From BiblePortal Wikipedia

Bridgeway Bible Dictionary [1]

Originally the Arnon River belonged to the people of Ammon and Moab. But the Amorite king, Sihon, attacked from the north and overran much of their land. Eventually he was stopped at the Arnon River. The Arnon therefore became the boundary between the Amorites to the north and the Moabites to the south ( Numbers 21:13).

When the Israelites under Moses were moving north towards Canaan, they conquered the Amorites and seized their territory ( Numbers 21:24). Later, when Israel’s territory east of Jordan was divided between its two and a half eastern tribes, the Arnon became the boundary between Israel’s tribe of Reuben and the neighbouring Moabites ( Deuteronomy 3:12;  Deuteronomy 3:16).

American Tract Society Bible Dictionary [2]

A river rising in the mountains east of the Dead Sea, into which it flows. It is now called Wady Modjeb, and anciently divided the territories of the Moabites in turn from those of the Ammonites, Amorites, and Reubenites,  Numbers 21:13;  Joshua 13:16 . It flows in a deep and wild ravine of the same name. Burckhardt, after reaching the ruins of Aroer, which stand on the edge of the precipice at the foot of which the Arnon flows, says, "From hence a footpath leads down to the river. The view which the Modjeb presents is very striking. From the bottom, where the river runs through a narrow stripe of verdant level about forty yards across, the steep and barren banks arise to a great height, covered with immense blocks of stone which have rolled down from the upper strata; so that, when viewed from above, the valley looks like a deep chasm, formed by some tremendous convulsion of the earth, into which there seems to be no possibility of descending to the bottom. The distance from the edge of one precipice to that of the opposite one, is about two miles in a straight line."

He was thirty-five minutes in descending to the riverbed. Here the heat of midsummer is extreme, and the river becomes almost dried up; but in the rainy season there is an impetuous torrent.

Smith's Bible Dictionary [3]

Ar'non. (Roaring). The river or torrent which formed the boundary between Moab and the Amorites, on the north of Moab,  Numbers 21:13-14;  Numbers 21:24;  Numbers 21:26;  Judges 11:22, and afterwards between Moab and Israel (Reuben).  Deuteronomy 2:24;  Deuteronomy 2:36; 3:8;  Deuteronomy 3:12;  Deuteronomy 3:16;  Deuteronomy 4:48;  Joshua 12:1-2;  Joshua 13:9;  Joshua 13:16;  Judges 11:13;  Judges 11:26. There can be no doubt that the Wady El-Mojeb of the present day is the Arnon. Its principal source is near Katrane, on the Haj route.

Hastings' Dictionary of the Bible [4]

ARNON . A valley with a stream in its bed, now called Wâdy el-Môjib , which gathers the waters from many tributary vales the ‘wadys’ [AV [Note: Authorized Version.] ‘brooks,’ RV [Note: Revised Version.] ‘valleys’] of Arnon (  Numbers 21:14 ) as it flows westward to the Dead Sea. It was the N. border of Moab. cutting it off from the land of the Amorites in old time (  Numbers 21:13 etc.), and later, from that of the Eastern tribes (  Joshua 12:1 etc.). It is named in   Isaiah 16:2 (‘the fords of Arnon’) and   Jeremiah 48:20 (where the reference may be to the inhabitants of the valley, or to a city of that name now unknown). Mesha made the ‘high way in Arnon,’ and built (possibly ‘fortified’) Aroer (Moabite Stone). This ‘high way’ probably followed the line of the Roman road, traces of which still remain, with indications of a bridge, some distance W. of Aroer the modern ‘Ar‘âir , or ‘Ar‘ar , which stands on the N. bank.

W. Ewing.

Fausset's Bible Dictionary [5]

("swift, noisy".) The torrent; boundary between Moab and the Amorites on the N., and afterward between Moab and Reuben ( Numbers 21:13-14;  Numbers 21:24;  Numbers 21:26;  Deuteronomy 2:24;  Deuteronomy 2:36). A branch of the Arnon (Seil es Saideh) flowing N.W. seemingly formed the eastern boundary of Moab ( Judges 11:18;  2 Kings 10:33). Aroer was by its northern brink; the ruins still bear. the name. Rising in the Arabian mountains (the branch Sell es Saideh in the mountains of Gilead near Kalaat el Katrane), it flows through the wilderness and falls into the Dead Sea. Now the wady el Mojeb, flowing through a precipitous, rugged, gloomy ravine. The sides are of red and brown sandstone where it meets the Dead Sea; it is 10 feet; deep at that point. The Roman road between Rabba and Dhiban crosses it at two hours' distance from Rabba.

