Evaluation of groundwater quality and its suitability by applying the geospatial and IWQI techniques for irrigation purposes in the southwestern coastal plain of Bangladesh

The groundwater quality for irrigation and drinking purposes has become a great concern because of salinity intrusion in the coastal zone of Bangladesh. The aim of this study is to investigate an irrigation water quality index (IWQI) by using the model of geostatistics and multivariate indices in the southwestern coastal part of Bangladesh. The spatial distribution of major cation (Ca 2+ , Mg 2+ , Na + , K + ) and anion (HCO 3 − , SO 4 2− , Cl − ) maps have been made by the interpolation of GIS based on the WHO standard. Principal component analysis and cluster analysis diagram have been used to explain the hydrochemical procedure in the aquifer. The analytical results show that aquifer water of this coastal study area is primarily of high salinity (NaCl rich). The IWQI, geostatistical analysis, and multivariate statistics (analysis of regression model) have revealed the areas of the spatial distribution and indicated the suitable-unsuitable areas for irrigation. According to IWQI, the total study area has split into 34.15% (good areas), 23.84% (permissible areas), 17.07% (dubitable areas), and 24.94% (severe areas), respectively, and no excellent groundwater areas have been identified. There was a vast relation with (NaCl) or salinity and the other effective parameters or higher amount of EC and TDS which was represented by the regression and geostatistical analysis model. Finally, remediation measures have also been suggested for the prediction of unsuitable zone.