In a nutshell

Basics of the program

What is the program? What problem does it target?

Water supply programs primarily target diseases such as diarrhea, trachoma, or schistosomiasis that are transmitted through water or that can be alleviated through improved hygiene.1 Of these, diarrhea has by far the largest potential burden of disease averted by improved access to clean water.2

What are the components required to implement this program - how does it work?

There are many types of improved water supply programs. A key distinction is between house connections, which provide water directly to a user's home, and public water points, which provide water at a shared, communal location, such as a standpost, borehole, or dug well.3 We focus on public water points, which are the types of water programs we most commonly see charities implementing.

Program track record

Micro evidence: Has this program been rigorously evaluated and shown to work?

More on our interpretation of "micro evidence" and evaluation quality here.

There appear to be few high-quality evaluations of water supply programs.4 According to the Disease Control Priorities Report, the "most authoritative"5 review of studies is Esrey (1991). Esrey reviewed 14 "rigorous" studies, including both house-connections and public water points, which evaluated programs aiming to improve water supplies. He found that programs had a modest impact on preventing diarrhea. But, he writes, "In the studies reporting a health benefit, the water supply was piped into or near the home, whereas in those studies reporting no benefit, the improved water supplies were protected wells, tubewells, and standpipes."6

A relatively recent study appears to be of higher quality than other studies we've seen, using a randomized rollout of spring protection to gauge the effect on water quality and health.7 It found a large improvement in the quality of available water,8 but some evidence of a smaller improvement in the quality of consumed water,9 and ultimately no significant impact on children's health.10

Why don't water supply programs work?

We believe that there are two primary reasons why these types of water supply programs may have little impact on diarrhea:

• There are many paths through which a child can acquire diarrhea, such as flies or food, and contaminated water is just one.11
  Note that improved hygiene, through hand washing, has itself had some success in reducing diarrhea.12 According to the Disease Control Priorities Report, increased access to water only has an impact on hygiene activity when either (a) the previous water source was more than 1 kilometer from the user's home or (b) the new source is connected directly to the user's home.13

In addition, the effectiveness of a program depends heavily on the particular local circumstances in which it is implemented. Projects that have succeeded in some locations, may fail in others.14

Finally, the reviews discussed above assume that water infrastructure remains in working order. However, historically, water infrastructure has frequently broken down or been abandoned. According to Kremer (2007), "Infrastructure maintenance has historically been a major problem in developing countries and in the rural water sector in particular. For instance, a quarter of India’s water infrastructure is believed to be in need of repair (Ray 2004). The World Development Report (World Bank 2004b) estimates that more than one-third of existing rural water infrastructure in South Asia is not functional. Miguel and Gugerty (forthcoming) report that in western Kenya, nearly 50 percent of borehole wells dug in the 1980s, and subsequently maintained using a community-based maintenance model, had fallen into disrepair by 2000."15

Whittington (2008) concurs, writing, "Rural water supply programs in developing countries have had a checkered history. In the 1980s sector professionals recognized that many rural water supply programs were in disarray (Churchill et al. 1987; Briscoe and DeFerranti 1988). Regardless of the type of technology utilized, rural water systems were not being repaired and many were simply abandoned."16

Macro evidence: Has this program played a role in large-scale success stories?

We know of no such large-scale success stories.

Recommendations and concerns

Do expert reviews of the comparative merits of interventions endorse this one?

The Disease Control Priorities Report states that water supply improvements have a relatively small effect on disease: "The full list of water-related infections is large and varied, but most are only marginally affected by water supply improvements."17 The report later states, "Providing a public water point appears to have little effect on health, even where the water provided is of good quality and replaces a traditional source that was heavily contaminated with fecal material."18 Improving water infrastructure could be effective, but only in relatively rare circumstances: "water supplies are likely to have an effect on diarrheal disease when they lead to hygiene behavior change - that is, when the old source of water was more than 30 minutes’ roundtrip away or when house connections are provided."19

The Copenhagen Consensus is more optimistic, but still cautious, recommending the intervention only in cases where there's reason to believe it fits the particular circumstances of the target group. The paper on water and sanitation concludes, "We believe that all four of the interventions discussed in Part II (rural boreholes and hand pumps, community-led total sanitation, point-of-use treatment with biosand filters, and large dams in Africa) hold considerable promise for improving the economic livelihoods and health conditions of hundreds of millions of people in developing countries. None of these interventions, however, is a panacea. The success of each intervention will depend on the specific context in which it is implemented. The social context matters, as well as the physical and economic contexts, particularly where behavioral change is required for positive outcomes."20

What are the potential downsides of the intervention?

