I don't think that the study you cited here supports a 52% reduction in diarrhoea risk for these wells. The 52% quote is:
Compared with an unimproved source, provision of an improved drinking water supply on premises with higher water quality reduced diarrhoea risk by 52% (n=2; 0·48 [0·26–0·87])
The wells created by Wells4Wellness do not deliver water to people's homes, as far as I can tell. Doing so would be substantially more expensive. That study also seems to only consider water to be 'improved' if it is chlorinated, filtered, or solar treated. Searching for 'well' in that paper does not yield any hits. I could not find strong studies comparing deep well water to chlorinated water.
Thanks for the input! You’re right, we misunderstood what that paper was saying. Looking into it some more, the most trustworthy number I can find is from the WHO, which says 11-16% diarrhea reduction from a protected well. They also say that “the health benefit is limited because these drinking-water sources may be microbially contaminated and because basic sanitation may not adequately protect the wider community from exposure to excreta.” This probably means that our mortality reduction estimate is also too high.
If we use 13.5% (the middle of the range reported by the WHO) instead of 52%, we get 12 DALYs saved per 1000 people per year. With that number, we get a cost effectiveness of $25 per DALY. Which seems more reasonable than what we were getting before, and is roughly the same cost effectiveness as chlorination. Unless there are other errors in our calculation that we haven’t spotted yet.
Executive summary: An exploratory, back-of-the-envelope evaluation by EA Salt Lake City argues that Wells4Wellness’s boreholes in Niger may avert disease at roughly ~$8 per DALY (or ~$4 per “DALY-equivalent” including economic effects), seemingly clearing Open Phil’s bar by a wide margin, but the authors stress substantial uncertainty and ask for feedback on key assumptions (effect sizes, costs, time-discounting).
Key points:
Method and core assumption: They proxy well water’s mortality impact using GiveWell’s chlorination estimates (12% U5 and 4% 5+ diarrhea-mortality reductions), reasoning Niger’s high diarrhea burden makes these figures conservative.
DALY estimate: With ~20% of the population under five, they derive ~39 DALYs averted per 1,000 people per year (corroborated by a second approach using 2016 Niger U5 diarrhea DALYs × 52% risk reduction → ~46/1,000/year; they adopt the lower 39 for conservatism).
Cost model: Assume an average $10k build cost (mix of basic and “chalet” wells), major repairs of $2k every ~10 years, a 50-year life, and 1,200 users per well → about $360/year totalized cost, ≈ $0.30 per person-year.
Cost-effectiveness: For 1,000 users/year at $300 totalized cost, ~$8/DALY; including GiveWell’s estimated economic/development spillovers roughly doubles benefits → ~$4 per DALY-equivalent.
Comparison to chlorination: A 2023 meta-analysis puts chlorination at $25–$65/DALY (best case ~$27/DALY in MCH settings), implying wells could be ~5–10× more cost-effective, aided by near-universal uptake vs. 30–50% adoption for many chlorination programs.
Open questions/uncertainties: Plausibility of the very low $0.30/person-year cost; appropriateness of treating benefits linearly over a 50-year horizon and how to discount future DALYs; whether using chlorination effects as a stand-in biases results; and how to value quality-of-life gains beyond DALYs/economic effects.
This comment was auto-generated by the EA Forum Team. Feel free to point out issues with this summary by replying to the comment, and contact us if you have feedback.
I think this idea and article are great. This (decision-relevant/skill-building work as a social group) seems like exactly like what EA Groups should be doing. The article is well-written, clear and potentially important.
I don't have enough knowledge to respond to your questions, but here's some thoughts:
Digging wells in Niger seems to be cost-effective, however I wouldn't necessarily generalise that digging wells is cost-effective. (You don't do this, just pointing out for others.)
As you say, a lot of the country is on a large aquifer. This might make this intervention very good in Niger, but not scalable to other places.
Similarly, you've taken maximum values for rate reductions due to Niger having a larger burden. This wouldn't translate to other places.
There's no data here about the overhead of Wells4Wellness (for example salary costs). This could change calculations.
With regards to your Question 4: What do you expect the 'major quality of life improvement' to look like?
(I ask this both genuinely, my knowledge of this area is poor, and as a 'coaching-style' question to answer your question).
Having said that, do you know if W4W is likely to have room for significantly more funding? It seems like a good organisation to support!
