Quality Assessments of Shallow Groundwaters for Drinking and Irrigation Purposes: Insights from a Case Study (Jinta Basin, Heihe Drainage Area, Northwest China)

Abstract

This study aimed to determine the hydrochemical characteristics and hydrogeochemical processes of shallow groundwater in the Jinta Basin, northwest China, and to evaluate the suitability of groundwater quality for drinking water and agricultural irrigation. A systematic hydrogeological survey was conducted in the study area from May 2017 to October 2018, during which 123 representative samples of groundwater were selected for analysis of chemical parameters and determination of the water quality index. The results showed that the pH of groundwater in the study area was weakly alkaline and ranged between 7.21–8.93. Dominant cations were Mg2+ and Na+ and the dominant anion was SO42−. Along the groundwater flow from the southwest to northeast, the dominant groundwater chemistry type in the recharge area was Mg-HCO3·SO4. After the transition of the groundwater types in the runoff area to Mg-SO4·HCO3 and Mg·Na-SO4, the groundwater type in the discharge area evolved into Na·Mg-SO4·Cl. The major factors driving the evolution of groundwater chemical types in the Jinta Basin were found to be rock weathering, evaporation and precipitation. The chemical components of groundwater mainly originated from the dissolution of silicate rock and evaporative concentration of salt under water-rock interaction, whereas the dissolution of carbonate had little influence. The quality of drinking water was divided into five groups, and 39.84% of samples fell within the high and good quality groups. The quality of agricultural irrigation water was divided into different grades according to different methods.