09/30/2026
Along with my recent posts about rainwater harvesting, I’ve gotten quite a few questions from people in desert communities about how to create similar earthworks in their own backyards. There isn’t one earthwork that works everywhere, the best place to start is by learning how water already moves across your land.
If you can, walk your property during a storm or shortly afterward. Look for where water enters, where it concentrates into little channels, where it slows down, where sediment collects, and where it naturally wants to pool. Those patterns give you a map for deciding where you can safely slow, spread, sink, or redirect runoff. Take pictures!
The small semicircular basins I’ve been working on go by several names: microcatchments, earth smiles, boomerang berms, or variations of net-and-pan earthworks. Whatever you call them, the principle is the same: instead of allowing rainwater to quickly run downhill and off the property, you create small opportunities for it to slow down, spread out, and soak into the soil.
With a semicircular catchment, the open side generally faces uphill toward the incoming runoff, while the excavated soil is used to build the curved berm on the downhill side. Water enters the shallow basin, spreads out behind the berm, and has more time to infiltrate. In a series of catchments, overflow from one can continue downslope toward another, creating a network of small places where water is slowed and absorbed along the way.
That overflow is an important part of the design. Every earthwork needs somewhere for excess water to go when the basin fills. The goal isn’t to stop drainage completely or create a little dam, it’s to slow the flow without concentrating it somewhere that will cause erosion or damage. During a large storm, water should be able to safely move around the ends of the berm or through a deliberately designed overflow and continue on its way.
Trees and shrubs can be positioned around these basins so their roots can grow toward the stored moisture without placing the trunk at the deepest point. Runoff carries sediment and organic material with it, and those materials gradually settle into the basin. A tree planted too low can eventually have its root flare or crown buried. I prefer to let the basin hydrate a larger area of soil that nearby roots can explore.
The goal is also infiltration, not a permanent pond. In most landscape situations, captured water should soak into the soil within about 24 hours. If it consistently sits much longer, that’s information too, you may need to reconsider the depth, location, soil conditions, or amount of runoff being directed into that basin.
Semicircular catchments are only one tool. Swales, infiltration basins, diversion swales, rock-lined channels, terraces, and other earthworks all have different jobs. A true infiltration swale is laid out level on contour, much like following a contour line on a topographic map, so water spreads across its length rather than racing toward one end. A diversion earthwork, on the other hand, intentionally has some grade because its job is to move water toward another location. That distinction matters.
This is also why I’m a big believer in starting small and observing. Dig one basin. Watch it through the next storm. See where the water enters, how high it gets, where it infiltrates, and where it overflows. Adjust it if necessary before repeating the pattern elsewhere. Earthworks don’t have to be a one-time construction project; they can evolve as you learn more about your land.
My favorite resource, and one I continue to learn from, is Brad Lancaster - Rainwater Harvesting for Drylands and Beyond series, along with the incredible community-scale rainwater harvesting efforts in projects like Tucson’s Dunbar Spring Neighborhood Foresters, shows what can happen when we begin treating rainwater as a resource rather than something we need to get off the landscape as quickly as possible.
You don’t have to reshape an entire property to make a difference. Start with the water that already falls there. Slow a little of it down. Give it somewhere useful to go. Observe what happens, make adjustments, and build from there.
Small changes accumulate. In the desert, a little water slowed in the right place can become deeper soil moisture, healthier plants, shade, habitat, and a more resilient landscape over time.
