eli5: Why does wet earth (like right after rain) absorb more water then dry earth (like right after a drought)?

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Title. I saw a video showing it happening, but I don’t understand why.

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11 Answers

Anonymous 0 Comments

Ultra basic answer is if you have an old , dry dish sponge and put it under running water ( not a tub or sink filled with water. ):

Initially the water’s going to roll over the dry sponge because it’s going to take some time for the sponge (or dirt in this case ) to actually absorb the water. All the holes that the sponge has that act as passages of water, all shrank and it’s more difficult for the water to pass INTO and absorb into the sponge. After some time of surface werness, the holes in the sponge become larger and Water is allowed to go further into this sponge.

Basic terms, that’s exactly what happens to dirt when it’s too dry. All the small passageways have closed , from becoming so dry and shrinking, and it’s harder for water to actually get into the dirt. instead it’s easier for the water to roll over the top.

Source: I also have a basement that will flood if there’s too long of a time without rain. If I know it’s been dry out for a couple days, and know a storm is going to hit in the next day, I will actually water the ground in front of my house a little bit to prevent the water from rolling into my basement. By watering lightly over an hour, the soil will absorb more, and move water out into my yard, instead of into the dry cinder blocks of my basement wall