Answer:
metaphor
Step-by-step explanation:
A metaphor is a literary device in which two distinct things are compared to each other. There is one common aspect among the two that helps in building the comparison. The similarities are hidden in the metaphors. When the comparison is made, the aspect of similarity is highlighted. In the given sentence 'riverbed' and 'spring' have been compared. The presence of dryness in both riverbed and spring have been compared. Such comparison helps in giving literary touch to the texts.