Closet wheel well water

[2000Chinook]

Looking into the closet, the raised section where the wheel well is, has been dry as the Sahara for the time I've had it sitting, even during heavy rains. It's only when I drive in wet ground conditions that the wheel well carpet becomes damp. I'm new to the forums and haven't seen anything highlighting this issue, but I may have missed it. Any ideas would be appreciated. Cheers.