In dry climatic zones ephemeral streams can appear suddenly and cause flash floods (very fast and sudden water flows). Ephemeral streams sometimes are called wadi (in arabic speaking countries) or arroyo (in spanish speaking countries).

An arroyo (/əˈrɔɪoʊ/; from Spanish arroyo Spanish: [aˈroʝo], “brook”), also called a wash, is a dry creek, stream bed or gulch that temporarily or seasonally fills and flows after sufficient rain.

What Does an Arroyo Look Like? An arroyo can be a shallow stream bed covered with mud or sand. It may be dry with cracks in the surface. An arroyo can also be cut deeply, forming a narrow channel in the ground.

Dry rivers are more than mere desiccated shells of their robustly flowing incarnations, say Australian ecologists. They have qualities and inhabitants distinct from their adjacent riversides wet-phase communities. They are places of isolation and re-connection, and oases for humans and wildlife.

In the Middle East, a Wadi is a dry riverbed that often fills briefly with water after strong rains.

Modern English usage differentiates wadis from canyons or washes by the action and prevalence of water. Wadis, as drainage courses, are formed by water, but are distinguished from river valleys or gullies in that surface water is intermittent or ephemeral. Wadis are generally dry year round, except after a rain.

1 : the bed or valley of a stream in regions of southwestern Asia and northern Africa that is usually dry except during the rainy season and that often forms an oasis : gully, wash. 2 : a shallow usually sharply defined depression in a desert region.

Any flowing wadi crossing can be dangerous. Even in shallow wadis, rocks and debris hidden underneath can be deadly. If attempting to cross a passable wadi ensure enough gap between you and the vehicle crossing in-front.

SPA — Al-Ahsa Oasis

An oasis is an area made fertile by a source of freshwater in an otherwise dry and arid region. Oases (more than one oasis) are irrigated by natural springs or other underground water sources.

Antarctic Desert

Cheesecake, cupcakes, jell-O, carrot cake, apple pie, ice cream, brownies, chocolate chip cookies and chocolate cake are the most popular desserts in America.

Atacama Desert

Dangerous Deserts: The Taklamakan Desert, pictured below at left, is called the Sea of Death, a sea from which no one escapes. The Taklamakan is the second largest desert in the world. It offers the Taklamakan traveler poisonous snakes, frequent sandstorms, boiling days, freezing nights, and intense water shortages.

Desert Dangers. There are some hazards unique to desert survival. These include insects (like scorpions), snakes, thorned plants and cacti, contaminated water, sunburn, eye irritation and climatic stress. Insects of almost every type abound in the desert.

Global warming is increasing the incidence of drought, which dries up water holes. Higher temperatures may produce an increasing number of wildfires that alter desert landscapes by eliminating slow-growing trees and shrubs and replacing them with fast-growing grasses.

Effects include land degradation, soil erosion and sterility, and a loss of biodiversity, with huge economic costs for nations where deserts are growing. To prevent desert expansion, WWF has worked to preserve and restore ecosystems in danger of desertification.