May 5, 2011

Geology Word of the Week: W is for Wadi (وادي‎ )

Posted by Evelyn Mervine

A Wadi, Oman, January 2009.

def. Wadi ( وادي):
1. An Arabic word meaning “valley.”
2. A valley or canyon– usually in an arid part of the world such as the Middle East– that contains an ephemeral streambed, which generally fills with water only after heavy rainfall.

In Arabic the word “wadi” means “valley.” However, in the Middle East and North Africa– where Arabic is spoken– the climate is arid, and rainfall is rare in most places. For example, where I do my thesis work in Oman, there are very arid places that receive rainfall only every few years. There are a few places in the Arab-speaking world that receive regular rainfall and where permanent rivers flow. However, many streams are ephemeral and only carve their valley channels after a rare rainstorm. Valleys which contain these ephemeral streams are called “wadis,” both in Arabic and in English. Many Arabic place names contain the word “wadi,” and the word “wadi” is often carried over into the English place name as well. For instance, “Wadi Al-Abyad (وادي الأبيض)” could be translated as “The White Wadi” on an English map.

Here are a few pictures of wadis in Oman:

Wadi Sunset, Oman, January 2009.
Ephemeral streambed, Oman, January 2009.
Herding goats up a wadi, Oman, January 2009.
Green wadi from a distance, Oman, January 2010.

A wadi transformed by recent rainfall, Oman, January 2010.
After a rainfall, a wadi can be transformed overnight from dull brown to lush green, as in the two final pictures above. During a rainfall, wadis may also flood dangerously. I’ve never seen a wadi in flood, but here is a scary YouTube video of a wadi flooding in Oman: