Hydrochemical characteristics of groundwater and evaluation of water quality in arid area of Northwest China: a case study in the plain area of Kuitun River Basin

The Kuitun River Basin, a typical arid area, is in Northwest China where water resources are extremely scarce. Comprehensive analysis of the hydrochemical characteristics and main types of groundwater in the plain area of the basin was conducted, revealing that the ion source and evolution law are helpful for evaluating water quality and water supply. In this study, 316 groups of groundwater samples were collected from 2017 to 2019. Descriptive statistics, correlation analysis, Piper three-line diagram, Gibbs diagram, principal component analysis (PCA), hierarchical cluster analysis (HCA), ion ratio method, and saturation index were used to evaluate hydrochemical characteristics, ion sources, and water quality of the groundwater. The results show that (1) the concentration of ions in groundwater varied greatly over region. Along the flow direction of groundwater, the concentration of ions in the fine soil plain diving (FSPD) increased more than that of gravel plain diving (GPD), and the areas with high ion concentrations were mainly distributed in the northeast of the study area. (2) There were 29 hydrochemical types in the study area. (3) The chemical ions originate from the evaporation, concentration, dissolution, and filtration of rocks. Both diving water and artesian water had different degrees of cation alternating adsorption, and the degree of exchange adsorption was as follows: fine soil plain artesian > FSPD > GDP. (4) Combined with the drinking water quality standards and irrigation suitability evaluation criteria in the study area, observations were as follows: drinking water quality in the study area has a regular deterioration trend from south to north, most groundwater is suitable for irrigation water, and a small portion of groundwater exhibits moderate Na + hazard and is highly endangered by salinity.