Agreed that the effectiveness well-digging probably does not generalize to other organizations or places
Their overhead is only $50k per year, so it's pretty small. And if we are thinking about the returns on an additional/marginal well, it probably doesn't make sense to include fixed costs in our calculations
QoL improvements: Not having to walk extended distance to get their water and then carry it back, being able to use more water because you don't have to carry it so far, not having to drink visually dirty water (https://www.wells4wellness.com/uploads/1/4/9/3/149316772/published/screenshot-278.png?1754683435)
As far as scaling goes, we plan to address that in our next post! They are a small organization, but it sounds like they could probably double in size (which would mean an additional $300k in "revenue" per year) without running out of good well options or organizational barriers anytime soon
A handful of us from EA Salt Lake City are dipping our toes into program evaluation, looking at the impact of an organization run by one of our members. This post highlights the progress we’ve made so far, as well as a number of questions that we’re hoping EA folks with a bit more experience can help us answer.
TLDR: We’ve found that digging wells in Niger easily clears Open Philanthropy's “Bar”, and we are looking for feedback to see if our analysis makes sense.
The Organization: Wells4Wellness
Wells4Wellness has been operating since 2009, digging (and importantly, maintaining) wells across Niger. Niger has one of the highest rates of death from unsafe water sources in the world at around 80 deaths per 100,000 people per year. Most of those deaths are children under 5 dying from diarrhea. A majority of the country is also sitting on top of the Irhazer-Iullemeden Basin, a large aquifer that Wells4Wellness has found surprisingly easy to tap in locations where clean water is needed most.
The founder (Pat Herath) and director of operations (Willie Herath) recently gave a presentation to the EA SLC group, where they gave us an overview of their organization and explained that they are dedicated to maintaining all their wells, which separates them from other well-drilling efforts that often don’t cover maintenance costs. And in the presentation, they shared a very compelling number - that Well4Wellness delivers clean water for $9 per person for life.
A group of us wanted to dig into this number a bit more. What is the impact of clean water for life? How does it compare to other similar interventions like chlorination and to cost-effective interventions recommended by GiveWell?
Our Current DALY Estimates
We borrowed heavily from GiveWell’s research into chlorination, using the (likely conservative) assumption that clean water from wells would be as effective as chlorination at averting deaths from diarrheal diseases. We used available statistics on mortality in Niger, the mortality rate reduction from clean water interventions, and the cost of creating a new well to estimate the cost-effectiveness of Wells4Wellness in dollars per DALY.
Mortality reductions:
GiveWell found the mortality rate reduction in children under 5 years old to be between 6-12% depending on the specifics of the population.
GiveWell found Over 5 mortality rates reductions between 1-4%.
Given that Niger’s diarrhea burden is higher than the 3 countries GW looked at, we took 12% as our Under 5 reduction and 4% as our Over 5 reduction.
DALYs saved:
According to UNICEF, there are 23 under-5 deaths in Niger per 1,000 each year. A 12% reduction would mean 2.76 lives are saved per 1,000.
Assuming an average of 57 years lived per life saved (just taking Niger’s life expectancy of 62 and subtracting 5), that means an intervention on 1,000 children would save 157 DALYs.
There are 5 over-5 deaths per 1,000 each year in the three countries GW looked at, and we’ll use that number since we couldn’t find a Niger-specific one. A 4% reduction would mean 0.2 lives are saved per 1,000.
Assuming an average of 47 years lived per life saved (just taking Niger’s life expectancy of 62 and subtracting the median age of 15), that means an intervention on 1,000 over 5’s would save 9 DALYs.
20% of the population is under 5.
An intervention on 1,000 people would save 39 DALYsper year of operation (under 5 DALYs: 157 * 0.2, over 5 DALYs: 9 * 0.8).
We also used a second method to calculate the DALYs saved:
First, we found an in-depth study which determined that in the year 2016 Niger had 442.1 DALYs lost from diarrheal diseases per 1000 children under 5.
A different study said that providing a clean drinking water supply reduced diarrhea risk by 52%.
Considering that 20% of the Nigerian population is under five, we get 442.1 * 52% * 20% = 46 DALYs saved per 1000 people who are given a clean source of drinking water for a year.
This estimate ignores the benefit to adults, but it includes both mortality and long-term health effects.
It is also reasonably close to our other estimate.
Going forward, we will use the smaller estimate of 39 DALYs saved per 1000 people per year to be conservative.
Costs and ROI
We found it difficult to estimate the costs per person per year of having access to well water.
Wells4Wellness provided us with some key numbers:
Wells provide water for around 1,200 - 1,600 people
Basic wells cost $5k - $6k to dig
Chalet wells cost $8k - $22k to dig
We don’t know the percentage of wells that are basic vs chalet, but if we assume ~ 50-50, we get an average of $10,000 for building a well. We also did a quick Google search and found a different organization that quotes their average cost to add a new well at $9,000, which is close enough to give us confidence that our number is reasonable.
Another key part of a well’s lifetime cost comes from maintenance. Minor repairs are covered by a “well purse” that is budgeted into the original well construction cost. Based on some data from Wells4Wellness on their financials and the major repairs they’ve performed each year, we estimate that major repairs will typically cost around $2,000. And we assume wells need some major repairs every 10ish years on average.
