Martapura River

The Martapura River (Sungai Martapura) is a river in southeast Borneo, Indonesia. It is a tributary of the Barito River. Other names for the river are Banjar Kecil River   or Kayutangi River and due to many activities of Chinese merchants in the past in the downstream area also called China River. It merges with the Barito River in Banjarmasin, flowing from the source in Martapura, Banjar Regency, South Kalimantan.

Etymology
The river name is taken from the city of Martapura, which was the capital of Banjar Kingdom in around 1630, specifically in the area of Kayu Tangi (hence also the name "Kayutangi River"). Another name is "Tatas River" (Indonesian: Sungai Tatas), pointing to the delta Tatas, which in 1787 was acquired by the Dutch East India Company (now the downtown of modern-day Banjarmasin).

Hydrology
The watershed area (Indonesian: daerah aliran sungai) of Martapura is 453.88 km2, with the main river length of 36566 m, and with all tributaries has a total length of 375.91 km, giving a river density level of 0.828 km/km2. The elevation difference between the upstream and downstream is 8.00 m, yielding a river gradient of 0.022%. The upstream area is the Riam Kanan Dam.

Geography
The river flows in the southeast area of Borneo with a predominantly tropical rainforest climate (designated as Af in the Köppen-Geiger climate classification). The annual average temperature in the area is 25 C. The warmest month is October, when the average temperature is around 28 C, and the coldest is July, at 24 C. The average annual rainfall is 2767 mm. The wettest month is February, with an average of 366 mm rainfall, and the driest is September, with a 75 mm rainfall.