An arroyo (/əˈrɔɪoʊ/), from Spanish arroyo (Spanish: [aˈroʝo], "brook"), also called a wash, is a dry watercourse that temporarily or seasonally fills and flows after sufficient rain.[1] Flash floods are common in arroyos following thunderstorms. It's akin to the Catalan rambla, which stems from the Arabic rámla, "dry river".
Similar landforms are referred to as wadi (in North Africa and Western Asia), chapp in the Gobi, laagate in the Kalahari, donga in South Africa, nullah in India, fiumare in Italy, and dry valley in England.[2][3]
The desert dry wash biome is restricted to the arroyos of the southwestern United States. Arroyos provide a water source to desert animals.
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.