Wady

( ) is traditionally a valley. In some cases it can refer to a dry riverbed that contains water only during times of heavy rain. Compare arroyo (creek), canyon, gulch, wash and gully.The term is very widely found in Arabic toponyms. Wadis tend to be associated with centers of human population because sub-surface water is sometimes available in wadis. Crossing wide wadis at certain times of the year can be dangerous, because of unexpected flash floods. Such flash floods cause many deaths each year in Saudi Arabia and many other Middle Eastern countries.
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(n.)
A ravine through which a brook flows; the channel of a water course, which is dry except in the rainy season.
  

UADI

n. บริเวณลำน้ำหรือลำธารที่แห้งผาก, ยกเว้นในช่วงฤดูฝน (อยู่ทางแอฟริกาเหนือ ตะวันออกกลางและเอเชียใต้); แหล่งอุดมสมบูรณ์ในทะเลทราย (syn. oasis)