We have not identified any widely recognized downsides.

Cost-effectiveness

The Disease Control Priorities report estimates that water supply programs can cost $159 per disability-adjusted life-year (DALY) averted when implemented in areas without existing access to water, though they cost far more ($1,974-6,396 per DALY) when implemented in areas with some existing infrastructure.21 (More on the DALY metric here.)

Using a simple conversion calculation,22 we estimate that ~$5,000 prevents a death from diarrhea and ~2,100 less severe diarrhea episodes. Note that this estimate assumes successful implementation in an area without previous access to clean water/infrastructure.

Sources

• Disease Control Priorities Project, Second Edition. 2006. Available for download online at http://dcp2.org/pubs/DCP, accessed 7/6/09.
• Esrey, Steven. 1991. "Effects of Improved Water Supply and Sanitation." Bulletin of the World Health Organization. 69(5):609-621. Available online at http://whqlibdoc.who.int/bulletin/1991/Vol69-No5/bulletin_1991_69(5)_609-621.pdf, accessed 6/30/09.
• Kremer, Michael, Jessica Leino, Edward Miguel, and Alix Peter Zwane. 2006. "Spring Cleaning: A Randomized Evaluation of Source Water Quality Improvement." Available online at http://www.economics.harvard.edu/faculty/kremer/files/springclean.pdf, accessed 7/6/09.
• Kremer, Michael, and Alix Peterson Zwane. 2007. "Cost-Effective Prevention of Diarrheal Diseases: A Critical Review (April 2007)." Center for Global Development Working Paper No. 117. Available online at http://www.brookings.edu/papers/2006/03development_kremer.aspx, accessed 7/6/09.
• Whittington, Dale, W. Michael Hanemann, Claudia Sadoff, Marc Jeuland. 2008. "Copenhagen Consensus 2008 Challenge Paper: Sanitation and Water." Available for download online at http://www.copenhagenconsensus.com/Default.aspx?ID=1150, accessed 7/6/09.

1. 1.

   DCP 2006, Pg 775.

2. 2.

   "Because the effect on diarrheal disease accounts for the vast majority of the effect, no effort is made to apportion the costs between their effectiveness in preventing the other diseases affected by water supply, sanitation, and hygiene." DCP 2006, Pg 789.

3. 3.

   DCP 2006, Pg 772.

4. 4.

   "A central shortcoming of the existing literature is its reliance on retrospective, nonrandomized approaches (for example, comparing outcomes in villages with wells to outcomes in other nearby villages without wells). Such comparisons are problematic because villages with and without wells may differ along other dimensions that also affect the incidence of diarrheal disease. For instance, a village may have a well because it is better organized or wealthier. These attributes may themselves make residents healthier, whether or not they have a village well, so disentangling the “well effect” from the “wealth effect” is in practice difficult, if not impossible. Controlling for all the important differences between villages in multivariate regression analysis may be difficult, if not impossible. Retrospective strategies are especially suspect in this context due to the considerable variation in diarrhea from year to year, as well as the possibility of underlying trends that may differ across even small geographic regions." Kremer 2007, Pg 8.

5. 5.

   DCP 2006, Pg 777.

6. 6.

   Esrey 1991, Pg 613.

7. 7.

   "Using a randomized impact evaluation approach, in which spring protection is phased-in across 200 springs in a randomized order, we estimate impacts on source water quality, household water quality, child health, and on household water collection choices and other health behaviors. Our approach differs from the existing literature on source water quality interventions in several ways. First, unlike many other studies, we are able to isolate the impact of a single treatment rather than a package of services. Second, we use a randomized design and a large sample size, and are able to take intra-cluster correlation into account. Third, rather than assuming or simulating ex post contamination between the source and the home, we have detailed longitudinal data on water quality at both points, where water contamination is measured by the fecal indicator bacteria E. coli. We are thus able to directly assess the extent to which source water quality improvements at springs translate into household water quality gains, and to evaluate the claim that source water quality improvements are most valuable in the presence of pre-existing household access to improved sanitation and good hygiene practices. " Kremer et al. 2006, Pg 3.

8. 8.

   "In our first empirical result, we find that spring protection is very effective in improving the quality of water at the source. Among “sole-source users”, those households that collected all of their drinking water from the sample spring at baseline, spring protection is also highly effective at improving household water quality." Kremer et al. 2006, Pg 4.

9. 9.

