This could be water that has been in situ (soil water) or at least very slow flow, water with tortuous flow paths (groundwater), water that has undergone evaporation on the surface, or even precipitation from earlier in the storm.
(This; could be; water that has been in situ (soil water) or at least very slow flow, water with tortuous flow paths (groundwater), water) (water; has been; in situ) (water; has undergone; evaporation; L:on the surface)
This water water
could be has been has undergone
water that has been in situ (soil water) or at least very slow flow, water with tortuous flow paths (groundwater), water
in situ
evaporation L:on the surface