring wells of the delta can be classified into 2 major water types: high and low salinity. Each water type is composed of cluster-types that have similar hydrogeochemical characteristics. The high salinity water type has 2 clusters (or sub-types), while the low salinity (or fresh water) has 4. From the Gibbs diagrams, results indicate that the high salinity in the groundwater is mostly influenced by either (or both) anthropogenic activities and salt water intrusion.