Checkdam gets its first rain

Here's a photo or 2 of my checkdam the day I built it in April this year. Third pic was 12 days later after putting some more rocks down on the tree clippings. Since then I've added some clay soil, a couple of cactuses and a small blackberry plant at the checkdam, plus a few seedling trees (protected by plastic bottles) in the fault lines of the rock.

This week the plot received its first noticeable rains. Here's a vid showing the effects and some more detail of the immediate area.

Awesome! I love to see practical "here are my challenges and here's what I did and here's what happened" videos like this.

I know very little about your island, so I have a question. How much (if you care to estimate, or happen to know) of your land's visibly barren character is inherent in its location and climate, versus how much of it is down to human disturbance, overgrazing, goats, or whatever the history of people there has wrought?

Not much soil, not much vegetation, not much rain. A permaculture challenge for sure, but I can see you've got the makings of a tiny oasis growing around your check dam!

Fun! Glad to see you putting the water to use.
Does the first check dam have any overflow point? It sort of looks like any overflow would go off the side which could wash out the bank.

Dan Boone wrote:How much (if you care to estimate, or happen to know) of your land's visibly barren character is inherent in its location and climate, versus how much of it is down to human disturbance, overgrazing, goats, or whatever the history of people there has wrought?

From what I've read when the Spanish conquered the islands they took a lot of trees for shipbuilding purposes. I'm not sure if the whole island was forested, but at higher altitudes there is still a lot of forest. There are trees that are native specifically to the canary islands, some of which are endangered, so I assume they were once thriving. GOats are a local problem that I have observed. A goat farmer might own just enough land to house his goats standing shoulder to shoulder, then takes them scavenging across "unused" land for days at a time to. I get visits a couple of times a year from hundreds of goats. Fencing requires planning permission, and is expensive. There are also fires every few years in the heavily forested parts. The islands are also extremely windy, which doesn't help soil building.

Steve Farmer wrote:Goats are a local problem that I have observed. A goat farmer might own just enough land to house his goats standing shoulder to shoulder, then takes them scavenging across "unused" land for days at a time to. I get visits a couple of times a year from hundreds of goats. Fencing requires planning permission, and is expensive.

Ouch! It's a weird system of governance that regulates fences but not livestock. Is there any recourse at law? (By which I mean, a way to credibly threaten the goat farmer with legal consequences if he deliberately turns his goats onto your land?)

Daniel Kaplan wrote:Fun! Glad to see you putting the water to use.
Does the first check dam have any overflow point? It sort of looks like any overflow would go off the side which could wash out the bank.

I arrived a few minutes before shooting the video, and the rain was heavy with the water washing over the top. I've thrown a silt and rock mixture on to the dam wall to build it up a little since the video was taken. I do wonder if a heavy persistent flow would wash the whole dam out, but the "banks" at the side are solid rock.

I also noted there was a fair amount of water flowing under the checkdam. The rocks are porous and the base of the soil area behind the dam was layered with tree cuttings and thhen small rocks before I put some clay soil down and the first few plants. I guess it's acting a bit like a French drain. I need to work out th sweetpoint between slowing down a bit more water and raising the wall and the water level, and allowing enough water thru to not burst the dam. I fear I will only find the breaking point when it breaks. I'm going to building a few more similar size checkdams nearby so can afford the occasional disaster. I've read for hours and watched a slew of videos, but more than doubled my knowledge with two hours of doing and observing.

I'm a total beginner at building these things, and I'm making every effort to observe the water to try to make improvements and repairs on the fly, and to witness problems as they happen. This particular checkdam was built in less than an hour so won't be a huge effort to rebuild, but if the trees I have been establishing get washed away then that would be a bigger loss.

My aim was mainly water retention with the expectation of a bit of silt being added with each rainfall to build up behind the dam. But I was impressed by the huge amount of silt and some useful plant matter that arrived during the last rainfall, which is equally as useful as the water. I can get water driven to the plot if necessary, but tonnes of silt showed up in a couple of days, for free. An unexpected bonus and something that is going to alter my thinking when upgrading to checkdam 2.0

Steve Farmer wrote:...tonnes of silt showed up in a couple of days, for free. An unexpected bonus...

To me this says the island is still engaged in the long process of sloughing off all its topsoil into the sea, thanks to those Spanish loggers and the excess goats. Catching it is both a bonus for you and a public service!

Looking good! If possible, I would continue making check dams all down that watercourse, to stop as much silt and water as possible. Because the depression seems to be rather deep, you can probably make the dams deeper and wider so a larger amount of soil is retained behind them. Any little depression like that could have a check dam or several check dams, depending on how many rocks you can gather. Better to err on the side of having dams which are too large than too small, as small ones might blow out in a heavy rain.

Tyler Ludens wrote: the depression seems to be rather deep, you can probably make the dams deeper and wider so a larger amount of soil is retained behind them. Any little depression like that could have a check dam or several check dams, depending on how many rocks you can gather.

