In recent years, there has been a significant progress in understanding the source and mobilization process, sediment-water interactions, and distributions of arsenic in groundwater environment in Bangladesh. However, the impacts of arsenic mitigation are still very limited. A social survey conducted during 2009-2011 in 96 villages in Matlab revealed that only 18% of total tubewells provide As-safe water. The safe water access also varied between 0 and 90 percent in the region due to lack of knowledge about the local geology and unplanned tubewell development. SASMIT, an initiative of KTH-International Groundwater Arsenic Research Group has developed a method for safe tubewell installation considering hydrogeological suitability, safe water access and other relevant social and demographic information into account.
Piezometers installed at 15 locations over an area of 410 km2, using local boring techniques allowed to delineate the hydrostratigraphy, characterize the aquifers in terms of sediment characteristics, water chemistry and hydraulic head distribution, which ultimately led to the identification of the suitable aquifers for tapping safe water. The piezometer locations with safe drinking water quality were then targeted for safe well installation based on the determination of safe buffer distances in a cluster of a few villages (mouzas). Social mapping of all the villages within the mauzas were done using GIS to evaluate the availability of safe water options for a cluster of households (bari). For safe well installations, priority was given to regions with safe water access, greater number of beneficiaries especially in poor households, and easy access to the site from a cluster of households. Through this approach, it was thus possible to make 95% of the newly installed wells As-safe thus scaled up the safe water access upto 40% in some mauzas. Thus the as a strategy to improve safe water access, the SASMIT study recommends investigating the hydrogeological suitability through installation of few piezometers with a minimum effort and based on the results the implementation plan can be made using GIS based social mappings for relatively uniform distribution and to maximize the safe water access.
Landforms comprising the older and younger flood plains (OFP & YFP) in Meghna basin surrounding Matlab, southeastern Bangladesh have been identified through the visual interpretation of Google Earth images. The interpretation reveals that the visually identified OFP and YFP are characterized by different geomorphic components. The fluvial geomorphology shows a close relation with the distribution of arsenic (As), manganese (Mn) and iron (Fe) in groundwater from the aquifers. It was interpreted that the fluvial processes which results the landforms in the active floodplain influence the groundwater As occurrences. Less active processes in the stable and well developed OFP decreases the risk of elevated As in groundwater. The off-white and white sand aquifers of the OFP are contended with low levels of As (<50 μg/L) but high levels of Mn and Fe, whereas the off-white aquifers of YFP are contended with high levels of As (>50 μg/L) and Fe but low levels of Mn. Thus, the landforms can be taken into consideration before installing tubewells in a floodplain area.