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Program: water supply programs to prevent disease

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In a nutshell

  • Problem: Death and sickness from drinking contaminated water; lack of access to water for adequate hygiene.
  • Program: Improving local water infrastructure to improve access to clean water.
  • Track record: There is evidence that improving water quality can lead to health improvements, but we find it to be more limited, and more contested, than the evidence behind our priority programs.
  • Cost-effectiveness: The most optimistic estimate we've seen comes to about $544 per death averted, but the cost could be $5,000 or higher in other cases.
  • Bottom line: We feel that this intervention can have strong and cost-effective impact, but that there are many relevant variables and a limited evidence base. Donors should require strong monitoring and evaluation, including long-term followup (to ensure that infrastructure does not fall into a disrepair, a substantial concern) from a charity working on this type of program.
Table of Contents

Basics of the program

What is the program? What problem does it target?

This page focuses on water supply programs focused on health issues (though there are other potential benefits to improving the water supply, such as saving time and labor). Relevant diseases include diarrhea, trachoma, and schistosomiasis all of which are transmitted through water or 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

Program track record

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

There appear to be few high-quality evaluations of water supply programs.4 According to the Disease Control Priorities in Developing Countries report, the "most authoritative"5 review of studies is Esrey et al. (1991), which found reductions in morbidity from diarrhea of about 25% due to water improvement projects.6

However, in reviewing this paper, the Disease Control Priorities report emphasizes that it found positive effects (of about 50% reduction in diarrhea incidence) only for projects that piped water "into or near the home" - not for projects that focused on a public water point.7 The report goes on to argue:8

  1. Food contamination is likely to be a more important source of diarrhea than water contamination
  2. Improving hygiene practices is more important than improving water quality in and of itself
  3. 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
  4. "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."

This conclusion is challenged by a relatively recent study that 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.9 The study attributed a 66% reduction in water contamination10 and a 24% reduction in diarrhea incidence11 to the intervention.

Overall, we feel that improving water supply has substantial potential health benefits, but we also see reason to believe the benefits depend heavily on the details of the project and context. We don't believe there is any approach to improving the water supply that has the same level of evidence support that our priority programs have.

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

An additional concern: the question of maintenance

According to Kremer and Zwane (2006):

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 2000.12

Whittington et al. (2008) concurs:

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.13

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 argues (details above):

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 ... 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.14

Note: In September 2011, we confirmed a number of errors in the estimates for the cost-effectiveness of deworming published in the Disease Control Priorities report. Based on those findings, we are currently rethinking our use of cost-effectiveness estimates, like the DCP2's, for which the full details of the calculations are not public. For more information, see our blog post on the topic.
The Copenhagen Consensus 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.15

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.16 (More on the DALY metric.)

Note: In September 2011, we confirmed a number of errors in the estimates for the cost-effectiveness of deworming published in the Disease Control Priorities report. Based on those findings, we are currently rethinking our use of cost-effectiveness estimates, like the DCP2's, for which the full details of the calculations are not public. For more information, see our blog post on the topic.
Using a simple conversion calculation,17 we estimate that ~$5,000 prevents a death from diarrhea and ~2,100 less severe diarrhea episodes.

The recent high-quality study of spring protection discussed above comes to a significantly more optimistic estimate: $16.75 per DALY, implying ~$544 per death averted.18

Note that these estimates assume successful implementation in an area without previous access to clean water/infrastructure. We also note that cost-effectiveness may be diminished when water infrastructure is not properly maintained, something that (as we discuss above) we feel is a legitimate concern.

Sources

  • 1.

    Jamison et al. 2006, Pg 775, Table 41.1.

  • 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." Jamison et al. 2006, Pg 789.

  • 3.

    "The report treated the following technologies as improved: household connection, public stand- pipe, borehole, protected (lined) dug well, protected spring, and rainwater collection.the user's dwelling...Within the broad category of those with reasonable access to an improved water supply, two significantly different levels of service can be distinguished:

    • house connections
    • public or community sources.

    In most settings, these subcategories correspond to very different levels of water consumption, different amounts of time spent collecting water, and as discussed in later sections, different health benefits." Jamison et al. 2006, Pg 772.

  • 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 and Zwane 2006, Pg 8.
    • "Numerous studies have sought to answer these questions, but they are hard to answer rigorously, for several reasons. First, it is almost impossible, ethically and politically, to randomize the intervention. Where the intervention is an improvement in the level of access to water, it cannot be blinded; no placebo exists for a standpost. Where quasi-experimental studies have been used - opportunistically exploiting an intervention allocated by political or technical means - significant confounding has frequently been found (Briscoe, Feachem, and Rahaman 1985).

      Confounding has been especially intractable in studies in which the allocation of facilities has been on a household basis, so that the exposure groups are self-selected - for instance, studies in which individual households that have chosen to install a private tap are compared with others that have chosen not to do so. The former households are likely to be wealthier, better educated, and more conscious of hygiene than their neighbors, so it would not be surprising if they were also more likely do many other things that protect their families from feco-oral disease. The more sophisticated studies have used multivariate models to control for confounding, but where relative risks are low and the exposure groups are self-selected, even those models do not guarantee that confounding is eliminated (Cairncross 1990).

      A further difficulty arises from the fact that cases off eco- oral disease in a given community cannot be considered independent events, because such diseases are infectious. The sample size, it can be argued, is the number of such villages rather than the number of individuals enrolled in the study. Yet a number of important studies in the literature compare a single intervention area with only one control area.

