We evaluated the impact of a programme to provide safe sources of drinking water in rural Bangladesh. The programme consisted of a package of subsidies and technical advice to enable the installation of deep tubewells. Deep tubewells access water from deep aquifers that are free from faecal and arsenic contamination, a major naturally occurring problem in much of rural Bangladesh.
The programme installed wells that provide water that is almost free from arsenic contamination, but not from faecal contamination. The programme successfully installed a total of 107 tubewells in 129 communities throughout 2016 and 2017. In communities where the programme has successfully installed a new water source, the median household is 1.6 minutes’ walk from the new source. The wells installed provide arsenic-safe drinking water, thereby essentially eliminating arsenic contamination at source for those who use them.
However, 34 per cent of installed tubewells unexpectedly tested positive for faecal contamination, compared with 46 per cent of other tubewells in the same communities, suggesting that the programme’s wells only reduce exposure to faecal contamination by approximately 26 per cent. This result is unexpected because the source water is isolated from faecal contamination, meaning that exposure must occur either through the pump body or as a result of shallow groundwater entering the tubewell system.
The test for faecal contamination is coarse, however, meaning that we cannot evaluate whether levels are lower in the installed wells, but only whether faecal contamination is present or not. We therefore may have not fully captured the reduction in exposure to faecal contamination at source.
The programme reduced arsenic contamination in household drinking water, but not faecal contamination. Each tubewell installed under the programme led to a reduction in arsenic contamination of household drinking water that is equivalent to its elimination at the World Health Organization level for about five households. However, each of these tubewells also led to an increase in faecal contamination that is equivalent to introducing faecal contamination into the drinking water of about two households (although we cannot reject a small reduction or no effect on faecal contamination in household drinking water).
Modest improvements in source water quality, with respect to faecal contamination, are offset by an increase in travel time and possibly by changes in storage behaviour. The programme somewhat improved faecal contamination at the source level, but also slightly increased travel time and induced small changes in storage behaviour, both of which increase the risk of faecal contamination in drinking water.
Our best estimates suggest that walking an extra minute to collect drinking water increases the risk of faecal contamination by approximately 1.7 per cent, while storing drinking water in the house increases the risk of faecal contamination by approximately 7 per cent. The consequences of these negative effects are modest because few households walk more than a minute to collect drinking water, and the majority of households did not change their storage behaviour as a result of the intervention.
Key takeaways: Our results suggest that, while deep tubewells can feasibly provide arsenic-safe water in rural Bangladesh, deep tubewell construction programmes may have a limited effect on faecal contamination. These results allay fears that deep tubewell construction programmes may substantially increase exposure to faecal contamination. However, they also suggest that construction of deep tubewells, in the absence of improvements to tubewell design or maintenance practices, is insufficient to resolve the faecal contamination problem in villages in rural Bangladesh. Further research is needed to quantify the extent of faecal contamination in deep tubewells and to understand the contamination channels.