Peru is reviving a pre-Incan technology for water

Ground storage of fresh water is a simple technique that people seem to resist. 'Controversial' is not the right word but in the permaculture community there is a definite divide between people who embrace it and those who resist. The interactions are... frustrating.

There's also a relationship between water, soil health and climate change. The rule of thumb is that an acre of land can store an additional 20k gallons of water by increasing the soil carbon by 1% (of overall fraction, not relative to previous carbon levels, so in most real world cases that may involve increasing carbon by 10-25%).

Interesting. As a European (dutch even, so more water interested) I would love to learn more.

I often felt that, in agriculture we (dutchies) have over engineered for short term profits. I wonder if the same holds for our water engineering.

North America used to be home to so many more beavers than at present. Europe, too?

Ben Goldfarb wrote Eager, about beavers and their place in a resilient ecosystem:

https://www.worldcat.org/title/eager-the-surprising-secret-l...

I saw an interesting farmer presentation on YouTube[1] the other day where he eventually starts talking about how cover crops have improved his land's ability to absorb and retain water. He even includes photos contrasting his neighbor's monoculture fields with his during rain storms.

https://www.youtube.com/watch?v=9yPjoh9YJMk

Too true. For example, compare the 2-meter long root ecosystem of prairie grass that holds water exceptionally well to that of wheat:

https://images.app.goo.gl/PHmVUNRwwBg8oUKv7

There is a really interesting example of the role of the surface vegetation for groundwater in Bamberger Ranch[1] in Central Texas.

Central Texas was massively overgrazed by cattle in the 1800's and 1900's, and the ecosystem was completely transformed from prairie grass dominant to cedar and mesquite dominant vegetation. This resulted in a drastic loss of groundwater and utterly transformed the ecosystem.

David Bamberger restored 5,500 acres to close to original condition and the results are amazing.

[1] https://bambergerranch.org/

Road runoff is usually pretty polluted in cities and some places have laws against capturing rainwater to protect downstream resources.

Storing water in ponds has to deal with evaporation, algae growth etc. Also expensive to build.

Storing water in tanks means buying and maintaining something as well.

I think the point here is the "low tech, thousands of years old and it works" part. Underground water doesn't evaporate or grow nasty stuff. You do have to have the right terrain I suppose but where you do this sounds awesome. The ground will actually even help with filtering out many nasties.

It's a capacity issue. The bandwidth of the amunas is enormous compared to a reservoir.

The first link is NSFW as a headsup

> In LA, everything is done to make sure the water yeets into the sea as quick as possible.

The infrastructure bill may change that [0]:

"Also, the money could fund stormwater capture and reuse projects, like the ones that filter rainwater into underground aquifers rather than let it flow into the ocean."

Anyone know how likely this actually is?

[0] https://laist.com/news/climate-environment/socal-could-get-b...

Especially if you already use plants adapted to a dry season.

There's a huge difference between surviving 50 days without rain and being able to survive 90 days without rain.

The biggest issue with the west was that it was in a historic wet period 100 years ago when water rights laws were solidified with different groundwater levels. Its a drought only relative to this time, historically in Southern california it is usually dry like this. The issue with runoff water in LA and other cities is that its super polluted. You don’t even want to swim in the ocean after a rain. If you wanted to be smart about it you would have to treat it, but it rains in earnest so few times that building that infrastructure would be too costly if its only going to be used when it deluges 6 times a year.

What the city has been doing instead is honestly a better long term move imo. They treat sewage and turn it into grey water, which is used to water public grass spaces like parks and is starting to be used as well as recharge local aquifers since the state says the ground is the best filter for grey water.

I think this is derivative of humans inability to comprehend large numbers.

Do I have enough water for me and my family? Yes, I'm not thirsty and my crops look fine.

Do we have enough water for 10 billion people for the next 150 years? We have no clue.

Stashing water underground is a great strategy for a hotter earth. See also the great stepwells of India. Just because something is old doesn’t mean it’s not effective and sustainable.

The linked paper

> Infiltrated water is retained for an average of 45 d before resurfacing, confirming the system’s ability to contribute to dry-season flows. We estimate that upscaling the system to the source-water areas of the city of Lima can potentially delay 99 × 106 m3 yr−1 of streamflow and increase dry-season flows by 7.5% on average, which may provide a critical complement to conventional engineering solutions for water security.

https://www.nature.com/articles/s41893-019-0307-1

Thank you so much. The article is just too polluted with pseudo intellectual nonsense, but water management is a very underappreciated discipline of engineering.

Although it seems impossible to measure how much water is stored in the deep soil, it is often possible to notice if it runs out. We had that last summer in the Netherlands. I suppose knowing we reached zero, and knowing the influx (mm rain, and the flow of the Rhine), and then also knowing the outflow means you can make a some sound estimate.

However, that requires a high density of weather stations and tooling at the influx and outputs.

It's not something you can just do through some regulation targeted at the water company. You'll need a specific branch of the government, since messing with water affects everyone, from erosion to trade, to agriculture to climate (the presence of water makes the climate a more mild climate)

In the Netherlands, this is all done by an independent water government, a democracy older than our democracy itself. It even predates notions of citizenship.

Article woo aside, underground water is not impossible to measure. Min well depth (or depth of dry wells) is a straightforward way to measure the aquifer level for a small area. It doesn’t tell you much but it tells you something. Combine with your neighbors taking the same measurement over time and you have a good data set. That is before you get to things like ‘geology’ which are known factors shaping underground water supplies.

Further, if water goes into a pit, you can measure or estimate how much is going in. If you can measure the shape of the pit you know how much is there. If you know surface area at a given level and temp/environmental conditions you can estimate evaporation. So you can say: X vol went in, Y evaporated, and Z is how much we now think is ground water based on current depth and evaporation (excluding animals and humans drinking).

It is much harder to associate the pit activity with a given well and obviously the scale here may be below the precision of any of the estimators.

> TLDRV They divert the rainy season water to natural aquifers and hope it reappears down river in the dry season.

Simple diversion of water is not what was discussed. Thank you for the summation, but you summarized the non-relevant information.

> The small scale of the effort currently makes me a little skeptical that it's achieving anything. Underground water is impossible to measure.

Even if you are not familiar with how vegetation works, there is proof contained later in the article. They discuss how removing portions of peat land caused the surrounding plants to dry out and die.