JABBOK jăb’ ək (יַבֹּק׃֙, LXX Ιαβοκ, meaning, flowing). A river of Trans-Jordan (Nahr ez-Zerkā=“river of blue”), about sixty m. in length, next to the Yarmuk River having greatest drainage area. It is a perennial stream, deriving from the twenty-eight to thirty-two inches of rainfall annually. Its average fall is c. eighty ft. per m., cutting a deep valley or gorge through the E Jordan Valley escarpment. The source lies in the vicinity of Ammān (ancient Rabbath-Ammon, and Hel. Philadelphia), from whence it swings eastward and northward, forming a large loop before wending westward to the Jordan Valley. The lower gorge is under sea level to a point seven m. E of the Rift, at an elevation of more than 2,000 ft. below the Gilead Plateau to the N, and the Amman Plateau to the S. Colorful oleanders line most of its banks in the hill country. After emerging into the Jordan Valley near Tell Deir ’Alla (prob. ancient Succoth), it meanders across the Ghor before joining the Jordan River near ed-Damiyeh (Biblical Adam).

The loop N of Ammān formed the western boundary of the Ammonites at the time of the Conquest (Num 21:24), and the contained area was settled by the tribe of Gad, as far W as present es-Salt. The western part of the river formed a physical and political boundary between the two parts of Gilead (Deut 3:12, 16; Josh 12:2-6), and also divided the kingdoms of Sihon and Og.

Nelson Glueck found numerous occupation sites in the Wadi ez-Zerkā in his surveys, and several Biblical cities were located on, or near, its course. The ford referred to in Genesis 32:22ff. has not been identified, but the place called Penuel (v. 31) is prob. Tulul edh-Dhahab, not far above Succoth.

Bibliography D. Baly, The Geography of the Bible (1957), 229; E. Orni and E. Efrat, Geography of Israel (1964), 91-94; Y. Aharoni, The Land of the Bible (1967), 31, 114, 115.