Brad Lancaster's Rainwater Harvesting Earthworks

Background & Cultural Context

Brad Lancaster is the American author and practitioner whose two-volume Rainwater Harvesting for Drylands and Beyond (2006, second edition 2013) provides the most thorough modern English-language treatment of passive water-harvesting earthworks for arid and semi-arid landscapes. Lancaster lives in a deliberately-designed water-harvesting demonstration site in Tucson, Arizona, and the work synthesizes Sonoran-Indigenous water practices, Australian Keyline (see related entry), and Israeli desert-agriculture techniques into a coherent framework for everyday application.

The defining principle is that water should be slowed, spread, and sunk where it falls, before it has the energy to cause erosion or to leave the property as runoff. A typical Lancaster-style intervention starts with mapping the site's water flows during a rainstorm — literally walking the property in the rain, observing where water runs, where it accumulates, where it leaves the property. The interventions are then designed to capture that flow with earthworks at progressively smaller scales as the water moves through the landscape.

The main intervention types are simple and powerful. Berms-and-basins (low earthen ridges that follow the contour, with shallow basins behind them) intercept and slow surface runoff, letting water infiltrate the soil rather than running off. Swales (the deeper trench-and-berm variant on contour) handle larger volumes of water on steeper slopes. Boomerang berms (crescent-shaped earthworks around the uphill side of a tree planting) capture water for individual trees in arid landscapes. Curb cuts at the street-property boundary allow stormwater from public streets to enter private landscape basins that grow shade trees, mesquites, and other useful plants.

Tucson is the most extensively documented Lancaster demonstration city. Through Lancaster's work and the Watershed Management Group he co-founded, Tucson has installed thousands of curb-cut interventions across its neighborhoods, transforming residential streets that previously shed all their rainfall into storm drains into neighborhood ecosystems that support shade trees, native plants, and wildlife. Per-capita water demand in Lancaster's own neighborhood has dropped substantially as the harvested-rainfall landscape replaced irrigated lawn.

The work draws on much older Indigenous and traditional practices. Sonoran Tohono O'odham agricultural compounds used floodwater farming and check-dam techniques for centuries; Anasazi checkdams in the Four Corners are another regional precedent; Mediterranean and Middle Eastern wadi-agriculture techniques — from the Nabataean cisterns of the Negev to Yemeni tabia terraces — provide the drylands-agriculture lineage. Lancaster's contribution has been to compile, systematize, and translate these diverse traditions into a practitioner vocabulary that homeowner-scale users can apply.

Modern Application

Starting a rainwater-harvesting intervention on a residential property is straightforward but rewards careful observation. Begin with a rainstorm walk: where does water flow on the property? Where does it pool? Where does it leave? Sketch the watershed boundaries and the major flow paths onto a site map. This observation alone often reveals opportunities for improvement that no published design guide would identify.

Common first-project interventions: (1) Cut the downspout — instead of directing roof runoff into a storm drain, redirect it into a planted basin in the landscape. A 100-square-meter roof captures approximately 600 liters of runoff per centimeter of rainfall, more than enough to irrigate a substantial shade tree. (2) Build a boomerang berm around a thirsty tree: the crescent-shaped earthen ridge captures rainfall and slowly releases it to the tree roots. (3) Mulch heavily: organic mulch (wood chips, straw, compost) over the basin slows evaporation, supports beneficial soil microbiology, and gradually builds soil organic matter.

Lancaster's two books provide the most thorough modern treatment of the engineering details. Volume 1 covers the conceptual framework and principles; Volume 2 covers detailed construction of specific earthwork types. The Watershed Management Group in Tucson runs hands-on workshops several times a year that take participants through the design and construction process on real sites. Several universities (the University of Arizona's permaculture program, the Rocky Mountain Permaculture Institute, others) offer comparable instruction.

Honest limits: passive rainwater harvesting captures the rainfall that lands on a given site and helps it infiltrate locally; it does not import water from elsewhere. In a year with severely below-average rainfall, no amount of earthwork engineering generates more water than the sky supplies. Drought-period water demand still has to be managed through storage, rationing, or external supply. Lancaster's work pairs passive earthworks with active rainwater catchment (roof cisterns, larger storage tanks) for this reason. The earthworks are the first and cheapest intervention; storage and supplemental supply build on that foundation.

Permitting and code considerations vary widely. In Tucson and several other Arizona municipalities, residential rainwater harvesting is explicitly encouraged through rebate programs and permissive zoning. In some US states (historically Colorado, though rules have softened since 2016) residential rainwater collection was subject to complex water-rights restrictions. Check local rules before installing large cisterns; for landscape earthworks, regulatory friction is rare. The Watershed Management Group and similar regional organizations publish jurisdiction-specific guides for the American Southwest, with comparable resources from Australian and African regional NGOs for other arid regions.