Q: Is there a significant difference between water quality in shallow wells and boreholes? Proponents of boreholes say they are preferable because they produce better quality water, while others say protected shallow wells can serve more people with water of acceptable quality at lower costs.
A. In a quick scan of the literature (see below), we found a few studies from Cambodia, Bangladesh and Zimbabwe that confirmed that the microbiological water quality of boreholes was better that of shallow wells. A Bangladesh study added that increased access to boreholes or borehole density lowered the risk of childhood diarrhoea. This confirms earlier studies that water quantity is a more important determinant of the health benefits than water quality.
Quick literature scan
A water quality study [1a, 1b] in rural Cambodia showed that a shallow aquifer was chemically less of a health risk than a deep aquifer; however, microbial contamination was considerable for both open and rope-pump shallow wells. Nevertheless, contaminants present in shallow wells may readily be removed by simple household water treatment.
A study [2a] in Bangladesh revealed that the risk of childhood diarrhoea was 46% lower in the 179 households that used a deep tube well than in the 364 that used a shallow tube well (P=0.032). Neither socioeconomic status, latrine density, population density nor study year had a significant influence on disease risk. Another study [2b] in Bangladesh concluded that increased access to tubewells (greater tubewell density) was associated with a lower risk of childhood diarrhoea. Intermediate-depth wells (40-90m) were associated with more childhood diarrhoea compared to shallower or deeper wells (90-300m).
Studies in Zimbabwe, Mozambique and Zambia showed that “significant improvements of the water quality can be achieved without the use of high technology solutions” by upgrading shallow family wells . Still, tests carried out between 1984-1985 in Zimbabwe, showed a significant difference between the microbiological water quality of tubewells and upgraded wells [3, tab. 1]. Lane and Robinson  countered that health benefits can be assured if the upgrading programmes are backed by effective health and hygiene education. “Furthermore, sector specialists worldwide now agree that the quantity of water used is a more important determinant of the health benefits of improved water supplies than the quality of water itself. UFWs [Upgraded Family Wells], being located adjacent to houses, result in much higher levels of water use than communal boreholes. Proximity also encourages the use of water for vegetable and fruit production and hence improved nutrition”.
[1a] Bennett, H.B. et al., 2010. Characterisation of the water quality from open and rope-pump shallow wells in rural Cambodia. Water Sci Technol. 2010;61(2):473-9. Available at: < doi:10.2166/wst.2010.817>
[1b] Sampson, M., 2008. Water quality assessment of hand dug wells. Phnom Penh, Cambodia: Ideas at Work. Available at: < http://bit.ly/KRU7hZ>
[2a] Escamilla, V. et al., 2011. Effect of deep tube well use on childhood diarrhoea in Bangladesh. In: Bulletin of the World Health Organization, vol. 89, no. 7, p. 521 – 527. Available at: Available at: <http://www.who.int/bulletin/volumes/89/7/10-085530.pdf> and <http://www.washdoc.info/docsearch/title/174799>
[2b] Wu, J. et al., 2011. Impact of tubewell access and tubewell depth on childhood diarrhea in Matlab, Bangladesh. Environ Health. 2011 Dec 22;10:109. Available at: <doi: 10.1186/1476-069X-10-109>
 Rogenhofer, E., 2005. Self supply in Busia Town, eastern Uganda. MSc. Thesis. Cranfield, UK: Cranfield University. Available at: <http://www.rwsn.ch/documentation/skatdocumentation.2010-12-07.5409359917/file>
 Lane, J. ed. and Robinson, P., 2002. Upgraded Family Wells in Zimbabwe : household-level water supplies for multiple uses. (Field note / WSP; no. 7). [online] Nairobi, Kenya: World Bank. Available at: <http://www.wsp.org/filez/pubs/af_bg_zm_wells.pdf> and <http://www.washdoc.info/docsearch/title/123819>