Investigation of Groundwater Quality and Its Suitability for Drinking and Agricultural Use in the South Central Part of the Coastal Region in Bangladesh

To examine the groundwater quality a total of 120 groundwater samples were collected from two southern districts; Barguna (27 points) and Patuakali (33 points) of Bangladesh in two seasons viz., pre-monsoon (60 samples) and post-monsoon (60 samples) in 2012. A comprehensive analysis has been conducted to explore the groundwater hydrochemistry and effects of major ions on the suitability for potable water and agricultural uses. Geochemical analyses have clearly shown that the seasonal effect does change the order of abundance of major ions in the groundwater, while principal component analysis confirmed the reasons of extreme salinity and hardness. Piper diagram showed that the predominant hydrochemical facies for the groundwater were Na+-Cl−-SO42− and Na+-K+-HCO3− types. The chloroalkaline index confirmed that the ion exchange was governed mainly in water phase. Equiline diagram explained the relationship among the alkali with total cations and anions where cations were more dominant than anions at 1:1 ratio. The Gibb’s diagram illustrated the chemical composition of water mainly influenced by precipitation from the water sources. The molar ratio Cl−/Σanions and Na+/Na++Cl− indicated that the groundwater of the study area was affected by seawater intrusion. In addition to unsuitable salinity (>5000 µs/cm), Kelly’s ratio, total hardness, sodium absorption ratio, residual Sodium carbonate, and Na  % clearly indicated that the groundwater in the study area were not suitable for drinking, irrigation, and domestic uses. Moreover, the spatial distribution maps were drawn to observe the spatial extent of EC, TDS, SAR, and SSP using IDW technique. Thus, considering all the above findings this area needs special attention to ensure the supply of potable water and to maintain sustainable agricultural activities.