The water and sediment quality in the Rajang River downstream of the Bakun Dam is being studied. The researchers looked at differences in water quality during different dam operations and found that pH levels were lower closer to the dam. Dissolved oxygen levels decreased when there was no spillway discharge. Rainfall events increased turbidity and decreased water clarity. Certain pollutants like phosphorus were mainly from human activities. Overall, the water quality in the river is classified as slightly polluted or polluted, with some parameters declining after the dam was built.