Exploring suitable sites for installing safe drinking water wells in coastal Bangladesh

Development, monitoring and management of drinking water resources, especially groundwater, are essential for sustainable water abstraction. The present study aimed to explore suitable locations and depths for installing tubewells for safe drinking water. Tala upazila of Satkhira district, in the coastal area of Bangladesh, was selected as the study area. Groundwater samples were collected from 632 shallow tubewells (STW) and deep tubewells (DTW). In-situ measurements were done for seven important water quality parameters, such as arsenic (As), iron (Fe), electrical conductivity (EC), temperature (T), Total Coliform-TC, E. coli and Faecal Coliform (FC). Weighted arithmetic water quality index (WQI) was used to calculate the suitability of drinking water collected from tubewells. Experimental value based maps for each parameter were prepared and safe aquifer sites were identified using WQI and geo-statistical as well as geo-spatial analysis. Range of As, Fe and EC were found to be below detection limit (bdl)–500 µg/L, bdl–18 mg/L and 165–8715 µS/cm, respectively and for STW, 88%, 99% and 100% and for DTW, 64%, 71% and 100% exceeded WHO drinking water standards. Comparatively high proportion of STW (TC-41%, E. coli−24% and FC-49%) contained coliform bacteria than DTW (TC-23%, E. coli−15% and FC-28%). Only small proportional areas, such as 24 km² for As, 27 km² for Fe, 113 km² for TC, 132 km² for E. coli and 102 km² for FC were found safe in DTW. Multiple patches of safe aquifer were identified at greater depths in the northern, north-central, central and south-western part of the study area. According to WQI, overall 39 km² area (12% of total area) was explored as suitable sites for installing tubewells where good to excellent quality water could be found in aquifers at greater depth. The findings will help policy makers, practitioners and local communities to find out the suitable locations and depths for installation of tubewells in the study area for abstraction safe drinking water.