In permaculture it is recommended to design long level, contoured swales throughout your property to catch rainwater. Long swales, however, won’t work when the property is small, or if it is already mostly planted, or if the hiring of large equipment or teams of diggers isn’t feasable, or if long swales aren’t part of a lovely garden. What then?
In the gardens for which I’ve written consultations I’ve recommended what Geoff Lawton (of the Permaculture Design Institute of Australia) calls fishscale swales. Small curved swales staggered up a slope so that rainwater can be caught and held. One overflows into another, just like a pinball machine.
Any swale, no matter how small, will help hold water. I put them in just above each plant, the width of the dripline of the plant. I also combine them with burying wood (hugelkultur). I don’t have a lot of branches or logs, but I do have a lot of extra pieces of lumber salvaged when the sheds were dismantled. These pieces are untreated (no paint or pressure treatment), and if they have nails and screws in them, even better! The hardware will mineraize the soil as it decomposes. This wood is already very old and dry, and thus will soak up water a treat. If you soak the wood in water, compost tea or a microbial brew before you bury it, that’s super. If not, don’t worry about it. The idea is that rainwater will accumulate in the swale, percolate into the soil and into the wood below it. There the wood will hold water as it breaks down, gradually irrigating and fertilizing the plant below.
Wood can be placed on top of the soil and buried as the swale is dug, or it can be dug into the ground and covered. The swale is filled with mulch o help retard weed growth; if by a walkway the scale filled with mulch then it may be walked on without fear of a twisted ankle.
Here I have a Mission fig that has been slow to grow due to irregular watering (NOT my fault!)
Figs like a little water and this area has been on the dry side. In the direction from which rainwater would flow, above the tree, I laid out a few pieces of old lumber, nails and all.
I happened to be brewing a large batch of microbial tea, so I threw the wood into a bucket of the stuff and let it absorb some.
They happen to be the width of the existing dripline of the tree; again, any swale and and wood will help. I dug a small swale the same length, a shovel’s width wide, and threw the dirt on top of the wood.
Then I filled the swale with mulch and voila! the job is done. This will now catch rainwater, hold moisture, and fertilize the tree, as well as finding something useful for junk lumber. Burying the wood sequesters the gasses released in decomposing materials into the soil rather than the air thus helping reduce greenhouse gasses.
Using fishscale swales and mini-hugelkultur beds when planting most native plants can really help them become established in a low-water situation. This wild rose (rosa rugusa) is being planted in a very dry area, and I wanted to bury the wood below soil level to keep it closer to the roots of the plant. I dug a small trench and laid out some boards, nails down.
Then as I dug the swale I layered the wood with dirt and a couple more boards until buried. I filled in the swale with mulch and planted the rose on the downhill side.
I threw in some coyote scat since it was lying there so conveniently. There’s quite a microbial boost for the rose!
Remember that here in a dry climate we need to plant so that the root ball is even with the ground, or make the whole catch basin a little lower. Otherwise the roots will dry out. Planting so that the root ball is a little above the ground is a common practice is rainy areas.
Remember native plants have communities. Certain plants grow with certain others because they are mutually beneficial. This rose was planted within the dripline of an Engelmann oak, one place it is found.
So swales don’t have to be gigantic earthworks projects. They can be small and alternated down a slope, or just individual ones above new or existing plants. Throw some wood into a mini-hugel between the swale and the plant and you’ll water less, fertilize naturally, and compost leftover wood. Don’t forget cotton clothing and bedding… that all works, too!