The only sources of the lake are rain water and an underground spring.

This knowledge rose in his mind like sweet, refreshing water from an underground spring.

I want to say that all fiction is fed by underground springs of personal fact.

They set up a colony around a well with an underground spring.

Something powerful enough to open the way for an underground spring.

There was probably an underground spring somewhere helping to heat it up.

The room with the underground hot springs had become familiar.

The village was named for the underground springs that its early settlers found.

Maybe an underground spring or river, the wind coming down the chimney at just the right angle.

There must be an underground spring near here; the ground is quite wet.