A rainfall simulator helps us understand grasslands

Landscape of Badlands National Park, South Dakota

Every year, trillions of gallons of rainfall and snowmelt pour into the grasslands of the Northern Great Plains. Much of that water winds up in the Missouri River, where it becomes drinking water for millions of people. But the role the grasslands play in capturing all that liquid is often poorly understood. Enter the rainfall simulator: a tool designed to connect those dots.


One acre of intact, unplowed, healthy grassland is believed to store thousands of gallons of water that would otherwise be lost. With grassland temperatures and droughts on the rise, keeping moisture in the soil is a big priority for ranchers and farmers. Returning to more natural ways of managing the landscape—involving less tilling and water loss—is good for both people and wildlife such as pollinators, pronghorn antelope, and plants.


Intact grasslands in the Northern Great Plains are rapidly disappearing. In 2014 alone, 1.4 million acres—an area roughly the size of Delaware—were converted into farmland for crops such as corn and soy.


Water loss Without a thick mat of vegetation to pull moisture into the soil, the soil can’t capture as much water.

Emissions Vast amounts of carbon stored in the root systems of native grasses are released into the atmosphere.

Habitat loss The region’s grassland birds and other wildlife lose critical habitat.

How it Works

Rainfall simulator
  1. To demonstrate the rainfall simulator, scientists from organizations such as the US Department of Agriculture collect soil samples from the surrounding area.
    • 1. Conventional till
    • 2. No till
    • 3. Overgrazed
    • 4. No till + cover crop
    • 5. Well-managed rotational grazed
  2. A revolving sprinkler head showers water over the soil, simulating rainfall. Within seconds, viewers begin to see how the water moves through different soil types.
  3. Two rows of collection jars hang beneath the simulator. The front row captures water that runs off of each soil sample (runoff), showing how much is lost. The back row collects water that has been absorbed through the soil’s surface, and represents good absorption.*
    *Results may vary. Levels shown are for illustration purposes only.
  4. Grasslands managed by ranchers on a rotational grazing schedule absorb more water, and tend to have a wider variety of grasses. Additionally, when cattle graze, their hooves make indentations in the soil that help water travel deep into the roots of grasses, where it can be stored for droughts and seasonal dry periods.


More than 75% of the Northern Great Plains is privately owned. Many of those landowners are ranchers who require intact, healthy grasslands to maintain their livelihoods. WWF is building partnerships with the region’s ranchers to help them find more sustainable—and more profitable—ways to produce their livestock.

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