Hydrochemical characteristics and quality assessment of groundwater for drinking and irrigation purposes in the Futuan River Basin, China

Groundwater is the major source of water for drinking and irrigation purposes in the Futuan River Basin, China. In this paper, 118 groundwater samples were collected and analyzed following standard methods to decipher the sodium adsorption ratio (SAR), sodium percentage (Na%), and residual sodium carbonate (RSC). The groundwater is classified as slightly acidic freshwater with medium hardness, and most of the samples are Ca-HCO3 and Ca-Cl types. The dominance of cations and anions follows the trend Ca2+ > Na+ > Mg2+ > K+ and HCO3- > Cl- > SO42- > NO3-, respectively. The total dissolved solids (TDS) values are higher in the coastal areas and near the townships. Gibbs plots and end-member diagrams indicate that the groundwater chemistry in the Futuan River Basin is mainly controlled by rock weathering, and most of the water chemistry originates from the weathering of silicate, as well as cation exchange. The groundwater of the study area is affected by a certain extent of evaporation, and three samples were influenced by sea water intrusion. Fuzzy comprehensive assessment showed that most of the samples were good to excellent for potable purposes and the SAR, Na%, and RSC indicate that most of the groundwater is suitable for irrigation. Controlling pollution sources, strengthening groundwater dynamic monitoring, optimizing the layout of groundwater exploitation, and reducing the amount of groundwater extraction are of great significance for the rational development and utilization of the groundwater resources in the Futuan River Basin.