   "However, among the 'multi-source users' – those households that collected at least some of their water from sources other than the sample spring at baseline – estimated home water quality gains are much smaller. We find that these multi-source users dramatically shifted their water collection trips towards protected springs after the intervention. We show in the formal model of source water choice that this sorting may account for the lack of observed home water quality gains, to the extent that some alternative water sources are less contaminated than the sample springs. A possible implication is that programs improving all water sources in an area might have larger impacts on home water quality than programs that only improve a subset of sources." Kremer et al. 2006, Pg 4.

10. 10.

    "Consistent with both the moderate home water quality gains and modest household willingness to pay for improved water we estimate, we find no evidence of large positive spring protection impacts on the average health or nutrition of young children in treatment households. Even for sole-source user households alone, a group that did experience significant home water quality gains, there are no statistically significant impacts on child health or nutrition, and this is true both for diarrhea as well as for child weight and height. This finding is consistent with an epidemiological model in which the primary causes of diarrhea are not waterborne. However, statistical power is a concern with these estimates, and ongoing project data collection will allow us to estimate child health and nutrition impacts more precisely." Kremer et al. 2006, Pgs 5-6.

11. 11.
    "Food microbiology. Studies of the microbiology of foods in developing countries—particularly the weaning foods fed to children in the age group most susceptible to diarrheal disease—have shown such food to be far more heavily contaminated with fecal bacteria than is drinking water (Lanata 2003), even when the water has been stored in open pots.
    • Seasonality of diarrhea. In countries with a seasonal variation in temperature, bacterial diarrheas peak in the warmer season, whereas viral diarrheas peak in the winter. This pattern suggests that the bacterial pathogens show environmental regrowth at some stage in their transmission route, which means that they must have a nutritional substrate. Water is, thus, a less likely vehicle than food.
    • Fly-control studies. Trials in rural Asia and Africa have shown that fly control can reduce diarrheal disease incidence by 23 percent (Chavasse and others 1999)." DCP 2006, Pgs 777-8.

12. 12.

    "A recent systematic review of the effect of hand washing with soap has shown that this simple measure is associated with a reduction of 43 percent in diarrheal disease and 48 percent in diarrheas with the more life-threatening etiologies (Curtis and Cairncross 2003)." DCP 2006, Pg 778.

13. 13.

    "The second step is an understanding of how the level of service and convenience of a water supply influence such hygiene practices in the home. Taking the amount of water used per capita as an indicator of hygiene changes, other things being equal, one finds that providing a source of water closer to the home—and therefore more convenient to use—has very little effect on water consumption unless the old source was more than 1 kilometer (30 minutes’ roundtrip journey) away from the user’s dwelling (Feachem and others 1978). However, water consumption doubles or triples when house connections are provided (White, Bradley, and White 1972), and reason exists to believe that much of the additional consumption is used for hygiene purposes. For example, Curtis and others (1995) found that provision of a yard tap nearly doubled the odds of a mother washing her hands after cleaning her child’s anus and more than doubled the odds that she would wash any fecally soiled linen immediately. In conclusion, water supplies are likely to have an effect on diarrheal disease when they lead to hygiene behavior change— that is, when the old source of water was more than 30 minutes’ roundtrip away or when house connections are provided." DCP 2006, Pg 778.

14. 14.

    "We believe that all four of the interventions discussed in Part II (rural boreholes and hand pumps, community-led total sanitation, point-of-use treatment with biosand filters, and large dams in Africa) hold considerable promise for improving the economic livelihoods and health conditions of hundreds of millions of people in developing countries. None of these interventions, however, is a panacea. The success of each intervention will depend on the specific context in which it is implemented. The social context matters, as well as the physical and economic contexts, particularly where behavioral change is required for positive outcomes." Whittington 2008, Pg 132.

15. 15.

    Kremer 2007, Pg 17.

16. 16.

    Whittington 2008, Pgs 57-8.

17. 17.

    DCP 2006, Pg 775.

18. 18.

    DCP 2006, Pg 777.

19. 19.

    DCP 2006, Pg 778.

20. 20.

    Whittington 2008, Pg 132.

21. 21.

    DCP 2006, Pg 72, Table 2.B.2.

22. 22.
    • We took data on 2004 (a) incidence (total cases); (b) deaths; (c) DALYs (using 3% discounting and no age weights, as the DCP does - see DCP 2006, Pg.29) from http://www.who.int/healthinfo/global_burden_disease/estimates_regional/e..., accessed 7/6/09
    • There were a total of ~67 cases per DALY, and ~2136 cases per death.
    • $159 per DALY averted thus implies $2.37 (159/67) per case averted. Assuming one would have to avert 2,136 cases to avert a single death implies a cost of ~$5,000 per death averted.