Very long winded. The actual technique is only described about 2/3s the way through. They're using canals to divert water into well draining soil.
"They use water canals called amunas – a Quechua word meaning "to retain" – to divert wet-season flows from mountain streams and route them to natural infiltration basins."
"Because the water moves more slowly underground as it travels through gravel and soil, it emerges downslope from springs months later, when the comuneros collect it to water their crops."
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%).
I didn't know it was controversial. In San Jose we have many (currently dry) ground water recharge ponds where water is let in for the purposes of seeping into the water table. Much of the city uses ground water, the resulting water is quite hard but has a decent flavor profile.
Some people think 'store water' and immediately jump to cisterns, or above-ground storage tanks. You simply cannot store a useful amount of water above ground, and exposing it to light and air (and thus mosquitoes) is a whole other set of problems.
Some people do it anyway, others get very upset about what they see as wasted time and resources.
Storing water [this way] is fundamentally about reserving the right to be wrong about where water 'needs to be' on your property, and I think without a way to correct it they feel like their hands are tied. The person I know who is loudest against this strategy is also very philosophical about not fighting nature. If a tree is happy, great. If it's not happy, then it wasn't meant to be. Let it go, get over the sunk cost, and try something else. To his thinking, trying things is cheap, forcing things is expensive (and arrogant).
Basically you want to slow the flow of water and increase the soil's permeability and retention capabilities. Beaver dams are a good way to start, but things like Hugelkultur burms, terracing and swales are all methods of capturing water run off and directing them into the ground where they can enter aquafers or be absorbed by the immediate soil.
These aren't large scale projects across rivers, but just enough to capture the run-off on one's own property. Mostly you are improving soil retention, and refilling the aquifer. Often times it's as simple as creating repeated depressions in the desert so that dust, seeds and wind blown matter can collect along with just enough water to start plant growth so that the topsoil can be stable once again.
Stopping is different from slowing. Slow water keeps streams from drying up in the summer. Lots of stories of seeps and seasonal streams coming back after years of having dried up.
Water retention needs to be made a bigger issue globally. Others eluded to the fact that what is effectively the draining of the water cycle in CA is a main cause of CA's water/fire problems, but that is also the problem in places like central Europe where the straightening of the rivers during industrialization (19th C.) is and has essentially been "draining the swamp" of the central European water cycle.
It's something I have had the hardest time getting people to understand. The various straightened rivers all throughout Europe that have far less retention capacity than in the past, are essentially drainage canals that are sucking the whole of the central European region dry of water, which will only compound problems.
There are a couple things going on that are fooling people into an illusion that everything being fine, but it is happening and it is causing the low rainfalls, the low snow packs, and the low cloud cover that increases temperatures that are all perceived as/blamed on global warming.
If Europeans don't stop the draining of the continent, the problems and heat will only accelerate. Just alone in order to prevent the necessity of using climate control systems that devour energy should be enough of an argument to try to restore the cloud cover and rainfalls that could lower temperatures to what they were like before the rivers were straightened and evaporation also caused more winds and breezes.
I can't speak for Peru specifically, but natural ecosystems play a huge role in absorbing and holding on to rain water, ensuring it doesn't all just flow back into the sea. This has been known for ages - I remember a friend who did environmental sciences telling me stories of cities in developing countries that cut all the nearby forests and as a side-effect also ruined their water supply.
So with that in mind I'm a bit surprised at the skepticism on display here.
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.
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.
I'm not sure why it's only happening in Peru, we should be doing this work world wide. I have similar water capturing techniques at my house where I redirect road runoff into a gentle stream and allow it to infiltrate my landscape, watering Maple, Apple, Plums trees, hydrating the landscape to reduce effects of multi-month droughts:
He doesn't say where he lives. While I agree with you that if he indeed lives in a place where the "road runoff" is nasty he should be careful, I really can't see why capturing rainwater should be banned. Of course "some places" is very vague so there might be good reasons but you'd have to provide much more context for me to believe that it's a good idea to prevent it.
If my house wasn't where it is, the ground on which it is built would absorb that water. Now I capture it and put it on my veggies or use it to flush the toilet which ends up going out to the septic drain field on the lwab and then it filters further down. I don't see any issues with that.
The issues with water capture is that you are basically building an illegal reservoir and not necessarily returning the water as it were if it just hit the ground. You might flush your toilet and think all is fine, but maybe now the creek in your back yard goes dry a week sooner in the year, and less tadpoles are able to be born or some other unforseen ecological effect. Or maybe downstream water users don’t get what they expect out of the watershed anymore due to illegal collecting.
The amunas are channels that slow the movement of water from mountain streams to farmers; "the diverted water spends between two weeks to eight months underground, with an average delay of 45 days".
As far as I can tell, they are used to retain water from the wet season into the dry season. How is that advantageous over using water storage at or near the endpoints? Perhaps ancient farmers didn't the ability to create underground storage, but how are amunas preferable now?
I imagine there's a good answer, but if it's in the article I overlooked it.
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 is nice to see acknowledgement that there was any activity at all in Peru prior to the Incas. Who knows, those earlier people, probably already speaking Quechua, might even have built this or that monumental structure, too, instead of waiting around for the Incas to come along and build everything, last-minute, just in time for the Spaniards to find.
