Sepik River

The Sepik () is the longest river on the island of New Guinea, and the third largest in Oceania by discharge volume after the Fly and Mamberamo. The majority of the river flows through the Papua New Guinea (PNG) provinces of Sandaun (formerly West Sepik) and East Sepik, with a small section flowing through the Indonesian province of Papua.

The Sepik has a large catchment area, and landforms that include swamplands, tropical rainforests and mountains. Biologically, the river system is often said to be possibly the largest uncontaminated freshwater wetland system in the Asia-Pacific region. But, in fact, numerous fish and plant species have been introduced into the Sepik since the mid-20th century.

Name

In 1884, Germany asserted control over the northeast quadrant of the island of New Guinea, which became part of the German colonial empire. The colony was initially managed by the Deutsche Neuguinea-Kompagnie or German New Guinea Company, a commercial enterprise that christened the territory Kaiser-Wilhelmsland. The first European ship to enter the Sepik estuary was the ''Samoa'' in May 1885. But the river, in fact, did not yet have a European name. It was thus termed ''Kaiserin Augustafluß'' by the explorer and scientist Otto Finsch, after the German Empress Augusta.

The word ''Sipik'' was first reported by A. Full as one of two names for the watercourse—the other being ''Abschima''—used by the natives living at the mouth of the river. A few years later, Leonhard Schultze applied the term ''Sepik'' to the entire watercourse, and it took, although Schultze also noted another name for the river, ''Azimar''. William Churchill, writing in the ''Bulletin of the American Geographical Society'', said "These are not names of the river, they are but names for small stretches of the river as known to the folk of this or that hamlet. We cannot reckon how many such names there may be in the course of more than of the system." Since "there is no indigenous name for the whole stream", Churchill concluded that "This is clearly a case where a European designation may properly be applied." He advocated for Kaiserin-Augusta, but that name faded with the German loss of colonial control over the territory after World War I. The word ''Sepik'' henceforth became the official name of the river.

Of course, each language group had one or more names of its own for the river. For example, the Iatmul people call the river ''Avusett'', a compound of "bone" (''ava'') and "lake" (''tset'').

Description

The river originates in the Victor Emanuel Range in the central highlands of Papua New Guinea. From its mountain headwaters near Telefomin, it travels north-west and leaves the mountains abruptly near ''Yapsei''. From there it flows into Indonesian Papua, before turning back north-east, for the majority of its journey following the great ''Central Depression''. Along its course it receives numerous tributaries from the Bewani and Torricelli Mountains to the north and the Central Range to the south, including the Yuat River formed by the ''Lai'' and the ''Jimmi''.

For most of the Sepik's length, the river winds in serpentine fashion, like the Amazon, to the Bismarck Sea off northern Papua New Guinea. Unlike many other large rivers, the Sepik has no delta whatsoever, but flows straight into the sea, about east of the town of Wewak. It is navigable for most of its length.

Hydrology

The river has a total length of over and has a drainage basin of over . Its meandering bed is wide and averages deep. There is a belt of active meanders along most of its course, that has created a floodplain up to wide, with extensive backwater swamps. There are around 1,500 oxbow and other lakes in the floodplain, the largest of which are the Chambri Lakes. Its annual sediment load is estimated at 115 million tonnes.

The Sepik basin is largely an undisturbed environment, with no major urban settlements, or mining and forestry activities, in the river catchment. April Salome Forest Management Area is located in Sepik River basin.

Its catchment is classified as type ''Af'' (tropical rainforest) according to Köppen climate classification, with a rainfall of 3,390 mm.

Discharge

^*1969/1970 water year 8,964 m³/s.

Sepik River discharge (m³/s) at Ambunti