possession in the late 19th century. Its name seems to come from an east-west river which was supposed to have run through it. The river was thought to have largely dried out - a wadi, as the name indicates - or have disappeared underground.

The Spanish name is derived from its previous name Rio do Ouro, given to it by its Portuguese discoverer Afonso Gonçalves Baldaia in 1436. The Portuguese prince Henry the Navigator