People's Dictionary of the Bible [6]

Arnon ( Är'Non ), Noisy. A stream running into the Dead Sea from the east, and which divided Moab from the Amorites.  Numbers 21:13;  Judges 11:8. The Arnon is about 60 miles long, 90 feet wide, and from four to ten feet deep at its mouth; full in winter, but nearly dry in summer; had several fords,  Isaiah 16:2, and "high places,"  Numbers 21:28; is referred to 24 times in the Bible. The reference to "high places" in  Isaiah 15:2, some Jewish scholars regard as the name of a place and read, "Beth-bamoth and Dibon are gone up to weep." Its modern name is el-Mojib. It runs through a deep ravine with precipitous limestone cliffs on either side, in some places over 2000 feet high. Ruins of forts, bridges, and buildings abound on its banks, and fish in its waters.

Morrish Bible Dictionary [7]

Ravine or wady with its mountain torrent, which formed the border between Moab and Ammon, now known as Wady Mojib. It has sources both north and south which unite, and its stream running nearly east and west, rushes through a deep ravine and falls into the Dead Sea at about its centre north and south.  Numbers 21:13-28;  Numbers 22:36;  Deuteronomy 2:24,36;  Judges 11:13-26;  Isaiah 16:2;  Jeremiah 48:20; etc.

Holman Bible Dictionary [8]

 Numbers 21:13 Numbers 21:24 Deuteronomy 3:8 Joshua 13:16 Judges 11:12-33 Isaiah 16:2 Jeremiah 48:20

Watson's Biblical & Theological Dictionary [9]

a river or brook, mentioned  Numbers 21:24 , and elsewhere. Its spring head is in the mountains of Gilead, or of the Moabites and it discharges itself into the Dead Sea.

Easton's Bible Dictionary [10]

 Deuteronomy 3:8,16

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [11]

(Heb. Arnon', אִרְנוֹן , a Murmur; Sept. Αρνῶν , sometimes Ἀρνών ), a river ( נִחִל , Torrent,  Deuteronomy 2:24, forming the southern boundary of trans-Jordanic Palestine (originally of the Amoritish territory,  Numbers 21:13;  Numbers 21:26), and separating it from the land of Moab ( Deuteronomy 3:8;  Deuteronomy 3:16;  Joshua 12:1;  Judges 11:22;  Isaiah 16:2;  Jeremiah 48:20). Josephus speaks of it as issuing from the mountains of Arabia (Ant. 4: 5, 1). Among these hills are probably to be sought the "heights of Arnon" ( Numbers 21:28). (See Bamoth).

It is also named in  Deuteronomy 2:36;  Deuteronomy 3:12;  Deuteronomy 4:48;  Joshua 12:2;  Joshua 13:9;  Joshua 13:16;  Judges 11:13;  Judges 11:26. From  Judges 11:18, it (i.e. one of its branches N.E. of Arnon) would seem to have been also the East border of Moab (see also  2 Kings 10:33). In many of the above passages it occurs in the formula for the site of Aroer, "which is by the brink of the river Amnon." In Numbers it is simply "Arnon," but in Deuteronomy and Joshua generally "the river Arnon" (A. V. sometimes "river of Arnon"). Isaiah ( Isaiah 16:2) mentions its fords; and in  Judges 11:26, a word of rare occurrence ( יָד , hand, comp.  Numbers 13:29) is used for the Sides of the stream. In the time of Jerome it was still known as Arnon; but in the Samarito-Arabic version of the Pentateuch by Abu-Said (10th to 12th century) it is given as el Afojeb. There can be no doubt that the Wady el-Mojeb of the present day is the Arnon (Seetzen, Reise, 1854, ii, 347; and in Ritter, Erdk. 15:1195). The ravine through which it flows is still the " locum vallis in praerupta demersae satis horribilem et periculosum" which it was in the days of Jerome (Onom.). The Roman road from Rabba to Dhiban crosses it at about two hours' distance from the former. On the south edge of tile ravine are some ruins called Mehatet el-Haj, and on the north edge, directly opposite, those still bearing the name of Arair. (See Aroer).

