Uncertain in WQI-based groundwater quality assessment methods: a case study in east of Beijing, China

Groundwater is a significance source of freshwater in both urban and rural areas of the world. With the increasing groundwater pollution, it is essential to analysis of groundwater chemical characteristics and evaluate groundwater quality for water supply purpose. The study proposes basic water quality index module (BWQIM) and integrated water quality index module (IWQIM) by combining indictors, weights and model on water quality index (WQI)-based, and evaluated the groundwater quality in Chaoyang District, Beijing. The IWQIM and BWQIM were compared. Fe, HCO3−, TDS and TH were identified as key parameters of groundwater quality assessment. The water quality assessment results of BWQIM are scattered. However, the evaluation results of IWQIM are basically consistent and not influenced by indicators and weights. This module solves the problem that the weight of over standard indexes is submerged when multiple indexes are used, it is more reasonable and effective for groundwater quality evaluation, and overall situation of groundwater in the study area was concentrated in good level. Groundwater in aquifers in the study area is weakly alkaline. The Ca–HCO3 type characterized the general hydrogeochemical composition of Chaoyang district groundwater. Most samples fall in the rock dominance zone, suggesting that rock weathering and rock-water interactions are the primary sources controlling groundwater chemistry and hydrochemical evolution. These findings can provide an effective tool for the groundwater management for drinking and the sustainable development of water resources.