Assessment of Groundwater Quality in Ha Tinh Province Using Water Quality Index

The Groundwater Quality Index (GWQI) was developed and applied to assessment of groundwater quality in Ha Tinh province. This study utilized water quality monitoring data in 2018 - 2020 period at 58 locations with a frequency of 4 times/year in 13 districts, towns and city in the province. Ten (10) parameters were selected (i = 1 - 10) to establish the GWQI, including: pH, total dissolved solids (TDS), hardness (HARD); sulfate (SO4), chemical oxygen demand (COD), ammonium as nitrogen (N-NH4), nitrate as nitrogen (N-NO3), total dissolved iron (Fe), total dissolved manganese (Mn) and total coliform (TC). The weight (wi) of each parameter was based on principal component analysis (PCA) using monitoring data in 2018 and 2019. The sub-index (qi) of each parameter was determined by a linear function, based on the limit value ​​specified in the National Technical Regulation on Domestic Water Quality (QCVN 01-1:2018/BYT). The GWQI as a function of wi and qi was calculated by the multiplicate formula. The results showed that in 2020, in the province 21.1% of GWQI values ​​ classified as VERY GOOD or GOOD, 31.9% as AVERAGE, 33.2% as POOR and 13.8% as VERY POOR.