Burckhardt was the first to give a satisfactory account of this river under the name which it now bears. It rises in the mountains of Gilead, near Katrane, whence it pursues a circuitous course of about eighty miles to the Dead Sea. It flows in a rocky bed, and, at the part visited by Burckhardt, in a channel so deep and precipitous as to appear inaccessible (comp. Seetzen, Monatl. Corresp. 18: 432); yet along this, winding among huge fragments of rock, lies the most frequented road, and, being not far from Diton, probably that taken by the Israelites. The descent into the valley from the south took Irby and Mangles (Letters, p. 461) one hour and a half; the descent from the north took Burckhardt (Syria, p. 372) thirty-five minutes. The last-named traveller declares that he had never felt such suffocating heat as he experienced in this valley from the concentrated rays of the sun and their reflection from the rocks. The stream is almost dried up in summer; but huge masses of rock, torn from the banks, and deposited high above the channel, evince its fulness and impetuosity in the rainy season. Irby and Mangles suppose that it is this which renders the valley of the Arnon less shrubby than that of most other streams in the country. "There are, however, a few tamarisks, and here and there are oleanders growing about it." On each face of the ravine traces of the paved Roman road are still found, with milestones, and one arch of a bridge, 31 feet 6 inches in span, is standing. I he stream runs through a level strip of grass some 40 yards in width, with a few oleanders and willows on the margin. Lieut. Lynch describes it at its mouth in April as "a considerable stream of water, clear, fresh, and moderately cool, and having some small fish in it" (Eapedition, p. 299). Where it bursts into the Dead Sea this stream is 82 feet wide and 4 feet deep, flowing through a chasm with perpendicular sides of red, brown, and yellow sandstone, 97 feet wide. It then runs through the delta in a S.W. course, narrowing as it goes, and is 10 feet where its waters meet those of the Dead Sea (Lynch, Report, May 3, 1847, p. 20).

According to the information given to Burckhardt, its principal source is near Katrane, on the Haj route. Hence, under the name of Seil es-Saideh, it flows N.W. to its junction with the W. Lejum, one hour E. of Arair, and then as W. Mojeb, more directly W. to the Dead Sea. The W. Mojeb receives on the north the streams of the W. Waleh, and on the south those of W. Shekik and W. Saliheh. At its junction with the Lejum (W. Enkeileh) is a piece of pasture-ground, in the midst of which stands a hill with ruins on it (Burck. p. 374). May not these ruins be the site of the mysterious " city that is in the midst of the river" ( Joshua 13:9;  Joshua 13:16; Deuteronomy ii, 36) so often coupled with Aroer ? From the above description of the ravine, it is plain that that city cannot have been situated immediately below Aroer, as has been conjectured.

International Standard Bible Encyclopedia [12]

ar´non ( ארנון , 'arnōn  ; Ἀρνῶν , Arnō̇n ): Is first mentioned in  Numbers 21:24 as the border between Moab and the Amorites. "The valleys of Arnon" in the next verse undoubtedly indicate the numerous wadies contributary to the main stream. It formed the southern boundary of the land assigned to Reuben (  Deuteronomy 3:12 ). The city of Aroer stood on the northern edge of the valley ( Deuteronomy 2:36;  Judges 12:2 , etc.). Arnon was claimed by the Ammonites as having marked the southern limit of their territory when Israel invaded the land ( Judges 11:13 ). They, however, had already been driven out by the Amorites, and the region north of Arnon was held by Sihon. From the inscription of Mesha on the Moabite Stone we gather that Moab had established herself on the north of the Arnon before the time of Omri. Under Omri and Ahab she was confined to the south of the river. A rebellion under Mesha was put down by Jehoram son of Ahab (2 Ki 3), and the expedition of Hazael against Israel reached the valley of the Arnon ( 2 Kings 10:33 ). But according to Mesha he regained for Moab the lost land; and this agrees with  Isaiah 15:1-9;  Isaiah 16:1-14 , where cities north of Arnon are located in Moab, e.g. Heshbon.

The modern name of Arnon is Wādy el - Mōjib , which enters the Dead Sea from the East about 11 miles North of el - Lisān . Some 13 miles East of the Dead Sea two streams, Seil es - Sa‛ideh from the South, and Wādy Enkeileh from the East, unite their waters and flow westward in the bottom of an enormous trench. The waters of Wādy Weleh come in from the Northeast. A wide stretch of country thus drains into the valley by means of a great network of smaller wadies - the "valleys of Arnon." The "fords of the Arnon" ( Isaiah 16:2 ) were doubtless crossed by Mesha's highway which he claims to have built in Arnon; and may be marked by the traces of the old Roman road and bridge immediately to the West of where, on the northern edge of the Wādy , stands ‛Arā‛ir , the ancient Aroer.

Kitto's Popular Cyclopedia of Biblial Literature [13]

Ar´non, a river forming the southern boundary of trans-Jordanic Palestine, and separating it from the land of Moab ( Numbers 21:13;  Numbers 21:26;  Deuteronomy 2:24;  Deuteronomy 3:8;  Deuteronomy 3:16;  Joshua 12:1;  Isaiah 16:2;  Jeremiah 48:20). It now bears the name of Wady Modjeb, and rises in the mountains of Gilead, near Katrane, whence it pursues a circuitous course of about eighty miles to the Dead Sea. It flows in a rocky bed, and, at the part visited by Burckhardt, in a channel so deep and precipitous as to appear inaccessible; yet along this, winding among huge fragments of rock, lies the most frequented road, and, not being far from Dibon, probably that taken by the Israelites. The stream is almost dried up in summer; but huge masses of rock, torn from the banks, and deposited high above the usual channel, evince its fulness and impetuosity in the rainy season.