Application of groundwater quality index (GWQI) and GIS in groundwater quality zoing in Pleistocene aquifer in Phu My town, Ba Ria – Vung Tau province

Abstract

Pleistocene aquifer is exploited for many purposes, including irrigation, domestic, production, and livestock use in Phu My town, Ba Ria – Vung Tau province. Groundwater Quality Index (GWQI) method combined with Geographic Information System (GIS) foundation is applied to determine the spatial variation as well as the suitability of groundwater in the study area. Water quality parameters in this study include pH, TDS, total hardness, Cl-, F-, NH4+, NO3-, SO42-, Pb2+, and Fe2+ were selected for analyzing from 17 monitoring wells in dry and wet seasons in 2017. The results indicate that water quality parameters such as Cl-, F-, NH4+-N, Pb2+ và Fe2+ exceed the maximum allowable levels by National Technical Regulation on Groundwater Quality. The groundwater quality, according to GWQI analysis results, shows that indicate 88% and 94% of the monitoring wells are from “good” to “excellent” type in the dry and wet seasons, respectively. The number of wells that have water quality from “poor” to “water unsuitable for drinking purpose” varies between the dry and wet seasons. Corresponding with the GWQI map, it shows that the area with good quality groundwater accounts for 98% of the total study area (331.44 km2) in the dry season and 94.5% of the study area (319.58 km2) in the wet season.

Evaluating Groundwater Quality Using Multivariate Statistical Analysis and Groundwater Quality Index

“…The causes of groundwater pollution at the GW24 site may be due to seawater intrusion and improper wastewater and waste management. Compared with other studies, the overall groundwater quality in Ca Mau was better than that in Ha Nam province (GWQI 67-369) [33], but it was worse than the groundwater quality in Ba Ria -Vung Tau [19] and the groundwater quality in Dong Thap, An Giang, Hau Giang, and Kien Giang [15]. The difference in results of GWQI in various areas in the current and former studies could be from the input data.…”

“…Former studies also measured pH values in groundwater. For example, pH in groundwater wells in the Ho Chi Minh City area was in the range of 3.4-7.4 [28], in the areas of Ba Ria -Vung Tau, it was 4.30-7.80 [19], and in the areas of Ha Nam Province, it was 6.19-7.33 [33]. A previous study also found that groundwater pH in the Mekong Delta of Vietnam was in the range of 6.54-7.76 [15].…”

“…For the overall groundwater quality that is presented for a well or an aquifer, the groundwater quality index (GWQI) is used. GWQI calculation requires the use of a set of preidentified groundwater quality data, so the groundwater quality between space and time is easily compared and ranked [8,9,15,19]. GWQI has been widely applied in several former studies [3,8,9,12,13,15].…”

“…GWQI has been widely applied in several former studies [3,8,9,12,13,15]. Recently, multivariate statistical methods, including principal component analysis (PCA) and cluster analysis (CA), have also been widely applied in studying groundwater quality [3,18,19]. PCA is used to reduce data size, providing information on potential polluting sources and key variables influencing groundwater quality [3,20].…”