Al-Jazira Plain is located in the northwest part of Iraq. It forms the southern slopes of Sinjar Mountain. Among the dens drainage system in Sijar Mountain, Wadi Al-Ajeej is one of the main valleys; running almost in NE – SW trend, besides Wadi Al-Thar'thar, which runs in NW – SE trend. Both valleys flow from the southern flank of themountain. Although the main trend of Wadi Al-Ajeej is NE – SW, but west of longitude 41ᴼ 40' N, the branches have NNW – SSE trend, some of them flow inside Iraqi territory from Syria. Historical books and geological evidences confirm that Wadi Al-Ajeej, which is the continuation of JaghJagh River in Syria was flowing much far from its nowadays course, starting almost from extreme northeastern parts of Syria; crossing Sinjar Mountain within the nowadays Syrian territory, and then running southeast to merge in the Euphrates River. The old crossing site (water gap) along Sinjar anticline is slightly towards west of the Iraqi – Syrian border. Even now, it forms a low land where it is occupied as unpaved truck to cross the mountain; inside Syria. The estimated age of abandoning Wadi Al-Ajeej to its original course is most probably during the Late Pleistocene.