Identifying safe drinking water source for establishing\ud sustainable urban water supply scheme in Rangunia\ud municipality, Bangladesh

Safe drinking water source identification is one of the vital components for designing and\ud establishing an urban water supply system. Nowadays, water consumption in a country is one of the\ud determining factors related to its development activities. Rapid growth of population and increased\ud urbanization activities particularly in developing countries offer great challenges to the water utility\ud managers and service providers. In this context, a major challenge is to ensure adequate supply of water with\ud acceptable quality to every city dwellers with minimum cost. However, it is quite difficult to achieve this\ud target, if there is a shortage in water availability from the existing sources imposed by water quantity and\ud quality issues. Therefore, a comprehensive assessment task should be undertaken prior to designing and\ud establishing a long-term water supply options in an urban area of a developing country like Bangladesh.\ud In Bangladesh, municipal water supply scheme mainly depends on the conventional water sources such as\ud surface water from the rivers and groundwater from the underlying aquifer. Although the groundwater\ud quality is satisfactory for drinking purpose and available abundantly in the shallow aquifer, quality\ud limitations of surface water impose economic constraints with additional treatment cost for system operation.\ud Nevertheless, water availability in both sources may vary from place to place, and must be quantified before\ud any planning and development of water supply scheme. Hence, this study attempts to identify appropriate\ud conventional water sources by mathematical modelling as an assessment case study before establishing a\ud sustainable urban water supply scheme at Rangunia municipality in Bangladesh, where there is no water\ud supply system at present.\ud Water demand in the Rangunia municipality is estimated up to the design year of 2040 based on the available\ud population census data. Based on the regional model assessment results, suitability of surface water and\ud groundwater sources against the existing and projected water demand has been evaluated. The Eastern Hill\ud Region Model (EHRM) developed and maintained by the Institute of Water Modelling (IWM), Bangladesh is\ud used for surface water source assessment. The flow simulation in the EHRM has been carried out by using\ud MIKE-11 software. For developing groundwater model, the hydrogeological setting and aquifer demarcation\ud in the municipality area is accomplished by analyzing the individual hydrostratigraphic sections produced\ud from the borehole lithology. The groundwater model domain covers a larger area (4574 sq. km.) to avoid the\ud boundary influence in model computation, which includes the study municipality (13.34 sq. km.). Therefore,\ud the developed groundwater model of the study area spreads over 22 upazillas (sub-districts) of Chittagong,\ud Rangamati and Khagrachhari districts in the eastern part of Bangladesh. Groundwater simulation is carried\ud out in an integrated MIKE-11 and MIKE-SHE software platform.\ud The simulation results along with measured water quality parameters indicate that none of the surface water\ud and groundwater source is suitable for long-term water supply option in Rangunia municipality even though\ud adequate quantity of water is available from both sources. Surface water source is highly associated with\ud water quality issues based on Bangladesh drinking water standard, whereas groundwater level shows a\ud decline trend on long-term exploitation. Therefore, the present study concludes that upon having a suitable\ud treatment of surface water, existing surface water and/or groundwater sources can be used as safe drinking water sources for developing sustainable water supply scheme in Rangunia municipality of Banglades