Nahal Og or Wadi Og (Hebrew: נחל אוג), or Wadi al-Muqallek, also spelled Wadi Muqallik (Arabic: وادي مكلك) is a winterbourne stream on the West Bank that drains the eastern slopes of the Mount of Olives range east of Jerusalem and runs for 30 km till the Dead Sea.^[1][2] It is the northernmost of the streams that flow from the Judaean Desert into the Dead Sea.^[1]

The Hebrew name of the stream is derived from the local sumac plant (Rhus tripartita), that grows in the wadi, which is named Og in Hebrew.^[2][3]

The wadi (seasonal stream) drains the slopes of the Mount of Olives, Mount Scopus and Abu Dis in Jerusalem at 800 m above sea level and descends till the Dead Sea at 400 m below sea level.^[3] The steepness of the stream results in heavy flooding during the winter,^[1] and in the past, parts of Highway 90 have been swept away.^[4][5] The stream sweeps mud and debris along with the water and sometimes during flooding times it is possible to see a trail of mud, hundreds of meters long, in the waters of the Dead Sea.^[6]

On the course of the wadi are the ruins of the Monastery of Theoctistus, known in Arabic as Deir Muqallik.^[7] They are hard to access, being situated quite high on the steep northern bank of the wadi at the spot where the valley deepens, turning into a canyon.^[7] According to Byzantine sources, it was established in the 5th century by Euthymius and Theoctistus.^[7] Archaeologists confirm that the main phase of the cave church complex and related structures date back to the 5th-7th century, the monastery's 'golden era', with signs of a far less significant habitation period during the Early-Mid Muslim period in the 7th-11th or 12th century.^[7] The cave church complex was established at the beginning of the 5th century, and at the end of the 8th the monastery was deserted.^[7]

At the foothills of the Judean mountains the stream passes by the Muslim shrine of Nabi Musa.^[6] In the plain, before reaching the Dead Sea, it also passes next to the kibbutz and Israeli settlement of Almog.^[2] Here, towards the end of the stream, a reservoir was built which stores waters from the floods that is used by Almog.^[6]

Panorama of Wadi Og from Og Lookout

31°46′39″N 35°25′40″E / 31.7775°N 35.4278°E / 31.7775; 35.4278