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

摘要

Safe drinking water source identification is one of the vital components for designing andudestablishing an urban water supply system. Nowadays, water consumption in a country is one of theuddetermining factors related to its development activities. Rapid growth of population and increasedudurbanization activities particularly in developing countries offer great challenges to the water utilityudmanagers and service providers. In this context, a major challenge is to ensure adequate supply of water withudacceptable quality to every city dwellers with minimum cost. However, it is quite difficult to achieve thisudtarget, if there is a shortage in water availability from the existing sources imposed by water quantity andudquality issues. Therefore, a comprehensive assessment task should be undertaken prior to designing andudestablishing a long-term water supply options in an urban area of a developing country like Bangladesh.udIn Bangladesh, municipal water supply scheme mainly depends on the conventional water sources such asudsurface water from the rivers and groundwater from the underlying aquifer. Although the groundwaterudquality is satisfactory for drinking purpose and available abundantly in the shallow aquifer, qualityudlimitations of surface water impose economic constraints with additional treatment cost for system operation.udNevertheless, water availability in both sources may vary from place to place, and must be quantified beforeudany planning and development of water supply scheme. Hence, this study attempts to identify appropriateudconventional water sources by mathematical modelling as an assessment case study before establishing audsustainable urban water supply scheme at Rangunia municipality in Bangladesh, where there is no waterudsupply system at present.udWater demand in the Rangunia municipality is estimated up to the design year of 2040 based on the availableudpopulation census data. Based on the regional model assessment results, suitability of surface water andudgroundwater sources against the existing and projected water demand has been evaluated. The Eastern HilludRegion Model (EHRM) developed and maintained by the Institute of Water Modelling (IWM), Bangladesh isudused for surface water source assessment. The flow simulation in the EHRM has been carried out by usingudMIKE-11 software. For developing groundwater model, the hydrogeological setting and aquifer demarcationudin the municipality area is accomplished by analyzing the individual hydrostratigraphic sections producedudfrom the borehole lithology. The groundwater model domain covers a larger area (4574 sq. km.) to avoid theudboundary influence in model computation, which includes the study municipality (13.34 sq. km.). Therefore,udthe developed groundwater model of the study area spreads over 22 upazillas (sub-districts) of Chittagong,udRangamati and Khagrachhari districts in the eastern part of Bangladesh. Groundwater simulation is carriedudout in an integrated MIKE-11 and MIKE-SHE software platform.udThe simulation results along with measured water quality parameters indicate that none of the surface waterudand groundwater source is suitable for long-term water supply option in Rangunia municipality even thoughudadequate quantity of water is available from both sources. Surface water source is highly associated withudwater quality issues based on Bangladesh drinking water standard, whereas groundwater level shows auddecline trend on long-term exploitation. Therefore, the present study concludes that upon having a suitableudtreatment 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 Bangladesh