A wadi is a dry riverbed or valley in a desert region that only carries water during periods of heavy rain. Wadis are significant in arid region geomorphology for understanding episodic streamflow, sediment transport, and the development of desert landscapes.
Reference: “Torrent valley”. Insight on the Scriptures. Vol. 2: Jehova – Zuzim and Index. Watch Tower Bible and Tract Society of New York. 1988. p. 1115. The term “wadi” (Arabic) is also used to designate a torrent valley … whereas others are torrents during the rainy season but dry up completely during the rainless season.