The Bian River or Mbian River is a river in Merauke Regency, South Papua, Indonesia. Its total length is 580.6 km and its width is around 70 – 1447.1 m. Some 900 people in its upper course are said to speak the language Bian Marind.

Geography

The river flows in the southern area of Papua with a predominantly tropical rainforest climate (designated as Af in the Köppen-Geiger climate classification). The annual average temperature in the area is 23 °C. The warmest month is October when the average temperature is around 25 °C, and the coldest is June, at 20 °C. The average annual rainfall is 2952 mm. The wettest month is May, with an average of 405 mm rainfall, and the driest is August, with 62 mm rainfall.

Ecology

In the district of Muting (Merauke Regency), the Bian River is a nature reserve by the order of the Ministry of Forestry as the habitat of various protected flora and fauna, among others: Archerfish and Asian arowana.