Thanks Ray! We'll ask about this, but our understanding is that since Wells4Wellness' wells are deep and pulling from an aquifer, they shouldn't be contaminated.

But the point about post-source contamination is a good one! That's why we switched from just taking GiveWell's chlorination numbers in our first post, to attempting to use well-specific numbers in this post. Unfortunately it was quite hard to find well-specific numbers, so it's a bit of a guessing game for now. But we are seeing that Wells4Wellness is cheaper than chlorination, so it can still be the case that chlorination has a larger impact, but Wells4Wellness is as or more effective per dollar

1. I think the 1,200 people all did not have access to clean water before the well (ie they weren't traveling further to other wells), but I'll see if Willie can confirm that!
2. Water supply-wise, I don't think there's any worry of the well running dry. As far as how much water can be extracted per day, I'm not sure and maybe Willie can help answer that as well, but in all our discussions we never heard of any issues related to this, so I suspect it's not a problem

Thanks for such a thoughtful reply Nick!

1. Fair points. We think the 50 year expected lifespan is reasonable, but we should probably account for uncertainty.
   1. Water-wise, it sounds like the basin under Niger is much larger than in other parts of Africa, so there isn't a risk of the water running out soon.
   2. But as you mention, there are still other uncertainties, and discounting would be the easiest way to deal with those.
   3. To avoid doing harder math, if we assume a 20 year lifespan and no discounting, we'd be at around $16 per DALY (instead of $10 per DALY).
2. Willie would probably have a better answer for you here and I think he's going to take a look at this! My understanding is that there are only a couple parts of the well that are at much risk of needing maintenance, and those parts are replaced roughly every 10 years. But there isn't an expectation that maintenance costs will increase over time
3. Good point! It looks like the U5 mortality rate in Niger has gone down ~ 10% in the past decade, so diarrhea morbidity also has probably improved. Maybe the easiest way to deal with this is through discounting? Or we can just assume the diarrhea burden goes down ~1% per year
4. Thanks. I can't figure out what our source was for 20%, but changing to 18% wouldn't make a big difference
5. No idea on this one! Hopefully Willie can talk a bit about that when he checks this out. 1,200 does seem high when I look up "how many people share a water well in africa?"
6. Thanks for sharing this! We hadn't seen your post but its very interesting!
   1. We agree the cross-sectional studies we cited are super limited, which is why we relied on GiveWell's chlorination mortality estimates in our initial draft.
   2. We moved away from GiveWell's numbers after we got a comment suggesting wells are a bit less effective than chlorination, because water can get contaminated between when its taken from the well and when its used.
   3. We should probably just use GiveWell's numbers and apply a small penalty for wells (can't imagine wells are more than 10-15% less effective?). That way we aren't relying on these meh papers, and can instead rely on a team that's spent a lot of time thinking about this.
   4. We get very similar estimates when we use GiveWell's numbers, so I don't think this would change much. Though if you're right that GiveWell might be underestimating the effect, that would obviously improve things.

My guess is that making some of the changes mentioned above might 2x-3x the cost per DALY, to something like $20-$30, which would still be great!

Thanks! 

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 

Does anyone know more about how the German university and immigration systems works? They accept anyone from any country who can get there and has a high school degree? And then how hard is it to stay in the country after graduation?

If they do accept anyone, and its easy to stay there after school, why aren't more people (who are a bit better off than the people Malengo's working with) doing this? Or maybe they are and I just haven't heard about it