The Mahakam: East Kalimantan's great river

The Mahakam is the longest river in East Kalimantan, running for about 980 kilometres from the mountains near the centre of Borneo to the Makassar Strait at Samarinda. It is the artery of the province: coal from the interior, timber, palm oil and people all move on it, and the towns along its banks grew up because of it.

For travellers, it is the way into the interior. Upriver from Samarinda and Tenggarong, the river passes through a lake district, then into Dayak country, where villages are reached only by boat and the forest is still the main fact of life. It is also the habitat of the pesut, a freshwater dolphin that is one of the rarest mammals in Indonesia.

Samarinda and the lower river

Samarinda is the provincial capital and the biggest city on the river, a busy, hot, commercial place with a waterfront, a mosque and a great deal of coal traffic. The river here is wide and brown, and the boats are constant: tugs pulling barges, ferries crossing, speedboats heading upstream.

The city is not a tourist destination, but it is a useful base and it has good seafood and a lively market. The waterfront promenade, the Masjid Islamic Center and the river itself are worth an afternoon. From Samarinda, boats run to Tenggarong and beyond, and the road follows the river for much of the way.

Tenggarong and the Kutai lakes

Tenggarong, about an hour upstream, was the capital of the Kutai Sultanate and holds the Mulawarman Museum, one of the best in Kalimantan. Beyond it the river opens into the lake district: Jempang, Semayang and Melintang, shallow lakes that fill in the wet season and shrink in the dry, with fishing villages on their shores.

The lakes are the heart of the Mahakam's ecology. They hold fish, birds and the pesut, and they flood the surrounding forest in the wet season, creating a vast nursery. In the dry season the water drops and the villages move onto the exposed lake bed, planting crops and grazing buffalo. It is a landscape that changes completely between seasons.

The pesut and the wildlife

The pesut, or Irrawaddy dolphin, is the river's most famous resident and one of its most endangered. Fewer than a hundred are thought to survive in the Mahakam, threatened by fishing nets, boat traffic, pollution and the loss of the lakes. Conservation efforts are serious but the numbers are not encouraging.

Seeing one is a matter of luck and patience. The best chance is in the lake district, early in the morning, with a local boatman who knows where they surface. Do not chase them, do not surround them and do not pay for shows. The dolphins are wild, and the point is to watch them from a respectful distance.

Travelling upstream

Boats run from Samarinda to Tenggarong and on to the lakes and the interior, some fast, some slow, some little more than a wooden hull with an outboard. The further you go, the more the journey becomes the point: villages, log camps, fishing traps, forest, and the occasional coal barge coming down.

Allow several days for a proper trip upstream, and arrange it through a local operator or guesthouse. The dry season, June to September, is easier; the wet season brings high water, which makes some channels passable and others dangerous. Bring cash, insect repellent and patience, and expect the schedule to change.

• Use Samarinda as the base for the lower river.
• Tenggarong and the Mulawarman Museum are an easy day trip.
• The lake district is best in the early morning.
• Never chase the pesut; watch from a distance.
• Allow several days for the upper river.

Practical notes for the river

Boats on the Mahakam range from fast passenger launches to slow wooden boats and chartered canoes. The fast boats are the practical choice for Tenggarong and the lakes; the slow boats are cheaper and more atmospheric, but they take much longer. For the upper river, you will need a chartered boat and a guide.

Tickets are bought at the jetty or through a guesthouse, and the schedules change with the water. In the dry season, low water can close some channels; in the wet season, high water can make others dangerous. Ask locally before you commit, and allow more time than the distance suggests.

Bring cash, insect repellent and a rain jacket. The villages are welcoming but conservative: dress modestly, ask before photographing, and do not expect Wi-Fi or hot water. The haze season, August to October, can make the river unpleasant and occasionally closes airports, so check the forecast if you are flying in.

Questions people actually ask

Can you see the pesut dolphin on the Mahakam?

It is possible, especially in the lake district around Jempang and Semayang, early in the morning with a local boatman. Numbers are very low, so sightings are not guaranteed. Never chase or surround the dolphins, and avoid operators that promise a show.

How do you travel up the Mahakam?

Boats leave from Samarinda for Tenggarong, the lakes and the interior, with a mix of fast and slow services. For anything beyond the lakes, arrange the trip through a local operator and allow several days. The dry season from June to September is the easiest time.