Fly (fleuve)

The Fly River is the third longest river in the island of New Guinea, after the Sepik River and Mamberamo River, with a total length of . It is the largest by volume of discharge in Oceania, the largest in the world without a single dam in its catchment, and overall the 20th-largest primary river in the world by discharge volume. It is located in the southwest of Papua New Guinea and in the South Papua province of Indonesia. It rises in the Victor Emanuel Range arm of the Star Mountains, and crosses the south-western lowlands before flowing into the Gulf of Papua in a large delta. The Fly-Strickland River system has a total length of , making it the longest river system of an island in the world. The Strickland River is the longest and largest tributary of Fly River, making it the farthest distance source of the Fly River. The Fly flows mostly through the Western Province of Papua New Guinea and for a small stretch, it forms the international boundary with western New Guinea. This section protrudes slightly to the west of the 141°E longitude line. To compensate for this slight gain in territory for Papua New Guinea, the border south of the Fly River is slightly east of the 141°E longitude line. As part of this deal, Indonesia has the right to use the Fly River to its mouth for navigation. The principal tributaries of the Fly are the Strickland and the Ok Tedi. Close to its mouth, the flow of the Fly River encounters a tidal bore, where an incoming high tide pushes water upstream until the tide changes. The range of this tidal bore is still undocumented. Average, minimum and maximum discharge of the Fly River at Ogwa (Lower Fly). Period from 1998 to 2022. The delta of the Fly River is over 100 km wide at its entrance, but only 11 km wide at the apex upstream of Kiwai Island. The delta contains 3 main distributary channels (the Southern, Northern, and Far Northern Entrances) that branch from a common point (the “apex”). The distributary channels are 5 to 15m in depth, separated by elongate, sand-mud islands that are stabilised by lush mangrove vegetation.