For both spies and soils, the word “infiltration” is very important.
“Infiltration” is a word used to describe how spies sneak into enemy land unseen. The word “infiltration” is also used to describe how water sneaks down into the ground.
A healthy soil has good infiltration. This means water easily moves into the ground and between the soil particles. Also, a healthy soil has what’s called good “water-holding capacity.” It’s good at holding the water that has seeped into it.
This parking lot has what is called “porous pavement.” It allows some water to infiltrate, or move down, into the ground.
Photo: USDA NRCS
Notice the little squares of gravel in this close-up of “porous pavement?” Water moves down through the gravel and into the ground. That way, there is less rainwater on top of the pavement.
Photo: Mike Hirschi, University of Illinois