My very first swale!

I live in hot, dry southwest Texas in an area with basically no soil--just limestone. I don't own land or a tractor, but I found someone who is willing to let me play on their land, and use their tractor. They don't have any sort of excavator or bucket, but I used a plough to break up the "soil" that I could, then a scraper to move it to one side. I could not get it very deep--perhaps in part due to my method, but I think largely because we are on bedrock. I'd love suggestions on what to do next. I was originally going to do 4 swales down the property (about 230 m long at about 3-5% grade), but after this first one turned out so shallow, I am thinking I should do more. I don't have a lot of resources to buy seeds, but I can at least collect a bunch of mesquite and Leucaena tree seeds.

Looks pretty nice to me. Swales don't necessarily need to be so deep, because a high swale mount also means it dries out faster. Yours is wide, so that makes the volume of water it can catch high as well. Did you create an overflow for really big rain events?

If you want to calculate how big the swales should be, someone made a calculator for that. You can find it here: https://www.permaculturereflections.com/swale-calculator/

Rene Nijstad wrote:Did you create an overflow for really big rain events?

Not yet. I was hoping for a medium rainstorm so I could see it in action and verify that it is actually level! I think there is a chance it will naturally overflow on the edges, but I plan to make an exit in the middle.

I actually used that swale calculator to plan the 4 swales, but I think that assumes a greater depth than what I achieved. I guess I can take measurements to estimate volume of the swale and compare that to what the tool says.

If you create an "exit" in the middle, a gully could quickly form. The idea behind a swale in a rain event is to make sure that the swale mount is level, such that the water tops it all at the same time, a tiny trickle of water over the whole thing, rather than a narrow, fast-moving rivulet-turned-torrent as the water finds the easiest way downhill, carrying particles of your swale mount with it.

I suggest that, instead, you close the ends, so that when your swales are full, they look like long ponds. I would also get whatever kind of groundcover will stay in place when it dries out, and make sure you've got it planted downhill, at the base of each swale mount. I would have some kind of deep-rooting, matting grass seed ready to spread on the slopes just before any lengthy rains.

As to where to get your seed, I like your wildcrafting solution. In addition, I would look at other wild plants growing in disturbed areas with minimal water or soil to speak of. I would identify them and their characteristics, and see what use other permies are putting them to. Roots are anchors and landscape cloth that grow in place, and that's just what you want to keep your swales from settling back into the terrain.

Just texturing the terrain will have noticeable effects. The swales will capture organic matter and silt particulates where they can become soil, and just keeping more water in the system will have a pronounced effect on soil life.

Good luck, and keep us posted.

-CK

I agree with Chris, but would also make an "overflow" area.  While the idea of the water topping it all at the same time is good, is you get water that actually fills the swale, somewhere along the line there is going to be a weak point.  It may be that the soil is a little less compact there or whatever, but it is nearly inevitable that there will be a blowout somewhere.  My feeling is that it is better to make an overflow that is somewhat lower than the top.  "Somewhat lower" is relative.  If you have a berm four feet deep, you may want to overflow to be 8 or 10 inches lower than the top.  If you only have a foot and a half berm, maybe four inches is better.  Regardless, I would make a low spot to release the water.  Line your overflow area with rocks to keep the spot from being a gully like Chris mentioned, and make a little stream to the next swale.  If you swales are level, it doesn't matter if the overflow is at an end, the middle, wherever.  After you get a big rain event, observation will be key to telling you if your swale is deep enough, or, in your case of not very deep soil, if you need several more at the same depth.  I'd love to see pictures when you get some rain to see how it works out.  Really nice job on the swale.

Chris Kott wrote:The idea behind a swale in a rain event is to make sure that the swale mount is level, such that the water tops it all at the same time, a tiny trickle of water over the whole thing, rather than a narrow, fast-moving rivulet-turned-torrent as the water finds the easiest way downhill

I cannot imagine that the mount is so perfectly level that water would trickle over it evenly across the length--surely there will be a low spot that will, as you say, form a fast-moving rivulet. My plan was to pack down a spot so it is definitely the low-point where water will first spill over, but to really reinforce that area with a lot of rocks to prevent erosion as much as possible.

We have a good variety of wildflowers here, so I can collect those seeds when spring comes. It has been a very dry winter, so I think we will have far less bloom than normal, but I'm sure I can find patches. I'll have to look around more to see which grasses are hanging on in this landscape.

The main goals are hydrating the landscape and adding organic matter to the dirt to create some soil. I'll definitely keep you posted!

Kevin Young wrote:

Chris Kott wrote:The idea behind a swale in a rain event is to make sure that the swale mount is level, such that the water tops it all at the same time, a tiny trickle of water over the whole thing, rather than a narrow, fast-moving rivulet-turned-torrent as the water finds the easiest way downhill

I cannot imagine that the mount is so perfectly level that water would trickle over it evenly across the length--surely there will be a low spot that will, as you say, form a fast-moving rivulet. My plan was to pack down a spot so it is definitely the low-point where water will first spill over, but to really reinforce that area with a lot of rocks to prevent erosion as much as possible.

We have a good variety of wildflowers here, so I can collect those seeds when spring comes. It has been a very dry winter, so I think we will have far less bloom than normal, but I'm sure I can find patches. I'll have to look around more to see which grasses are hanging on in this landscape.

The main goals are hydrating the landscape and adding organic matter to the dirt to create some soil. I'll definitely keep you posted!

I roughed out my swales without using a level or making an overflow. It naturally overflows at what just so happens to be the ideal spot. No problems with it taking any material with it.


Clover and sainfoin have been my good drought plants. I have alfalfa planted inside the swale and it does really well there. The sweet clover is wild and absolutely takes over every other year here. I've not planted a single seed of that.

Kevin, one idea with what you are doing is to fill the swales with organic matter. Mulch, wood chips, grass clippings, limbs, whatever can be collected. After a couple of years, plant into that organic matter and build new swales above those. That could have a tremendous impact. Once the first swales are planted, they could provide the organic matter for the next one.

Can you identify the low-growing stuff on either side of your swale? I would be interested in that, because they are the first things that will benefit from your swale. In your environment, I suspect that living root zones are what hold onto moisture in the soil, and probably exude it from internal stores to feed the necessary soil actors.

Honestly, if all you got was a thickening, an increase in size, lushness, and number of the native scrub, that would trap more moisture in the system, allowing for soil biology to survive peaks and valleys in moisture. It would then be possible to chop and drop for a transition to elements of dryland pasture.

I know that fungi make up the soil crust of some desert ecosystems, but I was wondering if anyone is cultivating limestone-loving lichens for use in transforming largely mineral xeriscapes into environments that can hold onto moisture better. They're literally tiny little algae bioreactors in a fungal infrastructure adapted to survive extreme environments. They're probably going to be one of the first introduced species to the Mars environment to oxygenate the atmosphere and build soil, largely because some have shown an ability to survive unshielded exposure to the harshness of space, so a little intermittent dessication isn't really a concern.

I would suggest that you look at what groundcovers are used in xeriscaping as well. It would be necessary to keep an eye out for invasive qualities, but it could make it easier to transition to a microbiome that has more water available for longer and more often.

But keep up the good work. We really appreciate pictures around here.

-CK