Diverting streams to go into different places increases the dwell time of the water by 45 days. when you have a rigid dry season, keeping the streams running for an extra 45 days is absolutely fucking huge. The clever part is that over the years the locals have managed to find the best place to divert water so it goes into springs that feed streams.
its a similar idea to a Johad, https://en.wikipedia.org/wiki/Johad which traps water for a number of days, increasing the dwell time and making the place wetter. The issue with Johads is that they can be a magnet for mosquitos. Johads differ in that they force the water into the soil rather than aquifers.
In LA, everything is done to make sure the water yeets into the sea as quick as possible. That water that would have hung around is replaced with the water from the LA aqueduct and the like. THe place gets drier, and hotter. I would wager, but can't assert that this water mismanagement is causing a large part of the drought in that area.
> 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."
Unlikely since it rains so few times the cost to benefit ratio is terrible. Instead the city has been treating wastewater and using that constant source of greywater to irrigate public parks and recharge aquifers.
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.
The problem is it could just be used just to extract more water rather than be part of a broader reforestation effort & cultural change around it's relationship to water. Joe Brewer criticized this a couple years ago: https://twitter.com/cognitivepolicy/status/12125332029649264...
What's interesting is water management historically was a huge area of research and work for cultures.
But if you look at a place like CA, despite supposed water shortages - there are very very few water projects to increase for example storage capacity. I'd be curious in last 10 years how much capacity has come online vs population growth. I mention supposed shortages because it's really a shortage of free or near free water.
We have passed a lot of bonds for water projects - with little to show for some reason. Not at all close to the details, but would be curious to know what is going on.
What's funny though is that folks are paying $5 for a tiny water bottle in an airport. They are rationing URBAN water use (where water is relatively insanely expensive already).
Even in CA where we have droughts - the amount of water used in ag / industrial is measured in ACRE FEET. And the cost is in pennies to dollars per ACRE FOOT. The scale is just totally different than your bottle of water or glass of water. You go to a restaurant "due to water shortage we aren't serving water"??
We've had insane population growth here. Last damns were in like 71 and maybe 79? So it's been 40+ years with no new reservoirs?
You'd better be working on desalination or maybe a small tax on water for all users (could be TINY) or something because otherwise yeah, you are going to have serious water problems.
We've doubled population since 71. You can't do that without doing something around reservoirs, water use in ag / industrial or supply improvements.
This article is poor. Talking about Lima was silly and it as usual avoids the actual reason water is scarce, high populations with high use techniques. And where's the pictures, a big part of the amunas is they look awesome, like England and their stone walls lets not pretend it's the most efficient way of doing it. They look cool. That's a important part of communities.
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.
Have you considered, as a service to humanity or yourself, to teach and share how this could be done "properly"? You clearly appear to have some knowledge of techniques that, while you think them obvious, other people don't seem to understand (not even on HN, as the downvotes indicate).
At the same time, these techniques could solve a lot of issues including people losing their livelihoods, mass migration, devastation or even wars.
So don't you think sharing how to do it would be worth infinitely more than your one-liner comment?
Can you explain where the article is wrong in saying that Peru has limited fresh water supplies? After that, explain “everywhere” including arid and desert regions. Please cite sources and your level of expertise.
The fact is that water is plentiful in some areas while insufficient in others (and the areas can change over time), but so fucking what - you cannot transport it efficiently enough. Well, sometimes you can: https://en.m.wikipedia.org/wiki/Great_Man-Made_River
Oh, as a native Southern Californian I completely understand this. It’s amazing to me that anyone can claim this is no big deal like there aren’t billions of dollars at stake in agriculture and industrial usage.
Poor, or incompatible with your personal political beliefs? The person I was responding to is a science denier who made a claim he couldn’t back up which is incompatible with most of human experience. It’s unclear why you are so committed to their defense?
Okay, so what was your goal? I asked him to explain a provocative take contradicting the article. This didn’t seem especially outlandish, but you reacted as if explaining what he meant was some kind of extraordinary burden.
> 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.
In page 15, table 2 they show that they put some Eosin https://en.wikipedia.org/wiki/Eosin upstream before the water entered the earth, and then they collected water from the springs downstream a few weeks later and measure how much Eosin was there, and used this to estimate how long the water was stored.
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.
I don't know what I was watching but someone mentioned and then drew a diagram showing that a well may be at a certain depth, to comfortably reach water, but the water level will drop as soon as you start pumping because the water has to move horizontally through the rock, and so you will get a gradient between 'water level' in the aquifer and water level at your well, and the faster you pump the higher the slope.
I guess there are some ways to work out permeability and volume based on how the levels at one well are affected by activity at the next well.
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.
I learned that it's fairly routine in wetland restoration work to sink shallow 'wells' (stand pipes) a couple feet down to measure water table levels over the course of a year or so. Wetlands - and in particular the plants that are adapted to them - can be permanent or seasonal, and can change over a 20 foot distance, so knowing which you have and where can be the difference between a failed or successful restoration.
> 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.
"They use water canals called amunas – a Quechua word meaning "to retain" – to divert wet-season flows from mountain streams and route them to natural infiltration basins."
"Because the water moves more slowly underground as it travels through gravel and soil, it emerges downslope from springs months later, when the comuneros collect it to water their crops."