Rocky Soil / Dry Land Swale Construction

Hello, my name is Erik Hans Rasmussen and I'm new to the world of permaculture. I've just moved to a property in Plymouth, CA which is located at the basin of a large, long valley between some mountainous uprisings on the side. At the bottom of the basin, there is a creek which runs seasonally when the rains begin to start. Most of the land is fairly dry, with hardy sagebrush and oak trees sparsely placed around the basin.

I want to build a swale around my cabin, which is located next to the creek. At it's highest levels, the creek runs between 3-5 feet in the early spring, and is completely dry in the summertime. The ground seems to retain almost no water during the hot summers, and the runoff is intense in the winter / early spring. Most of the water runs off the property and back into the creek. My questions are:

1. Since the soil is rocky (under 10 inches of topsoil), is it possible to import and compact clay to construct the swale to hold more water?
2. What is the best way to retain water in rocky soils? Is growing enough groundcover and brush / small tree systems during the late winter / early spring enough to fortify the soil with root systems to retain more water?

Additionally, there are several springs on the property, with the main spring producing upwards of 900 gal / day. I have thought about piping the water down to the area of the swale / dam system that I propose to build to continually keep it full during the hotter summer months, and hopefully have grown enough shade cover within 2 years to prevent as much evaporation as possible.

What do you guys think? Am I out of my mind, or can it be done? I am strongly opposed to any kind of irrigation system, seeing as I have such nice, flat land that I believe I could hold more water in. I'm aware that the water table will naturally rise once I dig out the swale and add ground cover / small trees in the first place, however the intense evaporation during the summer causes me concern that most of my plants will die unless they are extremely hardy.

I find these resources to be very helpful:

http://www.harvestingrainwater.com/

http://www.drylandsolutions.com

Tyler Ludens wrote:I find these resources to be very helpful:

http://www.harvestingrainwater.com/

http://www.drylandsolutions.com

Thanks! These are great resources. I really appreciate your time and effort.

Thanks Tyler for the links! They are very helpful.

Erik I only live a bit north of you (Auburn, CA) and have the same questions as you. It seems to difficult to keep the soil moist through the hot summer. I have had to use ditch water to make it through the long summer. Good luck to you!

According to what I have already read, it is not possible to rely on the stock of water in the ground with shallow soil (and 10 inches is shallow).
I do not know why you are opposed to irrigation, if you can explain...
I explain why I tell you this: If you are opposed to the technology behind, isn't bringing clay more energy to put in?
(I live in a place one cannot cultivate in without irrigation)

The concentration of trees around indicates to you how much surface the roots need to drink all year round, then it depends what you want to add there and how much surface you have for growing and if you want a food forest and veggies...

It depends if rocky soil is rock, or rock+earth too.
And if you want to stock the water into the ground, with little soil, then the plants will not like it.
When plants can stand a dry weather, usually then hate water logging, and that what you will have part of the year if you keep much water quite near the surface.
That is all that I do not understand unless I lack info because of course I know little of your place.

My reserve of water is in rock, in pure rock. It was caved with dynamite, and then coated with lime a long time ago before cement existed.
I do not have to water much the place below... you see what I mean!
But I can't tell how much I thank the people who did this big job!

is it rock, or caliche as the basement rock.?
If caliche, you can drill thru it, or use pool acid and digging bar.

if you want to store water in the soil, it needs biomass.
burying tree limbs and trunks is the easiest way to put it in there.

then the fungal/bacterial colonies can move it around to the roots of your other plants.

It would seem to me that importing clay would be a huge investment of time and energy and possibly cash. The best way to retain water is to build the swale, then fill it with lots and lots of mulch. Once you have a swale built on contour, you'll already be holding more water than you otherwise would. Adding mulch, then planting around the swale will hold a lot of water.
I also don't think it's a good idea to pipe the water down to keep the swale full unless you'll be building a dam or a pond or something. Once you have your swale planted, the first couple of rains will help keep the water on the land and the plants to grow. Even during a draught, you'll find that the plants won't be as bad off as if you just had a regular vegetable garden in the summer.
If you fill the swale with as much mulch as you can find, that will go a really long way to preventing evaporation and keeping the plants healthy during a draught.

Good luck!

So, with 12-24 inches of topsoil before you hit bedrock, you think that it's possible to mulch a countour swale enough to hold water throughout the 6-8 month dry period in the region? If so, I'm down to start digging pronto.

No, it will not be enough...

It depends if it is bed rock, then no.
If it is rocky soil, stones with earth, then you will hold more water of course.

I tell you what people say here: stones keep water in the soil.
Of course, if there is also earth, they mean that stones help stopping evaporation.

I have also read an ebook saying to forget about no irrigation through drought when you have a shallow soil.
You need 3 feet and more to keep water.

Xisca Nicolas wrote:No, it will not be enough...

It depends if it is bed rock, then no.
If it is rocky soil, stones with earth, then you will hold more water of course.

I tell you what people say here: stones keep water in the soil.
Of course, if there is also earth, they mean that stones help stopping evaporation.

I have also read an ebook saying to forget about no irrigation through drought when you have a shallow soil.
You need 3 feet and more to keep water.

It is bedrock. So basically, are you saying that bedrock is not a good water holder?

A bedrock can have cracks... but where it has not, it keeps water above better than sand, for sure.
BUT, what really holds water is earth (with humus better!).
(I mean the volume of water that you can save.
and this volume is sure large if you have a large land, but the amount of plant that can drink -and how long- depends on the thickness)

So, I mean that the thickness of your earth layer is actually not enough to keep a lot of water.
And, as water will evaporate, roots will not be able to go down enough.
More earth above will hold more water and enable your plants to live on your underground water much longer.

I cannot tell you how long plants can drink on the layer you have, but sure not long enough.

With 10" of soil depth prior to bedrock your water retention strategy is going to need to be different than someone with 3' of topsoil. You'll have to check local zoning regs to see what you are allowed to do but I would think a small(ish) pond at the uppermost region of your property with deeply mulched swales spaced somewhat more closely together than you might normally do will give you greater water retention than a single swale at the top of your property. Also, I would consider using hugelkulture swales as opposed to standard swales. (map your contour line, pile wood/brush on the downhill side, then dig the swale and put the dirt on top of the wood.) The problem you are going to run into with traditional permaculture methods of "slow, stop and sink" are you have a limited region to "sink" to. A good pond that you can pump from periodically (either via hand pump or gravity pumping) will go a long way to upping your storage capacity for water and minimizing the need for irrigation from external sources. Mulching will also be your friend in this situation, to minimize evapotranspiration, as well as slowly add organic matter to the soil. As a last ditch effort, you can also consider putting a pond at the bottom of your property and in a pinch, use a hand pump to irrigate your crops from it. Ultimately, if your end goal is to reach the point where you can garden without irrigation, you are going to need to really thicken up the soil layer of your property, or at least the areas where you plan to garden. On-contour hugelkulture swales and heavy mulching would be probably the most basic way to move in that direction. That's where I would start anyway.