Sounds like the Bimbache people could support 4x the population that the Spanish could (8,000 vs. 2,000), which makes sense (water being the limiting resource in that landscape).
Why discount pp156 again? The numbers are perfectly doable with a carefully placed tree that uses the surrounding landscape to funnel fog to it.
Lead pipes wouldn't be needed for the entire length — clay-lined spillways would more than suffice. I read it as using lead just to the cistern.
Before starting, let me say that I've found this conversation very interesting. Thank you for participating in it with me.
I discounted it for several reasons.
1) There's no corroborating evidence that the population was that high. I haven't found anything more than "sparse", but http://www.sharprazor.com/palma-history.htm gives some of the history of La Palma:
> The Guanches named their island Benahoare, and divided it into 12 kingdoms, each with its own ruler. Estimates of the Guanche population at the time of the conquest range from 1200 to over 4000.
La Palma is over twice as big as El Hierro (708.32 km2 vs. 278 km2) and it seems to support better agriculture and easier access to the sea. I find it difficult to believe that the population density of El Hierro was at least 4x more than that La Palma, when the best I can find is that the population of El Hierro was "sparse."
2) The numbers I see for modern fog harvesting are about 5 liters per square meter per day. The account says that a tree could fill 20,000 tuns/day, which is about 20 million liters. This needs about 4 million square meters. Assuming an 80 meter high tree and 32 meters across (the size of a larger redwood tree) gives a cross section of 2,500 sq. meters. There's no way these numbers are close to compatible.
3) Let's assume the tree can capture an excess of 1 liter per sq. meter cross section, even though there's no evidence that any tree can do that. Let's assume also that a single tree has a cross section of 2,500 sq. meters. That's 2,500 liters per day. Not bad, but people need about 2 liters per day as a minimum - and more if they do much activity. Even in this unlikely and extreme case, that's only enough to provide basic water needs for 1,000 people.
The WHO says "a minimum of 7.5 litres per capita per day will meet the requirements of most people under most conditions", so that's 330 people. And no animals.
(Another estimate is to look at the amount of water in fog. A cloud has about 0.5 g of water/cubic meter. However, this is too complex for me to figure out, because I don't know how much water you can extract with fog mining, I don't know what a tree or other plant can extract, I don't the wind speed, and I don't know the capture area.)
4) Why use lead pipes to lead to the cistern? Since clay is good enough for the cisterns, what's the advantage of using lead for those pipes?
Since each individual detail is not trustworthy, I find it hard to put any faith in the overall account. How are you certain that it isn't a tall tale, with little to no basis in reality?
Sounds like the Bimbache people could support 4x the population that the Spanish could (8,000 vs. 2,000), which makes sense (water being the limiting resource in that landscape).
Why discount pp156 again? The numbers are perfectly doable with a carefully placed tree that uses the surrounding landscape to funnel fog to it.
Lead pipes wouldn't be needed for the entire length — clay-lined spillways would more than suffice. I read it as using lead just to the cistern.
Great research, thanks!