To keep things simple, we make the (conservative) assumption that the well will only last for ~ 50 years, and the number of people using it will be constant every year. So over 50 years, there will be $8,000 of repairs and $10,000 of initial costs, which works out to around $360 a year in costs. With 1,200 people using the well, that’s $0.30 per person per year! That works out to about double the $9 cost per life from their presentation, but is still very impressive!
Cost per DALY:
If 1,000 people are served in a year, 39 DALYs will be saved at a cost of $300, or $8 per DALY
GiveWell also found that the economic effects of chlorination (see rows 147-152 HERE), through reduced healthcare costs and “development effects” (meaning children grow up healthier and earn more throughout their lives as a result), are worth roughly as much as the reductions in mortality. Incorporating those benefits changes our units from DALYs to something less straightforward, but we end up with a cost per DALY-equivalent of only $4!
$4 per DALY is more than 10x under Open Philanthropy’s bar! Too good to be true?
Comparison to Chlorination
We wanted to check how our results compare to water chlorination, which has previously been identified as a compelling cause area. This meta-analysis from 2023 estimates $25-65/DALY averted for chlorination, depending on the intervention. They found the most cost-effective intervention was integrating chlorine distribution and education into existing maternal and child health services, for an estimated $27/DALY averted. Chlorination interventions that involved more infrastructure - point-of-access chlorine dispensers or in-line chlorination - cost an estimated $62-65/DALY averted.
Compared to our estimates for Wells4Wellness, chlorination is ~5-10x more expensive per DALY averted!
Chlorination has received much more interest from EA groups than digging wells, and those groups have done more research than we have, so we are pretty surprised and confused by this result!
There are a few other points to note:
In the point-of-access chlorination interventions, uptake was around 50%, and in maternal and child health services uptake was only about 30%. The DALY estimates above take adoption rates into effect, but even still an intervention with a nearly 100% uptake (wells) is a lot more compelling.
Inline chlorination wouldn’t have the same problems with adoption rates, but it does require existing infrastructure to deliver the chlorinated water to people’s homes. None of the villages prioritized by Wells4Wellness have existing wells, let alone plumbing, so this doesn’t seem like a fair comparison for providing clean water in those areas.
Even if we assume the effects of chlorination and well digging are the exact same, chlorination costs around $1.70 per person per year, which is ~5x more than Wells4Wellness. Even if scaling up chlorine gets the price down to $0.50 per person per year as given here, our estimate for digging wells is still lower.
Time Horizon and Discounting
Our calculation used a 50-year window and divided the total cost by the DALYs saved over that time. For long time horizons, GiveWell has some discussion around discounting benefits that occur in the future, but there is no clear consensus on what the discount rate should be.
We think that even a 50 year lifetime for the wells is a conservative estimate, and that in reality they will last much longer. But there may be reasons to discount the benefits occurring that far in the future. For example, other sources of clean water could be built during that time to make the wells less important. Other reasons to discount future benefits are discussed in this article, though we did not find a clear recommendation on what discount rate to use.
Our Questions
Do our DALY estimates make sense? Are there any assumptions that we missed?
Is it really plausible that it only costs $0.30 per person per year to supply clean water via wells? Chlorination is considered very cost effective and costs around $2 per person per year.
Is our naive method of dividing total cost by total DALYs saved appropriate, or are there any established guidelines for discounting the DALYs saved in the future?
A source of fresh water seems like a major quality of life improvement that isn’t captured in DALYs or economic effects; how can we quantify this?
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I don't think that the study you cited here supports a 52% reduction in diarrhoea risk for these wells. The 52% quote is:
The wells created by Wells4Wellness do not deliver water to people's homes, as far as I can tell. Doing so would be substantially more expensive. That study also seems to only consider water to be 'improved' if it is chlorinated, filtered, or solar treated. Searching for 'well' in that paper does not yield any hits. I could not find strong studies comparing deep well water to chlorinated water.
Thanks for the input! You’re right, we misunderstood what that paper was saying. Looking into it some more, the most trustworthy number I can find is from the WHO, which says 11-16% diarrhea reduction from a protected well. They also say that “the health benefit is limited because these drinking-water sources may be microbially contaminated and because basic sanitation may not adequately protect the wider community from exposure to excreta.” This probably means that our mortality reduction estimate is also too high.
If we use 13.5% (the middle of the range reported by the WHO) instead of 52%, we get 12 DALYs saved per 1000 people per year. With that number, we get a cost effectiveness of $25 per DALY. Which seems more reasonable than what we were getting before, and is roughly the same cost effectiveness as chlorination. Unless there are other errors in our calculation that we haven’t spotted yet.