      Other epidemiological weaknesses exist in the data. Blum and Feachem (1983) reviewed 50 studies of the health effect of water supply and sanitation projects and noted that every one contained one or more of these basic errors of methodology. A further weakness in the evidence for the effect of water supply on diarrheal disease burden is that most of it relates to diarrheal disease morbidity, and significant assumptions are needed to extrapolate such evidence to an effect on diarrheal mortality." Jamison et al. 2006, Pgs 776-777.

  • 5.

    "Esrey and Habicht (1985) and Esrey and others (1991) reviewed the same literature from a different perspective. For more than a decade, this review has remained the most authoritative on the subject." Jamison et al. 2006, Pg 777.

  • 6.

    "The median reduction in diarrhoeal morbidity calculated from all the studies was 22%, and from the rigorous studies only, 26% (Table 3)." Esrey et al. 1991, Pg 612.

  • 7.

    "For more than a decade, this review has remained the most authoritative on the subject. However, the small reductions in disease that it reports for water supply conceal an important heterogeneity. Though these overall results are frequently quoted, the following remark by Esrey and others (1991, 613) has usually been overlooked:

    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 pro- tected wells, tubewells, and standpipes.

    In the studies in the two reviews by Esrey and Habicht (1985) and Esrey and others (1991) in which the water supply was provided in the home, the median reduction in diarrheal disease is 49 percent (from 12 studies), and the reduction from the two better studies is 63 percent. Those reductions are several times greater than the overall median impacts in table 41.3. The 63 percent figure will be used in the burden of disease calculations that follow. In the two better studies, the members of the comparison group were using not an unimproved water supply, but a protected water source away from the home. The reductions they found are, therefore, in addition to those resulting from a public standpost level of service." Jamison et al. 2006, Pg 777.

  • 8.

    "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. By contrast, moving the same tap from the street corner to the yard produces a substantial reduction in diarrheal morbidity. How is this pattern to be understood?

    The first step to an explanation is an understanding that most endemic diarrheal disease is transmitted by water-washed routes and is not waterborne. Although waterborne epidemics of diarrheal diseases such as cholera and typhoid have been notorious in the history of public health, the endemic pattern of transmission seems to be different, particularly in poor communities. Five types of evidence support this view:

    • Negative health impact studies. As mentioned earlier, Esrey
      and Habicht (1985) and Esrey and others (1991) cite a number of studies of the health impact of water supplies in
      which water quality improvements have failed to have a significant effect on diarrheal disease incidence.
    • Foodmicrobiology. 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).
    • Hand-washing studies. 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).

    Those five types of evidence suggest that domestic Hygiene - particularly food and hand hygiene - is the principal determinant of endemic diarrheal disease rates and not drinking water quality.

    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. " Jamison et al. 2006, Pgs 777-778.

  • 9.

    "The NGO planned for the water quality improvement intervention to be phased in over four years due to their financial and administrative constraints. Although all springs were eventually protected, for our analysis the springs protected in round 1 (January-April 2005) and round 2 (August-November 2005) are called the treatment springs and those that were protected later are the comparison group...A representative sample of households that regularly used each sample spring was selected at baseline...Water quality was measured at all sample springs and households using protocols based on those used at the U.S. Environmental Protection Agency. The water quality measure we use is contamination with E. coli, an indicator bacteria that is correlated with the presence of fecal matter. The household survey gathered baseline information about child diarrhea and anthropometrics, mothers' hygiene knowledge and behaviors (hand washing), household water collection and treatment behavior, and socioeconomic status." Kremer et al. 2009, Pgs 6-7.

  • 10.

    "Spring protection dramatically reduces fecal contamination of source water. The average reduction in In E. coli across all four rounds of data is -1.07, corresponding to a 66% reduction." Kremer et al. 2009, Pg 10.

  • 11.

    "Spring protection leads to statistically significant reductions in diarrhea for children under age 3 at baseline or born since the baseline survey. In the simplest specification taking advantage of the experimental design, diarrhea incidence falls by -4.5 percentage points...On a comparison group average of 19% of children with diarrhea in the past week, this is a drop of one quarter. We conclude that the moderate reductions in household water contamination caused by spring protection were sufficient to significantly reduce diarrhea incidence." Kremer et al. 2009, Pgs 12-13.

  • 12.

    Kremer and Zwane 2006, Pg 17.

  • 13.

    Whittington et al. 2008, Pgs 57-58.

  • 14.

    Jamison et al. 2006, Pgs 777-778.

  • 15.

    Whittington et al. 2008, Pg 132.

  • 16.

    Jamison et al. 2006, Pg 72, Table 2.B.2.

  • 17.
    • We took data on 2004 (a) incidence (total cases) from World Health Organization, "Disease and Injury Regional Estimates for 2004: Incidence for WHO Regions"; (b) deaths from World Health Organization, "Disease and Injury Regional Estimates for 2004: Deaths for WHO Regions"; (c) DALYs from World Health Organization, "Disease and Injury Regional Estimates for 2004: DALYs for WHO Regions" (using 3% discounting and no age weights, as the Disease Control Priorities in Developing Countries report does - see Jamison et al. 2006, Pg 29).
    • 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.
  • 18.

    "Using the household time values derived from our surveys, the bound on the value of ... avoiding a child diarrhea death is $769 ... Using a standard conversion from diarrhea to disability-adjusted life-years (DALYs), this corresponds to an upper bound on the value of averting one DALY of about $23.68 ... For comparison, we estimate that the cost per DALY averted for this intervention is $16.75." Kremer et al. 2009, Pg 21. In order to "replicate" the unspecified DALY-to-death conversion used by the authors, we applied the ratio between the estimated cost per DALY and the "value of averting one DALY" ($16.75 / $23.68) to the "value of avoiding a child diarrhea death" ($769). Also see the discussion of this study on our blog.

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