Now I've got this idea to build the dam up to form a longer !ived pool with a ring of trees around the edge for shade and some ducks to gley it. Maybe even top it up during the summer for a year round pond....

If you have any rocks left after all the check dams you could start making rock swales. Eventually they'd catch silt and debris. You could connect them to check dams so they got some of the overflow.

I would also favor much larger dams. If the rocks where several feet deep , you would be forming a well protected delta beneath them. The newly arrived silt would be topped with a rock mulch. This would prevent wind erosion and keep the sun off of tree roots.

 Do you have access to earthen materials that are being dumped? Concrete scraps, pottery shards, bricks,  bones etc.  could be useful when rocks are in short supply. There's room for a hundred fold increase in the quantity of dam materials, if a supply can be found.

great minds....

Since the video was taken, I've built the dam up a bit using a mix of rocks and the accumulated silt. I'm not sure if it's a check dam or if it's now a swale. I will have to see how much water passes thru in the next rain.

I'd like it to be a hybrid as I'd like to catch more silt, but I'd also like a larger and longer lived pool of water to be held up behind it. If it goes full swale on me then I will put a pipe or two in to allow water to pass at a raised level, rather than having the dam washed out. There is a poplar tree planted on the back of the swale, and I'll put some blackberry brambles on top then some more silt covering most of the blackberries so the culms become roots, aiming to help hold the soil together.

The tree in the plastic bottle at right is a Leucaena Leucocephala and won't appreciate having wet roots for too long. It will be moved either to the top of or behind the dam, or to the side just above the high water level. I'm still going to add some height, again with a mix of rocks and silt, and then will need to observe the next rain to find where it needs to be built up/reinforced, and final decision where trees go. Two trees just out of shot near bottom right of pic need to be moved out of the flood zone. This is at the boundary of my land. Upstream I'm thinking smaller check dams that won't be allowed to become anywhere near as swale-like.

At first I though "That's a bit hasty to be putting in a dam. There's no way to hold all the water from a rain, overflow pipe won't keep up, etc." But why not? It will take a bit more engineering to make a full on dam but it's probably doable. If it was me, however I think I'd go for something like a semipermeable gabion that filled side swales while the water was running. I just think that would be easier to make which would give me a better chance to affect a larger area. Even better would be to combine them all. That way the ephemeral springs that you create upstream will flow into the pond for a while.

Daniel Kaplan wrote:At first I though "That's a bit hasty to be putting in a dam. There's no way to hold all the water from a rain, overflow pipe won't keep up, etc." But why not? It will take a bit more engineering to make a full on dam but it's probably doable. If it was me, however I think I'd go for something like a semipermeable gabion that filled side swales while the water was running. I just think that would be easier to make.....

We get maybe 8" of rain per yr spread over 3 or 4 rainfalls and a few hours later the ground is bone dry. This checkdam has about half a days work in it and once I have learned some more thru observation and any pool has dried up completely I will remove it or seriously rehash it and rebuild it bigger and better with keyline foundation, baffled overflow pipe and trees accurately placed around the stored waters edge

If you precede this checkdam with other checkdams, the preceding checkdams release water slowly to keep the last one full much longer. That will seriously help any trees near it. I would also try growing millet on your new silt it's fast to germinate and should hold it together till the next rain. Millet is cheap here I hope it's cheap there too.
Catching silt at each check dam and planting a cover crop (like millet) will help keep it. As the silt gets deeper the cover crop will grow better till it grows to maturity. At that point your trees will be secure.

Do rabbits, goats, lizards eat millet? If they do, it won't last a day.

Can you put up a little fencing around some of these areas to protect from the goats at least? Posts set in old tires filled with concrete, or some similar arrangement, might work.

When I thought it was just rabbits and goats that I was up against, I used to put mesh round the plants. But the lizards would get thru this. It's so dry here that as soon as anything green comes up, it gets eaten. I have to plant trees protected in plastic bottles, or plants that are very spiny or poisonous. Blackberries and prickly pears get left alone, and these are forming the basis of my cover crop strategy. Maybe when the soil is improved and there is more shade, I will be able to grow stuff at a faster rate than the wildlife can eat it, and then can increase the diversity of ground cover.

Hi Steve!

Great pictures and video! I'm in southern AZ where rainwater harvesting is becoming popular. Here's a good resource. Brad Lancaster lives in Tucson and his books are great guides. Wish I'd had them when we started. http://www.harvestingrainwater.com/
It's good you're starting small and observing! My family's owned 60 acres of high desert for over 20 years-- it's easy to make mistakes that cause more problems than they solve...
I will be watching your progress!
~Joy

The dam (previously a checkdam) hasn't seen any flowing water since this thread was started over 4 mths ago. In the meantime I have been introducing small quantities of water upstream, observing leaks, and patching with clay.

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