Kayan River
The Kayan River is a river of Borneo island, flowing in the North Kalimantan province of Indonesia, about 1,600 km northeast of the capital Jakarta.
Course
The Kayan is a large river in Borneo. It is one of the largest and most important rivers in the province of Kalimantan Utara. It rises in the northern part of the island's central mountain range in the Ukeng Mountains and flows in a large delta into the Sulawesi Sea below the provincial capital Tanjung Selor.Geography and hydrology
The Kayan River rises on Mount Ukeng, passing Tanjung Selor city, and discharges into the Sulawesi Sea, with a total length of about and a basin size of, forming a wide area at the upstream and narrower in the center until downstream.The Kayan River is named after the Kayan Dayak tribe. Its headwaters originate in the Ukeng Mountains at an altitude of about above sea level. The river cuts through mountainous areas in a south-east, east-east and then north-east direction with high gradient rapids. It flows over Tanjung Selor for more than 70 km through coral and limestone hills to the town. Its banks are typically lined with nipas, with some coconut trees. Below the town it eventually ends in the wide Kayan Delta in the Sulawesi Sea.
The average width of its lower reaches is around. At the mouth it rises between. Depth is generally around. Tanjung Selor is navigable by larger boats. Higher up, it can be navigated by small boats, and the more rapids only by boat.
The catchment receives between 3,500 and 4,000 mm of rainfall per year.
Delta
The tidal delta covers an area of about 3,000 square kilometres. The deltas of the Kayan, Sekatak, Sesayap and Sembakung rivers form a continuous ‘delta complex’.Discharge
Tributaries
Kayan has 12 major tributaries. The Bahau is the largest of these.The main tributaries from the mouth:
Ecology and economy
The Bulungan district of the Kayan River in northern Kalimantan is characterised by rich biodiversity and includes ecosystems such as lowland tropical rainforest, montane forest, peat swamps, mangroves and karst. The Kayan Delta is home to at least 6 native mangrove species. The interior of the delta is dominated by nipah, while parts of the delta are home to mixed freshwater and saltwater ecosystems.The Kayan is vital for communities living along the river and in its delta, as they depend on it for freshwater, fisheries and agriculture. Dayak people living along the river depend on farming, agriculture and fishing. Their vast rice fields have been cultivated for generations.
Today, the Kayan watershed has become a centre for investment. Large areas have been converted into palm oil and timber plantations, mining areas, fish ponds and agricultural land.