Suitability of drinking water services in greater Southwestern coastal Bangladesh

Abstract

In Bangladesh, a major development challenge is to achieve the Sustainable Development Goal (SDG) 6.1 of safely managed drinking water, which not only accounts for access but also includes quality, quantity, reliability, and affordability aspects of water services. The challenges are even harder in water-stressed, hard-to-reach areas, such as the greater southwest coastal region, where complex hydrogeology and highly varying water quality contribute to highly vulnerable and insecure water environment. Investment decisions are often hindered by gaps in knowledge of detailed hydrogeology, and the coverage by different drinking water supply systems, especially for the poor and disadvantaged.

The objectives of this study were to analyze spatial inequality of groundwater quality risks and delineate safe aquifers in the study area (greater southwest coastal zone, including Satkhira, Khulna, Bagerhat, Barisal, Pirojpur, Barguna, Jhalokathi, Patualhali and Bhola districts), map drinking water insecurity hotspots, assess suitability of drinking water supply systems in different hydrogeologic and socio-economic settings, and hence identify drinking water investment priorities. The methodology included mapping of spatial inequality of groundwater risks and hence safe aquifers at union-scale from hydrogeology and water quality based on secondary data, delineating regional drinking water infrastructures and their functionality, based on secondary data base from different sources, estimating reliability index of existing water services via synthesizing climate resilience and functionality, delineating settlement areas along with socio-economic vulnerability and multi-dimensional poverty, and mapping drinking water insecurity hotspots via integration of different indicators derived from the above analysis. Three high water insecure areas were studied following a mixed method approach including semi-structured interviews and group discussions to investigate the suitable technologies/services and the factors that influence their suitability for specific conditions.

Groundwater quality maps using 9348 EC, 3524 As, 2771 Fe and 1887 Mn points indicate that more than 50% of the total 567 study area unions do not have suitable safe water according to the Bangladesh water quality guideline. This indicates high spatial variability of groundwater insecurity, and the need for alternative options. Since the deeper aquifers are found comparatively more suitable, deep tubewells are the prominent technology except the unions adjacent to the Sundarbans and the unions exposed to the sea where PSF and RWH are two main technologies for drinking water. DTWs and STWs are more functional while PSFs are the least functional technology. Additionally, due to the risk of frequently occurring storm surge hazard, the reliability also decreases in the Sundarbans surrounding areas where PSF and RWH are mainly used. Water insecurity also aligned with high poverty levels in the sea exposed unions, char lands and the Sundarbans surrounding areas.

Water insecurity hotspots at union-scale integrates five water security criteria i.e., water availability, quality, accessibility, affordability, and reliability. Water insecurity is higher in the southernmost unions of each district and southwest districts are more water insecure than southcentral districts. However, there are some scattered and pocket water insecure unions in other parts of the regions. But all of the water insecure unions have varying level of difficulties. Though the accessibility of water infrastructure is relatively better, higher poverty rate along with high spatial variability of groundwater quality and hydrogeologic heterogeneity contribute to high levels of water insecurity.

The deep dive analysis in three relatively very high-water insecure unions revealed that the suitability of water services is mainly determined by the availability of technology or services and the level of poverty in each area. People in high poverty area are using cheaper water and prefer free of cost option like RWH and pond. On the other hand, people in the low poverty area are using high-cost water and they prefer good quality water and services like RO-vendor, while the moderate poverty area is using moderate quality water and they prefer to consume moderate to high quality water. But their services are hindered by high cost of water and the unavailability of technology. Therefore, future investment should not focus on a single technology, rather need to consider the above discussed socioeconomic and hydrogeologic factors to determine the suitable option for a specific area.