Groundwater is water below the ground surface within saturated soil or rock. It differs from rainwater moving across the ground as runoff.
What this means at your property
Water appearing in a crawl space after rain may involve surface drainage, groundwater or plumbing. The timing is helpful evidence but does not, by itself, establish the source. Repairs should follow an investigation of the entry route.
What observations help identify the problem?
Record rainfall timing, where water first appears and whether it also occurs during dry weather. Share previous drainage or plumbing work so the appropriate specialist can investigate before finishes or barriers hide the area.