rainfall simulator soil runoff agriculture water pollution SEJ Norman Oklahoma circle of blue

Photo © Brett Walton / Circle of Blue
The rainfall simulator demonstrates the soil’s capacity to store and filter water. When heavy rain strikes bare fields and construction sites, the two soil samples in the middle, dirty water flows into rivers and streams. Click image to enlarge.

On a bright October morning in a hotel parking lot, Greg Scott turns on the rainfall simulator.

The machine’s swiveling nozzle sprays fat drops on five soil samples held in trays a few feet below. Some soil is bare; other samples are planted with prairie grass, wheat, and other field crops. Within minutes dirty, sediment-saturated water begins flowing off the plots that are not anchored by vegetation. In the other trays, the drops soak into the ground. The little water that does run off the planted trays is much cleaner, the color of green tea. The lesson of the artificial cloudburst is clear: neglect the soil and water will suffer.

A soil scientist with the Oklahoma Conservation Commission and a cattle rancher, Scott uses the contraption, hauled like a magician’s prop out of a trailer and onto the asphalt lot, to demonstrate how biologically diverse, untilled soils that are rich in organic matter can help solve agriculture’s twin challenges of water pollution and water scarcity.


“We have accepted for years that the dirty water was normal, and we’ve been putting up with that loss.”
–Greg Scott, soil scientist
Oklahoma Conservation Commission


Soil is having a moment. Several books in recent years — including Dirt by David Montgomery and The Soil Will Save Us by Kristin Ohlson — have cast the Earth’s skin in a starring role in the story of human progress and decline.

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