In The Weeds: Water Movement in Soil

“In The Weeds” is a series of posts that take a deeper look at the science of home lawn care.

Water Movement in Soil

How does water move through soil? You’ve probably heard at some point that water works its way down through the soil and into the groundwater. And it may seem reasonable that this is caused by gravity. Both are actually a bit off. Water moves through soil, but not just downward and not due to gravity. In the image here, you can see a vertical profile of soil. Water was dripped into the middle of the soil to see if it would simply drain downward. It didn’t As you can see from the growing circle, it spread out equally in all directions.

This even spread of water is due to capillary forces. Just as a sponge will draw water upwards and in all directions, so will the soil. Water only moves down into the groundwater when there is pressure from above literally pushing it downwards. That happens when rain or irrigation is applied to a soil profile that is already fully saturated.

Want to learn more? Keep an eye out for future additions to the “In The Weeds” series from Teed & Brown.

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