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What are wadis, and why do most of them remain dry?

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Arabian Desert The Arabian Desert, the largest desert in Asia, covering an area of about 900,000 square miles (2,300,000 square km).

A wadi is a valley or stream bed in desert regions, such as those found in the Arabian Peninsula, that is typically dry except during periods of seasonal or irregular rainfall. These features are also known as arroyos or dry washes in other parts of the world.12

Most wadis remain dry because of the extreme aridity of the desert environment, where annual precipitation is often very low and evaporation rates are exceptionally high. When rain does fall, it is frequently torrential and brief, causing flash floods that move rapidly through these channels.3452

These streams remain dry for the majority of the time due to several factors:
* High Evaporation and Percolation: As water flows through the wadi, much of it is lost to rapid evaporation or is absorbed into the dry, porous stream bed.26
* Limited Rainfall: The scarcity of consistent precipitation means there is rarely enough sustained water flow to maintain a perennial stream.35
* Dissipation: In many cases, the water from these ephemeral floods is so quickly dissipated by the environment that the stream eventually disappears, sometimes ending in a terminal mudflow.26