Seawater Begins Entering Shrinking Mahakam River in East Kalimantan
Seawater has begun entering the Mahakam River as the river’s flow continues to shrink due to the dry season in East Kalimantan. Nevertheless, the Balai Wilayah Sungai (BWS) Kalimantan IV Samarinda has confirmed that this condition has not yet affected raw water intake for public needs.
Head of BWS Kalimantan IV Samarinda, Andri Rachmanto Wibowo, said that the seawater intrusion is currently still occurring around the estuary area and is influenced by tides. The situation is different when the Mahakam’s flow is high, as the freshwater current is able to hold back seawater from moving further up the river.
“Because it has shrunk somewhat, some seawater has indeed entered, but it does not affect water intake for PDAM,” said Andri, as reported by detikKalimantan on Thursday (20/8/2026).
According to Andri, PDAM has quality standards for the raw water it uses to be processed into clean water. So far, the seawater intrusion has not reached a level that could disrupt raw water intake.
“PDAM has standards, and salty water is not allowed. So it is indeed still safe at the moment,” he said.
In addition to relying on the Mahakam River, Samarinda’s raw water needs are also supplied from the Lempake Dam. The dam has a capacity of around 900,000 cubic metres and is one of the supply sources for PDAM Samarinda.
“PDAM Samarinda also receives water from us, from the Lempake Dam. Its capacity is 900,000 cubic metres. So besides the Mahakam River, there is also supply from the Lempake Dam,” he explained.
Andri assured that raw water availability for the public is still sufficient to face the dry season. BWS is also managing water reserves in several dams so that they can be used according to priority needs.
“It is still sufficient and safe,” he said.
Mahakam Dolphins at Risk of Being Trapped
The shrinking condition of the Mahakam River in East Kalimantan poses a threat to the survival of the Mahakam dolphin. The Rare Aquatic Species of Indonesia (RASI) Conservation Foundation is concerned that dolphins moving along water channels could become trapped when parts of the river they pass through dry up or become disconnected.
Head of the Scientific Programme at RASI Conservation Foundation, Danielle Kreb, said the dry season has reduced the Mahakam’s water flow. Under such conditions, dolphins usually move further upstream to find waters that still have sufficient flow and food sources.
“The dolphins can travel further upstream and migrate as well. We are worried that a dolphin could become trapped in water where, for example, it passes through a section of the river that still has water, and then when it tries to return, the passage has already been cut off,” Danielle told detikKalimantan on Thursday (20/8/2026).
According to Danielle, this situation means the public needs to act as an early warning system. Residents who see dolphins struggling to move upstream or downstream are asked to immediately report the situation to parties who can take action.
“We really need an early warning system from the community so that if they see a dolphin, or even realise that a dolphin cannot move further upstream or downstream, they should contact RASI or the Marine Management Office (BPK), DKP, or local authorities in the village,” she said.